Ventricular arrhythmia inducibility predicts subsequent ICD activation in nonischemic cardiomyopathy patients: a DEFINITE substudy.
OBJECTIVE
We evaluated whether electrophysiologic (EP) inducibility predicts the subsequent occurrence of spontaneous ventricular tachycardia (VT) or ventricular fibrillation (VF) in the Defibrillators in Nonischemic Cardiomyopathy Treatment Evaluation (DEFINITE) trial.


BACKGROUND
Inducibility of ventricular arrhythmias has been widely used as a risk marker to select implantable cardioverter defibrillator (ICD) candidates, but is believed not to be predictive in nonischemic cardiomyopathy patients.


METHODS
In DEFINITE, patients randomized to the ICD arm, but not the conventional arm, underwent noninvasive EP testing via the ICD shortly after ICD implantation using up to three extrastimuli at three cycle lengths plus burst pacing. Inducibility was defined as monomorphic or polymorphic VT or VF lasting 15 seconds. Patients were followed for a median of 29 +/- 14 months (interquartile range = 2-41). An independent committee, blinded to inducibility status, characterized the rhythm triggering ICD shocks.


RESULTS
Inducibility, found in 29 of 204 patients (VT in 13, VF in 16), was associated with diabetes (41.4% vs 20.6%, P = 0.014) and a slightly higher ejection fraction (23.2 +/- 5.9 vs 20.5 +/- 5.7, P = 0.021). In follow-up, 34.5% of the inducible group (10 of 29) experienced ICD therapy for VT or VF or arrhythmic death versus 12.0% (21 of 175) noninducible patients (hazard ratio = 2.60, P = 0.014).


CONCLUSIONS
In DEFINITE patients, inducibility of either VT or VF was associated with an increased likelihood of subsequent ICD therapy for VT or VF, and should be one factor considered in risk stratifying nonischemic cardiomyopathy patients.
Daubert
James P
JP
Cardiology Division, Department of Medicine, University of Rochester Medical Center, Rochester, New York, USA. James.Daubert@duke.edu
Winters
Stephen L
SL
Subacius
Haris
H
Berger
Ronald D
RD
Ellenbogen
Kenneth A
KA
Taylor
Sarah G
SG
Schaechter
Andi
A
Howard
Adam
A
Kadish
Alan
A
D002304:Cardiac Pacing, Artificial / Q000706:statistics & numerical data*; D009202:Cardiomyopathies / Q000175:diagnosis* / Q000453:epidemiology* / Q000517:prevention & control; D017147:Defibrillators, Implantable; D022062:Electrophysiologic Techniques, Cardiac / Q000379:methods*; D005260:Female; D006801:Humans; D015994:Incidence; D008297:Male; D017202:Myocardial Ischemia / Q000150:complications / Q000175:diagnosis; D015203:Reproducibility of Results; D018570:Risk Assessment / Q000379:methods; D012307:Risk Factors; D012680:Sensitivity and Specificity; D017180:Tachycardia, Ventricular / Q000175:diagnosis* / Q000453:epidemiology* / Q000517:prevention & control; D014481:United States / Q000453:epidemiology