Response of the systemic and pulmonary circulation to converting-enzyme inhibition (captopril) at rest and during exercise in hypertensive patients.

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Abstract
Twenty Na-replete patients with hypertension were allocated either to a placebo or to a captopril treatment group. Each patient was investigated in rest-recumbent (RR) and rest-sitting (RS) positions and during an uninterrupted, graded, submaximal exercise test (up to the anaerobic threshold) before treatment, and with a similar protocol 75 min after treatment with captopril or placebo on the same morning. Captopril decreased brachial intraarterial pressure by 7/4 mm Hg at RR, by 16/10 mm Hg at RS and by 19/10 mm Hg during exercise (P < 0.001), based on a decrease of systemic vascular resistance (P < 0.001). Slight increases of cardiac output and of heart rate were noted at rest; cardiac output was not significantly affected during exercise, but the increase of heart rate of 2.4 beats/min was significant (P < 0.01). Captopril decreased pulmonary artery (P < 0.05) and capillary wedge pressures (P < 0.001), with unchanged pulmonary vascular resistance. The action of captopril is characterized by arteriolar and possibly venous dilatation both at rest and during exercise. Pulmonary vascular resistance is not affected.