Arrhythmia Flashcards
Where is the origin of supraventricular (SVT) arrhythmias?
above the ventricle
Where is the origin of ventricular arrhythmias?
ventricular muscle (common) or fascicles of conducting system (uncommon)
What conditions are examples of supraventricular tachycardia?
- atrial fibrillation
- atrial flutter
- ectopic atrial tachycardia
What conditions are examples of supraventricular Bradycardia?
- sinus bradycardia
- sinus pauses
What conditions are examples of ventricular arrhythmias?
- ventricular ectopics or premature ventricular complexes (PVC)
- ventricular tachycardia
- ventricular fibrillation
- asystole
What conditions are examples of atrio-ventricular node arrhythmias?
- AVN re-entry tachycardia
- AV reciprocating or AV reentrant tachycardia
- AV block
What is 1st, 2nd and 3rd degree AV block?
1st degree– still conducts but takes longer
2nd degree – lets some through and some not. Allows a smaller amount of conduction.
3rd degree – nothing gets through. Allows no conduction.
What abnormal anatomy conditions could cause arrhythmias?
- left ventricular hypertrophy
- accessory pathways
- congenital heart disease
how can the automatic nervous system cause arrhythmias?
- sympathetic stimulation (stress, exercise, hyperthyroidism)
- increased vagal tone causing bradycardia
What are some metabolic causes of arrhythmias?
- hypoxia (chronic pulmonary disease, pulmonary embolus)
- ischaemic myocardium (acute MI, angina)
- electrolyte imbalances (K+, Ca2+, Mg2+)
what is an inflammation cause of arrhythmias?
viral myocarditis
how can drugs cause arrhythmias?
direct electrophysiologic effects or via ANS
how can genetics cause arrhythmias?
mutations of genes encoding cardiac ion channel e.g. the congenital long QT syndrome.
What are ectopic beats?
beats or rhythms that originate in places other than the SA node
what are some causes of ectopic beats?
- altered automaticity (ischaemia, catecholamines)
- triggered activity (digoxin, long QT syndrome)
What conditions would cause an increase in phase 4 of the cardiac potential? (therefore causing increase in heart rate and ectopics)
- hyperthermia
- Hypoxia
- hypercapnia
- Cardiac dilation
- hypokalaemia, prolongs repolarisation
What conditions would cause an decrease in phase 4 of the cardiac potential? (therefore causing slowed conduction (bradycardia, heart block))
- hypothermia
- hyperkalaemia
what are the mechanism of re-entry?
requires more than one conduction pathway, with different speed of conduction (depolarisation) and recovery of excitability (refractoriness)
What are the symptoms of arrhythmias?
- palpitations
- SOB
- dizziness
- loss of consciousness (syncope)
- faintness
- sudden cardiac death
- angina, heart failure
What investigations can be done to diagnose a arrhythmias?
- ECG
- CXR
- echocardiogram
- stress ECG
- 24 hour ECG holter monitoring
- event recorder
- electrophysiological study
What would an ECG be used to assess?
- rhythm.
- signs of previous MI or pre-excitation (wolf parkinson white syndrome)
What would an exercise ECG assess?
- ischaemia
- exercise induced arrhythmias
What would an 24hr holter ECG be used to assess?
- paroxysmal arrhythmia
- to link symptoms to underlying heart rhythm
What would an Echocardiogram be used to assess?
structural heart disease e.g. enlarged atria in AF, LV dilatation, previous MI scan, aneurysm.
What would an electrophysciological study be used for?
- trigger the clincal arrhythmia and study its mechanism/Pathway
- opportunity to treat by delivering radiofrequency ablation to extra pathway.
What is sinus bradycardia?
< 60 beats/min
What are causes of sinus bradycardia?
- physiological e.g. athlete
- drugs (B-blocker)
- ischaemia (common in inferior STEMIs)
How do you treat sinus bradycardia?
- atropine (if acute e.g. acute MI)
- pacing if haemodynamic compromise (hypertension, CHF, angina, collapse)
What is sinus tachycardia?
HR > 100 beats/min
What are causes of sinus tachycardia?
- physiological (anxiety, fever, hypotension, aneamia)
- drugs
How do you treat sinus tachycardia?
- treat underlying cause
- B-adrenergic blockers
What are symptoms of atrial ectopic beats?
- asymptomatic
- palpitations
What are treatments of atrial ectopic beats?
- No treatment
- B-adrenergic blockers may help
- avoid stimulants (caffeine, cigarettes)
What is the acute management of supraventricular tachycardia?
- increase vagal tone (valsalva, carotid massage)
- slow conduction in the AVN (IV adenosine, IV verapamil)
What is the chronic management of supraventricular tachycardia?
- avoid stimulants
- EP study and radiofrequency ablation
- beta blockers
- antiarrhythmic drugs
What is Radiofrequency catheter ablation (RFCA)?
Selective cautery of cardiac tissue to prevent tachycardia, targeting either an automatic focus or part of a re-entry circuit
What does RFCA involve?
ECG Catheters placed in heart via femoral veins.
Intracardiac ECG recorded during sinus rhythm, tachycardia and during pacing manoeuvres to find the location and mechanism of the tachycardia
catheter placed over focus / pathway and tip heated to 55-65C
what are some causes of AVN conduction disease (heart block)?
- ageing
- acute MI
- myocarditis
- infiltrative disease (amyloid)
- Drugs (B-adrenergic blockers, calcium channel blockers)
- calcific aortic valve disease
- post-aortic valve surgery
- genetic (lenegre’s disease, myotonic dystrophy)
How long is the P-R interval in 1st degree AV block?
> 0.2 seconds
What are the two types of 2nd degree AV block?
- Mobitz I: progressive lengthening of the PR interval, eventually resulting in a dropped beat. usually vagal in tone.
- Mobitz II: pathological, may progress to complete heart block.
permanent pacemaker indicated.
What are the types of pacemakers?
- single chamber (paces the right atria or right ventricle only)
- dual chamber (paces the RA and RV) - maintains AV synchrony. used for AVN disease
What are the causes of ventricular ectopics?
- structural (LVH, Heart failurem myocarditis)
- metabolic (ischaemic heart disease, electrolytes)
