ECG: Arrhythmias in SA Flashcards
List the uses of an ECG
- dx of arrhythmias
- rule out arrhythmia in patients with hx of collapse
- chamber enlargement?
- electrolyte disturbances?
- dx pericardia effusion?
- monitor effectiveness of anti-arrthymic therapy
- monitor heart rhythm under GA
What are common P wave changes?
- absent = pathology in atria/SAN
- wide
- tall
What are common QRS changes?
- tall R = LV pathology
- deep S = RV pathology
- deep and wideS = dilated RV
What do small QRS complexes indicate?
Fluid in pericardium/fat animal/barell chested
What can a prolonged QT interval cause?
Excessive intracellular Ca and rapid fatal ventricular tachycardia
What abnormalities can be seen in the ST segment?
- decreases below baseline = hypoxia
- slopes into T wave = LV enlargement
How are arrhythmias classified?
Normal rhythm, bradyarrhythmias, tachyarrhythmias
List common bradyarrhythmias
Sinus arrest, sick sinus syndrome, sinus bradycardia, atrial standstill, AV blocks
What are the causes of sinus arrest?
- meds = sedatives, B blockers, Ca channel blockers, digoxin
- disease = high vagal tone, atrial disease, hypothyroidism
- metabolic = hypothermia
Describe the pathogenesis of sick sinus syndrome
SAN stops for period of time. Ectopic rescue beats come from the ventricles at a rate much lower than sinus rate, >20bpm). Animal may be okay, hypotensive, faint at rest.
What are the causes and tx of sick sinus syndrome>
Causes - hereditary (min Schnauzer, Westie), idiopathic disease
Tx - pacemaker, sympathomimetics, parasympatholytics
What are the causes of sinus bradycardia?
Meds = sedatives, anti-tachyarrhythmics Disease = hypothyroidism, increased ICP, dysautonomia Metabolic = hypothermia, hyperkalaemia
What are the causes of atrial standstill?
Persistent = idiopathic atrial cardiomyopathy, muscular dystrophies Temporary = hyperkalaemia, hypoadrenocorticism, oliguric renal failure
Describe the pathogenesis of AV blocks
Decreased PQ interval duration and slow conduction
What are the causes of primary AV block?
Can be normal in dogs with slow HR.
Drugs = sedatives, anti-tachyarrhythmics
Disease = high vagal tone, AVN fibrosis
Metabolic = hyperkalaemia
What are the causes of secondary AV block?
Can be normal in dogs with high vagal tone
Disease = vagally mediated, fibrosis/infiltration of AVN
Describe the pathogenesis adn tx of a third degree AV block
Pathogenesis - P and QRS completely dissociated. Ectopic beats ~ 50bpm, P waves ~100bpm
Tx = pacemaker, sympathomimetics, prasympatholytics
List tachyarrhythmias
Sinus tachycardia, supraventricular premature beat, supraventricular tachycardia, atrial fibrillation, ventricular prematire complex, VT, rapid VT
What are the causes of tachyarrhythmias?
Can be normal in nervous/excitable dogs
Drugs = anti-bradyarrhythmics
Disease = anaemia, pain, shock, dehydration, septicaemia, low CO2, hyperthyroidism
Describe the pathology of supraventricular premature beat
- electrical activity initiated from the atria, not SAN
- beats are premature, identical to sinus beats
- Disease = atrial dilation, atrial infiltration, atrial fibrosis, systemic disease
What are the causes and tx of supraventricular tachycardia?
Causes - congenital (bypass tract), disease (atrial dilation, atrial infiltration, atrial fibrosis, systemic disease)
Tx - digoxin, diltiazem, atenolol, solatol
Describe the pathogenesis of atrial fib
- associated with cardiomyopathy
- lose definitive P wave
- diff parts of atria fire at same time, AVN filters signals (300-500bpm)
What are the causes and tx of atrial fib?
Causes - atrial dilation, atrial infiltration, atrial fibrosis, occult DCM
Tx - digoxin, diltiazem, atenolol (slow AVN conduction)
What are the causes of VPC?
Disease = ventricular mycocardial dilation, inflammation, infiltration, fibrosis Systemic = anaemia, septicaemia, splenic mass, GDV, pyometra Metabolic = electrolyte imbalance Drugs = digoxin, atropine
What are the causes of ventricular tachycardia?
Disease = ventricular myocardial dilation, inflammation, infiltration, fibrosis Systemic = anaemia, septicaemia, splenic mass, GDV, pyometra Drugs = digoxin, atropine
What are the tx options for VT?
Lidocaine (IV in emergency), mexilitine, sotalol, amiodarone (long time to reach steady state)
What are the causes and tx options of rapid VT?
Causes = ventricular myocardial dilation, inflammation, infiltration, fibrosis, trauma, hypoxia Tx = lidocaine, mexilitine, sotalol, amidarone