Effect of nifedipine on segmental myocardial function in the anesthetized pig

Intravenous (i.v.) administration of 3 micrograms/kg nifedipine decreased arterial blood pressure (MBP) by 20%, but had only minor effects on cardiac output (CO), coronary blood flow (LAD flow), (LVdP/dt)max and systolic wall thickening (SWT). Intracoronary artery (i.c.) administration decreased MBP (20%) as well as CO and (LVdP/dt)max. This was accompanied by a 100% decrease in SWT, despite a 40% increase in LAD flow. We conclude that after i.v. injection nifedipine has no direct effect on the myocardium and acts mainly by reducing the after-load, while after i.c. injection a direct negative inotropic action is dominant.