Cardiac Flashcards
Primary causes of dysrhythmias
Structural heart disease
Metabolic disease
Electrolyte disorders
Trauma
Drugs and toxins
Sepsis
Neoplasia (especially ventricular)
If ECG shows a long pause and then ventricular escape, should dysrhythmia medication be given?
No
If ECG should very early VPC landing on top of a T wave should dysrhythmia medication be given?
Yes (make ventricle unstable as asked to depolarise as it repolarises, may fibrillate)
Specialist procedures for dysrhythmias other than antidysrhythmic drugs
Pacing
Ablation with catheters
Implantable cardiovertors
Brady dysrhythmia
Marked sinus arrythmia with regularly irregular rhythm, pauses terminated by P wave so no need for concern
Brady dysrhythmia
Persistent atrial standstill with no P waves, always significant so look for primary cause
Brady dysrhythmia
Third degree AV block, P wave unrelated to QRS complex which are wide and bizarre as P wave not conducting (blocked at AV node)
Supraventricular tachydysrhythmias
Narrow complex
Causes of tachydysrhythmias
Structural heart disease
Systemic disease
Sympathetic nervous system activation
Drugs and toxins
Commonly used anti-dysrhythmic drugs
Lidocaine (class 1, sodium channel blocker)
Sotalol (class 3, potassium channel blocker)
Diltiazem (class 4, calcium channel blocker)
Digoxin
Treatment of supraventricular tachycardia
Treat underlying primary condition (especially CHF)
Treat clinical signs of poor output: digoxin +/- diltiazem
Problem and treatment
Fast supraventricular tachycardia
Frequently in heart failure so treat and rate may drop
If still fast: diltiazem and/or digoxin
Treatment of primary supraventricular tachycardia causing clinical signs (cold extremities/collapse)
Diltiazem +/- sotalol
Vagal maneuver for supraventricular tachycardias
Increase vagal tone by pushing eyeballs in/massaging carotid
Conditions associated with ventricular premature complexes
Structural cardiac disease (congenital/aquired)
Drugs (digitalis glycosides, anaesthetics etc.)
Hypoxia
Autonomic tone
Systemic disease
Indications for antidysrhythmic therapy with VPCs
Short coupling interval (‘R on T’ phenomenom)
Clinical signs of dysrhythmia
Medical treatment of critical ventricular dysrhythmias
IV lignocaine
Medical treatment of stable/episodic ventricular dysrhythmias
Solatol (oral)
Normal sinus arrhythmia
Normal but seen secondary to high vagal tone (abolished by exercise/atropine)
No QRS after P wave
Secondary AV block, not significant
Ventricular escape complex
May be vagal, try atropine
Collapsing: treatment
No primary disease: pacemaker
Secondary to thoracic trauma
Improved by next day
Atropine to increase rate
Second degree AV block (P not followed by QRS)
Ventricular rate really low so almost certainly clinical
Pacemaker
Third degree AV block (P waves not producing QRS waves)
Needs treatment as probably clinical
Wide QRS complex
Supraventricular premature complex
If frequent will be poor filling with weak pulses/no pulse as aortic valve not opened (pulse deficit)
Supraventricular rhythm
P waves abnormal in middle = not coming from SAN = atrium is ‘sick’
Supraventricular tachycardia
Could be sinus or atrial as P waves with every QRS
Narrow complex = conducted through normal system
Dysrhythmia present and likely clinical signs
Very fast supraventricular tachycardia
Animal weak and collapsed with high HR
What commonly causes supraventricular tachycardia with atrial fibrillation (no P waves)?
Heart failure
Why in this ventricular tachycardia as some complexes normal?
Captured by P wave
Why does this dog have ventricular tachycardia?
P wave not associated with QRS
How can a dysrhythmia be diagnosed?
Paper ECG
5 min ECG
Holter monitor
Sedation for thoracic radiographs
Butorphanol
GA if stable
Identify species, enlarged cardiac chambers and evidence of cardiac failure
Dog
No cardiac chamber enlargement
Alveolar pattern and border obliteration (pulmonary oedema?)
Identify species, enlarged cardiac chambers and evidence of cardiac failure
Dog
Increased sternal contact = right sided enlargement
Ascites in abdomen
Identify species, enlarged cardiac chambers and evidence of cardiac failure
Dog
Right sided enlargement
Abdominal ascites
Identify species, enlarged cardiac chambers and evidence of cardiac failure
Cat
Heart looks like a heart = both atria enlarged = HCM likely
Bronchial pattern with beginning of an alveolar pattern
Abdominal ascites? Pulmonary oedema?
