Background: The prognostic importance reported for QRS duration in patients with heart failure (HF) and left ventricular dysfunction varies. No prior study has investigated the prognostic importance of change in QRS duration over time.
Methods and results: The Danish Investigations and Arrhythmia ON Dofetilide (DIAMOND) study randomized 1518 patients with HF to dofetilide (class III antiarrhythmic drug) or placebo. All patients had left ventricular dysfunction. QRS duration was systematically measured at randomization and every 3 months after that. During 10 years of follow-up, 1324 (89%) of the patients died. QRS duration increased from baseline by 1.36 ms (95% confidence interval [CI]: -0.26 to -2.98; P = .1) after 12 months and by 3.65 ms (CI: 0.22-7.07; P = .04) after 24 months. QRS duration measured at baseline was not of prognostic significance after multivariable adjustment (adjusted hazard ratio [HR] 1.01, CI: 0.99-1.04; P = .2 per 10-ms increment in QRS duration). The adjusted relative risk associated with a 10-ms increase in QRS duration over time was 2% (HR 1.02, CI: 1.01-1.04; P = .03). A 10-ms increment in QRS 12 months after randomization was associated with a HR of 1.05 (CI: 1.00-1.09; P = .03).
Conclusions: In patients with left ventricular dysfunction and HF, QRS duration increased over time and the increase was associated with increasing mortality.