Effectiveness of converting enzyme inhibition (enalapril) for mild congestive heart failure

The present study investigates the effectiveness of converting enzyme inhibition (CEI) on cardiac performance of patients with congestive heart failure (New York Heart Association functional class II). Outpatients (n = 12) were treated with enalapril, 5 to 10 mg twice daily, in addition to stable doses of digitalis and diuretic drugs. Before and after 4 and 12 weeks of treatment a treadmill exercise test and echocardiography were performed. Maximal oxygen uptake and exercise tolerance increased significantly and mean arterial pressure at rest and on exertion decreased significantly. Heart rate did not change. Left ventricular end-diastolic diameter decreased significantly. Serum angiotensin converting enzyme activity was reduced to nearly 0; plasma renin concentration, which was already elevated, increased further. Plasma norepinephrine levels did not change significantly. Treatment was tolerated well by all patients. CEI decreased preload and afterload, suggesting that they might have had an inappropriately elevated arteriolar and venous tone owing to a moderately stimulated renin angiotensin system and sympathetic nervous system. These conditions may lead to further deterioration of cardiac performance. By means of CEI one may be able to interrupt these pathogenetic mechanisms, relieving the already damaged heart from inappropriate elevations of preload and afterload and delaying or even preventing further deterioration of cardiac performance.