Fundamental role of angiotensin-converting enzyme inhibitors in the management of congestive heart failure

Hemodynamic Effects of the Angiotensin-Converting Enzyme Inhibitor, Ramipril, in Patients with Mild to Moderate Aortic Stenosis and Preserved Left Ventricular Function

Background

Angiotensin-converting enzyme (ACE) inhibitor use is presumed to be contraindicated in patients with aortic stenosis (AS). We determined the hemodynamic effects of ACE inhibitors in patients with mild to moderate aortic stenosis (AS) and preserved left ventricular function.

Methods

Thirteen elderly patients (mean [SD] age = 65 [17] years), with mild to moderate AS (aortic jet velocity 2.5–4.0 m/s), normal left ventricular and renal function, and no clinical coronary artery disease, were enrolled in a single-center, open-label trial comparing the hemodynamic effects at baseline and following titration of ramipril to a maximum dose of 7.5 mg twice daily. Patients were identified from echocardiography laboratory logs. Despite a presumed contraindication to ACE inhibitor use in AS patients, 30% (71 of 235) of patients otherwise meeting inclusion or exclusion criteria were excluded owing to current ACE inhibitor use. Patients were monitored with weekly clinic visits, biweekly laboratory tests, and monthly echocardiograms.

Results

There were no significant changes from baseline to week 8 in echocardiographic parameters, including mean (SD) aortic jet velocity [2.9 (0.4) vs 2.9 (0.4) m/s], calculated aortic transvalvular gradient [18 (6) vs 18 (6) mm Hg], or cardiac output [5.5 (1.2) vs 6.0 (2.1) L/min], or significant changes in blood pressure or heart rate. Early discontinuations were for asymptomatic low blood pressure (one patient) or a reversible creatinine increase of 0.3 mg/dL (one patient).

Conclusions

Short-term treatment with up to 7.5 mg twice daily of ramipril was well tolerated in patients with mild to moderate AS and preserved left ventricular function. A surprisingly high proportion of patients with documented AS were already receiving ACE inhibitors.

Relative efficacy of medical therapy and revascularization for improving exercise capacity in patients with chronic left ventricular dysfunction

BACKGROUND

In patients with left ventricular dysfunction one of the aims of therapy may be to improve functional capacity. This study compared the improvement of functional capacity in response to medical therapy with that caused by revascularization.

METHODS

Fifty-two patients with severe left ventricular dysfunction were divided into groups with ischemic cardiomyopathy undergoing revascularization (group A, n = 20) or incremental medical treatment (group B, n = 16) and a control group receiving maximal medical therapy at the start of the study (group C, n = 16). All patients underwent a baseline metabolic exercise test with evaluation of peak oxygen consumption and derived exercise capacity in metabolic equivalents (METS) with standard electrocardiographic and hemodynamic monitoring. Therapy was then optimized in the medical treatment group, whereas the revascularization group underwent coronary bypass grafting. All patients subsequently underwent follow-up metabolic exercise testing.

RESULTS

In groups A, B, and C resting left ventricular ejection fractions were comparable (26%+/-5%, 25%+/-7%, and 23%+/-8%, respectively), as were results of initial metabolic exercise tests (4.7+/-0.9 METS, 4.7+/-1.4 METS, and 5.2+/-1.4 METS). At follow-up group A improved exercise capacity from 4.7 to 5.6 METS (p = 0.01). Groups B (4.7 to 5.0 METS) and C (5.2 to 5.6 METS) had no significant improvement. The mean respiratory exchange ratio improved significantly in group A (1.14 to 1.20, p = 0.02), as did left ventricular ejection fraction (26% to 31%, p = 0.02). However, neither parameter changed significantly in groups B or C.

CONCLUSIONS

In patients with severe left ventricular dysfunction improvements of exercise capacity are more marked after coronary revascularization than may be obtained after maximization of medical therapy.

Comparison of some pharmacokinetic parameters of 5 angiotensin-converting enzyme inhibitors in normal beagles

This study was designed to determine the degree of inhibition of the angiotensin-converting enzyme (ACE) in 5 normal dogs given single doses of conventionally used ACE inhibitors (ACEis). In addition the time required for that inhibition to return to 50% of the difference between maximum and zero (control values) was measured as an estimate of duration of action. The 5 ACEis (with dosages given in parentheses) were benazapril (0.5 mg/kg), captopril (2.0 mg/kg), enalapril (0.5 mg/kg), lisinopril (0.5 mg/kg), and ramipril (0.25 mg/kg). Blood samples for ACE activities were obtained before dosing and at 1.5, 3.0, 6.0, 12.0, and 24.0 hours after dosing. All ACEis except captopril decreased ACE activities to approximately 25% of control by the 1.5- to 3.0-hour sample, and ACE activities returned to 50% of the difference by the 12-hour sample. The value of AVE activity returned to normal by 24 hours for benazapril, whereas values for ACE activity remained below normal for enalapril, lisinopril, and ramipril at 24 hours. For captopril, however, ACE levels decreased to approximately 80% of control by the 1.5-hour recording, and returned to levels not different from control by the 3-hour recording. Based upon this study performed on normal dogs given a single dose, no pharmacokinetic advantage or disadvantage is apparent for any ACEi except captopril, which, at the dosage used, decreased ACE levels to a much lesser degree and shorter time.

Recent advances in the treatment of congestive heart failure

Treatment of heart failure should include correction of the underlying cause. These causes include large left to right shunts, obstructive lesions, arrhythmias, primary myocardial disease etc. The main pharmacological therapy includes inotropic agents, vasodilators and diuretics. Inotropic agents increase myocardial contractility and include digoxin, intravenous dopamine, dobutamine and isoproterenol. Vasodilators improve cardiac pump performance by decreasing the vascular resistance and/or increasing the venous capacitance. Commonly used vasodilator agents include angiotensin converting enzyme inhibitors (captopril, enalapril etc.), hydralazine, prazosin hydrochloride etc. Diuretics inhibit salt and water reabsorption promoting their excretion. Furosemide, thiazide diuretics, aldactone, are commonly used diuretics. Electrolyte and acid-base imbalance can occur on chronic diuretic therapy. Cardiac transplantation is considered for patients where all medical management has failed.