Beta-Blocker and Exercise Capacity

Dear Editor-in-Chief With great interest, we read the paper published by Beloka et al (1) about the effects of β-adrenergic blockade on exercise capacity and gas exchange variables. The paper addresses the important issue of how to handle these medications in the interpretation of exercise responses. In a crossover design, a β-blocker intake did result in significantly reduced exercise capacity as assessed by peak oxygen uptake (V˙O2) and V˙O2 at anaerobic threshold (AT) as well as parameters generally accepted to describe ventilatory efficiency [ventilation (V˙E)/V˙O2 and V˙E/carbon dioxide output (V˙CO2)]. This is in line with results derived by others (2,5). However, results obtained after acute administration of β-blockers in 14 young healthy adults should not lead to conclusions derived for the interpretation of exercise capacity and parameters of ventilatory efficiency in general populations. Our own data compiled within the Study of Health in Northern Pomerania, a large-scale population based cohort study in the northeast of Germany, might shed further light on this issue. In this study, 1708 volunteers-21.4% on cardio-selective β-blockers-[874 females: mean body mass index (BMI) 27.3 ± 5.1 kg·m−2, 43% smokers; 834 males: mean BMI 28.1 ± 4.1 kg·m−2, 70.3% smokers] aged 25-85 yr (mean 52.0 ± 13.6 yr) underwent cardiopulmonary exercise testing according to a modified Jones protocol on a bicycle. The study details have been published elsewhere (3). Subjects with known cardiopulmonary, cardiovascular (except arterial hypertension), muscular, neurological, or endocrine diseases, evidence of lung function abnormalities assessed by spirometry, bodyplethysmography, and diffusing capacity, evidence of echocardiographic abnormalities, or any medication (except cardioselective β-blockers) were excluded-comprising a final study population of 1076 healthy volunteers with 5% being on β-blocker medication. Analysis of variance adjusted to gender, age and weight was performed in order to evaluate the influence of specific interfering factors on V˙O2peak, V˙O2AT, and V˙E/V˙CO2 slope: cardio-selective β-blocker, smoking habits, arterial hypertension, and BMI. Analysis of variance was performed on both the absolute values of V˙O2peak and V˙O2AT (mL·min−1) and the body weight-corrected results (mL·min−1·kg−1). According to smoking habits, a significant difference was proved between the current and the former smokers as well as the nonsmokers (P = 0.003 for V˙O2peak). Obesity (cutoff BMI, 30 kg·m−2) revealed a significant influence on all selected parameters (P = 0.002 for V˙O2peak). Arterial hypertension did not influence exercise capacity and ventilatory efficiency. Finally, the use of β-blockers did not correlate with any of the variables describing oxygen uptake or ventilatory efficiency (P = 0.525 for V˙O2peak). Even after exclusion of obese and active smoking volunteers [comprising a study sample of 534 (281 female) subjects], again the analysis of variance did not show any influence of cardioselective β-blocker medication on exercise capacity and ventilatory efficiency as compared with subjects without any medication (P = 0.407 for V˙O2peak). In conclusion, in healthy volunteers, chronic cardioselective β-blocker medication did not show a significant interference with exercise capacity and ventilatory efficiency. From our understanding, the effects described by Beloka et al. cannot be extrapolated to the interpretation of exercise capacity and ventilatory efficiency in a general population with chronic β-blocker intake. Sven Gläser Christoph Schäper Ralf Ewert Beate Koch Department of Internal Medicine B Division of Pulmonary Medicine and Infectious Diseases Ernst-Moritz-Arndt University Greifswald Greifswald, Germany Henry Völzke Institute for Community Medicine SHIP/Clinical-Epidemiological Research Ernst-Moritz-Arndt University Greifswald Greifswald, Germany Christian F. Opitz Department of Cardiology DRK-Kliniken Berlin/Koepenick Berlin, Germany