Acute and subacute haemodynamic effects of enalapril. Non-invasive studies of a new converting enzyme inhibitor for antihypertensive treatment.

After a run-in period on placebo, 15 patients with primary hypertension got antihypertensive treatment with enalapril in single therapy during six weeks. Before and four hours after drug administration simultaneous non-invasive recordings of ECG, phonocardiogram and carotid pulse tracing or apexcardiogram or impedance cardiogram were made. After six weeks' therapy the recordings were repeated 12 hours and four hours after dose intake. The results showed enalapril to be a potent antihypertensive agent with considerable effect already four hours after the first dose intake. The blood pressure reduction was explained by a decrease in total peripheral resistance, semiquantitatively measured with impedance cardiography. Cardiac output was significantly higher during long-term treatment than before therapy started, due to a significant increase in stroke volume. Lef ventricular (LV) diastolic function was not altered but a considerable improvement in LV systolic function was achieved as judged from the systolic time intervals. Open questioning regarding side effects indicated good tolerance.