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

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.

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).

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 (peakVO₂ ): pp-peakVO₂ . The secondary outcome was to report adverse CV events (CV deaths or hospitalizations) at follow-up.

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 peakVO₂ and pp-peakVO₂ 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.

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.