[The influence of pressure loading upon haemodynamics and myocardial metabolism during beta-adrenoreceptor blockade (author's transl)].

This study compares the effects of a primary increase in afterload (induced by angiotensin) upon haemodynamics, myocardial function and metabolism of anaesthetized, closed chest dogs with (n = 7) and without (n = 7) beta-adrenoreceptor blockade. In both groups cardiac index (-20%) and stroke index (-30 resp. 40%) decreased by afterload increase. Pressure loading and beta-adrenoreceptor blockade were associated with a higher left ventricular enddiastolic pressure (+60%) and a higher heart rate (+35%) than in the control group. The high left ventricular enddiastolic pressure is supposed to be induced by the loss of homoiometric autoregulation. The increase in heart rate is due to the Bainbridge reflex. In the group of dogs with beta-adrenoreceptor blockade the myocardial oxygen consumption rose in proportion more than in the control group. The clinical implications are discussed.