Effect of ICD Therapies on Mortality in the OMNI Trial.
BACKGROUND
Analyses from primary prevention trials on implantable cardioverter defibrillator (ICD) therapy have shown an association between shocks and increased mortality. Recent data suggest a similar association with antitachycardia pacing (ATP).


OBJECTIVE
The OMNI study is an observational study of pacemaker and ICD use. We aim to examine associations between ICD therapies and mortality in this setting.


METHODS
A total of 2,255 OMNI patients with ICDs were included. Treated episodes were classified as appropriate or inappropriate. Patients were assigned into 1 of 3 groups depending on whether the episode required ATP only, single shock, or multiple shocks, and then followed for all-cause mortality. Additionally, we aimed to determine the frequency with which inappropriate ATP precipitated ventricular arrhythmias that led to shock, since this has been suggested as a mechanism of harm.


RESULTS
Over a mean follow-up of 39 ± 19 months, there were a total of 470 deaths (21%). Compared to patients with no treated episodes, patients with appropriate therapy had greater risk of death. Hazard ratios were 1.46 (95% confidence interval [CI] 1.05-2.02; P = 0.023) for the ATP-only group, 2.11 (95% CI 1.51-2.96; P < 0.001) for the single-shock group, and 2.55 (95% CI 1.43-4.57; P = 0.002) for the multishock group. There was no significant association between any type of inappropriate therapy and increased mortality. We identified only 7 instances of inappropriate ATP precipitating ventricular arrhythmia resulting in shock.


CONCLUSIONS
Patients receiving appropriate therapy of all types had increased mortality compared to those with no episodes. Furthermore, inappropriate ATP rarely precipitates ventricular arrhythmias.
UT Southwestern Medical Center, Dallas, Texas, USA.
Shining
S
Sun
Medtronic Inc, Minneapolis, Minnesota, USA.
James
J
Johnson
Medtronic Inc, Minneapolis, Minnesota, USA.
Paul
P
Degroot
Medtronic Inc, Minneapolis, Minnesota, USA.
Mark L
ML
Brown
UT Southwestern Medical Center, Dallas, Texas, USA.|VA North Texas Health Care System, Dallas, Texas, USA.
Owen
O
Obel
D000368:Aged; D002304:Cardiac Pacing, Artificial / Q000009:adverse effects / Q000401:mortality*; D017147:Defibrillators, Implantable; D004554:Electric Countershock / Q000009:adverse effects / Q000295:instrumentation* / Q000401:mortality*; D022062:Electrophysiologic Techniques, Cardiac; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D011358:Product Surveillance, Postmarketing; D011475:Prosthesis Failure; D012307:Risk Factors; D017180:Tachycardia, Ventricular / Q000175:diagnosis / Q000503:physiopathology / Q000628:therapy*; D013997:Time Factors; D016896:Treatment Outcome; D014481:United States; D014693:Ventricular Fibrillation / Q000175:diagnosis / Q000503:physiopathology / Q000628:therapy*
ICD therapy; OMNI trial; antitachycardia pacing; implantable cardioverter defibrillator; mortality