Usefulness of the Valsalva maneuver in management of the long QT syndrome.

Exercise or isoproterenol infusion may evoke ventricular arrhythmias in patients with the long QT syndrome. We examined the electrocardiographic effects of the Valsalva maneuver in eight patients with the long QT syndrome and nine healthy subjects. The Valsalva maneuver lengthened the QTc interval in both groups, but the lengthening was greater in the patients. In the patients who were having frequent attacks of ventricular tachycardia, the Valsalva-induced prolongation of the QTc interval was particularly remarkable and was associated with the development of T-wave alternans and short runs of ventricular tachycardia. Propranolol effectively suppressed the lengthening of the QTc interval during Valsalva strain and prevented Valsalva-induced ventricular arrhythmia. These results suggest that the Valsalva maneuver may be useful in evaluating the risk of ventricular tachyarrhythmias and the efficacy of drug treatment in patients with the long QT syndrome.