Arrhythmias: Type IA Comparison

Question 1

Whatso are the type IA drugs and what do they block?

Answer 1

quinidine

disopyramide

procainamide

they block the sodium and potassium channels (type III action)

Question 2

What are the effects of IA on the heart?

Answer 2

it reduces excitablity, automaticity, and prolongs refractoriness

Question 3

What is the effect of electrocardiogram on quinidine, disopyramide, and procainamide?

Answer 3

• prolongs QT interval (potassium channel blocking)
• modest increase in QRS duration(sodium channel blockade or intermediate recovery time constant)
• QT prolongation—-> increase after-depolarization @ low heart rate if hypokalemia is present

Question 4

What are the clinical uses of quinidine, disopyramide, and procainamide?

Answer 4

1. maintain sinus rhthym in patients with atrial flutter or fibrillation
2. prevent ventricular tachycardia and ventricular fibrillation
3. convert atrial fibrillation—-> sinus rhythm w/ digoxin