Electrophysiologic and antiarrhythmic actions of bepridil: Comparison with verapamil and ajmaline for atrioventricular reentrant tachycardia

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Bepridil (2 mg/kg intravenously) was given to 20 patients with atrioventricular (AV) reentrant tachycardia and its effects were compared with those of verapamil (0.15 mg/kg intravenously) in 8 patients and ajmaline (0.75 mg/kg intravenously) in 12. After baseline electrophysiologic measurements, the drugs were given during sustained AV reentrant tachycardia (8 patients had dual AV nodal pathways and 12 had an accessory AV pathway). Verapamil terminated AV reentrant tachycardia in 7 patients and bepridil terminated it in 6. In 8 of the patients who received ajmaline, AV reentrant tachycardia was terminated and in 6 of this group bepridil did so. Bepridil was more successful in terminating AV reentrant tachycardia in those with dual AV nodal pathways than in those with an accessory AV pathway. Bepridil slowed sinus rate by 10% (p <0.0001), whereas verapamil did not change it significantly. Both verapamil and bepridil administration prolonged AV nodal conduction (39% and 44%, respectively), lengthened AV nodal effective refractory period (18% and 17% respectively) and increased the Wenckebach cycle length of the AV node (24% and 25%, respectively) to a significant degree (p <0.05). Bepridil also lengthened atrial and ventricular effective refractory periods (p <0.01) and QT interval (p <0.0001) in the group as a whole; in those receiving ajmaline and bepridil only atrial refractoriness was significantly altered (p <0.05). After treatment for 3 to 5 days with oral bepridil, 19 patients underwent repeat study. There was further slowing in sinus rate and prolongation in both atrial effective refractory period and QT interval; the AV Wenckebach cycle length had returned toward the control level, but was still significantly increased (p <0.01). In the 17 cases in whom reinducibility of AV reentry tachycardla was tested, 7 had no inducible arrhythmia, 6 had non-sustained AV reentrant tachycardia and 4 had sustained but slower tachycardia. Thus, bepridil has both AV nodal and myocardial electrophysiologic actions which suggest a useful role in the treatment and prophylaxis of supraventricular arrhythmias.