Bundle branch blocks and the risk of mortality in the Atherosclerosis Risk in Communities study

The main objective of our study was to evaluate the associations between different categories of bundle branch blocks (BBBs) and mortality and to consider possible impact of QRS prolongation in these associations.

This analysis included 15 408 participants (mean age 54 years, 55.2% women, and 26.9% blacks) from the Atherosclerosis Risk in Communities study. We used Cox regression to examine associations between left BBB (LBBB), right BBB (RBBB) and indetermined type of ventricular conduction defect [intraventricular conduction defect (IVCD)] with coronary heart disease (CHD) death and all-cause mortality.

During a mean 21 years of follow-up, 4767 deaths occurred; of these, 728 were CHD deaths. Compared to No-BBB, LBBB and IVCD were strongly associated with increased CHD death (hazard ratios 4.11 and 3.18, respectively; P < 0.001 for both). Furthermore, compared to No-BBB with QRS duration less than 100 ms, CHD mortality risk was increased 1.33-fold for the No-BBB group with QRS duration 100-109 ms, and 1.48-fold with QRS duration 110-119 ms, 3.52-fold for pooled LBBB-IVCD group with QRS duration less than 140 ms and 4.96-fold for pooled LBBB-IVCD group with QRS duration at least 140 ms (P < 0.001). However, mortality risk was not significantly increased for lone RBBB. For all-cause mortality, trends similar to those for CHD death were observed within the BBB groups, although at lower levels of risk.

Prevalent LBBB and IVCD, but not RBBB, are associated with increased risk of CHD death and all-cause mortality. Mortality risk is further increased as the QRS duration is prolonged above 140 ms.