U3 O1 - cardiovascular emergencies Flashcards

Question

What is the aim of the bodys compensatory mechanisms?

Answer 1

the body’s priorities are to preserve arterial blood pressure and tissue perfusion, especially of the main organs. The previously discussed compensatory mechanisms exist to support this and are especially adapted to address decreased blood volume

Answer 2

Some of the compensatory mechanisms, especially the chronic ones, can cause problems in the patient with heart failure/ cardiogenic shock e.g. fluid retention.

Answer 3

Forward failure (low output) can occur secondary to several conditions including - 1. Arrhythmias a. Heart blocks b. Supraventricular tachycardia c. Ventricular tachycardia 2. Dilated cardiomyopathy (DCM)

Answer 4

These will vary depending on the severity of the condition and are often related to compensatory mechanisms. There will usually be respiratory signs as well when there is concurrent congestive heart failure. The patient’s heart rate is often very rapid - even faster than could be expected in a patient with hypovolaemia Clinical signs may include the following 1. exercise intolerance, syncope or collapse due to decreased cardiac output 2. pale mucous membranes 3. weak pulse +/- pulse deficits 4. prolonged CRT (> 2seconds) 5. cold extremities 6. hypotension 7. altered mentation 8. tachycardia (N.B. cats may have bradycardia) 9. reduced urine output The patient may have cachexia (weakness and wasting due to chronic illness) if tissue perfusion has been poor for a while. There may also be a cardiac murmur, arrhythmia and signs of respiratory difficulty/ distress- tachypnoea, orthopnoea, cyanosis, blood- stained frothy liquid from the mouth/ nose, etc. (Tabor, 2016). The respiratory signs are due to chronic/ congestive heart failure where fluid is retained and can lead to pulmonary oedema/pleural effusion.

Answer 5

Inappropriate bradycardia in a collapsed patient with poor pulse quality should also prompt assessment for an underlying cause (e.g. hyperkalaemia). Any patient with bradycardia or tachycardia on presentation should have an ECG carried out. Arrythmias are not always evident on auscultation and, whilst the ECG only gives information about the electrical conduction through the heart and not the heart’s pumping ability, if a treatable arrhythmia is present the cardiac function should improve.

Answer 6

cachexia (weakness and wasting due to chronic illness)

Answer 7

``` In early compensatory shock the systolic blood pressure is often normal or slightly reduced; in the early stages of decompensatory shock the patient is likely to be hypotensive (60-70 mmHg) and in late decompensatory shock there is likely to be marked hypotension (<60 mm Hg) which is not responsive to intravenous fluid therapy ```

Answer 8

Davis (2015) discusses using the shock index as a means of quantifying the severity of the shock and response to treatment in veterinary patients. The shock index is the ratio of the heart rate to systolic blood pressure (HR/SBP) and can be used in the clinical assessment of patients to determine if they are in shock - however this is currently more commonly used in human than veterinary medicine.

Answer 9

An ECG recording will enable assessment of heart rate and rhythm - it will identify the presence and type of cardiac arrhythmia if present (Unit 1, Outcome 2). It should be noted that an ECG gives information about the electrical conduction system of the heart. On its own it does not indicate how the heart is functioning or whether the patient is in heart failure. It should always be used in combination with physical examination and other diagnostics.

Answer 10

Measurement of blood urea nitrogen (BUN) and creatinine can be used to determine if there is pre-renal azotaemia secondary to poor renal perfusion. Urine output should also be assessed as the patient is likely to be oliguric if there is decreased renal perfusion. N.B. If there is pre-renal azotaemia, the urine specific gravity is like to be normal or increased (> 1.030 dog/ > 1.035 cat) i.e. more concentrated. With renal azotaemia, the urine specific gravity is likely to be decreased (1.008-1.012) as the nephrons are not functioning so cannot concentrate urine. SDMA testing and IRIS staging should be considered if the patient is thought to be concurrently in renal failure, allowing for ongoing monitoring of its status

Answer 11

Blood gas, acid-base, pH and electrolyte measurements are of great value in assessing the patient- there is likely to be hypoxaemia, hypercapnia and acidosis. N.B. the only way to accurately identify hypoxaemia is with the use of arterial blood gas sampling, although this can be technically challenging. Measuring serum electrolytes may help to identify the cause of a cardiac arrhythmia or potential complications e.g. bradycardia may arise due to hypoadrenocorticism or urethral obstruction (hyperkalaemia).

Answer 12

Serial blood lactate assessment is useful to provide information about the patient’s perfusion status and response to treatment. Hyperlactataemia will develop because of anaerobic respiration secondary to decreased cell perfusion and oxygen delivery

Answer 13

FAST/POCUS ultrasound evaluation can demonstrate the presence of abdominal, pleural or pericardial effusion. Short, targeted echocardiographic examination can be performed, in the emergency patient, with the aim of getting specific information about the heart but without compromising the patient further (Matos and Summerfield, 2018). More comprehensive echocardiography can be performed once the patient is more stable to confirm the diagnosis and assess cardiac structure and function

Answer 14

If an underlying cardiac cause is suspected, thoracic radiography could be performed to assess the heart size and shape; and demonstrate signs of congestive heart failure (engorged pulmonary veins, perihilar pulmonary oedema, pleural effusion etc.). However, radiography should only be performed if the patient is stable- it is contraindicated if it causes increased patient stress especially in a patient with breathing difficulties.

Answer 15

``` If an underlying cardiac cause is suspected, thoracic radiography could be performed to assess the heart size and shape; and demonstrate signs of congestive heart failure (engorged pulmonary veins, perihilar pulmonary oedema, pleural effusion etc.). ```

Answer 16

Oxygen supplementation should be provided in the manner least likely to stress the patient whilst also increasing blood oxygen levels. Patient movement should be restricted with the patient supported in sternal recumbency, if possible, in a manner that does not interfere with its ability to breath. The patient should be cage rested in a quiet area with minimum stress and closely monitored. Intravenous access should be obtained, as soon as possible, on veterinary direction, without stressing the patient. For most cardiac patients restraint can induce stress and a sensation of panic. This can be mitigated by using fear free techniques and minimal restraint approaches. N.B. Medical management will depend on the underlying cause and presenting signs e.g. forward failure/cardiogenic shock or backward failure and will be discussed in the relevant sections.

Answer 17

The patient will probably require diuretic therapy (furosemide) for management of pulmonary oedema which has developed secondary to the pump failure

Answer 18

Inotropes - drugs which increase cardiac contractility and systolic output

Answer 19

Antiarrhythmics – drugs used to correct an abnormal heart rhythm e.g. lidocaine for ventricular tachycardia

Answer 20

Pimobendan – this drug has positive inotropic and vasodilator properties - it is called an inodilator. Since becoming available as a licenced intravenous preparation, it has been used as a first line drug in the management of acute congestive cardiac failure and can also be used in a patient with cardiogenic shock, although it is less potent than dobutamine.

Answer 21

Pimobendan

Answer 22

Dobutamine - this can be administered for a short period as a positive inotrope to a patient with cardiogenic shock, heart failure due to systolic dysfunction or septic shock (BSAVA, 2020). It can also be used provide myocardial support in a hypotensive patient (BSAVA, 2020). It is a shortacting, positive inotrope, titrated to effect, and delivered as a constant rate infusion (CRI). As this drug is a sympathomimetic, the patient should be monitored closely for adverse signs e.g. supraventricular/ ventricular arrhythmias and hypertension.

Answer 23

Dopamine - this drug has a similar effect to dobutamine and is useful for improving haemodynamic status especially in septic patients - accessing dopamine can be problematic, however. Dobutamine is preferred for patients in heart failure (BSAVA, 2020). Dopamine is a catecholamine, precursor of noradrenaline, with sympathomimetic effects (BSAVA, 2020). It has effects on dopaminergic, beta-1 and alpha-1 adrenergic receptors (BSAVA, 2020). It is also a potent, short-acting drug so it is administered as a CRI to patients that are effectively volume resuscitated- the effects of dopamine depend on the dose administered. At low doses, dopamine acts on dopaminergic and beta receptors- this causes vasodilation, increased force of contraction (positive inotrope) and increased heart rate (positive chronotrope) (BSAVA, 2020). At higher doses, there are more alpha-1 effects which leads to peripheral vasoconstriction. Perivascular administration can cause tissue ischaemia and slough (BSAVA, 2020). Patients should be monitored closely for adverse signs during administration e.g. tachycardia, arrhythmia and hypertension.

Answer 24

Receptor type Alpha-1 adrenergic (α-1) Location Blood Vessel effect Vasoconstriction

Answer 25

Receptor type Beta- 1 adrenergic (β-1) Location Heart ``` Effect Positive inotrope (increased strength) Positive chronotrope (increased rate) ```

Answer 26

Receptor type Beta- 2 adrenergic (β-2) Location Blood Vessels Effect Vasodilation

Answer 27

Receptor type Dopamine Location Blood vessels e.g. kidney Effect Vasodilation (other effects elsewhere) (low dose) Vasoconstriction (high dose)

Answer 28

Anti-arrhythmic medications may be required for specific cardiac rhythm disturbances- especially serious tachydysrhythmias. N.B. Prompt identification and management of underlying electrolyte abnormalities (e.g. hyperkalaemia hypomagnesia) is essential.

