ECG Cardiac Pharmacology 5

Question 1

Ibutilide is a Class III antiarrhythmic agent used for acute conversion of which arrhythmias?

Accepted Answer

Atrial flutter and atrial fibrillation

Answer

Ibutilide is an IV Class III agent approved for acute pharmacologic cardioversion of recent-onset atrial flutter and atrial fibrillation.

Question 2

A patient receiving quinidine develops syncope with a polymorphic ventricular tachycardia. This syndrome is historically called:

Accepted Answer

Quinidine syncope (torsades de pointes)

Answer

Quinidine syncope is caused by torsades de pointes due to QT prolongation, which is a paradoxical proarrhythmic effect of this Class IA drug.

Question 3

Beta-blocker therapy after myocardial infarction reduces mortality primarily by which mechanism?

Accepted Answer

Reducing sympathetically-driven ventricular arrhythmias and reinfarction

Answer

Post-MI beta-blockers reduce mortality by suppressing catecholamine-induced ventricular arrhythmias, decreasing heart rate and myocardial oxygen demand, and preventing reinfarction.

Question 4

When interpreting ECG effects of hyperkalemia versus cardiac glycoside toxicity, which finding helps differentiate digoxin toxicity?

Accepted Answer

Bidirectional ventricular tachycardia is specific to digoxin toxicity

Answer

Bidirectional ventricular tachycardia — alternating QRS axis — is a highly specific ECG pattern for severe digoxin toxicity and is rarely seen with hyperkalemia.

Question 5

Sotalol has properties of which two Vaughan Williams antiarrhythmic classes?

Accepted Answer

Class II (beta-blocker) and Class III (potassium channel blocker)

Answer

Sotalol is unique in combining beta-adrenergic blockade (Class II) with potassium channel blockade to prolong repolarization (Class III), resulting in QT prolongation.

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ECG Cardiac Pharmacology 5