Atrial Fibrillation & Arrhythmias Flashcards
What is arrhythmia?
It is a disturbance in the electrical rhythm of the heart.
What is the pathway of impulses in the heart in a healthy individual vs. an individual with arrhythmia?
- Impulse originates from the SA node
- It then travels to the AV node
- It then travels to the Bundle of His & purkinje fibres
- The ventricles receive this & contract
In arrhythmia, these pulses are disrupted & the heart does not beat normally.
What are the 3 classifications of arrhythmias?
- By heart rate
- Tachycardia/bradycardia - By the origin of the electrical impulses
- Atria: supraventricular arrhythmias
- Ventricles: ventricular arrhythmias - By its time course
- Paroxysmal: comes and goes
- Persistant
- Permanent
What is atrial fibrillation?
It is a form of supraventricular arrhythmias (originating from the atria, not SA node), causing disorganised electrical impulses.
This can also cause tachycardia.
Not all of these atrial impulses get conducted from the AV node; this causes the ventricular rate to be lower.
Which part of an electrocardiogram is absent in AF?
P wave is absent due to the disrupted atrial depolarisation.
What are the causes of AF?
- Cardiac:
- Area of infarction after MI
- Valvular disease causing atrial stretching - Non-cardiac:
- Hyperthyroidism
- Anaemia
- Acute infections
- Electrolyte abnormalities - Drugs
- B2 agonists
- Thyroxine
- Alcohol/caffeine
What mechanisms are triggered during AF?
Inflammatory responses are triggered in the myocardium during AF.
Myofibroblasts are activated and cytokines are released, causing:
1. Myocyte apoptosis
2. Abnormal electrical/structural remodelling
3. Fibrosis development (causing scarring/thick tissue)
What are the classes/mechanisms of anti-arrhythmic drugs?
CLASS IA: quinidine, procainamide
- Na+ channel blockers
CLASS 1B: lidocaine, phenytoin
- Na+ channel blockers
CLASS 1C: flecainide, propafenone
- Na+ channel blockers
CLASS II: propanolol, metoprolol
- B-blockers
CLASS III: amiodarone, sotalol
- K+ channel blockers
CLASS IV: verapamil, diltiazem
- Ca2+ channel blockers
CLASS V: adenosine, digoxin
- Unknown mechanism
What is rhythm and rate control?
Rhythm control can be:
- Medically stable (chemical) - flecainide (no IHD) or amiodarone (with IHD)
- Medically unstable (electrical) - electrical shock given
Rate control:
- Controlling ventricular rate but staying in AF
- B blockers used (atenolol, propanolol; class II drugs)
- Rate limiting CCB’s used (verapamil, diltiazem; class IV drugs)
- Digoxin used as mono-therapy (class V)
- B blocker + CCB NEVER given together as it can increase the risk of a heart attack
What is ablation?
It is the destruction of abnormal sources of electrical impulses.
Patients with permanent AF use pacers and AV node ablation as treatment
What is the CHA2DS2-VASC system?
It is a scoring system to show how likely a patient is to have a blood clot/stroke.
1 point is awarded for every characteristic, except >75yrs & has had a stroke = scores 2 points each
1 point = no therapy/aspirin considered
2+ = warfarin/DOAC/NOAC given
What is the HASBLED system?
It is a scoring system used to show the risk of bleeding in a patient.
What are the benefits of using a NOAC?
NOAC: Novel anticoagulants
- It is 1st line choice
- Less interactions
- Good safety
- Fixed dose regimen
What can be taken to reverse warfarin’s effects?
K+ supplements.
What is the mechanism of action of dabigatran, compared to rivaroxaban/apixaban/edoxaban?
Dabigatran: is a direct thrombin inhibitor
Rivaroxiban/apixaban/edoxaban: are all oral factor Xa inhibitors (hence the x in their name)
