The prevalence, and prognostic implication of left bundle branch block (LBBB) patients with stable coronary artery disease (CAD) is unknown.

To describe the prevalence, incidence and prognostic implications of LBBB in patients with stable CAD.

CLARIFY is an international registry of more than 30.000 patients with stable CAD. LBBB was defined as a QRS complex>120 milliseconds. Patients with previous pacemaker implantation or defibrillator were excluded. The primary outcome was a composite of cardiovascular (CV) Death, MI or stroke, and secondary outcomes included hospitalization for heart failure (HF) or the need for pacemaker implantation.

From the 23.457 patients with available data, 1.041 (4.4%) had LBBB at baseline and 1.237 (5.3%) during 5-year follow-up. Only 21 patients with newly diagnosed LBBB overtime, had a documented MI the same year. Compared to patients without LBBB, patients with LBBB had a higher risk profile regarding age (67.2±10.1 versus 63.6±10.4 years, P<0.0001), history of coronary artery bypass grafting (29.2% vs. 23.7%, P<0.0001), diabetes (35.1% vs. 28.4%, P<0.0001), and HF (25.2% vs. 16.8%, P<0.0001). In multivariate analysis there was no difference in the rate of primary outcome between LBBB or no-LBBB patients (adjusted HR 1.04, 95% CI 0.85–1.29). Patients with LBBB had a higher rate of pacemaker implantation (adjusted HR 2.21, 95% CI 1.55–3.15, P<0.0001) and hospitalization for HF (adjusted HR 1.53, 95% CI 1.25–1.88, P<0.0001) (Table 1, Fig. 1).

The prevalence of LBBB in patients with stable CAD was 4.4% and 5.3% with 5-year follow-up. The majority of newly diagnosed LBBB were not contemporary of myocardial infarction. LBBB was not associated with a higher rate of major adverse cardiovascular events, but with a higher risk of pacemaker implantation and hospitalization for heart failure. This is the first study reporting such results in a broad population of stable CAD patients.