When Rhythm Control Backfires: A Case of Severe QT Prolongation and Polymorphic Ventricular Tachycardia Following Dual Antiarrhythmic Therapy.

Class III antiarrhythmic agents are widely used for rhythm control in atrial fibrillation, but their proarrhythmic potential, particularly when combined, poses significant clinical risk. We report a case of life-threatening QT prolongation and polymorphic ventricular tachycardia resulting from concurrent sotalol and amiodarone therapy without appropriate washout.  An 88-year-old female patient on chronic sotalol therapy (80 mg twice daily) presented with atrial fibrillation with rapid ventricular response. Intravenous amiodarone was administered without sotalol washout, resulting in severe QT prolongation (QTc 626 ms), deep T-wave inversions, and non-sustained ventricular tachycardia (NSVT). The patient was successfully managed with overdrive pacing, increasing the heart rate from 60 to 80 beats per minute, which suppressed the ventricular arrhythmias and prevented progression to torsades de pointes. This case underscores the critical importance of recognizing drug-drug interactions between class III antiarrhythmic agents and the necessity of appropriate washout periods. Overdrive pacing remains an effective temporizing measure for drug-induced torsades de pointes. Clinicians must be highly cautious while using multiple QT-prolonging agents, particularly in elderly patients with multiple comorbidities.