Background/aims: Studies of the prognostic importance of QRS duration in patients with heart failure (HF) have shown conflicting results and few studies have estimated the importance after myocardial infarction (MI).
Methods: The Danish Investigations and Arrhythmia ON Dofetilide (DIAMOND) study randomised 3028 patients to dofetilide (class III antiarrhythmic) or placebo. The study consisted of two almost identical trials conducted simultaneously. One trial included 1518 patients with chronic HF and the other trial 1510 patients with a recent MI. All patients had left ventricular dysfunction. Dofetilide did not influence mortality in either trial. QRS duration was systematically measured at randomisation and was available in 2972 patients.
Results: Over a 10 year observation period 1037 (70%) patients in the MI study and 1324 (87%) in the HF study died. In the MI study, risk of death increased 6% for each 10 ms increase in QRS duration (HR=1.06/10 ms increase in QRS (CI=1.04-1.09), p<0.0001) whereas QRS duration had no influence in the HF study after multivariable adjustment. The difference between HF and MI was significant (p<0.0004 for interaction).
Conclusion: QRS duration predicts death in patients with left ventricular dysfunction who have suffered MI. In patients with HF QRS duration is not predictive of mortality.