Effect of isradipine on left ventricular relaxation and diastolic filling

The effect of two calcium antagonists on left ventricular (LV) relaxation and diastolic filling was evaluated in 16 randomized patients. Isradipine and nifedipine were administered intravenously in a maximum dose of 60 micrograms/min for isradipine and 63 micrograms/min for nifedipine. Heart rate was increased significantly (p less than 0.01) by both study agents. LV end-diastolic pressure remained unchanged whereas peak systolic pressure decreased significantly (p less than 0.01). The reduction in systolic pressure was significantly greater (p less than 0.05) after isradipine (delta P of 30 mm Hg) than after nifedipine (delta P of 13 mm Hg). The time constant decreased from 65 to 56 ms (p less than 0.05) after isradipine and from 62 to 59 ms (NS) after nifedipine. LV filling remained unchanged. It is concluded that both calcium antagonists are associated with a significant reduction in LV afterload accompanied by a reflex increase in heart rate. Isradipine is a more potent vasodilator than nifedipine at the same infusion rate. A beneficial effect on LV relaxation with isradipine, but not nifedipine, may be due to its less pronounced negative inotropic effect or its more potent afterload-reducing action.