Is wider worse? QRS duration predicts cardiac mortality in patients with right bundle branch block

Background: Increasing QRS duration may be of prognostic significance in patients with right bundle branch block (RBBB) and may assist in predicting overall cardiovascular risk. Methods: To test this hypothesis, we examined the Computerized Patient Records of patients with complete and persistent RBBB. Primary and secondary end points were all-cause and cardiac mortality. The effects of QRS duration on death rates were analyzed using the Cox proportional hazards regression model (P < 0.05). We identified 52,852 patients with EKGs and selected all those with diagnosis of RBBB (QRS >= 120 ms) between January 2000 and January 2004. Some patients had EKG records confirming RBBB since 1987. The QRS durations were categorized into four groups: 120-129, 130-139, 140-149, and >= 150 ms. Results: A total of 997 (1.9%) patients (mean age 68.9 +/- 10 years) with RBBB were followed for 1-226 (median 45) months. All-cause mortality occurred in 344 (34.5%), cardiac deaths in 59 (5.9%), noncardiac in 191 (19.2%), and unknown causes in 94 (9.4%) patients. Mean left ventricular EF for cardiac patients was 38 +/- 15%. In patients with cardiac deaths, QRS duration was associated with increased morality (P < 0.007). For every 10 ms increase in QRS duration, the risk of death rose by 26.6%. The effect of QRS duration on all cause mortality was not statistically significant (P < 0.43). Conclusion: Increasing QRS duration was an independent predictor of cardiac mortality in patients with RBBB, but had no influence on all-cause mortality. QRS duration has added prognostic information to the presence of right bundle branch block.