QRS prolongation in patients with acute coronary syndromes.

BACKGROUND: QRS prolongation with or without bundle branch block (BBB) has been associated with adverse outcome in myocardial infarction; we examined the relationship between QRS duration and outcome in a broad spectrum of patients with acute coronary syndrome (ACS). METHOD AND RESULTS: Core laboratory evaluation of the presenting electrocardiogram in Canadian ACS Registry patients (n = 5,003) showed 4,289 (85.7%) had QRS <120 milliseconds, 202 (4.0%) patients had QRS > or =120 milliseconds without BBB, 262 (5.2%) had left BBB (LBBB), and 250 (5.0%) had right BBB. Compared to patients with QRS <120 milliseconds, patients with QRS > or =120 milliseconds without BBB had higher in-hospital (3.5% vs 1.9%, odds ratio [OR] 1.87, 95% CI 0.85-4.09, P = .12) and 1-year mortality (14.9% vs 7.7%, OR 2.10, 95% CI 1.38-3.18, P = .001). In-hospital and 1-year mortality was significantly higher in patients with BBB (eg, LBBB compared with QRS <120 milliseconds) (5.0% vs 1.9%, OR 2.71, 95% CI 1.49-4.94, P = .001, and 23.8% vs 7.7%, OR 3.74, 95% CI 2.72-5.13, P < .001). Analyzed as a continuous variable and after adjustment for validated prognosticators, QRS duration was an independent predictor of 1-year death (OR 1.11, 95% CI 1.06-1.16, P < .001) and death/myocardial infarction (OR 1.06, 95% CI 1.02-1.11, P = .003). However, when using clinically applicable QRS duration evaluation, only LBBB was an independent predictor of 1-year mortality (OR 1.93, 95% CI 1.28-2.90, P = .002). CONCLUSIONS: In patients presenting with a broad spectrum of suspected ACS, QRS prolongation-particularly in the setting of LBBB-is an independent predictor of in-hospital and 1-year mortality.