Cardiovascular system & cardiac emergencies Flashcards
What do clinical signs of pericardial effusion normally reflect?
Poor cardiac output and systemic venous congestion
What are some echocardiographic findings of pericardial effusion?
right atrial collapse, mass lesions, poor left ventricular filling, effusion, abnormal cardiac wall motion
What is immediately indicated for cardiac tamponade?
Pericardiocentesis
What are the clinical signs or symptoms of pericardial effusion?
Exercise intolerance, dyspnoea, tachypnoea, ascites, collapse/syncope, +- cough, GI signs, pulsus paradoxus, weak femoral pulses, muffled heart sounds
What are some nursing interventions for pericardial effusion?
ECG & Resp monitoring, IVFT, oxygen therapy (where indicated), monitor jugular distension, BP and pulse monitoring, patient comfort
What are some radiographic findings of pericardial effusion?
Globoid cardiac shadow ‘ basketball heart’, cardiomegaly, pleural effusion, hepatomegaly, caudal vena cava distension, pulmonary oedema, tracheal deviation, metastatic lung lesions
What is a pericardial effusion?
Fluid accumulation within the pericardium which leads to cardiac dysfunction that is most commonly neoplastic or idiopathic in origin.
What is cardiac tamponade?
Cardiac tamponade is when there is increased intrapericardial pressure that exceeds normal diastolic pressure leading to reduced ventricular filling and therefore reduced cardiac output.
What are the signs of cardiac tamponade?
Tachypnoea, dyspnoea, reduced arterial BP, weak femoral pulses, tachycardia, jugular distension
What is pulsus paradoxus?
abnormally large decrease in stroke volume, systolic blood pressure and pulse wave amplitude during inspiration (>10mmHg).
What is the normal amount of pericardial fluid?
0.25ml/kg of body weight
What are the 2 most common neoplasms causing pericardial effusions and what are their characteristics?
Haemangiosarcoma: most common, haemorrhagic effusion (HCT >7%, TP >30%), most arise in RA or auricle or heart base.
Chemodectoma: heart base mass, arise from chemoreceptor of the aorta.
When would you most likely encounter a transudative pericardial effusion? What are some characteristics?
Congestive heart failure, hypoalbuminaemia, congenital pericardial malformations, toxaemias.
clear, low cell count <1000ug/L (<8000 when modified), SG <1.012, protein <2.5g/dL
When would you most likely encounter a exudative pericardial effusion? What are some characteristics?
extension of pleural or mediastinal infection, bite wounds, plant awn migration, some bacteria i.e. aspergillosis, actinomycosis, coccidiodomycosis, leptospirosis, idiopathic pericardial effusion
cloudy or opaque, high nucleated cell count (>3000/ul), protein >3g/dl, SG >1.015
What dictates the rate of cardiac tamponade?
Rate of pericardial fluid accumulation and distensibility of the pericardial sac.
Rapid + small vol = intrapericardial pressure increase rapidly due to pericardial tissue stretching slowly
Slow + large vol = implies gradual filling and ability to maintain lower intracardial pressure for longer as the pericardium has time to stretch
What is meant by the term cardiomyopathy’?
Heart muscle disease that is associated with cardiac dysfunction.
What are the four basic types of cardiomyopathies?
- Dilated cardiomyopathy 2. Restrictive cardiomyopathy 3. Hypertrophic cardiomyopathy 4. Arrhythmogenic right ventricular cardiomyopathy (ARVC)
What is the etiopathogenesis of HCM?
ventricular hypertrophy in the absence of haemodynamic and metabolic cause.
- nondilated ventricle
- maine coon and ragdoll cats at most risk
What is the etiopathogenesis of RCM?
impaired ventricular filling in the absence of ventricular wall thickening (hypertrophy) or pericardial disease. Applied when there is atrial enlargement with normal or near normal ventricle.
