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.
Dhar
Ritesh
R
Institute for Clinical Research and Health Policy Studies, Department of Medicine, Tufts Medical Center, Tufts University School of Medicine, Boston, Massachusetts, USA.
Alsheikh-Ali
Alawi A
AA
Estes
N A Mark
NA
Moss
Arthur J
AJ
Zareba
Wojciech
W
Daubert
James P
JP
Greenberg
Henry
H
Case
Robert B
RB
Kent
David M
DM
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