Answer 29

This should include monitoring patient demeanour, respiration rate and pattern, heart rate and rhythm and perfusion parameters e.g. central and peripheral pulses, temperature (core and peripheral), mucous membrane colour and CRT. Urine output (normal - 1-2ml/kg/hour), blood pressure and pulse oximeter readings. Ideally, blood gases, pH and lactate levels should all be measured regularly if arterial blood sampling is possible. It is important to monitor the patient for any adverse signs too e.g. dehydration from excessive diuretic administration or hypotension from over administration of vasodilators. Renal parameters should ideally be monitored alongside electrolyte levels, especially potassium, as furosemide causes increased urine excretion of potassium.

Answer 30

``` Backward failure (also called congestive heart/ cardiac failure) is when one or both ventricles is unable to pump all the blood they contain. As well as not meeting the oxygen demands of the tissues, with backward failure there is a progressive build-up of fluid in the heart chambers and blood vessels behind the failing ventricle(s). If the left ventricle is failing, this results in increased pulmonary venous pressure and / or if the right ventricle is failing there is increased systemic venous pressure. The build - up of fluid in the veins results in fluid leaking from capillaries into tissues (e.g. pulmonary oedema) or body cavities (effusion). These changes in hydrostatic pressure can be attributed to Frank Starling’s Law. Frank Starling’s Law is explained by Delicce and Makaryus (2020). This build-up of fluid results in clinical signs of congestive heart failure. It is further compounded by inappropriate stimulation of the compensatory mechanism caused by decreased tissue perfusion ```

Answer 31

In left-sided backward heart failure in dogs, the excess fluid causes pulmonary vein distention which can, in turn, lead to pulmonary oedema developing. In cats, the fluid tends to accumulate in the pleural space instead resulting in a pleural effusion- N.B. remember that by the time a cat displays clinical signs of respiratory difficulty it is already very compromised.

Answer 32

Any patient with pulmonary oedema or pleural effusion will have dyspnoea and exercise intolerance. As RVNs who may be triaging these patients, it is especially important to avoid causing any stress. Oxygen therapy should be provided in a stress-free manner whilst the veterinary surgeon performs additional stabilisation measures e.g. administration of diuretics or thoracocentesis. Careful assessment and auscultation during the triage process are essential; as well as having a good underpinning knowledge of the risks of handling these very fragile patients

Answer 33

In right sided backward failure, the excess fluid builds up in the venae cavae leading to jugular distention, hepatomegaly and ultimately ascites. As with patients with forward failure, in a few cases of backward failure, cardiogenic shock will arise if the circulation is insufficient to adequately perfuse the major organs. N.B. depending on the underlying cardiac abnormality, some patients will have a combination of forward and backward heart failure. The pathophysiology, however, of right-sided heart failure is similar. Fluid overload of the right side of the heart results in distention of the cranial and caudal venae cavae, jugular veins and the liver leading to hepatic congestion and hepatomegaly. This in turn can lead to ascites developing in cats and dogs. Subcutaneous oedema may also be present in some cases, although is less common.

Answer 34

Impaired cardiac function, of any cause, which results in decreased cardiac output and decreased blood pressure, causes a sympatho-adrenal response with corresponding compensatory mechanisms

Answer 35

the main, chronic compensatory mechanism being activated, the renin-angiotensin- aldosterone system

Answer 36

the main, chronic compensatory mechanism being activated, the renin-angiotensin- aldosterone system (RAAS), sodium, chloride and water are retained by the kidneys and peripheral vasoconstriction occurs

Answer 37

This compensatory mechanism is beneficial in the hypovolaemic patient (e.g. blood loss), as the fluid retention helps to increase the stroke volume and cardiac output by increasing cardiac preload i.e. more fluid is returned to the heart.

Answer 38

However, in a patient with a failing heart, the decreased cardiac output is due to heart failure rather than decreased blood volume. The patient has sufficient blood volume but poor pumping ability. In addition, because of peripheral vasoconstriction, there will be increased resistance to blood flow, further compounding the problem for the ‘pump’. In the patient with heart failure, chronic activation of RAAS leads to progressive increase in fluid volume in the circulatory system. This is called congestive heart failure. The fluid progressively backs-up behind the left ventricle (in left-sided failure) with the resulting, increased hydrostatic pressure in the pulmonary veins leading to pulmonary oedema or pleural effusion, as previously outlined.

Answer 39

Backward (congestive) heart failure may arise secondary to conditions including: 1. endocardiosis / myxomatous mitral valve disease (dogs- common) 2. hypertrophic cardiomyopathy (cats- common) 3. dilated cardiomyopathy (dogs- quite common) 4. congenital defects (relatively rare) 5. endocarditis (rare)

Answer 40

Congestive cardiac failure is usually a chronic condition but a patient may present as an emergency with dyspnoea, if pulmonary oedema or pleural effusion has developed to such an extent that the patient is now compromised. It is important to note that these patients may have been showing indications of an issue for some time. They may not have been checked, however, as often exercise intolerance and lethargy are attributed to aging. There may be a cough which the client has been monitoring. When taking a telephone call or triaging such a patient, it is important to be aware that even if the patient is already diagnosed/ on medication, even a minor change in the its condition may indicate decompensation. Some of the clinical signs of a patient presenting with backward failure are like those of a patient presenting with forward failure, especially in severe cases with cardiogenic shock: 1. exercise intolerance or collapse 2. altered mentation 3. rapid, weak pulses 4. tachycardia (N.B. a cat may have bradycardia) 5. cold extremities 6. pale or cyanotic mucous membranes 7. prolonged CRT 8. hypotension Additional signs may include cough, lethargy, inappetence, vomiting/ diarrhoea and cachexia.

Answer 41

Dogs with congestive heart failure will typically be tachycardic due to the sympathoadrenal response, which increases the heart rate in an attempt to maintain cardiac output. Heart rate and rhythm are less reliable indicators of congestive cardiac failure in cats- their clinical findings are more variable. An affected cat may have tachycardia, a normal heart rate, or reflex bradycardia. Thoracic auscultation may reveal a heart murmur and/or arrhythmia e.g. gallop rhythm in a cat with hypertrophic cardiomyopathy. Crackles may be heard on pulmonary auscultation if pulmonary oedema is present; or lung sounds may be quiet if there is a pleural effusion. A cat may have clinical signs of an underlying condition e.g. hyperthyroidism with weight loss, hair loss, goitre etc. With right-sided heart failure, jugular distension, ascites and, occasionally, subcutaneous oedema may be present. A cat in congestive heart failure may be hypothermic.

Answer 42

Cats, and dogs less commonly, may present as emergencies due to aortic thromboembolism (ATE) - cardiac disease (3.1.7). Pulmonary thromboembolism (PTE) is another rare but serious complication of heart disease that may occur in dogs and cats. PTE may also be a complication of Angiostrongylus vasorum infection in some canine patients. Patients that present with thromboembolic disease need to be assessed carefully. The outcome for these patients is often poor. However, treatment of the underlying process, if possible, is key to patient recovery. While the underlying disease will need to need appropriate treatment high quality nursing care is vital for the recovery of these patients. During hospitalisation, these patients require intensive care nursing, on a 1:1 basis, with close monitoring of cardiovascular and respiratory function and monitoring for signs of improvement or deterioration. Pain management, recumbency care and respiratory system function are additional important considerations

Answer 43

Sometimes a patient with congestive cardiac failure presents as a serious emergency- collapsed, distressed and profoundly dyspnoeic due to fulminant (severe / sudden onset) pulmonary oedema. There may be blood-stained, watery fluid coming from the oral/ nasal cavity; the mucous membranes will be pale, probably cyanotic, with prolonged CRT; the tongue may appear cyanosed; central pulses will be rapid and weak and the heart sounds may be muffled by harsh, crackles from the lung fields. These patients require urgent attention to relieve suffering.

Answer 44

Acute stabilisation of congestive heart/ cardiac failure (CHF/ CCF), as advised in the ACVIM Consensus Statement (2009) cited by Matos and Summerfield (2018), includes hospitalisation for strict rest and monitoring; oxygen therapy; opioid sedation if anxious/ agitated; furosemide IV (or IM); and appropriate cardiovascular drugs e.g. vasodilators, positive inotropes. Thoracocentesis may be indicated if the patient has a pleural effusion. N.B. It should be noted that abdominocentesis is rarely indicated in a patient with ascites due to the potential serious complications. If ascites is affecting a patient’s ability to ventilate properly, a small volume may rarely need to be removed but only enough alleviate pressure on the diaphragm. In addition to the risk of infection, if a large volume of ascitic fluid is removed from the abdomen acute changes in intra-abdominal pressure, potential acid-base and electrolyte disturbances and alteration in proteins can all lead to complications.

Answer 45

Initial stabilisation of the dyspnoeic patient consists of decreasing oxygen requirements (by limiting activity and stress – an initial hands-off approach) and providing oxygen therapy by the means that causes least stress to the patient. If the patient is collapsed and unconscious, it will require to be intubated and ventilated. Opioid administration may decrease stress and relieve anxiety thereby, hopefully, improving patient breathing and allowing for examination. Handling should be kept to a minimum and the patient should be in a quiet, low-stress environment. An intravenous catheter should ideally be placed as soon as possible to ensure IV access should the patient ‘crash’. The decision on whether to place an intravenous catheter should be made, however, with consideration of the patient's condition- a risk to benefit assessment should be made, and each patient considered individually. For example, if attempting to place an IV catheter causes stress it could seriously worsen the patient’s condition. Veterinary guidance should be sought prior to placement of an IV catheter in such cases.

Answer 46

If the patient has signs of congestive heart failure, a diuretic, usually furosemide will be required via the intravenous or intramuscular route. Administration by oral or subcutaneous routes is not advised, in the emergency patient, as absorption will be significantly reduced in the patient with congestive heart failure. Furosemide, a loop diuretic, is the main diuretic used in the management of CHF/ CCF (Matos and Summerfield, 2018). It has a rapid onset of action after IV administration- with an effect often being apparent as soon as five minutes after IV treatment but certainly within the first hour. Instead of, or following, bolus treatment, a furosemide CRI may be administered. Close monitoring of the patient’s respiratory rate is an effective way of monitoring the response to diuretic treatment If the patient has a pleural effusion, thoracocentesis will be required rather than treatment with diuretics. inotropes may be used in the management of cardiogenic shock and forward heart failure. Brown and Willis (n.d.) outline the management of the canine patient presenting with acute congestive heart failure. Because pimobendan has both positive inotropic and vasodilator activity, it is often used with furosemide as first-line treatment.