- unknown cause but myocardial functional deficits (i.e. fibrosis) impair relaxation and result in diastolic dysfunction
- sequelae of endomyocardial inflamamtion
What occurs as a result of impaired myocardial relaxation and diminished chamber compliance in feline cardiomyopathies?
Altered presure-volume relationship where diastolic pressure is high and ventricular volume in normal or small. This results in atrial enlargment and venous congestion
- low stroke volume
- lower cardiac output
What causes impaired myocardial relaxation in HCM?
Intrinsic functional deficits in cardiomyocytes and ischaemia related to hypertrophy, as well as abnormalities in intramural coronary arteries.
What explains poor chamber compliance in feline cardiomyopathies?
Hypertrophy and fibrosis which stiffen the ventricle
Describe systolic anterior motion of the mitral valve.
Abnormal drag forces cause systolic movement of the mitral valve leaflets towards the septum. This causes a dynamic left ventricular outflow tract obstruction leading to mitral valve regurgitation. This decreases the preload and also afterload, increasing contractility. Still unsure of prognostic indicator in HCM but poorer prognosis observed. It is most commonly associated with causing cardiac murmurs in cats.
What is the most common site of thrombus formation in feline heart disease?
Left atrium
How does FATE occur?
Partial or full dislodgement of a thrombus (likely from the LA) forms an embolism typically in the aortic trifurcation - or terminal point of the abdominal aorta.
What is the assumed risk factors and causes of FATE?
- feline cardiomyopathies
- blood stasis associated with LA enlargement
How does the clinical syndrome of FATE result??
Not solely by the arterial occlusion caused by the thrombus but also by the release of vasoactive mediators by the thrombus (serotonin, prostaglandins) which decrease blood flow via collateral circulation. This contributes to the development of ischaemia.
What are some signs and symptoms of feline cardiomyopathy?
- tachypnoea
- dyspnoea
- signs of CHF
- presence of a heart murmur (SAM)
- cyanosis
- signs of thromboembolism (cold HL, weak/absent femoral pulse, hypothermia, painful HL, HL ataxia)
- inappetence
- bradycardia
- crackles on lung auscultation
What are some echocardiographic findings of feline HCM?
- ventricular hypertrophy without chamber dilation
- Left atrial enlargement due to diastolic dysfunction
- Mitral valve regurgitation (due to LA enlargement and +- SAM)
How do we treat FATE?
- narcotic analgesia i.e. fentanyl CRI
- antithrombotics i.e. LMWH, dalteparin, clopidogrel
- oxygen therapy where indicated
- warming to at least 37.2r (shown to improve short term survival to 50%)
- treatment of CHF
- treatment of underlying heart disease
- reduce stree
- potentially low dose aspirin
What should be routinely monitored in FATE patients?
- HR
- BP
- rectal temperature
- pain
- oxygenation
- RR + RE
- pulse quality (particularly femoral pulse)
- peripheral temperature and pad colour
How do we treat feline heart failure?
- oxygen therapy
- anxiolysis
- diuretic therapy
- nitrate therapy
- potentially b-blockers
- ACE inhibitors
What should be routinely monitored in feline heart failure patients?
- HR
- RR + RE
- Body weight
- Urination
- BP
- Body temperature
- Water intake
- PCV/TP
- Kidney function
What is dilated cardiomyopathy? What are some risk factors of DCM?
Chamber dilation and impaired systolic - and often diastolic - dysfunction of one or both ventricles. It is an adult onset disease and some breed predisposition has been identified in: doberman, boxers, cocker spaniels, great danes and wolf hounds. It has also been associated with taurine deficiency in cats.
What are some physical exam findings in patients with DCM?
- systolic apical murmur 1-3/6
- chaotic heart rhythm (Afib, VPC)
- Signs of L or R heart failure
- cardiogenic shock
What are thoracic radiographic findings in patients with DCM?
- cardiomegaly
- signs of CHF
- hepatomegaly
What are some echocardiographic findings in patients with DCM?
