The prognostic significance of intermediate QRS prolongation in acute myocardial infarction.

Complete right and left bundle branch block and advanced atrioventricular block present on admission electrocardiograms of patients with acute myocardial infarction, are associated with poor short and long-term outcome. Little is known about the impact of intermediate QRS prolongation (0.09-0.11 s) on the prognosis of acute myocardial infarction. In this study, among 1100 consecutive patients with acute myocardial infarction treated with thrombolysis, the QRS duration on admission electrocardiogram was <0.09 s in 536 (48%) patients, between 0.09 and 0.11 s in 496 (45%) patients and >0.11 s in 78 (7%) patients. QRS duration was strongly associated with 7-day (0.6%, 6%,18%, P<0.001), 30-day (1%, 8%, 22%, P<0.001) and 1-year (3%, 11%, 26%, P<0.001) all-cause mortality. After adjustment for significant variables associated with 1-year mortality, including age, female gender, diabetes mellitus, systemic hypertension, previous myocardial infarction, anterior myocardial infarction and Killip class> or =2 on admission, both levels of QRS prolongation remained significant independent predictors of short and long-term all-cause mortality.