Altered adaptive responses to training by nonselective beta-adrenergic blockade in coronary artery disease

To examine the alterations in adaptive responses to training by nonselective beta-adrenergic blockade in patients with coronary artery disease (CAD), 26 patients were studied. Thirteen patients, aged 48 +/- 2 years (mean +/- standard error) were treated with beta-adrenergic blocking agents and another 13, aged 55 +/- 2 years, were control subjects. The 2 groups were similar in terms of initial maximal attainable O2 consumption (VO2max): 24 +/- 1 vs 25 +/- 2 ml/kg/min, patients and control subjects, respectively), and intensity (87 +/- 3.0 vs 88 +/- 2% of attainable VO2max), frequency (4 +/- 0.2 vs 4.0 +/- 0.3 days/week), and duration (12 months) of training. Maximal attainable VO2 increased to the same extent (36% vs 35%) in both groups. Heart rate (HR) at rest decreased to a similar extent in both groups (p less than 0.001). During submaximal exercise at the same exercise intensities, HR decreased in both groups, but to a larger extent in the control group than in the beta-blocker group after training. In the later, the reduced HR during submaximal exercise was solely due to training-induced bradycardia at rest. In contrast, the slower HR during submaximal exercise in control subjects after training was attributable to both bradycardia at rest and a smaller increase in HR during submaximal exercise. In both groups, the half-time of HR deceleration after cessation of exercise decreased (p less than 0.005) after training. However, the training-induced decrease in the half-time was significantly larger (p less than 0.025) in control subjects than in patients.(ABSTRACT TRUNCATED AT 250 WORDS)