Acute nifedipine withdrawal: consequences of preoperative and late cessation of therapy in patients with prior unstable angina.

Reports of acute ischemic events after withdrawal of calcium antagonist therapy in outpatients and during bypass surgery in patients with prior angina at rest prompted the examination of the effect of nifedipine withdrawal in 81 patients who had completed a prospective, double-blind randomized trial of nifedipine versus placebo for rest angina. Thirty-nine patients underwent bypass surgery for uncontrolled angina or left main coronary artery disease. No significant difference between patients withdrawn from nifedipine or placebo was seen in the incidence of perioperative myocardial infarction, hypotension requiring intraaortic balloon counterpulsation, vasopressor or vasodilator requirements or incidence of significant arrhythmias. An additional 42 patients had completed 2 years on a protocol consisting of nitrates and propranolol in addition to nifedipine or placebo. During a mean of 66 hours of continuous monitoring after withdrawal of nifedipine or placebo, heart rate and blood pressure were unchanged. A worsening of previously present angina at rest occurred in five patients who had continued to experience rest angina before drug withdrawal, four of whom were withdrawn from nifedipine. No patient with class I to III angina experienced new onset of rest angina during drug withdrawal. No patient experienced myocardial infarction. There was no significant difference between patients withdrawn from nifedipine or placebo in the duration or frequency of ischemic ST changes on continuous electrocardiographic monitoring, or in duration or positive results of serial exercise treadmill testing. Thus, no early adverse effects of acute nifedipine withdrawal were found in patients with prior rest angina at the time of bypass surgery or in stable patients receiving long-term medical therapy.(ABSTRACT TRUNCATED AT 250 WORDS)