- mitral and/or tricuspid valve insufficiency
- ventricular and atrial dilation
- reduced systolic and potentially diastolic function
- increased E-point septal separation
How is DCM treated long term?
- Diuretics (furosemide 1-4mg/kg PO q8-12; spironolactone 1-2mg/kg PO q12; hydrochlorothiazide 1mg/kg PO q24)
- ACE inhibitors (enalipril 0.5mg/kg PO q12-24; benazipril 0.25-0.5mg/kg PO q12-24; lisinopril 0.5mg/kg PO q24)
- Digoxin 0.003mg/kg PO q12
- Pimobendan 0.25-0.3mg/kg PO q12
- diet (low sodium, high protein)
- supplements (taurine 500mg PO q12, Omega-3, L-carnitine)
What is arrhythmogenic right ventricular cardiomyopathy (ARVC)? What breed is is commonly identified in and how is it identified?
ARVC is a myocardial disease that is characterised by fatty or fibrofatty infiltration of the RV due to a genetic mutation that codes striatin. It causes the myocardium to break down over time and results in lethal tachydysrhythmias. It is often referred to as ‘boxer cardiomyopathy’ due to high prevalence in boxers. It is identified via Holter study (VPC >100 in 24h, R-on-T and fast rate tachydysrhythmia).
What medications are selected to treat ARVC
Sotalol, mexilitine, lidocaine. L-carnitine may also be considered.
What are some symptoms of ARVC?
- collapse
- syncope
- AFib
- VPC
- Sudden death
- LHS heart failure
What is cardiogenic shock?
Cardiogenic shock is cardiac dysfunction which results in inadequate cellular energy production, despite adequate intravascular volume.
List the clinical signs of cardiogenic shock.
- global hypoperfusion
- Unresponsiveness/disorientation/depression
- tachycardia or bradycardia (with or without arrhythmia)
- cool extremeties
- pallor and prolonged CRT
- Metabolic acidosis with or without compensatory respiratory alkalosis
- GI signs
- Azotaemia
What is the goal of treating cardiogenic shock?
Restoration of cardiac output to normalise tissue perfusion and cellular metabolism.
What are some examples of systolic failure that may result in cardiogenic shock?
DCM, Sepsis, endomyocarditis, mechanical failure (rare) and myocardial infarction.
What are some examples of diastolic failure that may result in cardiogenic shock?
Cardiac tamponade, HCM, tachydysrhythmia, hypovolaemia.
What is the basic definition of heart failure?
Pathophysiologic state where the heart is unable to pump sufficient blood to meet the metabolic demands of the tissue while maintaining normal arterial and venous pressures.
What is the basic definition of systolic heart failure?
A defect in the contractile or pumping function of the heart.
What is the basic definition of diastolic heart failure?
A defect in the relaxation or filling function of the heart.
What is the basic definition of congestive heart failure?
A clinical syndrome that results from abnormal cardiac function causing accumulation and retention of fluid leading to signs of oedema and congestion.
What is the basic definition of forward heart failure?
Decrease in cardiac output that results in inadequate delivery of blood to the arterial system resulting in organ hypoperfusion. Congestion of organs and tissues occurs due to reduced renal perfusion, and the accumulation of plasma fluid and ECF. I.e. DCM.
What is the basic definition of backward heart failure?
Increased pressure within the pulmonary vasculature and LA due to elevated filling pressures. This causes elevated capillary hydrostatic pressures and transudation of fluid into the interstitium leading to pulmonary oedema. I.e. MVD.
What is the basic definition of circulatory failure?
When there is inadequate delivery of oxygenated blood to meet the metabolic demands of body tissue.
What is meant by the term myocardial infarction?
Myocardial damage due to a lack of oxygenated blood supply to the heart leading to myocardial tissue death likely from malignant dysrhythmia or CHF. Can also result from hypercoagulable or hypofibrinolytic states.
