Cardiac Arrhythmias Flashcards
Where is the origin in a supraventricular arrythmia?
Above ventricle i.e. SA, atrial muscle, AV node or HIS node
What are ectopic beats?
Beats or rhythms that originate in places other than the SA node
Whta may cause single beats or take over and pace the heart, dictating its entire rhythm?
Ectopic focus
Name three supraventricular tachycardias?
- Atrial fibrillation
- Atrial flutter
- Ectopic atrial tachycardia
Name two bradycardia (supraventricular arrhythmias)?
- Sinus bradycardia
2. Sinus pauses
Name three atrio-ventricular node arrythmias?
- AVN re-entry
- Acessory pathway (e.g. WPW)
- AV block - 1st, 2nd and 3rd degree
Name 4 ventricular arrythmias?
- Premature ventricular complex (PVC)
- Ventricular tachycardia
- Ventricular fibrillation
- Asystole
What can abnormal anatomy e.g. left ventricular hypertrophy, accessory pathways and congenital HD cause?
Arrythmias
What are two autonomic causes of arrythmias?
- Sympathetic stimulation - nervousness, exercise, CHF, hyperthyroid
- Increased vagal tone (bradycardia, heart block)
What are three metabolic causes of arrythmias?
- Hypoxic myocardium: chronic pulmonary disease, PE
- Ischaemic myocardium: acute MI, angina
- Electrolye imbalances: imbalances of K, Ca, Mg
What inflammation cause is there of arrythmias?
Viral myocarditis
Name a mutation of cardiac ion channels that can cause arrythmias?
The congenital long QT syndrome
What two conditions can alter automacitiy?
Ischaemia and catecholamines
What two things can cause re-entry?
WPW syndrome - accessory pathway tachycardia
Previous MI
What does hypothermia do to phase 4 slope?
Decreases it
What do hypoxia and hypercapnia do to phase 4 slope?
Increase it
What does cardiac dilatation do to phase 4 slope?
Increases it
What increases automaticity of neighbouring cells?
Local areas of ischaemia or necrosis
Whay does hypokalaemia do to phase 4 slope?
Increases it and also increases ectopics, prolongs repolarisation
What is the term for: in the terminal phase of AP (phase 3), a small depolarisation may occur (called an after depolarisation), and if of sufficient magnitute may reach threshold and lead to a sustained train of depolarisations
Triggered activity
What mechanism underlyes digoxin toxicity, Torsades de Pointes in long QT syndrome and hypokalaemia?
Triggered activity
What requires available circuit, unidirectional block, and different conduction speed in limbs of circuit?
Re-entry
Where is the origin in a ventricular arrhythmia?
Ventricle
What type of conditions promote functional block?
Conditions that depress conduction velocity or shorten refractory period promote functional block
What are four main investigations you would do for arrythmias?
- 12 lead ECG
- CXR
- Echocardiogram
- Stress ECG
What are signs on an ECG of a previous MI?
Q waves
What does pre-excitation suggest, when seen on an ECG?
Wolf Parkinson White syndrome
What investigation can assess for ischaemia and excersise induced arrythmias?
Exercise ECG
What investigation is used to assess for paroxysmal arrythmia?
24hr Holter ECG
What investigation can assess for structural disease? (e.g. enlarged atria ain AF, LV dilatation or previous MI scar, aneurysm)
Echo
What study triggers arrythmia to study its mechanism and gives an opportunity to treat the arrythmia by radiofrequency ablation?
Electrophysiological study
What condition can be asymptomatic, palpitations, there is generally no treatment, b-adrenergic blockers may help and you need to avoid stimulants like caffeine?
Atrial ectopic beats
What type of STEMI is bradycardia related ischaemia common in?
Inferior STEMIs
What are the two treatment options for sinus bradycardia?
- Atropine (if acute)
2. Pacing if: haemodynamic compromise such as hypotension, CHF, angina or collapse
What drugs can be used to treat sinus tachycardia?
- B-adrenergic blockers
16 year old girl, fast palpitations, alert, no distress, good colour, HR very fast and normal physical exam?
Narrow complex tachycardia, SVT
What three things may supra-ventricular tachycardia be due to?
- AV nodal re-entrant tachycardia
- Accessory pathway tachycardia i.e. Wolff Parkinson White syndrome
- Ectopic atrial tachycardia
What would you do as initial emergency treatment for an infant with SVT?
Peds vagal maneovres
What emergency initial step would you do for a child with SVT?
Blow through straw or carotid massage
What emergency step would you do for an adult with AVT?
Carotid sinus massage
For management of supra-ventricular tachycardia, what would you give after you have performed vagal manoeuvres, carotid massage?
IV adenosine
IV verapamil
What 3 steps of chronic management for SVTs are there?
- Avoid stimulants
- Radiofrequency ablation
- Antiarrythmic drugs (Class II or IV)
What is selective cautery of cardiac tissue to prevent tachycardia, targeting either an automatic focus or part of a re-entry circuit?
Ablation
What three steps are involved in ablation?
- Catheters placed in heart via femoral veins
- Intracardiac ECG recorded during sinus rhythm, tachycardia and during pacing manoeuvres
- Catheter placed over focus/pathway and tip heated to 55-65C
What investigation shows the activation sequence of the heart and has more detail than a surface ECG?
Intracardiac ECG
What type of arrythmic disease can ageing, acute MIs, myocarditis and infiltrative disease (amyloid) cause?
AVN conduction disease
What two classes of drugs cause AVN conduction disease?
B-blockers
Calcium channel blockers
What two genetic causes are there of AVN conduction disease?
Lenergreâs disease
Myotonic dystrophy
Can calcific aortic valve disease and post-aortic valve surgery lead to AVN conduction disease?
Yes
In first degree AV block, what is the PR interval like?
Longer than >0.2 seconds
What is the treatment for first degree AV block?
None
What degree of block is an intermittent block at the AVN (dropped beats)?
2nd degree AV block
What are the two types of 2nd degree AV block?
Mobitz I
Mobitz II
Give two features of Mobitz type I 2nd degree AV block?
- Progressive lengthening of the PR interval, eventually resulting in a dropped beat
- Usually vagal in tone