Vasodilator therapy of hypertensive acute left ventricular failure: comparison of captopril-prazosin with hydralazine-isosorbide dinitrate.

A prospective study to evaluate and compare the cardiorespiratory effects and clinical efficacy of the Neurohormonal inhibitors (Captopril 50 mg+prazosin 1 mg only) and direct arteriolar and venular dilators (Intravenous hydralazine 30 mg+oral isosorbide dinitrate 30 mg) used as vasodilator therapy, was undertaken in a randomized, single blind study in 17 Nigerian patients with hypertensive acute left ventricular failure. Both vasodilator regimes separately and significantly reduced the systolic and diastolic blood pressures (P<0.001 ANOVA), heart rate (P<0.001 ANOVA), and the respiratory rate (P<0.05 ANOVA), the double product, but increased the peak expiratory flow rate (P<0.05 ANOVA). However, the neurohormonal antagonists, captopril and prazosin (n=9) caused a statistically significantly greater reduction in heart rate (P<0.05 ANOVA) respiratory rate (P<0.05 ANOVA) and induced a significantly greater increase in the self-paced exercise capacity, 24 h after initiation of treatment, (P<0.02) compared to the hydralazine and isosorbide dinitrate combination (n=8). Five of the nine patients on the neurohormonal antagonist therapy were ambulant at 24 h, compared to none of the eight patients receiving conventional venular and arteriolar dilators hydralazine and isosorbide dinitrate (chi2=5.84 dfi P<0.05). There was a significant inverse correlation between the systolic blood pressure heart rate product, and the distance covered during symptom limited self paced exercise capacity (r=-0.58, P=0.0146 ANOVA). One of eight patients in the hydralazine+isosorbide nitrate combination died, but there was no mortality in the captopril+prazosin group. These findings collectively suggest that captopril+prazosin combination may be a superior vasodilator therapy compared to hydralazine-isosorbide dinitrate, in hypertensive acute pulmonary oedema.