Electrophysiologic effects of oral diltiazem before and after beta blockade

Abstract

Summary:We conducted electrophysiologic (EP) studies and cstirnated the sinus nodc function and atrioventricular ( A V ) conduction in 10 patients with suspected coronary arterial disease (age range 35-55 years) before and during diltiazem therapy (60 mg thrice daily for 5-7 days). The effect of beta blockade (0.1 mg/kg of intravenous propranolol) was evaluated in both EP studies. The mean spontaneous sinus cycle length (SCL) and the AV nodal Wenckebach cycle lengths (AVWB) were significantly higher (p < 0.05) after propranolol alone (9 I3 f 13 1 and 504 197 ms, respectively) compared with baseline values (SCL: 827f 149 ms, AVWB: 439f 173 ms). Diltiazem alone failed to influence the SCL and AVWB significantly. Nonc of the other parameters (sinoatrial conduction time, corrected sinus node recovery time, AH and HV intervals, AV nodal and atrial effective refractory periods) were significantly influenced by propranolol, diltiazem, or the combination. No patient developed AV block, sinus arrest/sinoatrial exit block, or symptomatic sinus brddycardia following beta blockade after diltiazem administration. Oral diltiiizeni therapy alone and after beta blockade does not appear to adversely influence the sinus node function and AV conduction in patients below the age of 55 years. The combination of diltiazem and beta blocker thus appears safe in selected patients with coronary arterial disease.