Maximal functional capacity in subjects with isolated left bundle branch block: A pilot study

BACKGROUND: Left bundle branch block (LBBB) has been commonly associated with adverse cardiovascular (CV) events, but the effect of an isolated LBBB on maximal functional capacity is not well characterized. OBJECTIVE: To evaluate maximal functional capacity in adults with isolated LBBB and compare it to healthy population‐derived predicted values (adjusted for sex, age, weight, and height). METHODS: This descriptive pilot study included subjects with isolated LBBB derived from outpatient clinics of two academic hospitals. All subjects underwent maximal cardiopulmonary exercise testing (CPET) and a Global Physical Activity Questionnaire (GPAQ). The primary outcome was to evaluate maximal functional capacity according to population‐derived predicted values of peak oxygen consumption (peakVO(2)): pp‐peakVO(2). The secondary outcome was to report adverse CV events (CV deaths or hospitalizations) at follow‐up. RESULTS: A total of 27 (18 women and 9 men) participants were included. The median (interquartile range) age of the sample and time to screening from the first LBBB diagnosis were 62 (51−71) and 3.4 (1.1−8.4) years, respectively. The results of the GPAQ score showed that 19 patients were highly active, and 8 were moderately active. The median of peakVO(2) and pp‐peakVO(2) were 19.3 (15−22.5) ml/kg/min and 88% (79.3%−104.4%), respectively. There were no adverse CV events at a median follow‐up after CPET of 3.1 (2.7−3.4) years. CONCLUSION: In this pilot study, adults with isolated LBBB showed reduced maximal functional capacity, despite the absence of cardiac disease and a baseline moderate to highly active lifestyle.