Cardiac Arrhythmia Flashcards
describe supraventricular arrhythmia
supraventricular tachycardia;
atrial fibrillation (heart quivering)
atrial flutter (very fast)
ectopic atrial tachycardia (SA rhythm overdriven)
bradycardia;
sinus bradycardia
sinus pauses
describe ventricular arrhythmia
ventricular ectopics or premature ventricular complexes
ventricular tachycardia
ventricular fibrillation
asystole (heart does not depolarise)
describe AV node arrythmias
AVN re-entry tachycardia AV reciprocating or AV reentrant tachycardia AV block; 1st degree - slower 2nd degree - intermittent 3rd degree - complete block
describe anatomical causes of arrhythmia
left ventricular hypertrophy (pressure problems)
accessory pathways
congenital heart disease
describe autonomic nervous system causes of arrhythmia
sympathetic stimulation - stress, exercise, hyperthyroidism, automaticity
increased vagal tone causing bradycardia
describe metabolic causes of arrhythmia
hypoxia - chronic pulmonary disease, pulmonary embolus
ischaemic myocardium - acute MI, angina
electrolyte imbalance - K, Ca, Mg
describe inflammation causes of arrhythmia
viral myocarditis
describe drug causes of arrhythmia
direct electrophysiologic effects or via autonomic nervous system
describe genetic causes of arrhythmia
mutations of genes encoding cardiac ion channels e.g. the congenital long QT syndrome
describe electrophysiological mechanisms
ectopic beats - beats or rhythms that originate in places other than the SA node; altered automaticity (e.g. ischaemia, catecholamines) triggered activity (e.g. digoxin, long QT syndrome)
re-entry - requires more than one conduction pathway, with different speed of conduction (depolarisation) and recovery of excitability (refractoriness);
accessory pathway tachycardia, previous MI, congenital heart disease
describe the mechanism of tachycardia
ectopic focus may cause single beats or a sustained run of beats, that if faster than sinus rhythm, take over the intrinsic rhythm
re-entry - triggered by an ectopic beat, resulting in a self perpetuating circuit
may or may not be life threatening depending on how they affect cardiac output
describe changes in the action potential in arrhythmia
increases phase 4 slope causing increase in heart rate, ectopics; hyperthermia hypoxia hypercapnia cardiac dilation hypokalaemia, prolongs repolarisations
decreases phase 4 slope causing slowed conduction (bradycardia, heart block);
hypothermia
hyperkalaemia
symptoms of arrhythmia
palpitations shortness of breath dizziness syncope presyncope sudden cardiac death angina, heart failure
tests for investigating arrhythmia
ECG - assess rhythm, previous MI (Q-waves), pre-excitation
CXR
echocardiogram - structural disease (enlarged atria, LV dilatation, previous MI scar, aneurysm)
exercise ECG - ischaemia
24 hour ECG - paroxysmal arrhythmia, link symptoms to underlying heart rhythm
event recorder
electrophysiology - triggers the clinical arrhythmia via radio-frequency ablation and studies mechanisms
describe normal sinus arrhythmia
variation in heart rate, due to reflex changes in vagal tone during respiratory cycle
inspiration reduces vagal tone and increases heart rate
describe sinus bradycardia
bradycardia; <60 beats/min physiological e.g. athlete drugs - beta-blocker ischaemia - common in inferior STEMI
treatment of sinus bradycardia
atropine (if acute e.g. MI)
pacing if haemodynamic compromise - hypotension, CHF, angina, collapse
describe sinus tachycardia
tachycardia;
HR>100 beats/min
physiological e.g. anxiety, fever, hypotension, anaemia
inappropriate (drugs)
treatment for sinus tachycardia
treat underlying cause
b-adrenergic blockers
describe atrial ectopic beats
symptoms;
asymptomatic
palpitations
no treatment - adrenergic blockers may help avoid stimulants (e.g. caffeine, cigarettes)
describe causes of normal supraventricular tachycardia
AV nodal re-entrant tachycardia
AV reciprocating tachycardia/AV reentrant tachycardia (via accessory pathway)
ectopic atrial tachycardia
management of supraventricular tachycardia
acute;
increase vagal tone - valsalva, carotid management
slow conduction in AVN - IV adenosine, IV verapamil
chronic; avoid stimulants electrophysiologic study and radio-frequency ablation (selective cautery of cardiac tissue to prevent tachycardia, targeting either an automatic focus or part of re-entry circuit) beta blockers anti-arrhythmic drugs
describe causes of AVN conduction disease - heart block
ageing process acute MI myocarditis infiltrative disease - amyloid drugs - B-adrenergic, CCB calcific aortic valve disease post-aortic valve surgery genetic - lenegre's disease, myotonic dystrophy
describe 1st degree AV block
slow conduction
PR interval longer >0.2 seconds
no treatment - long term follow up recommended as more advanced block may develop
rule out other pathology
