Antiarrhythmic Drugs

Question 1

2 arrhythmogenic mechanisms

Answer 1

1. abnormal automaticity

2. abnormal conduction

Question 2

Torsades de Pointes is often induced by anti-arrhythmics and other drugs that change the shape of the AP and prolong QT interval.

What is the ECG morphology?

Answer 2

polymorphic ventricular tachycardia, with waxing and waning QRS amplitude

it’s also associated with long QT syndrome

Question 3

Singh-Vaughan Williams Classification

Answer 3

Class 1: Sodium channel blockers (1A: prolong, 1B: shorten, 1C: no effect)
Class 2: Beta-adrenoreceptor blockers
Class 3: Potassium channel blockers
Class 4: CCBs
Class 5: Miscellaneous

Question 4

Class 1 antiarrhythmics act on what phase of cardiac action potential?

Answer 4

phase 0

Question 5

1. Group 1A drugs ________ the AP duration
2. Group 1B drugs ________ the AP duration
3. Group 1C drugs ________ the AP duration

Answer 5

1. prolong
2. shorten
3. no effect

Question 6

mechanism of action of group 1 anti-arrhythmics

Answer 6

have local anesthetic activity
slow or block conduction in ischemic and depolarized cells (no effect on normal tissues)
use dependent or state dependent in their action

Question 7

most selective of gorup 1 anti-arrhythmics

Answer 7

group 1B

significant effects on Na channels in ischemic tissue

Question 8

which drug has characteristics of all groups?

Answer 8

amiodarone

groups 1-4, but more prominently 1A