Demonstration of training effect during chronic β-adrenergic blockade in patients with coronary artery disease

Abstract

Attenuation of exercise-induced increases in heart rate and cardiac output by chronic β-adrenergic blockade has been thought to compromise benefit of exercise training in patients with coronary artery disease (CAD). To assess this important issue, 35 CAD patients were evaluated by a 3-month walk-jog-cycle training program: 14 patients received no β blocker (group 1), 14 received propranolol, 30-80 mg/day (group 2), and seven patients received propranolol, 120-240 mg/day (group 3). The extent of CAD, resting heart rate before training blood pressue and V̇O2 max were similar (p=NS) in each group. The maximal exercise heart rate (mean ± SD, 147 ± 21 beats/min in group 1 vs 120 ± 10 beats/min in group 2 and 115 ± 12 beats/min in group 3 (both p<0.05 vs group 1). The V̇O2 max before training was 25 ± 5.0 ml/kg/min in group 1 vs 23 ± 3.2 ml/kg/min in group 2 and 26 ± 2.8 ml/kg/min in group 3 (all p = NS). Training consisted of three 1-hour periods per week at a heart rate of 70-85% of the maximal pretraining heart rate. In each group, V̇O2 increased (<0.05) after training: group 1, 27%; group 2, 30%; group 3, 46%. The double product was unchanged after training (p = NS) in each group. These data indicate that substantial effects may be achieved in CAD patients despite therapeutic doses of β blockers and a reduced training HR. Thus, there appears to be no indication to reduce β blockers in CAD patients engaged in cardiac rehabilitation.