RESUMO
The aim of this study was to investigate the haemodynamics of the beta 1-selective beta-blocker bisoprolol at plasma concentrations that would be expected to block completely the cardiac beta-receptors. Seven patients with stable exercise-dependent angina pectoris received 40 mg bisoprolol, and six patients received 10 mg bisoprolol orally as a single dose. Before and 1.5 h after administration, the following parameters were measured at rest and during physical exercise within the framework of an invasive diagnostic investigation: cardiac output, blood pressure in the systemic and pulmonary circulation, heart rate, and ST-segment change. Further haemodynamic factors were derived from these parameters. Before beta-blockade, the change from rest to exercise resulted in an increase in heart rate, blood pressure, and cardiac index, and also in an increase in pulmonary capillary wedge pressure as an indication of ischaemically induced left-ventricular dysfunction. After 40 mg bisoprolol, under exercise conditions, the cardiac index decreased as a consequence of reduced heart rate, and the mean pulmonary capillary wedge pressure increased slightly, compared with baseline. This finding was attributable to clearer changes in three patients; however, as an overall result, an improvement of oxygen consumption also was achieved in these patients. Measured by reduction in cardiac index, no appreciable increase in effect was achieved at bisoprolol plasma concentrations greater than 60 ng/ml. In angina pectoris patients, bisoprolol possesses the typical haemodynamic profile of a beta-adrenoceptor antagonist. There was no indication of a beta-blockade-independent negative inotropic effect of bisoprolol. Forty mg bisoprolol was shown to be an unnecessarily high dose. It may be deduced that the therapeutic dose range of bisoprolol is between 5 and 20 mg.
