Relationship of QRS duration at baseline and changes over 60 min after fibrinolysis to 30-day mortality with different locations of ST elevation myocardial infarction: results from the Hirulog and Early Reperfusion or Occlusion-2 trial.

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

Methods: Measuring QRS duration in patients with normal conduction or right bundle branch block Methods: HERO-2 trial with prospective collection of electrocardiograms at randomisation and at 60 min after fibrinolytic therapy Methods: 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 Methods: 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.

Conclusions: 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.