JACC Case Rep. 2026 Sep 2:110193. doi: 10.1016/j.jaccas.2026.110193. Online ahead of print.
ABSTRACT
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.
PMID:42684237 | DOI:10.1016/j.jaccas.2026.110193