Antiarrhythmics

Question 1

Adverse effect associated with class 1A antiarrhythmic related with QT prolongation. Mechanism.

Answer 1

Torsades

Block K+ channel

Question 2

What should you do to make safer the initiation doses of quinidine? In which case?

Answer 2

Previous digitalization ▶️ slow AV conduction
Atrial fibrillation

*quinidine alone yield reflex tachycardia ▶️ Alfa blocker (hypotension), muscarinic block (⬆️ HR, AV conduction)

Question 3

What is the antiarrhythmic that increase the action potential duration (APD) instead of decrease it? Then which is the antiarrhythmic effect?

Answer 3

Class 1B: lidocaine, mexiletine ▶️ block the fast Na+ channels in inactivated state ▶️ block the slow Na+ “window” current
Antiarrhythmic ▶️ ⬆️ diastole and extends time of recovery

Question 4

Treatment of torsades. Which antiarrhythmics avoid?

Answer 4

⬇️ K+, ⬇️ Mg+2 correction

⬆️ APD: drugs (isoproterenol) or pacing

Question 5

Which antiarrhythmic is contraindicated in post-MI, structural and ischemic heart disease?

Answer 5

Class IC - Flecainide, Propafenone

Question 6

Treatment for B-blocker overdose

Answer 6

Saline
Atropine
Glucagon▶️⬆️cAMP