Do traditional VT zones improve outcome in primary prevention ICD patients?
OBJECTIVE
We reviewed outcomes in our primary prevention implantable cardioverter defibrillator (ICD) population according to whether the device was programmed with a single ventricular fibrillation (VF) zone or with two zones including a ventricular tachycardia (VT) zone in addition to a VF zone.


METHODS
This retrospective study examined 137 patients with primary prevention ICDs implanted at our institution between 2004 and 2006. Device programming and events during follow-up were reviewed. Outcomes included all-cause mortality, time to first shock, and incidence of shocks.


RESULTS
Eighty-seven ICDs were programmed with a single VF zone (mean >193 ± 1 beats per minute [bpm]) comprising shocks only. Fifty ICDs had two zones (mean VT zone >171 ± 2 bpm; VF zone >205 ± 2 bpm), comprising antitachycardia pacing (100%), shocks (96%), and supraventricular (SVT) discriminators (98%) . Discriminator "time out" functions were disabled. Mean follow-up was 30 ± 0.5 months and similar in both groups. All-cause mortality (12.6% and 12.0%) and time to first shock were similar. However, the two-zone group received more shocks (32.0% vs 13.8% P = 0.01). Five of 16 shocks in these patients were inappropriate for SVT rhythms. The single-zone group had no inappropriate shocks for SVTs. Eighteen of 21 appropriate shocks were for ventricular arrhythmias at rates >200 bpm (three VF, 15 VT). This suggests that primary prevention ICD patients infrequently suffer ventricular arrhythmias at rates <200 bpm and that ATP may play a role in terminating rapid VTs.


CONCLUSIONS
Patients with two-zone devices received more shocks without any mortality benefit.
Duncan
Edward
E
Department of Cardiology, Barts and the London NHS Trust, London, UK.
Thomas
Glyn
G
Johns
Neville
N
Pfeffer
Cameron
C
Appanna
Gautham
G
Shah
Nirav
N
Hunter
Ross
R
Finlay
Malcolm
M
Schilling
Richard J
RJ
Sporton
Simon
S
D000368:Aged; D009202:Cardiomyopathies / Q000150:complications / Q000628:therapy; D017147:Defibrillators, Implantable; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D017202:Myocardial Ischemia / Q000628:therapy; D011322:Primary Prevention / Q000295:instrumentation*; D012189:Retrospective Studies; D013318:Stroke Volume; D013617:Tachycardia, Supraventricular / Q000175:diagnosis / Q000401:mortality / Q000517:prevention & control / Q000628:therapy; D017180:Tachycardia, Ventricular / Q000209:etiology / Q000401:mortality / Q000517:prevention & control*; D016896:Treatment Outcome; D014693:Ventricular Fibrillation / Q000517:prevention & control / Q000628:therapy