Answer 47

A patient receiving diuretic therapy must be closely monitored for signs of dehydration, pre-renal azotaemia and electrolyte abnormalities. Animals receiving diuretic therapy will have increased fluid loss, so it is sensible to measure ins and outs and calculate fluid balance over 4-6hrs, as well as regular bodyweight checks. It is important to consider that these patients are often middle aged to older patients and may have concurrent disease processes which can affect the treatment options in some cases

Answer 48

Other vasodilators (venodilators, arteriodilators or mixed) may be used as second line treatment (Swift, 2018). These help to expand the storage capacity of blood vessels, especially veins. This decreases the cardiac preload which is useful in backward heart failure and can decrease pulmonary and systemic congestion.

Answer 49

Arteriodilators reduce the afterload, which can make it easier for the heart to pump blood especially in forward failure. They also help to re-establish a blood supply to the periphery. Vasodilators, especially arterial dilators, lead to decreased systemic resistance allowing ‘…. rapid ‘unloading’ of the ventricle’ (Matos and Summerfield, 2018) and can be extremely helpful in patients with severe pulmonary oedema.

Answer 50

Sodium nitroprusside is a very rapid acting and potent vasodilator that may be used in the management of severe, acute congestive cardiac failure. It must be administered as a CRI and titrated to effect. A patient receiving sodium nitroprusside should have its blood pressure closely monitored, ideally direct arterial, as hypotension is a potential risk (Matos and Summerfield, 2018). It is less likely to be used now for cost reasons.

Answer 51

Glyceryl trinitrate/ nitro-glycerine (e.g. Percutol™) is a potent vasodilator which can be used in the short-term emergency management of acute, cardiac pulmonary oedema (BSAVA, 2020) ‘although its efficacy is debatable’. It is applied topically- the person applying the product MUST wear gloves and avoid handling the area of application to prevent a sudden vasodilatory effect which would cause a sudden drop in blood pressure. This could cause the individual to faint/collapse.

Answer 52

Once the patient has been stabilised a more thorough cardiovascular assessment should be performed (auscultation, pulse assessment, BP recording, echocardiography, radiography etc.) A heart murmur may be audible in a patient with e.g. valvular disease or cardiomyopathy. Diagnostics should only be performed once the patient has been stabilised sufficiently to allow safe handling. By this stage the function of the patient’s cardiovascular and respiratory system should have improved sufficiently to be able to tolerate an increase in heart rate, respiratory rate and oxygen requirement without decompensating. Ongoing supplemental oxygen therapy should be provided in a or POCUS/FAST thoracic/ abdominal ultrasound scans can be performed cage/ kennel side and require minimal restraint/ patient positioning. Specific information can be gained from these e.g. cardiac chamber size, degree of ventricular contractility, presence of pericardial effusion with targeted echocardiography (Matos and Summerfield, 2018); presence of pleural effusion, abdominal effusion, pneumothorax and/or pericardial effusion with POCUS/FAST scans. Thoracocentesis may be required for emergency management and diagnostics in the case of a patient with pleural effusion. The patient should not be positioned for radiography whilst still dyspnoeic, due to the risk of deterioration. The only relatively safe view for a dyspnoeic patient is the dorso-ventral view - however careful risk versus benefit assessments need to be carried out. Radiography is generally not indicated in the dyspnoeic patient as the required information can generally be obtained using other safer diagnostic techniques. Cats/ small dogs may sometimes sit on a cassette for a dorso-ventral view; or can be X-rayed through the oxygen tent/cage. Thoracic radiographs of a patient with congestive cardiac failure may reveal pulmonary oedema, cardiomegaly, tracheal elevation, left atrial enlargement and pulmonary vein distension.

Answer 53

It is good practice to describe the stage of the cardiac cycle where the murmur is heard e.g. systole or diastole; describe the anatomic location where it is most audible and grade it based on how loud it is

Answer 54

Most murmurs occur during systole.

Answer 55

A murmur due to mitral valve disease will usually be loudest over the left thorax at the 5th - 6 th intercostal spaces.

Answer 56

a murmur due to tricuspid valve disease which will be loudest on the right thorax at the 3 rd - 5th intercostal spaces

Answer 57

The murmur from aortic stenosis can be heard on both | the right and left thorax at the 2nd - 4th intercostal spaces.

Answer 58

Diagnostics should only be performed once the patient has been stabilised sufficiently to allow safe handling. By this stage the function of the patient’s cardiovascular and respiratory system should have improved sufficiently to be able to tolerate an increase in heart rate, respiratory rate and oxygen requirement without decompensating. Ongoing supplemental oxygen therapy should be provided in a

Answer 59

Electrocardiography (ECG) is especially useful in the acute cardiac presentation – it demonstrates heart rate and rhythm and is useful for identifying arrhythmias, especially if they are intermittent. Holter monitors may be used for longer recordings. ECG is helpful in identifying arrhythmias associated with electrolyte abnormalities e.g. hyperkalaemia, however, it does not give any information about heart function.

Answer 60

A more detailed ultrasound examination of the heart, echocardiography/ ‘echo’, is valuable at identifying the cause of the heart disease (e.g. DCM and HCM) and recognising complicating factors (e.g. smoke signal in cats with ATE). Congenital structural abnormalities of the heart e.g. atrial septal defect (ASD), ventricular septal defect (VSD) and patent ductus arteriosus (PDA) may be identified. Echo can also demonstrate cardiac function e.g. how effective ventricular contraction is; and will also demonstrate any abnormal, regurgitant blood flow such as that seen with valvular disease, HCM and pulmonary hypertension.

Answer 61

Ongoing assessment of patient oxygenation status should be performed. This can be done using pulse oximetry but arterial blood gas analysis is more accurate and thus preferred. Venous blood gas analysis can be performed in a patient who cannot have an arterial catheter placed.

Answer 62

Blood gases, pH and acid-base status; serum electrolytes; lactate and renal biochemical parameters should be monitored to assess effectiveness of treatment and identify any potential side-effects e.g. prerenal azotaemia due to dehydration caused by excessive diuretic administration.

Answer 63

Serum troponin levels can be assessed as an indicator of myocardial damage

Answer 64

Confirmation of Angiostrongylus vasorum, as a cause of cardiorespiratory disease, may be done by identifying L1 larval stages in faeces; or by using Elisa SNAP tests

Answer 65

a loop diuretic, it increases urine production, fluid and potassium loss. The patient should be monitored closely for evidence of dehydration, oliguria, hypokalaemia and pre-renal azotaemia.

Answer 66

orally administered angiotensin converting enzyme (ACE) inhibitors (ACE-i) e.g. benazepril may be used in the ongoing management of congestive cardiac failure. By inhibiting angiotensin converting enzyme (ACE) which normally converts angiotensin I to angiotensin II, the renin- angiotensin- aldosterone system (RAAS) is interrupted. The effects of angiotensin II e.g. peripheral vasoconstriction and release of aldosterone are partially blocked by ACE-i. By causing vasodilation of arteries and veins, ACE-i reduce both the pre-and afterload on the heart. As they decrease aldosterone release, they also decrease sodium and chloride resorption in the distal convoluted tubules of the kidneys and the accompanying water retention- thus helping to decrease congestion. Potential adverse effects include hypotension, hyperkalaemia (especially if used with potassium sparing diuretics e.g. spironolactone) and azotaemia

Answer 67

Pimobendan should not be used in animals with | hypertrophic cardiomyopathy

Answer 68

Pimobendan is a phosphodiesterase, inhibitor with both inotropic and vasodilator effects- it is commonly used in the management of heart failure in animals with valve insufficiency or dilated cardiomyopathy. The EPIC study has evaluated the use of pimobendan in dogs with stage B2 myxomatous mitral valve disease

Answer 69

In most cases, they are not due to primary heart disease but tend to arise secondary to another problem which affects the conducting system in the heart e.g. hyperkalaemia causing bradycardia. They will often accompany or develop in response to other emergency conditions with electrolyte abnormalities e.g. GDV. If an arrhythmia is newly detected in an ECC patient, it is important to report this promptly- it may decrease cardiac output further, seriously complicating the underlying condition and possibly causing myocardial ischaemia

Answer 70

An ECG recording is the best way of confirming that an arrhythmia is present. As this could arise at any time in an ECC patient and could be intermittent, ECG recording is an important part of patient monitoring. ECGs provide no information about myocardial and valve function but can be used to calculate the patient’s heart rate, assess the heart rhythm and the morphology of complexes. An ECG can confirm the presence and type of arrhythmia – enabling the veterinary surgeon to decide whether emergency treatment is required and what this should be. Often management of the primary underlying condition e.g. intravenous fluid therapy in the case of hypovolaemic shock or analgesics in the case of acute abdominal pain eliminates the arrhythmia.

Answer 71

Not all arrhythmias require emergency treatment and it is important to be aware that any drug used to treat an arrhythmia has the potential to cause another arrhythmia i.e. they are proarrhythmic

Answer 72

Arrhythmias can develop in association with conditions such as - hypoadrenocorticism, GDV, urethral obstruction, DCM and hyperthermia. RVNs should be able to recognise abnormal patterns present on an ECG and know their significance and the importance of prompt reporting to a veterinary surgeon. This is not a diagnosis but a significant clinical finding / observation.

Answer 73

To get the best information from an ECG recording it is important to set the machine up, calibrate it and attach the electrodes correctly. Electrodes should be placed according to the following table (UK/ European lead convention). N.B. The USA uses a different lead colour system Electrode Red Limb Right forelimb Green Left hind limb Yellow Left forelimb Black (reference) (if present) Right hind limb

Answer 74

When setting up the ECG, the speed of the tracing should be noted so that the heart rate can be calculated- standard machines record at 50mm / second or 25mm / second

Answer 75

Lead II is generally the easiest to interpret although other recordings can also be obtained. When analysing Lead II, each normal heartbeat should have a corresponding P wave, a QRS complex and a T wave

Answer 76

the P wave corresponds to contraction of the atria

Answer 77

the QRS complex is contraction of the ventricles

Answer 78

the T wave is repolarisation prior to the next contraction

Answer 79

When examining an ECG- • the rate and rhythm of contractions should be assessed • the P, QRS, T waves should all look the same • all expected waves (P, QRS and T) should be present i.e. there should be a QRS and T wave corresponding to each P wave and vice versus. • the height (or depth) of waves should be measured • the shape of the complexes should be assessed-are they normal or are they wide and bizarre? • the presence and frequency of any abnormalities should be recorded – this becomes an important factor in the decision to treat some arrhythmias alongside patient assessment.

Answer 80

