Association of prolonged QRS duration with ventricular tachyarrhythmias and sudden cardiac death in the Multicenter Automatic Defibrillator Implantation Trial II (MADIT-II).

Background: There is conflicting literature on the relationship between prolonged QRS duration (QRSd) and arrhythmic events, including sudden cardiac death (SCD), in heart failure patients with or without implantable cardioverter-defibrillators (ICDs).

Objective: The purpose of this study was to evaluate the prognostic significance of prolonged QRSd relative to arrhythmic outcomes in medically and ICD-treated patients enrolled in the Multicenter Automatic Defibrillator Implantation Trial (MADIT) II.

Methods: Using a Cox proportional hazards model adjusting for ejection fraction, heart failure class, and blood urea nitrogen, we estimated the association of prolonged QRSd >/=140 ms with SCD in the medically treated arm and SCD or first appropriate ICD therapy for rapid ventricular tachycardia/fibrillation (VT/VF; cycle length
Results: In the medically treated arm, prolonged QRSd was a significant independent predictor of SCD (hazard ratio 2.12; 95% confidence interval 1.20-3.76; P = .01). However, in the ICD-treated arm, prolonged QRSd did not predict SCD or rapid VT/VF (hazard ratio 0.77; 95% CI 0.47-1.24; P = .28). The difference in the prognostic effect of prolonged QRSd in these two groups was significant (P<.01). These results were not affected by varying the cycle length that defines rapid VT/VF or the duration that defines QRSd prolongation.

Conclusions: In patients with prior myocardial infarction and EF