Haemodynamic effects of sustained treatment with prazosin and metoprolol, alone and in combination, in borderline hypertensive heart failure.

The sustained haemodynamic effects of prazosin (20-30 mg) and metoprolol (400-800 mg) alone and combined (half-dose) were evaluated in five patients with hypertension, left ventricular hypertrophy, and radiological cardiac enlargement. Measurements were made at rest and during isometric handgrip exercise. Blood pressure at rest was equally well controlled on each regimen. The heart rate and cardiac output (thermodilution) were reduced by metoprolol, even when combined with prazosin. Systolic ejection time was prolonged by metoprolol, but there were no changes in left ventricular dimensions at rest. During isometric handgrip the pressure increments were similar on each of the three regimens, although absolute diastolic pressure was lower on combined therapy. The arterial pressure increment on prazosin therapy was predominantly due to a rapid rise in heart rate and cardiac output, whereas with metoprolol and combined therapy the major contribution to the response was by peripheral vasoconstriction. Moreover, with the latter regimens there was a rapid rise in pulmonary artery occluded pressure, which did not occur with prazosin therapy. In conclusion, metoprolol alone, or combined with prazosin, caused significant depression of cardiac function, which was apparent only when the patients were subjected to the haemodynamic stress of isometric exercise.