Oral verapamil and calcium infusion in patients with sick sinus syndrome

Electrophysiologic and circulatory effects of a single oral dose of verapamil (120 mg) were evaluated in 8 patients with symptomatic sick sinus syndrome. Ninety min. after verapamil, calcium gluconate (1375 mg) was infused in an attempt to reverse the depressor actions of the drug. Verapamil significantly increased sinus node recovery time (P less than 0.05) and atrioventricular conduction time (P less than 0.01), and decreased both systolic (P less than 0.01) and diastolic blood pressure (P less than 0.05) and spontaneous heart rate (P less than 0.01). Intravenous calcium significantly reversed blood pressure reduction (P less than 0.001) and further lowered heart rate (P less than 0.05) without affecting sinus node recovery time and atrioventricular conduction significantly. There was no significant correlation between plasma verapamil concentrations and any of the cardiovascular parameters. These data confirm that verapamil is principly contraindicated in patients with sinus node dysfunction and demonstrate that the actual calcium dose, although partly reversing blood pressure reduction, cannot reverse the depressant action of the drug on the sinus and atrioventricular node in such patients.