The effect of a new calcium antagonist (Ro 11-1781) on the cardiac conduction system in man.

Using His bundle electrograms and atrial pacing the effects of Ro 11-1781, a new calcium antagonist, was studied in 13 patients with normal A--V conduction. Following an intravenous bolus of 2 mg/kg Ro 11-1781 the A--V nodal conduction time (A--H interval) was prolonged in all patients during sinus rhythm, atrial incremental and premature pacing. Wenckebach periods above the bundle of His occurred at lower atrial driving rates following the drug. The functional and effective refractory period of the A--V node were prolonged after the administration of Ro 11-1781. No significant effect of Ro 11-1781 on the remainder of the conduction system was observed. Heart rate and the corrected sinus node recovery time changed variably. The increase of the A--H time in response to Ro 11-1781 was completely reversed by Atropine.