Relation of antianginal efficacy of nifedipine to degree of coronary arterial narrowing and to presence of coronary collateral vessels.

Thirty-six patients with chronic stable angina pectoris or with stable and vasospastic components of angina pectoris were classified by coronary arteriographic findings into 4 groups. Patients in group A had a single stenotic coronary artery; patients in groups B, C and D had occluded arteries, but these arteries had been collateralized to varying degrees, and an epicardial coronary steal phenomenon was possible. All patients underwent multiple exercise tests before and after randomized, double-blind, crossover treatment with 20 mg of nifedipine, 20 mg of isosorbide dinitrate, a combination of both, and placebo. Maximal and mean ST-segment depression, occurrence of angina pectoris and heart rate were evaluated. After nifedipine treatment, mean ischemic ST-segment depression was reduced 21% in group A (p less than 0.05), but was not significantly altered in the other groups (group B, 2% decrease; group C, 10% increase; group D, 3% decrease). However, isosorbide dinitrate reduced ST-segment depression significantly in all groups (group A, 29%, p less than 0.001; group B, 18%, p less than 0.01; group C, 19%, p less than 0.05; group D, 33%, p less than 0.05). The combination with nifedipine did not further improve the effect of isosorbide dinitrate. Maximal ST-segment depression and angina pectoris paralleled the changes in mean ST depression during the different medications. Heart rate at rest was not significantly changed after nifedipine treatment in any group, but increased significantly after isosorbide dinitrate treatment in groups B and C (group B, 12%, p less than 0.01; group C, 9%, p less than 0.05); heart rate during exercise did not differ significantly in any group or after any form of medication from placebo.