The impact of Beta Blockade on cardio-respiratory system and symptoms during exercise

Abstract

<b>Background:</b> Beta-blocking drugs(BB) reduce cardiac work and prolong life in patients with cardiovascular dysfunction. VO2= HR x Stroke Volume x a-vO2 difference. <b>Research questions:</b> Do BB reduce the capacity to exercise, maximal power output(MPO), VO2 max, and increase the perceived effort required to cycle and breath during exercise? <b>Methods:</b> Retrospective observational study of 42,771 subjects performing incremental cycle ergometry to capacity. Subjects were divided by BB usage. Baseline and exercise&nbsp; physiological characteristics and perceived exertion were compared. Forward stepwise linear additive regression was performed with MPO as the dependent factor and height, age, sex, muscle strength, HR max, VO2/HR, FEV1 and DLCO as independent contributors. <b>Results:</b> 7,787 were receiving BB compared to 34,984 not receiving BB. MPO was modestly higher in those receiving BB(751 vs 794 kpm/min p&lt;0.0001). HR was reduced by 18.27%(18.15-18.38 95% CI) (p&lt;0.0001) while VO2/HR was increased by 19.5%(19.3-19.7 95% CI). The effort required to cycle and breathe(Borg 0-10) was not significantly increased by BB. Maximum HR was second only to quadriceps strength in contributing to MPO: MPO =-350+9.82*Quads(kg)+5.11*HRmax+73BB (r=0.7981) <b>Interpretation:</b> Increases in O2 pulse minimize the reduction in exercise intolerance associated with BB in practice. BB limit oxygen delivery in those unable to increase their O2 Pulse (SV X HR X a-vO2 diff).