Effect of Beta-Blockade on Heart Rate and VO2 Kinetics during Recovery in Patients with Coronary Artery Disease

Abstract

Background: Recently, there has been heightened interest in the functional and prognostic applications of VO₂ and heart rate kinetics during the early recovery phase from exercise in patients with cardiovascular disease. However, the effect of beta-blockade on these responses is unknown. The purpose of this study was to evaluate the effects of beta-blockade on VO₂ and heart rate kinetics during recovery from exercise in patients with coronary artery disease (CAD), and compare these responses to those of normal individuals and patients with chronic heart failure (CHF). Methods: A cardiopulmonary exercise test using a ramp protocol was performed in 18 healthy subjects, 18 patients with CAD not taking a beta-blocker, 19 patients with CAD taking a cardioselective beta-blocker (metoprolol), 19 patients with mild or moderate CHF, and 19 patients with moderately severe CHF. The kinetics of oxygen uptake and heart rate were calculated and expressed as a single exponential relation between heart rate or VO₂ and time during the first 3 min of recovery. Results: No differences in time of recovery of VO₂ were found between normal subjects and CAD patients, whether or not they were taking a beta-blocker; VO₂ in recovery was slowed only among patients with moderately severe CHF. The slope of the decline in heart rate during recovery was steeper in patients with CAD taking a beta-blocker compared with the other groups (p < 0.05). Conclusion: In patients with CAD, cardioselective beta-blockade causes a faster decline in heart rate during the early recovery period without any effect on VO₂ recovery kinetics. The effect of beta-blockade should be accounted for when considering the prognostic utility of heart rate recovery.