Beta-adrenergic blockade effects on aerobic capacity and chronotropic response

Abstract

Cardio-pulmonary exercise testing (CPET) and beta-blockers are frequently prescribed in thoracic pre-surgery and pulmonary rehabilitation. However, the effects of these drugs on aerobic capacity (VO2max) and cardio-vascular variables are still under-understood, possibly leading to incomplete CPET interpretation. Twenty-one young healthy adults repeated three cyclo-ergometer CPET one week apart. CPET were performed 2h after a random, double blind, cross over single dose intake of 2.5 mg or 5 mg of a cardio-selective β-blocker (bisoprolol) or placebo. Gaz exchange, heart rate (HR), blood pressure (BP) were measured and oxygen pulse were calculated as VO2/HR. CPET maximal performance remained unaffected by any treatment, with a maximal respiratory exchange ratio above 1.15 in all tests and identical maximal workload or VO2. Dose-dependent effects of beta-blockers were observable on resting and maximal HR and BP associated with decreased chronotropic response, assessed by the HR/VO2 slope. * Placebo vs both other groups, $ inter B-blocker groups. *:p<0,05; **:p<0,01; ***:p<0,001; VE:ventilation; VCO2:carbon dioxide The present results suggest that a single dose of beta-blockers unaffects exercise ventilation and aerobic capacity with higher O2 Pulse compensating lower HR in healthy subjects.  A lower chronotropic response or HR/VO2 slope should be taken into account during CPET interpretation.