The effect of slow-release nifedipine on ST-segment depression induced by effort test. Correlations with serum levels.

To study the anti-ischemic effect of slow-release nifedipine ten patients with stable angina pectoris and a positive effort test were selected. Nifedipinemia was measured by a gas chromatographic method. At the peak level of effort intensity slow-release nifedipine significantly decreased the mean ST-segment depression (p < 0.05) and the ischemic score (p < 0.01) when compared to the control effort test, without decreasing the double product. Nifedipine induced no more tachycardia additional to that produced by effort. At the beginning of the effort test the level of nifedipine (15.9 +/- 2.51 ng/ml) was superior to the value considered as minimal effective and was positively correlated with the ischemic score (r = 0.67; p < 0.05). A worsening of ischemia was noted in 2 patients probably due to a steal phenomenon.