Effects of verapamil on anterior ST segment and ventricular fibrillation cycle length in patients with Brugada syndrome

PurposeThis study examined the effects of verapamil (5-10 mg intravenous) on the cardiac electrical activity of 10 Brugada syndrome (BS) patients having vasospastic angina, atrial fibrillation, and/or hypertension.ResultsVerapamil showed no significant change in the ST-segment elevation. Likewise, there was no significant change in the lengths of QRS complex, HV and corrected QT intervals, or effective refractory period at the right ventricle. The conduction time between right ventricular apex and outflow tract, measured at 400-millisecond pacing, was mildly prolonged by verapamil. At baseline, induced ventricular fibrillation (VF) was terminated by a 200-J shock in all patients. After verapamil, VF was reinduced in 7, was noninducible in 2, and self-terminated in 1 patient. Mean F-F interval was shorter after than before verapamil, and a 360-J shock was required in 2 of the 7 patients.ConclusionIn some BS patients, calcium channel blockade may modify the electrical characteristics of VF.