``` The underlying disease process is not likely to be diagnosed from an ECG recording alone- it is important that veterinary nurses can, however, recognise and identify the type of arrhythmia. • Tachyarrhythmias or bradyarrhythmia? • Regular or irregular arrhythmia? • P wave for every QRS complex? • QRS complex for every P wave? • Morphology of QRS complex? • Morphology of T wave? • Ventricular or supraventricular (above the ventricles e.g. atria) in origin? ```

Answer 81

Arrhythmias are classified as ventricular or supraventricular in origin.

Answer 82

Ventricular arrhythmias arise in the ventricles. Because the normal conduction pathway is not followed the QRS complexes appear wide and bizarre

Answer 83

Supraventricular arrhythmias arise in the atria, at a point other than the sino-atrial node (SA node), and then conduct via the atrio-ventricular node (AV node) to the ventricles. The QRS complexes appear more like normal complexes although they are often tall and thin. The arrhythmia may cause the heart rate to be too slow (bradyarrhythmia) or too fast (tachyarrhythmia).

Answer 84

Atrial fibrillation is an abnormal heart rhythm characterised by rapid and irregular beating of the atria.

Answer 85

Fibrillation can be described as rapid, irregular contractions – ‘quivering’ rather than normal coordinated chamber contractions

Answer 86

This is a quite common arrhythmia in dogs but is rare in cats.

Answer 87

Many dogs with atrial fibrillation have dilated cardiomyopathy (DCM) - the arrhythmia develops secondary to left atrial stretching. Atrial fibrillation may be the first indication of occult DCM in giant breed dogs e.g. Irish Wolfhounds with no previous clinical signs of heart disease. It also occasionally arises in giant breed dogs with no underlying heart disease. In some patients it will be a coincidental finding such as in a large breed dog with a GDV who has an ECG assessment prior to surgery.

Answer 88

Many dogs with atrial fibrillation have dilated cardiomyopathy (DCM) - the arrhythmia develops secondary to left atrial stretching. Atrial fibrillation may be the first indication of occult DCM in giant breed dogs e.g. Irish Wolfhounds with no previous clinical signs of heart disease. It also occasionally arises in giant breed dogs with no underlying heart disease. In some patients it will be a coincidental finding such as in a large breed dog with a GDV who has an ECG assessment prior to surgery.

Answer 89

The typical ECG findings are- supraventricular QRS complexes (narrow and upright); irregularly irregular rhythm with low ventricular rates and no visible P waves – as these abnormal contractions do not arise from the SA node. Fibrillation (‘f’ waves) are present instead. The heart rate may be normal but is often tachycardic.

Answer 90

If the dog has DCM and congestive cardiac failure, diuretics, inotropes and ACE inhibitors may be used in the management. Additional drugs that might be used are calcium channel blockers e.g. diltiazem or beta-blockers e.g. sotalol to slow the heart rate. Digoxin may also be used to slow the ventricular rate and act as a positive inotrope (Stephenson, 2011). More recently drugs such as amiodarone have been used (Mills, 2015). There are a few reports of efforts to use transthoracic biphasic electrical cardioversion techniques in dogs with atrial fibrillation and then maintaining them on amiodarone. These cases are, however, few although the results have been promising

Answer 91

Treatment of atrial fibrillation is aimed at decreasing the heart rate and increasing cardiac output- unlike horses and people where treatment tries to convert the heart back to normal rhythm.

Answer 92

A supraventricular beat occurs when an abnormal electrical impulse starts at an ectopic site that it is above (‘supra’) the AV node- i.e. atrial in origin rather than ventricular. There may be a re-entrant rhythm. With a re-entrant rhythm, depolarisation starts in one part of the heart, spreads to the atria, through an accessory pathway, before re-entering the ventricles via the AV node. The ectopic beat occurs prior to normal sino-atrial depolarisation and is therefore ‘premature’ (i.e. it occurs earlier than expected). This ectopic beat is therefore called an atrial premature contraction (APC).

Answer 93

Atrial premature contraction

Answer 94

If there are 3 or more APCs in a row, the arrhythmia is called supraventricular tachycardia (SVT).

Answer 95

The QRS complexes of APCs/ SVT are almost like normal QRS complexes, often narrow and upright, rather than the wide and bizarre looking complexes seen with ventricular premature contractions (VPCs) or ventricular tachycardia. There may or may not be associated P waves. The rate of SVT can be 170-350 bpm.

Answer 96

SVT in dog is usually associated with underlying cardiac disease, or sometimes systemic disease, (e.g. toxicity, hypovolaemia, ischaemia) but it is occasionally a primary condition

Answer 97

If frequent, with associated clinical signs, weakness/collapse, treatment will be required. The first line of treatment is to treat the underlying cause where possible (e.g. hypovolaemia). Initial emergency management of SVT may involve mediating the vaso-vagal reflex using ocular pressure. If unsuccessful, medication such as beta blockers or calcium channel blockers may be required.

Answer 98

This is when a patient has bradycardia associated with an arrythmia

Answer 99

This is when the sinus rhythm is inappropriately slow for the breed

Answer 100

Rather than being a primary cardiac problem, it is likely to be secondary to some other disease which increases vagal tone e.g. increased intracranial pressure or brachycephalic obstructive airway disease or electrolyte abnormalities e.g. hyperkalaemia It may arise due to a problem with the sino-atrial (SA) node or secondary to other conditions e.g. hypothyroidism, hypoadrenocorticism, hypocalcaemia or vasovagal reaction

Answer 101

It may be a ‘normal’ finding in e.g. older, brachycephalic dogs secondary to high vagal tone- greyhounds may also be affected

Answer 102

On ECG, a normal sinus rhythm is seen with a slow heart rate (<60 bpm dog).

Answer 103

a 1:1 ratio of P: QRS i.e. each P wave has a corresponding QRS

Answer 104

weakness, exercise intolerance and/or lethargy

Answer 105

Treatment is dictated by the underlying cause and whether the patient is showing clinical signs due to the arrhythmia e.g. managing hyperkalaemia in a patient with hypoadrenocorticism. However, the bradycardia may be temporarily managed using an anticholinergic depending on the cause and the effect it is having on the patient’s cardiovascular status e.g. atropine sulphate or glycopyrrolate. If this is unsuccessful, positive inotropes e.g. dopamine, dobutamine may be required.

Answer 106

This is where a problem arises with the sino-atrial (S-A) node (or A-V node) where it fails to discharge – it is a degenerative condition. It is almost exclusively dog that are affected although the cause is generally unknown. Due to the decreased S-A output, the heart rate will be abnormally slow or there will be periods of asystole- the S-A node normally starts functioning again, but this condition is likely to be recurrent.

