Effects of Isolated LBBB on Maximal Functional Capacity

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.

The main objective of the study is to evaluate the effect of LBBB on maximum functional capacity (objectively evaluated by the maximum oxygen consumption -VO2max- at peak exercise in a cardiopulmonary stress test -CPET-) in subjects with LBBB without known cardiovascular disease and compare these data with controls without LBBB.

This is a prospective study that will be carried out in a single centre. All patients with a diagnosis of LBBB and without evidence of structural heart disease in imaging tests will be enrolled. For each candidate with LBBB, one control without LBBB and matched for age, sex, body surface area, and daily physical activity will be selected. All included subjects will undergo a CPET and echocardiography. A sample size estimation [alpha: 0.05, power: 80%, and a clinically significant VO2max difference between groups of at least 10%] of 148 subjects (74 subjects with LBBB + 74 controls) would be necessary to test our hypothesis.

Inclusion criteria

• Adult >18 years old
• ECG criteria of left bundle branch block (for controls without left bundle branch block )
• Provide informed consent

Exclusion criteria

• Inability to perform a maximal baseline exercise test;
• Structural heart disease, valve heart disease or diastolic dysfunction estimated by two-dimensional echocardiography;
• Previous ischemic heart disease, heart failure, myocardiopathy or myocarditis
• Effort angina during cardiopulmonary exercise testing (CPET);
• Any moderate pulmonary disease;
• Anaemia
• Left ventricular ejection fraction < 55%.