Influence of nifedipine on left ventricular systolic and diastolic function: Relationships to manifestations of ischemia and congestive failure

In addition to the favorable effects of calcium antagonists on symptoms related to coronary spasm, we recently documented preclusion of ergonovine-induced coronary spasm angiographically in four patients with proved Prinzmetal's angina.To determine whether nifedipine has similar “relaxing” or negative inotropic actions on left ventricular myocardial function, we studied 19 patients with various degrees of left ventricular dysfunction before and after nifedipine (20 mg sublingually) during cardiac catheterization. Left ventricular afterload was reduced, with a significant (13 percent) decline in arterial pressure; left ventricular diastolic pressures were unchanged. Left ventricular ejection function was augmented, with significant increases in ejection fraction (14 percent), mean velocity of circumferential fiber shortening (41 percent), systolic ejection rate (25 percent), and end-systolic $\text{pressure}\text{volume}$ ratio (19 percent). Cardiac index increased significantly by 16 percent. Early diastolic relaxation, diastolic pressure-volume relations and end diastolic stiffness remained unchanged after nifedipine. When patients were categorized (Group I: left ventricular end-diastolic volume ≤ 90 ml/m², end-diastolic pressure ≤ 20 mm Hg; Group II: end-diastolic volume > 90 ml/m², end-diastolic pressure > 20 mm Hg), highly pertinent differences were apparent. Nifedipine significantly reduced left ventricular preload and end-diastolic pressures in Group II but not in Group I patients. Enhancement of left ventricular ejection function in Group II patients was significantly more prominent than that in patients with normal baseline function. Although diastolic properties were insignificantly changed overall, the left ventricular diastolic pressure-volume relation was displaced downward by nifedipine in Group II, but not in Group I patients. Both systemic and pulmonary vascular resistance declined significantly more in Group II patients, whereas cardiac index was increased 25 percent compared with a negligible change in group I patients. These results indicate beneficial effects of nifedipine on myocardial oxygen requirements, particularly in patients with impaired left ventricular function in whom left ventricular preload and afterload were both significantly reduced, cardiac index augmented and the pressure-volume relation shifted downward.To confirm predicted symptomatic benefits in 13 other patients with fixed coronary, disease, incremental atrial pacing to anginal threshold was performed before and 30 minutes after nifedipine (20 mg sublingually). Mean paced heart rate at onset of angina increased 19.3 percent after nifedipine. Concomitantly, aortic pressure decreased significantly by 22.1 percent at the onset of angina; double product was unchanged at the anginal threshold. Thus, although left ventricular afterload was reduced by nifedipine, the anginal threshold was unchanged in terms of myocardial oxygen requirements.In concert, these results indicate that therapeutically effective influences of nifedipine in patients with fixed coronary disease are attributable basically to hemodynamic alterations consequent upon left ventricular afterload reduction. Nevertheless, such effects imply therapeutic benefit, the reduced afterload concomitantly permitting greater exercise-induced tachycardia before the anginal threshold is reached.