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.
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Funding: The Hirulog and Early Reperfusion or Occlusion (HERO)-2 trial was funded by The Medicines Company.
Competing interests: HDW received research grants from Alexion, Sanofi-Aventis, Eli Lilly, Merck Sharpe & Dohme, The Medicines Company, NIH, Neuren, Glaxo Smith Kline, Pfizer, Roche, Fournier Janssen Cilag, Johnson & Johnson, Proctor & Gamble and Schering Plough. He has also received honoraria from Sanofi Aventis and The Medicines Company and consultancy fees from the Medicines Company, Neuren Pharma, Glaxo Smith Kline, Bayer and Sanofi Aventis. PEGA received a research grant from The Medicines Company. He also received payment for Speaker’s Bureau from CSL Ltd and Honoraria from CSL Ltd, and received consultancy fees from CSL Limited.
Ethics approval: Ethics approval was provided by the Multi-region Ethics Committee, Ministry of Health, Wellington, New Zealand.
Patient consent: Obtained.