Arrhythmia rate distribution and tachyarrhythmia therapy in an ICD population: results from the INTRINSIC RV trial.
BACKGROUND
Appropriate implantable cardioverter-defibrillator (ICD) therapy for ventricular tachycardia (VT) or ventricular fibrillation (VF) depends, in part, on the programming of tachycardia zones.


OBJECTIVE
We assessed events treated with ICD shocks or antitachycardia pacing (ATP) in the Inhibition of Unnecessary RV Pacing with AV Search Hysteresis in ICDs (INTRINSIC RV) trial.


METHODS
ATP and shock episodes from 1530 patients with dual-chamber ICDs were analyzed.


RESULTS
For episodes in which electrograms were stored and adjudicated, ATP was delivered for 763 episodes (182 patients), shock-only was delivered for 300 episodes (146 patients), and shock following ATP was delivered for 81 episodes (56 patients). ATP was delivered appropriately for 507 episodes (130 patients), with 93% success, and inappropriately for 256 episodes (89 patients). For ATP episodes, appropriate (VT: 170 ± 28 bpm) and inappropriate (not VT: 165 ± 21 bpm) rates did not differ (P = .16). When the initial therapy was shock, onset rates were higher for appropriate therapy than for inappropriate therapy (224 ± 46 bpm vs 187 ± 31 bpm; P <.001). Inappropriate ATP was more likely to be followed by a shock (odds ratio 2.49; 95% confidence interval 1.56-3.97; P <.001). Fifty-eight percent (225 of 381) of shocked episodes had rates <200 bpm. For episodes between 200 and 250 bpm, 20% (23 of 113) were polymorphic VT or VF, 59% were monomorphic VT, 19% were supraventricular, and <1% was artifact. For episodes >250 bpm, 37% were VF, 28% polymorphic VT, 23% monomorphic VT, 7% supraventricular, and 5% artifact.


CONCLUSIONS
In a general ICD population, ATP treated VT effectively or obviated the need for shock. Most ventricular arrhythmias <250 bpm were not VF. Proper zone programming may identify and treat VT without shock.
Division of Cardiovascular Medicine, University of Iowa Hospitals and Clinics, Iowa City, Iowa 52242, USA.
Renee M
RM
Sullivan
Andrea M
AM
Russo
Kellie Chase
KC
Berg
Kira Q
KQ
Stolen
Milan
M
Seth
David
D
Perschbacher
John D
JD
Day
Brian
B
Olshansky
D000368:Aged; D002304:Cardiac Pacing, Artificial / Q000009:adverse effects / Q000379:methods / Q000592:standards / Q000706:statistics & numerical data; D002317:Cardiovascular Agents / Q000008:administration & dosage / Q000009:adverse effects; D016757:Death, Sudden, Cardiac / Q000209:etiology / Q000517:prevention & control; D017147:Defibrillators, Implantable / Q000009:adverse effects / Q000592:standards / Q000706:statistics & numerical data; D004554:Electric Countershock / Q000009:adverse effects / Q000379:methods / Q000706:statistics & numerical data; D004562:Electrocardiography; D019544:Equipment Failure Analysis / Q000706:statistics & numerical data*; D006304:Health Status; D006801:Humans; D008297:Male; D008875:Middle Aged; D008991:Monitoring, Physiologic; D010043:Outcome and Process Assessment, Health Care; D017180:Tachycardia, Ventricular / Q000145:classification / Q000175:diagnosis / Q000401:mortality / Q000628:therapy; D016896:Treatment Outcome
D002317:Cardiovascular Agents