Abstract

Objective: To discern if the prognostic meaning of QRS prolongation differs according to the location of ST elevation acute myocardial infarction

Design: Measuring QRS duration in patients with normal conduction or right bundle branch block

Setting: HERO-2 trial with prospective collection of electrocardiograms at randomisation and at 60 min after fibrinolytic therapy

Patients: 12 456 patients with normal conduction at both randomisation and 60-min time points and 510 with right bundle branch block (RBBB) at both time points

Main outcome measure: 30-day mortality.

Results: On the baseline ECG, there was a positive association between QRS duration and 30-day mortality with anterior acute myocardial infarction (AMI) (p<0.0001 for those with normal conduction and  = 0.007 for those with RBBB) but not with inferior AMI (p = 0.29 and p = 0.32, respectively). For anterior AMI, with or without RBBB, an increment of 20 ms increase in QRS duration predicted a significant 30–40% relative increase in 30-day mortality both before and after adjusting for clinical and ECG variables including baseline ST elevation and presence of Q waves. The association was not present for inferior AMI. Changes in QRS duration over 60 min after fibrinolytic therapy were uncommon and unrelated to mortality.

Conclusion: Baseline QRS duration independently stratifies 30-day mortality in patients with anterior AMI, even when unaccompanied by RBBB, but does not stratify mortality risk in patients with inferior AMI.