Effects of nicardipine and urapidil on length-dependent regulation of myocardial function in coronary artery surgery patients

Objective: To assess effects of a decrease in left ventricular (LV) afterload (pharmacologically induced by nicardipine and urapidil) on myocardial contraction and relaxation, with emphasis on the effects on load dependence of myocardial function. Design: Prospective, blinded study. Setting: University hospital. Participants: Coronary artery surgery patients. Interventions: Alterations of systolic load were effected by leg elevation in control conditions and after administration of either nicardipine or urapidil before and after cardiopulmonary bypass. Measurements and Main Results: High-fidelity LV pressure tracings were obtained at end-expiration while hearts were paced at a fixed rate of 90 beats/min. Hemodynamic effects of leg elevation were compared before and after nicardipine, 7 mu g/kg (n = 15), and before and after urapidil, 0.4 mg/kg (n = 15). The effects of leg elevation on parameters of contraction and relaxation were coupled. Both nicardipine and urapidil similarly decreased systolic pressures and peripheral resistance. Nicardipine decreased rate of pressure development (dP/dt(max)) and slowed LV pressure fall, whereas load dependence of LV relaxation was not altered. Urapidil did not alter dP/dt(max), rate of LV pressure fall, or load dependence of relaxation. Similar results were observed after cardiopulmonary bypass. Conclusions: The results of the present study indicate that a pharmacologically induced moderate reduction in LV afterload with nicardipine or urapidil did not alter the length-dependent regulation of myocardial function. Copyright (C) 1999 by W.B. Saunders Company.