Answer 107

Breeds which are predisposed include West Highland White Terriers, Cocker Spaniels and Miniature Schnauzers- it is usually older animals that are affected (~ 6-10 years)

Answer 108

The dog may have episodes of collapse/fainting during the asystole although some cases are asymptomatic. Asystole can be present for several seconds

Answer 109

During sinus arrest no impulses are generated by the S-A node so no P waves will be seen. After a period of asystole, a ventricular escape beat/complex may be seen this is generated by a ventricular pacemaker when there is no S-A node activity. The ECG will show periods of bradycardia or no electrical activity (asystole) due to sinus arrest; this may be followed by paroxysmal supraventricular tachycardia and no associated P wave. Patients often respond poorly to medical treatment e.g. atropine so may need a pacemaker to be fitted.

Answer 110

With a heart block, there is a delay or complete blockage of the impulse from the SA node going through the AV node

Answer 111

This may arise due to a disease or a drug-related | effect at the AV node.

Answer 112

Delayed conduction through the AV node is called a first-degree block- the ECG will show a longer interval between the P wave and corresponding QRS complex. With a second-degree heart block, there is a longer conduction delay- some P waves will not have a corresponding QRS i.e. there are dropped beats. With a third-degree heart block, there is a complete lack of conduction through the AV node. In cases of 3 rd degree block, ventricular ‘escape beats/ complexes’ occur which permit the heart to still beat- without these escape beats the animal would die. The rate of the ventricular escape beats is typically 20-40 beats per minutes. A tracing of a 2nd degree AV block is shown. Note the presence of some P-waves with no associated QRS complexes. Those complexes that do occur are normal in morphology- this shows that this is a 2 nd degree block (there has been conduction through the AV node so the QRS complex has a normal shape).

Answer 113

The patient will show clinical signs associated with decreased cardiac output e.g. lethargy, syncope and collapse

Answer 114

Management of the underlying condition (e.g. hypoadrenocorticism may resolve the AV block. If not vagolytic drugs, such as atropine sulphate and glycopyrrolate, may be tried. In cases of severe second or third-degree block, implantation of a pacemaker is typically required.

Answer 115

This is a lack of atrial activity (i.e. no atrial contraction) due to failure of atrial myocardial cell depolarisation, even though the S-A node has created an impulse.

Answer 116

It could be caused by atrial muscle myopathy but is often due to hyperkalaemia. Atrial asystole may be secondary to cardiac pathology but is commonly associated with hyperkalaemia secondary to e.g. hypoadrenocorticism or urethral obstruction. Generally, the heart sounds and pulses are normal but slow. Typically, dogs with hyperkalaemia have bradycardia although cats may have tachycardia.

Answer 117

The ventricles continue to function. The impulse, created by the SA node, does reach the AV node, despite no atrial muscle depolarisation. This then results in ventricular depolarisation and contraction- this is called sino-ventricular rhythm.

Answer 118

The ECG show a lack of P waves. The heart rate is regular but normally slow (< 60 bpm in dogs) because of the escape rhythm. The QRS complexes can appear normal or may be slightly wide.

Answer 119

A patient with hyperkalaemia should have appropriate fluid resuscitation as appropriate to stimulate diuresis and excretion of potassium. If additional treatment is required, hyperkalaemia may be treated with intravenous soluble/neutral insulininsulin causes movement of glucose and potassium from the extracellular space into cells. Dextrose is also administered to avoid hypoglycaemia. Half the dextrose can be given as a bolus with the rest administered over 4-6 hours (BSAVA, 2020)). Injections of 10% calcium gluconate (over 15 minutes) may help protect the myocardium from the arrhythmogenic effects of the hyperkalaemia. IV calcium should be given slowly, whilst an ECG is being recorded, due to the risk of cardiac arrest. Treatment of the underlying cause of the hyperkalaemia is essential

Answer 120

Bicarbonate therapy can very rarely be used in the treatment of severe hyperkalaemia but it has to be administered with care due to the risk of serious sideeffects- the risks are greater if it is administered rapidly (Poli, 2017). Adverse effects of bicarbonate administration are metabolic alkalosis and hypocalcaemia – therefore it should only be used when acid-base status can be measured. Both insulin and bicarbonate treatments encourage potassium ions to move into the intracellular space. It should be noted that whilst bicarbonate is mentioned in many sources for reducing potassium levels the focus should be on appropriate fluid resuscitation, restoring urine output and stabilising the patient’s condition appropriately. Only when other techniques have failed should bicarbonate be considered due to the potentially fatal side effects.

Answer 121

This is when a patient has an arrythmia causing tachycardia. It may be supraventricular e.g. of atrial origin

Answer 122

Examples of supraventricular tachycardia include atrial tachycardia, atrial flutter and atrial fibrillation. Ventricular tachycardia and ventricular fibrillation are examples of tachyarrhythmias of ventricular origin. If there is a supraventricular arrythmia, on ECG, the QRS complexes usually appear relatively normal although they may be taller and narrower than normal. If the tachyarrhythmia is of ventricular origin, the QRS complexes usually appear wide and bizarre as they have originated directly within the ventricles rather than via the conduction mechanism.

Answer 123

With a ventricular arrhythmia, the SA node no longer controls the ventricular contractions. Another area in the ventricles takes over the pacemaker role. As the normal electrical pathway is not followed, the appearance of these complexes is unusual e.g. usually wide and bizarre and without a corresponding P wave indicating atrial involvement.

Answer 124

A ventricular dysrhythmia may arise as a serious complication of another condition e.g. GDV and it is important to be aware of this possibility when monitoring patients.

Answer 125

Ventricular beats occur when an abnormal electrical impulse starts at an ectopic site that it is below the AV node (i.e. ventricular in origin, not atrial). The ectopic beat occurs prior to normal sino-atrial depolarisation - thus the beat is ‘premature’ (i.e. it occurs before it is expected). Therefore, they are called ventricular premature contractions (VPCs). The VPC/beat starts at an aberrant/unusual location in the ventricles and therefore does not follow the normal conduction pathway. As it takes longer for the conduction to occur, the complex appears wider on ECG and there is no associated P wave.

Answer 126

VPCs can sometimes be present in low numbers in healthy animals without being a problem. They can also arise secondary to other problems e.g. GDV/Splenectomy or surgery. Sometimes VPCs occur in patterns e.g. every second beat or every third beat is a VPC

Answer 127

If a VPC occurs on the downward slope of the previous T wave (i.e. right at the end of the previous normal contraction) – this is called R-on -T phenomenon. If present, this is potentially very serious- the end of the T wave is ‘a vulnerable period’ and anything abnormal at this period can predispose a patient to ventricular fibrillation

Answer 128

When there are 3 or more VPCs together but the heart rate is not much more than usual (~ 140 - 170 per minute in a dog), the ECG rhythm is termed an accelerated idioventricular rhythm (AIVR). This heart rate is not fast enough to be considered true ventricular tachycardia

Answer 129

If there are 3 or more VPCs in a run and the heart rate | is significantly increased (~ > 170/180bpm), this is called ventricular tachycardia

Answer 130

An accelerated idioventricular rhythm may occur for the same reasons as ventricular tachycardia (see below). It is often secondary to non-cardiac disease in hospitalised patients e.g. GDV, pyometra, post-trauma, pancreatitis etc. but is generally considered to be benign rhythm because at this rate, there is unlikely to be decreased cardiac output, haemodynamic compromise or hypotension. Treatment is usually not required for AIVR however the patient and ECG should be closely monitored for progression to ventricular tachycardia.

Answer 131

This is demonstrated by three or more ventricular premature contractions occurring at a high heart rate (typically greater than 170/180 bpm but often around 220 bpm or more). The origin of the electrical impulse is from the ventricle rather than the sinoatrial node. The QRS complexes are therefore wide and bizarre with no associated p-wave. This is an example of ventricular tachycardia

Answer 132

Primary cardiac disease o Structural - e.g. dilated cardiomyopathy (DCM) o Arrhythmogenic right ventricular cardiomyopathy in Boxers