What is meant by the term traumatic myocarditis?
myocardial injury associated with malignant arrhythmias as a result of blunt force thoracic trauma.
What is believed to cause myocardial contusion?
compressive and contusive forces of the thoracic cage, and rapid acceleration/deceleration of the thoracic cavity.
What is suspected to cause dysrhythmias in myocardial contusion?
the ratio of refractory period and action potential duration, and elevation of resting membrane potential in damaged myocaridal cells.
What is the most common dysrhythmia seen in traumatic myocarditis? What are some other possible dysrhythmias?
1 VPC and ST segment elevation
Other: Afib, sinus arrest, 2-3 AVB
How is traumatic myocarditis diagnosed?
Based primarily on high index of suspicion:
1. F# of extremeties, spine or pelvis
2. External evidence of thoracic trauma
3. Rad evidence of contusions, pneumothorax, haemothorax, diapragmatic rupture. rib F#
4. Neurological injury
* Histopath gold standard but only achievable through biopsy
What is the treatment goal of traumatic myocarditis?
Not to completely resolve cardiac dysrhythmias but to obtain HR <140bpm and re-establish adequate tissue perfusion.
- antiarrhythmic therapy i.e. lidocaine, procainamide, cautious use of b-blockers
What may cause a bradydysrhythmia?
- alterations of autonomic tone
- electrolyte disturbances
- drug exposure
- trauma
- hypoxia
- inflammation/infiltration of myocardium
- degenerative disease of the conduction system
Draw ‘sinus arrhythmia’. What is a sinus arrhythmia? What are the characteristics? When is it treated?
- usually secondary to systemic disease that causes increased vagal tone. The resolution of the disease process results in increased heart rate and resolution.
- P wave associated with QRS complex
- may have wandering pacemaker if marked vagotonia the cause
- usually narrow QRS complexes
- if reduced consciousness, hypertension and abnormal breathing concerns of increased ICP (cushing’s reflex)
- if severe bradycardia having systemic effects treat with anticholinergic i.e. atropine, glycopyrrolate
Draw ‘sinus arrest’. What is sinus arrest? What are the characteristics? When is it treated?
prolonged pause with no atrial activation or p wave
What is a sinus block?
Failure of an impulse to leave the sinus node
What causes syncope in bradydysrrhythmia?
Sinus arrest over 6-8sec causing significantly reduced cardiac output
What is sick sinus syndrome (SSS)?
Periods of normal sinus rhythm or sinus bradycardia interspersed by periods of long sinus arrest (10-12sec). It occurs when junctional and ventricular pacemakers fail to initiate escape beats.
Describe bradycardia-tachycardia syndrome
Variant of SSS where the heart fluctuates between a tachycardic and bradycardic state.
Draw 1AVB. What are the characteristics? What is likely to cause it?
atrial impulses are conducted to the ventricles but the P-R interval in prolonged (>130ms Dogs; >90ms Cats).
- increased vagal tone
- drug induced (Ca blockers, digoxin, b blockers)
- AV node fibrosis
Draw TYPE I 2AVB. What are the characteristics?
Some p waves not associated with a QRS that may or may not compromise a patient’s haemodynamic state. Type I the P-R Interval increases and ends in heart block.
- Usually benign
Draw TYPE 2 2AVB. What are the characteristics?
Unexpected occurrence of blocked p wave. P-R interval constant before the block. QRS +- wide
- Usually worsens
- Atropine 0.04mg/kg IV
Draw 3AVB. What are the characteristics? What is likely to cause it?
Absence of conducting p waves to ventricles. Independant atrial and ventricular activities. There is a resulting significant decrease in cardiac output.
- 20-60bpm Dogs; 60-120bpm Cats
- myocardial fibrosis, inflammation, infiltration, drug toxicity (Ca blockers, digoxin, b blocker), age-related fibrodegenrative disease
- In cats most likely associated with structural heart disease.