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To the Editor: Dr McBride and colleagues¹ found that a dietary supplement containing ephedra significantly prolonged the QT interval. The authors reported, though, that none of the participants who received ephedra was found to have a corrected QT (QTc) interval greater than 500 milliseconds, a point beyond which drug-induced torsade de pointes frequently occurs.² This is not surprising given the small number of participants in their study and the absence of structural heart disease among them.

It is more surprising, however, that the supplement resulted in a 23-millisecond increase in QTc relative to placebo. The mean (SD) QT dispersion in the group receiving the supplement was 60.7 (27.6) milliseconds. To put this in perspective, amiodarone has been reported to result in a similar increase of 25-milliseconds in QTc in patients with a history of ventricular arrhythmia.³ In a large series of patients with myocardial infarction,⁴ a population at high risk . . . [Full Text of this Article]

Mori J. Krantz, MD
Mkrantz{at}dhha.org
Cardiology Division
University of Colorado
Denver

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