Answer 133

Abnormal autonomic activity o High sympathetic tone ▪ e.g. pain

Answer 134

Electrolyte disturbances | o Hypercalcaemia

Answer 135

Drugs/hormones/toxins o Caffeine o Cocaine o Cardiac glycosides

Answer 136

Ischaemia o Hypovolaemia o Anaemia o Thromboembolic disease

Answer 137

Neoplasia o Lymphosarcoma o Haemangiosarcoma

Answer 138

``` Inflammation/inflammatory mediators Trauma Ischaemia Drugs Electrolyte disturbances Primary cardiac disease Abnormal autonomic activity ```

Answer 139

With very rapid heart rates (> 250-300 bpm), there is likely to be decreased cardiac filling and therefore there will be decreased cardiac output and associated signsrelated to hypoperfusion e.g. exercise intolerance, syncope or collapse. Although as these patients may already be hospitalised due to serious conditions, they may already be recumbent and inactive. Therefore, it is also essential to monitor perfusion parameters. Signs of haemodynamic compromise in a patient with ventricular tachycardia include altered mentation, pale mucous membranes, prolonged CRT, weak or absent peripheral pulses (‘pulseless V Tach’)., hypotension, hypothermia decreased urine output etc

Answer 140

Serious consequences of ventricular tachycardia, associated with haemodynamic compromise, include: • Decreased systemic tissue perfusion (cardiogenic shock) • Decreased cardiac perfusion • Development of a malignant arrhythmia (i.e. ventricular fibrillation) • Development of myocardial failure if prolonged tachycardia • Sudden death may also occur.

Answer 141

Ventricular tachycardia is a serious arrhythmia although it does not always require treatment. Treatment may not be effective and can have adverse effects. Generally, if the patient’s heart rate is extremely rapid (> 250-300 bpm) treatment will be required to prevent ventricular fibrillation and sudden death, although other sources state that treatment might be required above ~ 160- 200 bpm. Whether treatment is required is case dependent and will depend on the degree of haemodynamic compromise and the underlying cause in each case. Patients with underlying heart disease (e.g. dilated cardiomyopathy, arrhythmogenic right ventricular cardiomyopathy and hypertrophic cardiomyopathy) are more likely to require treatment due to the risk of cardiac arrest. The main priority for a patient with ventricular tachycardia is to ensure the underlying disease process, if present, is being managed appropriately e.g. IVFT for hypovolaemia, dehydration; monitoring oxygenation, electrolytes and blood gas status and treating accordingly. Intravenous lidocaine is usually the first choice of treatment for ventricular tachycardia– it is usually started as a bolus and continued as a CRI. If there is a poor response to the first bolus, this can be repeated 2-3 times over a 10-minute period if required. N.B. Once a bolus of lidocaine has been administered there is usually a rapid response. If the response is appropriate, the patient is most likely to have ongoing CRI treatment rather than repeated boluses. Other treatment options could be tried if lidocaine is ineffective- however, if the response to lidocaine is poor the patient’s general condition should be reassessed. It is more likely that the underlying disease process is responsible for the poor response e.g. hypokalaemia. Other drugs that might be used in the management of ventricular tachycardia, depending on the underlying cause, include procainamide, beta-blockers, magnesium, sotalol and amiodarone

Answer 142

It is essential to monitor the patient for signs of lidocaine toxicity, especially if repeated boluses are administered. Signs of toxicity can be neurological e.g. seizures, cardiac e.g. bradycardia and/or gastrointestinal e.g. vomiting. Cats are much more sensitive to the toxic effects than dogs. If toxicity does arise then intra-venous lipid emulsion can be administered. However, care must be taken not to volume overload the patient.

Answer 143

Ventricular Fibrillation: this is a very serious condition which will result in patient death unless instantly recognised and treated- it is considered to be a ‘pre-terminal’ condition. Because there are no effective ventricular contractions, they are all chaotic, there is no cardiac output

Answer 144

The ECG shows an irregular, wavy baseline with no | recognised complexes.

Answer 145

The patient will require immediate CPR and defibrillation – this is a shockable rhythm. N.B. it is important to ensure that the ECG leads are correctly attached – poor skin contact can cause a similar appearance. Matos and Summerfield (2018) state that electrical defibrillation is the only effective treatment option for ventricular fibrillation.

Answer 146

Pulseless Electrical Activity (PEA) in this condition, there are electrical impulses within the heart but no corresponding contractions. Pulseless electrical activity is the condition in which, despite a normal heart rate and rhythm on ECG, there is an absence of myocardial contractions so no cardiac output. It is a type of asystole. There are no audible heart beats or palpable pulses as there is no cardiac output but there is normal or slow electrical activity visible on the ECG. The patient will be collapsed. In addition to CPR, adrenaline, atropine or an inotrope may be used.

Answer 147

This is the most common arrest arrythmia in dogs and cats-there are no contractions and so no cardiac output. It can develop with any end-stage disease e.g. cardiac or pulmonary. It can also be caused occasionally by very high vagal tone. Generally, it has an extremely poor prognosis. Prompt cardiopulmonary resuscitation (CPR) in accordance with the RECOVER guidelines is the only treatment option for asystole and PEA

Answer 148

Treatment of an arrhythmia will depend on multiple factors. The first (and probably the most important) is whether there are clinical signs associated with the arrhythmia. If a patient is ‘clinical’ – i.e. showing signs of cardiogenic shock then it requires treatment. Treatment of any underlying condition is the priority and some arrhythmias will resolve when this is addressed e.g. GDV patient. If the animal is clinically normal, then emergency treatment is less likely to be required although the patient should be monitored closely and an underlying cause identified, where possible. The second consideration is the ECG rhythm and morphology of the complexes. The heart rate, the complex morphology and whether the arrhythmia is sustained are all important factors. Treatment will be decided by the veterinary surgeon responsible for the case- there are no hard and fast rules but the following provides pre-treatment guidance

Answer 149

When to treat 1. Clinical signs consistent with poor perfusion ( hypoperfusion) a. Pulse quality/ lack of peripheral pulse b. Pale mucous membranes c. Prolonged capillary refill time d. MENTATION- decreased 2. Objective data consistent with poor perfusion a. Increased lactate b. Low blood pressure 3. High heart rate - How high is high? a. There is no set value but many vets will treat if significantly increased (> 160 if cardiac pathology or > 250 bpm if no cardiac pathology). Important to monitor trends and ensure the veterinary surgeon is promptly alerted to any abnormal rhythm irrespective of the rate. 4. Multiform complexes a. When all the ventricular complexes look different. 5. ‘R on T’ (VT only) a. When the R of the complex appears above the previous T. As discussed previously, this is a very fast rhythm which may progress to ventricular fibrillation.

Answer 150

Treatment involves managing the causal disease where possible – treat the treatable prior to the administration of any drugs. The medical treatment of any supraventricular tachycardia (including atrial fibrillation) is based upon slowing down the heart rate. This is typically achieved with a calcium channel blocker (e.g. diltiazem) or a beta blocker (e.g. atenolol). Some drugs such as sotalol have multiple effects including beta-blocking and potassium channel block that slows repolarisation.

Answer 151

Treatment involves managing the causal disease where possible. For example, if a dog is significantly anaemic, then the anaemia should be corrected prior to administration of anti-arrhythmic medication which could have a proarrhythmic effect. Medical treatment of ventricular tachycardia may result in conversion of the electrical rhythm into sinus rhythm or may just slow the heart rate down. A reduction in heart rate from 220 to 140, even if an abnormal ventricular rhythm remains, would still be considered successful. Ideally, though, the rhythm will be converted back to into sinus rhythm again. Lidocaine is typically the first line agent in dogs with ventricular tachycardia- a bolus is administered slowly IV over 1-3 minutes followed by an intravenous CRI. Lidocaine is a sodium channel blocker that should be administrated intravenously as it has low bioavailability. It has a short half-life and so should be given as a constant rate infusion. As discussed previously other drugs may be used if there is a poor response to lidocaine.

Answer 152

The pericardium is a thin-walled sac surrounding the heart which normally contains a volume of fluid to aid lubrication and reduce friction.

Answer 153

Pericardial effusion is a relatively common cause of emergency presentations, especially in dogs, due to signs of right-sided forward heart failure which develops secondary to the presence of fluid accumulation in the pericardium. Occasionally the signs are caused by a soft-tissue mass e.g. tumour within the pericardial sac. Pericardial effusion occurs in the cat but is less common than in dogs.

Answer 154

Cardiac tamponade is a serious form of pericardial effusion where the fluid in the pericardium compresses the heart to such an extent that cardiac filling is significantly impeded. If cardiac filling is reduced to this extent, less blood will enter the ventricles during diastole resulting in significantly decreased cardiac output during ventricular contraction (systole). With cardiac tamponade the pericardial pressures exceed right atrial pressures. The abnormal presence of fluid in the pericardium puts pressure on the thin-walled right atrium, causing it to, partially or completely, collapse. As the right ventricle is also relatively thin walled it can also be prevented from expanding by the pericardial effusion. This means that the right ventricle cannot fill sufficiently with blood during diastole (decreased diastolic function). If the chambers are unable to fill with blood (preload) then there is a decreased amount for the heart to pump when it contracts. As a result, the stroke volume, and thus the cardiac output, is decreased. If the cardiac output is insufficient to maintain a blood supply to the tissues, the animal will show signs of cardiogenic or obstructive shock – cardiac tamponade. Cardiac tamponade is rare in cats

Answer 155

Causes of pericardial effusions include: 1. Haemorrhage a. Neoplasia e.g. haemangiosarcoma b. Coagulopathy c. Idiopathic d. Trauma (rare) e. Left atrial tear (very rare) 2. Pericarditis (often idiopathic) 3. Congestive heart failure (cats) 4. Infection e.g. FIP/toxoplasmosis in cats 5. Neoplasia e.g. chemodectoma, mesothelioma

Answer 156

``` The clinical signs depend upon the volume of fluid present in the pericardial sac and the rate at which it develops. With an acute effusion (short time-course), serious clinical signs can result from a relatively low volume effusion; however, with a chronic effusion (longer time-course) a large volume effusion might have built up before signs are apparent due to the gradual stretching of the pericardium. Depending on the severity of the effusion and the rate it develops, a patient may present with non-specific signs varying from lethargy, anorexia, cough, GI signs to collapse especially if acute onset. With a chronic pericardial effusion, there may be a history of lethargy, exercise intolerance and progressive abdominal distention. More serious clinical signs are seen with a rapid accumulation of a large volume effusion. ```

Answer 157

If the animal has tamponade it will have signs consistent with decreased cardiac output (cardiogenic shock) and hypoperfusion. Clinical findings of hypoperfusion include tachycardia, pale mucous membranes, prolonged CRT, absent peripheral pulses +/- weak central pulses etc. ➢ Beck’s triad is likely to be present in a patient with cardiac tamponade- low arterial blood pressure, distended jugular veins and muffled heart sounds.

