1. Propranolol, when used for treating arterial hypertension, may influence determinants of both cardiac and vascular function; the consequent changes in cardiac performance may result from the interaction of different and possibly opposite effects.
2. Cardiac function was investigated in fifty-four primary hypertensive men in the pretreatment state and after 3 weeks of propranolol therapy at a daily dose of 320 mg.
3. β-Receptor blockade caused depression of pre-injection left ventricular function, which was unrelated to the direction and the extent of changes in peripheral circulation.
4. The ejection left ventricular function could be either depressed or improved depending on the direction to which treatment shifted the vascular resistance, and consequently, the impedance to left ventricular ejection.
5. Withdrawal of the adrenergic support is probably the major factor responsible for the poor ventricular adaptation to an augmented impedance.