Background: In the reperfusion era the clinical characteristics of intermediate QRS prolongation without bundle-branch block (BBB) remain unclear in patients with ST-segment elevation myocardial infarction (STEMI).
Methods and results: A total of 465 patients with STEMI within 24 h of onset were classified into 3 groups according to QRS duration on presenting electrocardiograms: 338 patients had QRS duration <100 ms (group N), 71 had QRS duration >or=100 ms without BBB (group W), and 56 had BBB (group B). The frequency of Killip class >1 was higher in group W (28%) than in group N (12%), but lower than in group B (47%) (p<0.05, respectively). The percentages of patients with non-anterior infarction (69% vs 42%, 47%), 3-vessel disease (30% vs 9%, 16%), and coronary artery bypass graft surgery (24% vs 4%, 13%) were higher in group W than in groups N and B (all p<0.05). In group W, 6-month-mortality was similar to that in group N, but lower than that in group B (4%, 3% vs 25%, p<0.05 respectively).
Conclusions: In the reperfusion era, although patients with intermediate QRS prolongation without BBB have more severe coronary disease, 6-month-mortality is similar to those with normal conduction, but lower than those with BBB.