Answer 158

In chronic cases, there may be signs of right-sided, forward heart failure including hepatomegaly, ascites and jugular vein distension, often with a pronounced jugular pulse as the return of blood back to the right side of the heart is impeded. Thoracic auscultation will reveal muffled (or absent) heart sounds; and if there is pleural effusion (secondary to right sided heart failure) the lung sounds will also be quiet.

Answer 159

Pulsus paradoxicus may also be present if a patient has tamponade- the quality of the pulse alters with respiration. With pulsus paradoxicus, the arterial blood pressure decreases during inspiration. This is because the increased intrathoracic pressure during inspiration increases venous return to the right side of the heart causing it to enlarge. The combination of the enlarged right heart and the tamponade further compress the left side of the heart so decreasing the stroke volume meaning that the pulse is weaker during inspiration.

Answer 160

Initial stabilisation of a patient presenting with signs of hypoperfusion, +/- respiratory distress, will include supplementary oxygen, by the means most accepted by the patient and strict cage rest in a minimal stress environment. An intravenous catheter should be placed on veterinary direction as soon as the patient will tolerate it. However, the patient may be severely dyspnoeic and so precautions need to be taken to minimise increased oxygen demand during the stabilisation period. The definitive management of this condition is pericardiocentesis which should be performed as soon as possible. Whilst intravenous fluids are sometimes given in these circumstances, as with other cases of cardiogenic shock, hypovolaemia is not the problem. Although IVFT may provide some short-term relief (by increasing intravascular volume) the problem is impaired ventricular filling secondary to cardiac tamponade, not hypovolaemia - inappropriate IVFT may lead to clinical signs associated with over infusion. Emergency administration of diuretics are unlikely to be indicated with pericardial effusion despite the signs of right-sided failure that might be present e.g. hepatomegaly, jugular distention and ascites. They could cause the patient to become dehydrated leading to hypovolaemia and thus further decreased ventricular filling leading to a worsening of the clinical signs. As soon as the cardiac tamponade is alleviated (from pericardiocentesis) the signs of right-sided failure should resolve.

Answer 161

The most sensitive, specific and easiest way, to confirm the presence of a pericardial effusion is with ultrasound/ echocardiography. This can be performed rapidly and with minimal to no stress to the patient. Anechoic fluid will be visible within the pericardial sac. In addition, the presence of a pleural effusion and ascites if present, can be confirmed. Ultrasound can confirm the presence of tamponade which would require urgent treatment. It can also identify any abnormal masses within the pericardium

Answer 162

Radiography can be performed but is insensitive for a diagnosis of pericardial effusion. It may demonstrate an enlarged, globoid cardiac silhouette. However, because fluid and soft tissue cannot be differentiated radiographically, it is not possible to differentiate pericardial effusion from other causes of cardiomegaly e.g. DCM. In addition, obtaining radiographs will be more stressful for the animal- thus ultrasound is the diagnostic modality of choice.

Answer 163

Electrocardiography (ECG) may show tachycardia, small complexes, occasional escape beats. There will be a changing electrical axis as the heart swings about within the fluid of the pericardial sac. This can result in an ECG appearance called electrical alternans – the QRS complexes alternate in height with each beat.

Answer 164

``` Clotting times (PT, aPTT, ACT) should be assessed prior to pericardiocentesis to ensure that the pericardial effusion has not occurred secondary to a coagulopathy (e.g. anticoagulant rodenticide intoxication). Pericardiocentesis is contraindicated if there is a coagulopathy. In that scenario stabilising the coagulopathy will lead to resolution and re-absorption of the pericardial effusion. ```

Answer 165

Arterial blood pressure should also be monitored. Hypotension could indicate severe cardiac tamponade and therefore the need for prompt emergency treatment pericardiocentesis

Answer 166

Pericardiocentesis removes fluid from the pericardial space reducing the pressure on the cardiac chambers, thereby enabling increased ventricular filling (increased preload) during diastole. This in turn will lead to increased stroke volume during systole so a return to normal cardiac output. The fluid type can also be analysed so pericardiocentesis is also diagnostic.

Answer 167

Unless the patient is collapsed, it is likely to be sedated for the procedure to ensure it is still and to minimise discomfort. A cardiovascularly sparing sedation protocol is required e.g. an opiate (butorphanol) and benzodiazepine (midazolam) combination. Whilst, pericardiocentesis is not a particularly painful procedure, it is important to be aware that the patient may have concurrent illness, such as osteo-arthritis, that might elicit pain that could be worsened with handling and restraint. Drugs such as acepromazine and alpha-2 agonists should be avoided due to their hypotensive effects.

Answer 168

``` Equipment for pericardiocentesis Clippers Surgical scrub to prepare sterile site Commercial pericardiocentesis kits are available Or 14 – 18 gauge over the needle catheter of a suitable length for the patient Three-way tap IV extension tubing 50-60ml syringe Kidney dish Local anaesthetic Sterile gloves Scalpel blade Sample pots (EDTA, plain) and slides Ultrasound ECG ```

Answer 169

Pericardiocentesis may be performed on the left or right side of the thorax although a right sided approach is preferred by many. There is a ‘cardiac notch’ between the right cranial and caudal lung lobes which decreases the risk of iatrogenic lung puncture; and there are fewer coronary vessels on the right side (Olcott, 2010). There are, however, potential risks associated with either left or right sided pericardiocentesis. The patient can be positioned in sternal or left lateral recumbency - however sternal is likely to be better tolerated in the very compromised patient. The lateral thorax is clipped upwards from the sternum to the mid-thorax from ~ rib 3 to rib 9 and surgically prepared. A ‘window’ into the pericardial effusion can be detected with the use of ultrasound. The area of the chest to be penetrated (usually 4th to 6th intercostal space just below the costo-chondral junction) is infiltrated with local anaesthetic 5-10 minutes prior to the procedure. It is important to have ECG leads attached during this procedure to identify ventricular premature complexes (VPCs) that will occur if the catheter touches the epicardium. Ideally the procedure is performed with ultrasound guidance. The catheter is attached to the IV extension tubing, three-way tap and syringe A small skin incision is made with the scalpel blade. One operator advances the catheter through the incision and into the pericardial sac whilst the other gently pulls back on the syringe plunger to aspirate the free fluid. Initially a small amount of the fluid should be placed in a plain tube to see if it clots- if it does clot then there is a concern that it is fresh blood that has been aspirated from the heart. In this case, the catheter should be removed, and the procedure started again. Samples of the pericardial fluid, which is generally sanguinous in appearance, should be collected into plain and EDTA tubes for analysis. The PCV should be checked and compared with venous blood. It would be expected to be lower than the peripheral blood unless there has been a recent, acute pericardial haemorrhage. If there is ongoing active pericardial bleeding, pericardiocentesis is contraindicate. A smear should be made to look for evidence of neoplastic cells or schistocytes that may be associated with haemangiosarcoma of the heart base- a common cause of haemopericardium. Some fluid can be sent for culture and sensitivity testing. Thereafter the rest of the effusion should be drained - progress can be monitored using ultrasound to determine if all the fluid has been removed. The effusion should be drained slowly to allow adequate re-filling of cardiac chambers and avoid dramatic changes in pressure.

Answer 170

Once the fluid has been removed, the patient’s perfusion parameters should start to improve e.g. the heart rate should return to normal, although arrhythmias may persist for a bit longer. The patient should be much brighter once the sedation has worn off, as normal perfusion has been restored. Ongoing nursing care should focus on monitoring for any complications of the procedure (e.g. haemorrhage, pneumothorax, arrhythmias); as well as monitoring for recurrence of the effusion (e.g. recurrence of tachycardia and signs of poor perfusion.

Answer 171

Affected cats usually present acutely and in distress with a thromboembolism affecting at least one limb- it is a condition with high morbidity and mortality. Commonly owners will report the patient being normal in the time up to presentation where they are commonly found collapsed, in extreme pain and unable to use hind limbs.

Answer 172

FATE occurs most commonly occurs secondary to hypertrophic or restrictive cardiomyopathy in cats although there is often no previous history of cardiac disease. Left atrial enlargement occurs secondary to the heart disease and blood movement within this chamber is turbulent. This can lead to micro-thrombi and thrombus formation within the left atrium. Emboli from these thrombi break off and enter the systemic circulation via the aorta. Depending on their size, these typically lodge at the aortic trifurcation, or just beyond it, restricting or completely cutting off blood flow to one or both hind limbs. A thrombus can lodge elsewhere including forelimb arteries, cerebral arteries and even the renal arteries. Sometimes a thrombus only causes a partial obstruction, initially, but it will continue to enlarge. Mortality is high with this condition- many cats die soon after the condition develops or are euthanased on humane grounds.