Clopidogrel
Prevent blood clots, high risk in heart disease
What is your top differential?
6y MN Dobermann, some weight loss, 2w history of coughing (worse at night, soft cough), exercise intolerance and tripping on walks, BAR, tachypnoea/tachycardia, occasionally irregularly irregular heart rate and weak, bilateral femoral pulses with occasional pulse deficits
Dilated cardiomyopathy
(Echo, ECG, radiograph, bloods)
Treatment for dilated cardiomyopathy
Pimobendan (helps heart contract more strongly)
Diuretics (prevent congestive heart failure)
Meaning of positive hepatojugular reflex
Gentle cranial abdominal pressure causes jugular vein to become more prominent
Signifies that right ventricle cannot accomodate the augmented venous return
What does this DV thoracic radiograph show?
Pleural effusion
Cardiac tamponade
Increased pressure around the heart (pericardial disease)
Presentation and prognosis of acute pericardial effusion
Sudden onset of exercise intolerance, collapse, shock and rapid death if untreated
Poor prognosis
Presentation and prognosis of chronic pericardial effusion
More common than acute
Typical signs of right sided heart failure (ascites, progressive exercise intolerance, lethargy, GI signs, collapse)
Differentials for pericardial disease in dogs
Cardiac neoplasia (haemangiosarcoma, heart base tumour, mesothelioma, lymphosarcoma)
Idiopathic (haemorrhagic)
Left atrial rupture
Coagulopathies (DIC, IMHA)
Uraemic
Infection (bacterial and fungal)
Differentials for pericardial disease in cats
CHF
FIP
Pericardial effusion ECG
Tachycardia, small complexes
Treatment of pericardial effusion
(Drugs e.g. diuretics not effective)
Oxygen, IVFT, pericardiocentesis (therapeutic and diagnostic), pericardial strip
Pericardiocentesis technique
Monitor via ECG
Ultrasound guided
Catheter between 4th and 6th intercostal space at level of costochondral junction
Check for blood clots (iatrogenic damage, blood in pericardial effusion will have exhausted clotting factors)
Indications for pericardiectomy
Mesothelioma
Idiopathic pericardial disease, 3rd recurrence
Constrictive pericardial disease
What is the arrow pointing to?
Pericardial cyst
Radiographic views for heart
Dorsoventral
Right lateral
Normal size heart
Lateral: 3.5 rib spaces max
DV: 2/3 of width at thorax at rib 6 max
Whole cardiac silhouette grossly enlarged, globular appearance, outline distinct, secondary signs of right sided failure
Pericardial effusion
Trachea pushed up
Generalised heart enlargement, hard to differentiate from pericardial effusion
What causes this bulge (rather than cardiac waist) and big pulmonary vessel (compared to artery)?
Left sided heart enlargement
What causes this displaced trachea, less sternal contact and alveolar pattern (pulmonary oedema, arrows)?
Left heart failure
What causes sternal contact (arrows), pulmonary oedema, ascites and backwards D curve?
Right sided heart enlargement
What is wrong with the heart in this dog thorax radiograph?
Microcardia (looks like cat heart)
Where is the right and left side of the heart on radiograph? (Clock)
Normal size of heart in a cat
DV: 2/3 width of thorax at 5th rib
Lateral: 2 IC spaces
How does the feline heart change with age?
Moveable thorax so more horizontal heart and prominent aortic arch
Causes of central cyanosis (desaturation of arterial blood or presence of Hb derivative)
Reduced inspired oxygen
Alveolar hypoventilation (high carbon dioxide)
Diffusion impairment
Anatomic R to L shunting
Haemaglobinopathy
Causes of peripheral cyanosis (desaturation of blood due to a regional reduction in blood flow)
Central cyanosis
Decreased arterial supply
Peripheral vasoconstriction
Arterial thromboembolism
Low cardiac output
Obstruction of venous drainage
Cardiac causes of cyanosis
Congenital heart disease
Tetralogy of fallot (pulmonic stenosis, VSD, over-riding aorta, right ventricular hypertrophy/dilation)
What view is this?
Right parasternal long axis 4 chamber view
What view is this?
Right parasternal long axis 5 chamber view
What view is this?
Right parasternal short axis view, LV at pap. mm. level
What view is this?
Right parasternal short axis at chorda tendinae
What view is this?
Fish mouth/right parasternal short axis at mitral valve
What view is this?
Right parasternal short axis at aortic valve
How do you know is the left atrium is enlarged?
