Digoxin, Converting-Enzyme Inhibition (Quinapril), and the Combination in Patients with Congestive Heart Failure Functional Class II and Sinus Rhythm

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Abstract
In a randomized single-blind cross-over trial, the efficacy of digoxin, angiotensin-converting enzyme (ACE) inhibition by quinapril, and their combination on exercise tolerance, heart size (echocardiography), and neurohumoral systems was investigated in 19 outpatients with congestive heart failure (CHF) New York Heart Association functional class II and sinus rhythm. Baseline therapy consisted of 25 mg hydrochlorothiazide and remained unchanged. After treatment with quinapril, exercise tolerance significantly increased (606 vs. 644 s, 2 p < 0.03) and left ventricular end-diastolic dimension (63 vs. 58 mm, 2p < 0.03), mean arterial blood pressure (MABP, 100 vs. 92 mm Hg, 2p < 0.03) and plasma norepinephrine (NE) levels (378 vs. 323 pg/ml, 2p < 0.03) were significantly reduced. Digoxin increased resting systolic blood pressure (SBP 133 vs. 142 mm Hg, 2p < 0.03). Combined administration of both drugs significantly increased fractional shortening (24 vs. 28%, 2p < 0.03), reflecting the positive inotropic action of digoxin in combination with afterload reduction. However, there was no further increase in exercise tolerance. Our data suggest that early administration of ACE inhibitors may be beneficial in patients with mild CHF and sinus rhythm, although the magnitude of improvement was less substantial than that reported for patients with more severe CHF.