Calcium-channel blockers and beta blockers: advantages and disadvantages of combination therapy in chronic stable angina pectoris

Abstract

In electrophysiologic studies we have previously shown that the calcium-channel blockers nifedipine, verapamil, and diltiazem have different actions on the atrioventricular node: nifedipine has no evident effect at a dose of 7.5 micrograms/kg of body weight intravenously, whereas verapamil (0.15 mg/kg) and diltiazem (0.25 mg/kg) both prolong the AH interval significantly and terminate or slow reciprocating atrioventricular tachycardia involving the atrioventricular node alone or in association with an accessory pathway. None of the calcium-channel blockers tested influenced intraventricular conduction, but all increased the sinus rate. Since these properties suggested that it would be safer to combine nifedipine, rather than verapamil and diltiazem, with beta-adrenergic blockers in the treatment of ischemic heart disease, we tested this combination for efficacy and safety. Our previous results have now been reviewed, and they show that according to both subjective and objective criteria, nifedipine adds benefits to the action of propranolol in the management of chronic stable angina pectoris. No adverse effects were seen in our series, and beneficial influences were noted in patients with elevation of blood pressure. Side effects reported by others and said to arise from the interaction between nifedipine and beta blockers are analyzed, and prudence is suggested before the combination, or indeed any negative inotropic agent, is given to patients with impaired left ventricular function. The previous reports cannot be taken to indicate that nifedipine has a greater tendency to produce adverse effects in this combination than does the beta-adrenergic blocker.