Ao:LA </= 1.5 in dogs, 1.4 in cats
RPLA LV:LA
~1:1
Settings to measure chamber sizes
M-mode in dogs
2DE in cats
Secondary myocardial disease
Infective myocarditis
Deficiency diseases (e.g. taurine)
Toxic causes (e.g. some chemotherapy drugs)
Dilated cardiomyopathy
Impaired myocardial contractility with dilation of LV (+/- RV)
Tachyarrhythmias common
Dobermann, Newfoundland, IWH etc., middle aged
Occult phase (Holter monitor) and symptomatic phase (CHF, syncope, weight loss, cough, death)
Pimobendan +/- diltiazem (if arrhythmia remains)
Boxer cardiomyopathy
Arrhythmogenic right ventricular cardiomyopathy
Myofibre atrophy, fibrosis and fatty infiltration
Asymptomatic (v. arrhythmias), symptomatic (syncopal/weak from v. arrhythmias, normal heart size/LV function), CHF
Holter monitor: >500VPCs/24h
Treat LCHF if necessary and solatol (beta blocker)
Hypertrophic cardiomyopathy in dogs
Rare
Young to middle aged large breed dogs, M>F
Syncope/sudden death, CHF, dysrhythmias
Gallop heard if in sinus rhythm
Most common heart disease in the cat
Hypertrophic cardiomyopathy
Hypertrophic cardiomyopathy in the cat
Inappropriate myocardial hypertrophy of non-dilated left ventricle
Diagnosis of exclusion
Gallop sounds
Feline restricted cardiomyopathy
Endocardial, subendocardial or myocardial fibrosis
Atrial enlargement , mild LV hypertrophy, diastolic failure
Common cause of feline DCM (becoming rarer)
Taurine deficiency
Feline DCM
Poor contractility
Dilation of all 4 chambers especially LV and LA
Arrhythmias and pleural effusion common, can have bradyarrhythmia
Older cats
Murmur with PMI left apex, radiates dorsally and to right thorax
Murmur of mitral insufficiency (left apex: MV area)
Indications of significant heart disease
Grade III murmur or louder (without anaemia)
HR >120bpm
Loss of sinus arrhythmia
Precordial thrill
Dysrhythmia +/- pulse deficits
Weight loss?
What heart problem is not diagnosed by echocardiography?
Congestive heart failure
M mode findings in chronic valve disease
Hypermotile (end stage has severe systolic dysfunction)
Ruptured chordae tendonae
Mitral valve prolapses into atrium (flailing valve leaflet)
Acute emergency with LCHF (severe dyspnoea, cyanotic)
Progression of valvular heart disease (overload of cardiac chambers)
Ruptured chordae tendonae
Intractable cough
Pulmonary hypertension
Left atrial tear
Tussive syncope
Left atrial tear
Causes pericardial effusion
Can present with acute cardiac tamponade
Avoid pericardiocentesis (moving clot)
Tussive syncope
Usually small breed dog (COPD, CDVD, brachycephalic, collapsing trachea)
Syncope, coughing, wretching/gagging
Increased intrathoracic pressure, decreased cerebral blood flow, tachyarrhythmias
Endocarditis
Rare
Dog»_space; cat
Continuous murmur
Systemic signs
Other systems involved? Blood culture/urine/teeth
CHF due to valve damage, can be years later
Cause of heart failure
Cardiac output falls, detected as a fall in blood pressure
Compensatory mechanisms good in acute situation but long term make heart work harder and problem becomes worse
Compensatory mechanism for reduced cardiac output
HR increased
Vasoconstriction
Contractility increased
Salt and water retained
Heart failure treatment
Diuretics (reduce fluid build up)
ACE inhibitors +/- aldosterone antagonists (antagonise RAAS)
Pimobendan (vasodilate)
Ideal surgical treatment of patent ductus arteriosus
Amplatz device (placed via jugular vein or femoral artery)
Indications for a pacemaker
‘Symptomatic bradycardia
Advanced second/third degree atrioventricular block
Persistent atrial standstill
Sick sinus syndrome
Vasovagal syndrome
Second degree atrioventricular block
P waves not always followed by QRS but still linked
Third degree atrioventricular block
QRS not in any way related to P wave
Atrial standstill
No P waves, just ventricles firing slowly and randomly
Technique for putting a pacemaker in
Implanted transvenously using endocardial leads
(Rarely open surgery using epicardial leads)
Human pacemaker
How do you carry out a pericardiocentesis?
Large bore cannula, 16-14G, three way stopcock
20/60ml syringe
Extension tube/giving set
4-6th intercostal space just below costochondral junction
