The effects of nisoldipine alone and in combination with beta-adrenoceptor blockade on systemic haemodynamics and myocardial performance in conscious pigs

The peak effects of 10 mg nisoldipine p.o. with or without 80 mg propranolol p.o. on systemic and regional haemodynamics in conscious pigs were investigated. Nisoldipine increased heart rate (70%), cardiac output (67%) and maxLVdP/dt (75%), but decreased mean arterial pressure (21%) as systemic vascular conductance increased by 120%. Left ventricular systolic and end-diastolic pressures were not affected. Vasodilatation occurred in most organs. The increase in left ventricular blood flow (150%) favoured the epicardial (195%) over the endocardial (110%) layers. As a result the endo-epi blood flow ratio decreased by 30%. When nisoldipine was administered simultaneously with propranolol, heart rate (29%), cardiac output (35%) and systemic vascular conductance (65%) increased, but maxLVdP/dt did not change. Mean arterial (18%) and left ventricular systolic (10%) pressure decreased; left ventricular end-diastolic pressure was again unaffected. In most organs vasodilatation was attenuated, but still present, compared to the changes after nisoldipine alone. The increase in epicardial blood flow (70%) again exceeded that in endocardial blood flow (35%), however, the endo-epi ratio decreased by only 15%. In the presence of propranolol, nisoldipine did not exert a negative inotropic action while the reflex-tachycardia was attenuated. In addition, no detrimental effects on perfusion of regional vascular beds were observed.