Effects of metoprolol on rest and exercise cardiac function and plasma catecholamines in chronic congestive heart failure secondary to ischemic or idiopathic cardiomyopathy

Abstract

To define the effects of 2 months of metoprolol therapy on cardiac function, aerobic performance and sympathetic nervous system activity, metoprolol (75 to 100 mg/day) was administered to 10 patients with chronic congestive heart failure (CHF). Metoprolol was discontinued in 2 patients because of worsening CHF. In the remaining 8 patients, peak oxygen uptake increased significantly (14.8 ± 3.0 to 16.1 ± 2.5 ml/kg/min, p < 0.05) as did the oxygen pulse (9.0 ± 2.2 to 12.6 ±1.8 ml/beat, p < 0.02). Resting heart rate (87 ± 18 to 62 ± 9 beats/min, p < 0.05) and peak exercise heart rate (133 ± 13 to 105 ± 30 beats/min, p < 0.02) were both reduced. Mean resting ejection fraction increased from 0.15 ± 0.06 to 0.25 ± 0.11 and peak exercise ejection fraction also tended to increase (0.19 ± 0.11 to 0.28 ± 0.15, difference not significant). Both resting plasma norepinephrine (613 ± 706 to 303 ± 142 pg/ml, p < 0.05) and epinephrine (71 ± 50 to 40 ± 21 pg/ml, p < 0.05) were reduced. Circulating lymphocyte β-adrenergic receptor number was unchanged (1,334 ± 292 to 1,344 ± 456 receptors/cell, difference not significant). It is concluded that metoprolol therapy is associated with improvements in rest and exercise ventricular performance and maximal aerobic capacity. These improvements are associated with a decline in resting sympathetic nervous system activity.