Incidence of drug-induced torsades de pointes with intravenous amiodarone

Abstract

Aim: To define the incidence, presentation, and outcomes of drug-induced Torsades de Pointes (TdP) with intravenous (IV) amiodarone. Methods: From January 2014 to August 2016 a total of 268 patients received IV amiodarone, 142 for ventricular tachycardia, 104 for atrial flutter/fibrillation, and 22 for incessant atrial tachycardia. A uniform dosing of amiodarone to yield 1 gm/day was used in all patients. Results: Four of the 268 patients (M:F 1:3) with mean age of 51.25 + 9.17 years developed pause dependent TdP degenerating to VF, after a mean dose of 690 + 176.63 mg, infused over 12 + 5.88 h. The QTc that was 505 + 9.02 ms at the time of TdP normalized to 433.75 + 6.13 ms 48–72 h after stopping amiodarone. There was no immediate or late mortality, and patients are well at 5–10 months of follow-up. None of the patients tested positive for LQTS genes. Conclusion: The incidence of drug-induced TdP with IV amiodarone is about 1.5%. Risk factors include female sex, left ventricular dysfunction, electrolyte abnormalities, baseline prolonged QTc, concomitant beta-blocker, and digoxin therapy. Amiodarone induced TdP has favorable prognosis if recognized and treated promptly, and these patients should not receive amiodarone by any route in future.

Keywords

• Amiodarone
• Torsades de pointes
• Proarrhythmia
• Acquired LQT