Answer 173

The signs will depend on location of the thrombus; and whether the obstruction is complete or incomplete- the patient shows signs of severe pain and distress due to ischaemia. There will be paresis or paralysis of the affected limb (s) - if the clot lodges and completely obstructs the caudal aorta the cat will be unable to use both hind legs. There may be a previous history of heart disease but often here is none. Affected cats usually present with per-acute, sudden onset extreme distress, difficulty moving and are often yowling. The presenting signs can be like those of trauma or acute neurological conditions. They will often be open mouth breathing and tachypnoeic due to stress and pain rather than cardiac signs. They are likely to have all or some of the five P’s- paralysis, paresis, pain, lack of pulse, pallor (or cyanotic pads) and polar (cold) distal limbs/ extremities. If the cat has pre-existing congestive cardiac failure, there may additionally be signs associated with that e.g. dyspnoea secondary to pleural effusion.

Answer 174

The cat will be very painful and may be crying out. It may resent any handling - it is important not to cause any further distress as this may cause cardiac arrest. It is likely to be tachypnoeic due to pain and distress. It may be dyspnoeic from concurrent congestive heart failure. Auscultation of the thorax may reveal tachycardia, a gallop rhythm or decreased heart sounds if pleural effusion is present. Palpation of the affected limbs, usually hind-limbs, will reveal decreased or absent femoral pulses (one or both) - the affected limbs will be cold with pale or cyanotic pads. There will be diminished or no neurological function in the hind-limb (s) - the cat will have paresis or complete paralysis and will be dragging the affected limb, usually hind limbs. The rectal temperature may be decreased due to lack of blood flow and the sympatho-adrenal response.

Answer 175

Opioid analgesia is the main initial priority. Handling of the patient should be kept to a minimum and the cat placed into a comfortable kennel where movement can be restricted. Oxygen therapy is indicated if the cat is dyspnoeic. Fentanyl and methadone have a rapid onset of action and are commonly used to manage pain in these patients. Buprenorphine, as a partial agonist indicated for mild to moderate pain, would not generally be sufficient for a patient with ATE.

Answer 176

The absence of a (hind-limb) pulse can be confirmed with Doppler. Stress-induced hyperglycaemia and azotaemia may be present. Comparison of the serum glucose and lactate levels from affected and unaffected limbs can be performed. Due to anaerobic respiration, glucose will be low and lactate high in the compromised limbs compared to the normal limbs. Echocardiography will demonstrate the underlying cardiac disease (e.g. hypertrophic or restrictive cardiomyopathy). The left atrium will likely be enlarged and there may be a thrombus in the left atrium or ‘smoke sign’ which is consistent with formation of micro-thrombi. Thoracic radiography can be performed (if/ when the patient can tolerate this) - this may reveal cardiomegaly +/- signs of congestive heart failure. ECG can also be useful in diagnosing arrythmias.

Answer 177

The current advised regime is to manage pain and prevent further clot formation using thromboprophylaxis/ anticoagulation therapy. Treatment of the underlying heart disease (+/- congestive heart failure) will also be necessary- e.g. furosemide and ACE inhibitors as discussed previously. Supportive therapy should be aimed at maintaining body temperature as many patients are hypothermic on presentation; hydration and nutritional status. IVFT may be required but it is essential to avoid over infusion in a cat with congestive cardiac failure.

Answer 178

Aspirin or clopidogrel can be used to inhibit platelet aggregation thus preventing further clot formation. They do not have any effect on pre-existing clots

Answer 179

Heparin (either unfractionated or, more recently, low molecular weight) may be used to prevent further clot formation by blocking the coagulation cascade. However, there is some debate as to its efficacy

Answer 180

Thrombolysis (breaking down the clot) is not currently recommended. There is a high risk of reperfusion injury and increased mortality associated with thrombolysis.

Answer 181

Physiotherapy In mild cases, limb manipulation and massage may facilitate blood flow if the cat can tolerate handling. Physiotherapy will be important for the longer-term management and recuperation process.

Answer 182

The cat will need to be monitored closely for signs of pain, using a validated pain scoring method, with the analgesic plan being reviewed as required. Ongoing monitoring of the circulation to the affected area is important. Increasing levels of pain can be seen despite adequate analgesia and multi modal techniques are needed. The cat may also be in congestive heart failure (or at risk of) and should be monitored for signs of dyspnoea. Whilst limb movement will sometimes return, it may take a long time and may not be complete. Appropriate nursing and management of the neurological signs will be required. Because clots may also embolise to the kidneys, renal values should be monitored- especially as heart medication may also affect these. Affected cats are at risk of reperfusion injury within a few days of the thromboembolic event. As the blood supply returns to the affected limbs, waste products and electrolytes that have accumulated from damaged cells enter the systemic circulation. This can result in severe hyperkalaemia and metabolic acidosis

Answer 183

Nursing care for these patients is focused on pain management and a validated pain scoring scale must be used. Knowledge of the side effects of medications administered to manage pain is necessary for effective monitoring of these patients. As they are commonly on oxygen therapy for longer periods of time, ocular lubrication, especially for a patient receiving pure mu opioids, is indicated to stop the corneas drying. Recumbency care should focus on maintaining comfort, maximising ventilation, preventing lung atelectasis and pressure sores from lying in one position for too long. Patients should be positioned in sternal as much as possible. However, if this is not tolerated, placing in left lateral for two hours, then into sternal for two hours then into right lateral for two hours can be helpful. The patient can be placed in a padded trough to facilitate maintaining in sternal recumbency. Bladder management becomes an important part of recumbency care. Although there is no reason for this patient not to be able to urinate, they will often be unable to access a litter tray due to the paresis; and therefore need wicking bedding and regular hygiene checks. If the cat is long haired, clipping hair around the perineum may help prevent urine scald. In some patients an indwelling urinary catheter and closed collection system may be required. Physiotherapy and gentle application of heat are beneficial but must be performed on the direction of the veterinary surgeon. 12-24 hours following the initial presentation, it can be useful, if the patient tolerates it, to apply a gentle heat source for 10 minutes every 2 hours to encourage mild vasodilation. However, these patients should not be placed on a static heat source due to their inability to move and the significant risk of burns. Nutritional support is important – often due to the severe pain associated with this condition, these patients will not eat voluntarily. The main focus will be pain management; however, a feeding tube may need to be considered for short term support. The cat is also at risk of a further thromboembolic event so close monitoring should be performed for this. Because of this the long-term prognosis is usually poor. Some cats may be euthanased soon after presentation, on humane grounds, or if they fail to respond to treatment

Answer 184

Systemic hypertension is the pathological syndrome due to elevated systemic arterial blood pressure. The importance of systemic hypertension as a condition in animals is increasingly recognised, especially in cats

Answer 185

It can be a primary condition or is often secondary to other conditions. Potential secondary causes include phaeochromocytomas, renal failure, diabetes mellitus, hyperthyroidism (cats) and hyperadrenocorticism (dogs). Animals will also present with severe hypertension secondary to raised intra cranial pressure (ICP; Cushing’s reflex- discussed further in unit 5)

Answer 186

Elevation of systemic blood pressure can lead to tissue damage especially nervous, ocular and renal. This can result in neuron damage/cerebral haemorrhage; retinal or intraocular haemorrhage/retinal detachment; or kidney damage. Sudden development of clinical signs secondary to systemic hypertension may be a reason for an emergency presentation e.g. sudden onset blindness, ataxia, signs of vestibular disease etc.

Answer 187

none or minimal BP substage AP0

Answer 188

Low | BP substage AP1

Answer 189

Moderate | BP substage AP2

Answer 190

High | BP substage AP3

Answer 191

Pulmonary hypertension is caused by elevated pulmonary artery blood pressure. Pulmonary arterial hypertension (PAH) is a rare, but increasingly recognised condition, characterised by an increase in pulmonary vascular resistance which leads to right ventricular failure ‘cor pulmonale’ (Williams, 2011). The increase in pulmonary arterial pressure (PAP) can result from left sided heart disease, pulmonary over-circulation, chronic pulmonary disease or vascular obstruction e.g. due to Angiostrongylus vasorum. Pulmonary pressures can be measured by pulmonary arterial catheterisation or more commonly by using echocardiography.

Answer 192

Affected animals are typically exercise-intolerant and have episodes of collapse. Ultimately, right-sided failure or (ascites etc.) cardiac arrhythmias may develop.

Answer 193

Treatment is aimed at the underlying cause (e.g. furosemide, ACEi if left sided heart disease); parasiticide therapy for Angiostrongylus vasorum; and pulmonary vasodilators that will reduce the pulmonary pressures. Sildenafil is a phosphodiesterase (V) inhibitor that enhances nitric oxide (NO)-mediated pulmonary vasodilation (BSAVA, 2020). It has been shown to reduce pulmonary arterial pressures, increase exercise tolerance and improve quality of life in dogs with PAH. Pimobendan can also be used in dogs with PAH.

Answer 194

``` Peripheral and central pulses Mentation Body Temperature- core and peripheral Urine output ( should be 1-2 ml/hr) Blood Pressure Respiratory Rate CRT ( should be 1-2 seconds) Blood gases Blood Lactate ```

Answer 195

The correct answer is: Backward heart failure

Answer 196

The correct answer is: Atrial fibrillation

Answer 197

The correct answer is: Diltiazem

Answer 198

The correct answer is: All of the above

Answer 199

The correct answer is: Intercostal spaces 2-8 from sternum to the mid-thoracic region

Answer 200

The correct answer is: Clopidogrel

Answer 201

The correct answer is: PT/aPTT or Activated clotting time