A subset of patients with angina pectoris despite angiographically normal coronary arteries have limited coronary flow reserve as a consequence of dysfunctional small coronary arteries, a syndrome we have called microvascular angina (MVA). Although calcium channel blockers are useful therapy in the majority of MVA patients, approximately 1/3 continue to have angina. Eighteen MVA patients symptomatic despite trials of commercially available calcium channel blockers participated in a drug trial using a new dihydropyridine derivative, nicardipine. Compared to baseline study off all medications, MVA patients demonstrated approximately one minute improvement in exercise duration and two minute prolongation of time to onset of angina during treadmill exercise testing using the Bruce protocol on nicardipine 30 mg three times daily for three weeks, without any change in myocardial oxygen consumption at peak exercise or peak expiratory flow rate. Sixteen patients subsequently participated in a randomized, double blind study of nicardipine 30 mg three times daily and identical appearing placebo, each for one month. Two patients developed generalized macular rashes on nicardipine and were withdrawn from this phase of the study. The remaining fourteen patients demonstrated no significant differences in treadmill exercise duration and myocardial oxygen consumption or symptom end-point between nicardipine and placebo phases. Thus nicardipine was of demonstrable benefit to only a minority of MVA patients who were symptomatic failures on conventional calcium channel blockers.
