Plasma renin in congestive heart failure in man

Vasodilator therapy for acute myocardial infarction and chronic congestive heart failure

Vasodilator therapy is useful adjunctive therapy in the management of both acute and chronic heart failure. Arteriolar dilators, such as hydralazine, increase cardiac output by decreasing the elevated peripheral vascular resistance that occurs in heart failure. Venodilators, such as nitrates, decrease ventricular filling pressures by redistributing blood so that more is pooled in peripheral veins. Vasodilators that produce both effects (nitro-prusside, prazosin, captopril, for example) are usually helpful in short-term improvement of hemodynamics. Long-term treatment with nonparenteral vasodilators often reduces symptoms and increases exercise tolerance, although there is inconclusive evidence regarding the effects of these agents on mortality. In acute myocardial infarction, intravenous vasodilators frequently improve cardiac performance. Evidence regarding their beneficial effects on infarct size and immediate mortality is encouraging but inconclusive. There is little evidence that they prolong life in patients who survive cardiogenic shock and leave the hospital. Thus, vasodilators can improve hemodynamics and lessen symptoms, but more evidence is needed regarding their long-term effects on survival.

Vasodilator therapy of severe congestive heart failure: the special importance of angiotensin-converting enzyme inhibition with captopril

Successful ambulatory afterload reduction therapy of severe chronic congestive heart failure (CHF) required the extensive evaluation of hemodynamic effects of vasodilator agents, precise characterization of differential cardiocirculatory actions, and objective confirmation of extended salutary improvements of the heart failure state. This article describes results of a series of investigations with the angiotensin-converting enzyme (ACE) inhibitor captopril (CPT) in several patients with severe CHF. CPT causes predominant peripheral venodilation, resulting in marked decline in elevated left ventricular preload and modest augmentation of the depressed cardiac output. These hemodymanic effects of oral CPT are similar to the effects of nitroprusside and prazosin on increased ventricular preload, but the latter vasodilators cause greater rise in low cardiac pump output. Importantly, the beneficial cardiocirculatory action of oral CPT provided prolonged cardiac benefits with symptomatic improvements confirmed by objective enhancement in left ventricular function documented by cardiac catheterization, echocardiography, nuclear scintigraphy, and treadmill exercise. Thus, ACE inhibition with oral CPT successfully provides marked long-term augmentation of cardiac performance and clinical status in refractory CHF.

Hemodynamic effects of captropril in chronic heart failure: efficacy of low-dose treatment and comparison with prazosin

The acute hemodynamic effects and long-term therapeutic actions of low doses of the oral angiotensin-converting enzyme (ACE) inhibitor captopril (CPT) were evaluated in 18 patients with severe chronic congestive heart failure (CHF). Increasing doses of 1, 2.5, 6.25, 12.5, and 25 mg of CPT were given at 2-hour intervals. Increased stroke volume index (SVI) and reduced mean pulmonary capillary wedge (PCW) pressure occurred at 1 hour (p less than 0.05) with an associated decline of blood pressure. Maximal hemodynamic improvement for the group was seen at 6 and 7 hours following the 6.25 and 12.5 mg doses when SVI was elevated 35% and mean PCW pressure decreased 40% from control. CPT in doses of 12.5 to 50 mg every 8 hours was continued long term in these 18 CHF patients. Four patients died, and one was noncompliant; drug therapy was withdrawn in two patients with symptomatic hypertension and in one patient who experienced an alteration in taste. The remaining 10 patients showed significant improvement in symptoms and treadmill exercise duration at 3 months after CPT therapy was started. Moreover, repeat hemodynamic measurements were similar to optimal measurements obtained during the initial study. In a further study, the acute hemodynamic and hormonal effect of sequentially randomized 5 mg prazosin and 25 mg CPT were compared in 10 CHF patients. While both drugs reduced PCW pressure and vascular resistance, CPT effects were greater. Further, CPT alone effected a small rise in cardiac index and minor decline in heart rate, and CPT diminished aldosterone levels and increased plasma renin activity while prazosin did not.

Prazosin and captopril in chronic heart failure: comparison of acute haemodynamic and hormonal effects

Ten patients with severe chronic heart failure were given prazosin 5 mg and captopril 25 mg in random order on consecutive days. Small increases in cardiac index and reductions in heart rate were effected by both drugs, but these alterations and the accompanying increases in stroke volume index were significant only following captopril. Both drugs significantly reduced mean pulmonary capillary wedge pressure and mean right atrial pressure and also systemic vascular resistance and blood pressure, the effect of captopril being greater than that of prazosin. Following captopril, plasma aldosterone levels were significantly reduced and plasma renin activity increased from control values, whereas prazosin did not alter these hormone indices.

