Exercise Heart Rate During Beta-Blockade

Abstract

This study tried to determine the diurnal exercise heart rate (HR) changes in trained subjects with coronary artery disease who were either chronically medicated with beta-blockers or were nonmedicated control patients. There were 6 patients in the atenolol group, 5 patients in the metoprolol group, and 11 patients in the control group. All subjects undertook symptom-limited maximal exercise tolerance tests (ETT) by cycle ergometry 2 hours after administering medication for exercise prescription and four submaximal cycle ergometer training sessions at 1, 4, 8, and 12 hours after medication administration. HR, systolic blood pressure, diastolic blood pressure, and rate of perceived exertion (RPE) were recorded at rest, 30 watts (W), 60 W, and target training HR work loads. Blood plasma lactate levels were evaluated at target training HR work loads. Data were analyzed by repeated analysis of variance (ANOVA). When significant differences were found, the Neuman-Keuls test was applied to identify at what times differences occurred. Control patients showed no significant diurnal changes for HR, systolic blood pressure, diastolic blood pressure, rate-pressure product (RPP), RPE, or plasma lactate at rest, 30 W, 60 W, or target training HR work load. Patients in the metoprolol group demonstrated significant HR fluctuations at rest, 30 W, and 60 W, whereas differences for patients in the atenolol group occurred at rest and at 30 W only. At target training HR, the work loads varied significantly over time for the atenolol and metoprolol groups, but RPE varied significantly only for the metoprolol group. Blood plasma lactate levels did not fluctuate significantly for either group. Significant diurnal changes in systolic blood pressure were exhibited only by the atenolol group at 30 W and 60 W. Only the metoprolol group cycling at 30 W exhibited significant variations for diastolic blood pressure. Significant RPP changes were found for the atenolol and metoprolol groups at 30 W and 60 W, but not at target training HR. It appeared that both medications provided a similar degree of beta-blockade 1 to 4 hours after medication was administered. However, atenolol provided more attenuation in the cardiovascular response than did metoprolol during later-day stationary cycle exercise (8 to 12 hours after medication administration).