Recurrent Torsades de Pointes Precipitated by Berberine Supplement.

BACKGROUND: Acquired long QT syndrome and torsades de pointes (TdP) can be triggered by dietary supplements, which do not go through strict safety testing. CASE SUMMARY: A 61-year-old man had syncope and recurrent TdP (QTc 669 ms), with an initial electrocardiogram phenotype indistinguishable from congenital LQT2. He was taking several over-the-counter supplements including berberine, dihydroberberine, turmeric, and quercetin and had mild hypomagnesemia. Genetic testing for congenital long QT syndrome was negative. Management included defibrillation, intravenous magnesium, supplement discontinuation, nadolol, and a wearable cardioverter-defibrillator. The QT interval normalized, and nadolol was later discontinued without arrhythmia recurrence. DISCUSSION: This case illustrates a "multihit" model, in which supplement-mediated cardiac channel blockade, drug interactions increasing supplement exposure, and hypomagnesemia converged to provoke life-threatening arrhythmia. TAKE-HOME MESSAGES: Common supplements like berberine can cause TdP through multiple proarrhythmic mechanisms. Thorough evaluation for extrinsic triggers is essential, even when the electrocardiographic phenotype suggests a genetic disorder.