Angiotensin-converting enzyme inhibition in congestive heart failure: the concept

Plasma renin activity frequently is increased in patients with congestive heart failure. This increase in inversely related to serum sodium concentration, but is not correlated with hemodynamic measurements. Nonetheless, inhibition of converting enzyme activity by administration of teprotide or captopril results in a decrease in systemic vascular resistance that is directly related to the control plasma renin activity. These data suggest that angiotensin II contributes to the systemic vasoconstriction of heart failure and that chronic inhibition of the renin-angiotensin system may have a salutary effect on left ventricular performance in patients with heart failure.

Clinical and haemodynamic effects of low dose captopril in severe chronic heart failure

1 The clinical and haemodynamic effects of low doses of the oral converting-enzyme inhibitor captopril were studied in 18 patients with severe chronic heart failure. Increasing doses of 1 mg, 2.5 mg, 6.25 mg, 12.5 mg, and 25 mg captopril were given at two hour intervals with haemodynamic monitoring. Graded haemodynamic improvement (increased stroke volume index and reduced mean pulmonary capillary wedge pressure) occurred from one hour with reduction of blood pressure closely associated. 2 Maximal haemodynamic improvement for the group was seen at six and seven hours after the 6.25 mg and 12.5 mg doses, when stroke volume index was increased by 35% and mean pulmonary capillary wedge pressure reduced by 40% from control. Captopril 12.5 mg-50 mg eight hourly was continued long-term but withdrawn in two patients with symptomatic hypotension and one patient with altered taste. 3 Four patients died and one was non-compliant with therapy. At three months 10 patients showed significant improvement in symptoms, treadmill exercise duration, and echocardiographic indices of left ventricular size and function. The results of repeat haemodynamic measurements were similar to optimal measurements obtained during the initial study. 4 At two years six patients remained alive, five having maintained their symptomatic improvement. Thus small doses of captopril produce haemodynamic improvement in heart failure with a closely associated reduction of blood pressure. Symptomatic and haemodynamic benefit is maintained with long-term treatment.

Efficacy of oral angiotensin-converting enzyme inhibition with captopril therapy in severe chronic normotensive congestive heart failure

To evaluate the therapeutic efficacy of oral angiotensin-converting inhibition (ACE) with captopril in chronic normotensive congestive heart failure (CHF), acute and cardiocirculatory actions were determined by cardiac catheterization and forearm plethysmography, and ambulatory effects were assessed by echocardiography, nuclear angiography, treadmill exercise, and clinical symptomatology in 10 severe CHF patients. Captopril (90 mg) produced marked (peak 1 hour) and sustained (5 hours) left ventricular filling pressure (23 to 15 mm Hg), systemic vascular resistance decreases, and cardiac index increase (1.99 to 2.41 L/min/m2), while mean blood pressure declined mildly (87 to 80 mm Hg) without heart rate change. Both forearm venous tone and vascular resistance decreased considerably. After 1 week of ambulatory therapy (90 mg three times daily), nuclear angiographic ejection and echocardiogram shortening fractions increased, and exercise duration (341 to 453 sec) and New York Heart Association functional class (3.6 to 2.2) improved. Thus ACE-induced vasodilation by oral captopril improved cardiac performance and clinical status in refractory CHF.

Low-dose captopril in chronic heart failure: acute haemodynamic effects and long-term treatment

The acute haemodynamic effects of low doses of the oral converting-enzyme inhibitor, captopril, were studied in 18 patients with severe chronic heart failure. The effects of long-term therapy were also evaluated. Increasing doses (1 mg, 2.5 mg, 6.25 mg, 12.5 mg, and 25 mg) of captopril were given at 2 h intervals with haemodynamic monitoring. Graded haemodynamic improvement (increased stroke-volume index and reduced mean pulmonary capillary wedge pressure) was noted from 1 hand was closely associated with reduction of blood pressure. Maximal haemodynamic improvement for the group was seen at 6 h and 7 h after the 6.25 mg and 12.5 mg doses, when stroke-volume index had risen 35% and mean pulmonary capillary wedge pressure had fallen 40% from control. Captopril 12.5-50 mg every 8 h was continued long term but was withdrawn in 2 patients with symptomatic hypotension and 1 patient with altered taste. 4 patients died and 1 was noncompliant with therapy. At 3 months, 10 patients showed significant improvement in symptoms, treadmill-exercise duration, and echocardiographic indices of left-ventricular size and function. Repeat haemodynamic measurements were similar to optimum measurements obtained during the initial study.

