AF Overview

Question 1

Explain the mechanism of action of beta blockers

Answer 1

1. beta blockers reduce phase 4 slope
2. This reduces rate of firing
3. as a result, automaticity decreases
4. they lead to prolonged repolarisation of AV node
5. this increases effective refractory period
6. which decreases ventricular rate

Question 2

explain the mechanism of action of calcium channel blockers

Answer 2

1. CCBs block L type channels and increase threshold potential of SA node
2. this decreases automaticity
3. they reduce conduction velocity of AV node and increase effective refractory period of AV node
4. which decreases ventricular rate

Question 3

what is the mechanism of action of digoxin

Answer 3

1. increases refractory period in AV node
2. stimulates parasympathetic system through the neurotransmitter, Ach
3. prolongs action potential duration

Question 4

Why won’t digoxin work well in active patients

Answer 4

active patients stimulate the sympathetic system whereas digoxin works by stimulating the parasympathetic system

Question 5

explain the mechanism of action of flecanide

Answer 5

1. Class 1C antiarrhythmic agent
2. causes Na+ channel blockade which decreases Phase 0 upstroke velocity
3. This reduces conduction velocity and decreases re-entry

Question 6

What is the mechanism of action of class 1A drugs

Answer 6

1. result in prolonged repolarisation which increases effective refractory period
2. this decreases re-entry

Question 7

what is the mechanism of action of sotalol and amiodarone in rhythm control

Answer 7

1. involved in blocking K+ channels
2. increase the refractory period
3. this decreases re-entrant rhythms

Question 8

what is ablation therapy

Answer 8

1. radio frequency
2. cyro-ablation
   - burning of cells out to stop extra action potentials from coming fro pulmonary veins
   - to stop trigger of AF