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 </=260 ms) in the ICD-treated arm.


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 </=30%, prolonged QRSd does not predict SCD/VT/VF in ICD-treated patients but does predict SCD in medically treated patients. This underscores the nonequivalence of VT/VF and SCD and the need for caution in inferring risk of SCD when using nonrandomized databases that include only patients with ICDs.
Institute for Clinical Research and Health Policy Studies, Department of Medicine, Tufts Medical Center, Tufts University School of Medicine, Boston, Massachusetts, USA.
Ritesh
R
Dhar
Alawi A
AA
Alsheikh-Ali
N A Mark
NA
Estes
Arthur J
AJ
Moss
Wojciech
W
Zareba
James P
JP
Daubert
Henry
H
Greenberg
Robert B
RB
Case
David M
DM
Kent
D001806:Blood Urea Nitrogen; D016757:Death, Sudden, Cardiac / Q000209:etiology / Q000517:prevention & control*; D017147:Defibrillators, Implantable; D005260:Female; D006329:Heart Conduction System / Q000503:physiopathology*; D006801:Humans; D008297:Male; D008875:Middle Aged; D011379:Prognosis; D016016:Proportional Hazards Models; D012307:Risk Factors; D012720:Severity of Illness Index; D013318:Stroke Volume; D017180:Tachycardia, Ventricular / Q000503:physiopathology / Q000628:therapy*; D013997:Time Factors