Treatment of chronic congestive heart failure with captopril, an oral inhibitor of angiotensin-converting enzyme

The renin-angiotensin system is thought to maintain elevated systemic vascular resistance in heart failure. The hemodynamic effects of captopril (SQ 14225), an oral inhibitor of angiotensin-converting enzyme, were measured in 10 patients with stable congestive heart failure poorly controlled by digitalis and diuretics. At single daily doses of 25 to 150 mg, the cardiac index rose from 1.75 +/- 0.18 to 2.27 +/- 0.39 (mean +/- S.D.) liters per minute per square meter (P less than 0.001), and pulmonary-wedge pressure fell from 26.5 +/- 7.5 to 17.3 +/- 6.1 mm Hg (P less than 0.01). Systemic vascular resistance decreased from 2006 +/- 300 to 1393 +/- 238 dyne seconds per centimeter (P less than 0.001), and mean arterial pressure fell from 83.7 +/- 7.0 to 70.3 +/- 9.9 mm Hg (P less than 0.001) (mean +/- S.D.). Heart rate did not change appreciably. Hemodynamic alterations peaked at 90 minutes and persisted for three to four hours. Control plasma renin activity ranged from 1.1 to 7.3 ng per milliliter per hour and did not correlate with changes in hemodynamic values. Three patients on long-term treatment maintained clinical improvement. Although its mechanism of action has not been completely elucidated, captopril may prove useful in the treatment of chronic congestive heart failure.

Role of the renin-angiotensin system in the systemic vasoconstriction of chronic congestive heart failure

In 15 patients with severe chronic left ventricular failure, plasma renin activity (PRA) ranged widely, from 0.2--39 ng/ml/hr. The level of PRA was unrelated to cardiac output (CO) or pulmonary artery wedge pressure (PWP), but was slightly negatively correlated with mean arterial pressure (MAP) (r = -0.45) and systemic vascular resistance (SVR) (r = -0.40). After infusion of the angiotensin converting enzyme inhibitor teprotide (SQ 20,881) PWP fell from 26.3 +/- 1.3 (SEM) to 20.3 +/- 1.4 mm Hg (P less than 0.001), CO rose from 3.94 +/- 0.23 to 4.75 +/- 0.31 l/min (P less than 0.001), MAP fell from 87.5 +/- 3.8 to 77.9 +/- 4.1 mm Hg (P less than 0.001) and SVR from 1619 +/- 148 to 1252 +/- 137 dyne-sec-cm-5 (P less than 0.001). The fall in MAP and in SVR was significantly correlated with control PRA (r = 0.68 and r = 0.58, respectively). When subjects were divided on the basis of control PRA the hemodynamic response to teprotide was greatest in the high renin group. PRA rose after teprotide (8.7 +/- 3.4 to 37.9 +/- 7.7 ng/ml/hr, P less than 0.05) but plasma norepinephrine fell (619.1 +/- 103.6 to 449.7 +/- 75.7, P less than 0.05). The renin-angiotensin system thus appears to have an important role in the elevated SVR in some patients with heart failure. Chronic inhibition of converting enzyme should be explored as a possible therapeutic approach.

Angiotensin converting enzyme inhibition in patients with congestive heart failure

The etiology of afterload elevation in congestive cardiac failure is unclear, but experimental evidence suggests a role for the renin-angiotensin system in maintaining elevated peripheral vascular resistance. The angiotensin converting enzyme inhibitor SQ20,881 was administered to eight patients with congestive cardiac failure (four hypertensives, four normotensives) during or one day after diagnostic cardiac catheterization. Various hemodynamic measurements performed before and during blockade indicate that this agent caused improvement in cardiac function in all patients by decreasing afterload. This improvement correlated with the decrease in total vascular resistance but was independent of the baseline blood pressure and plasma renin activity. These results suggest that inhibition of angiotensin converting enzyme is a worthwhile approach to the treatment of congestive heart failure, although its exact mechanism of action remains unclear.