Defibrillation threshold testing fails to show clinical benefit during long-term follow-up of patients undergoing cardiac resynchronization therapy defibrillator implantation.
BACKGROUND
The utility of defibrillation threshold testing in patients undergoing implantable cardioverter-defibrillator (ICD) implantation is controversial. Higher defibrillation thresholds have been noted in patients undergoing implantation of cardiac resynchronization therapy defibrillators (CRT-D). Since the risks and potential benefits of testing may be higher in this population, we sought to assess the impact of defibrillation safety margin or vulnerability safety margin testing in CRT-D recipients.


RESULTS
A total of 256 consecutive subjects who underwent CRT-D implantation between January 2003 and December 2007 were retrospectively reviewed. Subjects were divided into two groups based on whether (n= 204) or not (n= 52) safety margin testing was performed. Patient characteristics, tachyarrhythmia therapies, procedural results, and clinical outcomes were recorded. Baseline characteristics, including heart failure (HF) severity, were comparable between the groups. Four cases of HF exacerbation (2%), including one leading to one death, were recorded in the tested group immediately post-implantation. No complications were observed in the untested group. After a mean follow-up of 32 ± 20 months, the proportion of appropriate shocks in the two groups was similar (31 vs. 25%, P = 0.49). There were three cases of failed appropriate shocks in the tested group, despite adequate safety margins at implantation, whereas no failed shocks were noted in the untested group. Survival was similar in the two groups.


CONCLUSIONS
Defibrillation efficacy testing during implant of CRT-D was associated with increased morbidity and did not predict the success of future device therapy or improve survival during long-term follow-up.
UCLA Cardiac Arrhythmia Center, Ronald Reagan UCLA Medical Center, Los Angeles, CA 90095, USA. ymichowitz@gmail.com
Yoav
Y
Michowitz
Nicolas
N
Lellouche
Tahmeed
T
Contractor
Tara
T
Bourke
Isaac
I
Wiener
Eric
E
Buch
Noel
N
Boyle
Malcolm
M
Bersohn
Kalyanam
K
Shivkumar
D000368:Aged; D058406:Cardiac Resynchronization Therapy / Q000009:adverse effects* / Q000706:statistics & numerical data; D017147:Defibrillators, Implantable / Q000009:adverse effects* / Q000706:statistics & numerical data; D003935:Diagnostic Techniques, Cardiovascular / Q000009:adverse effects* / Q000706:statistics & numerical data; D018572:Disease-Free Survival; D005260:Female; D005500:Follow-Up Studies; D006333:Heart Failure / Q000453:epidemiology / Q000628:therapy; D006801:Humans; D053208:Kaplan-Meier Estimate; D008297:Male; D008875:Middle Aged; D012189:Retrospective Studies; D012307:Risk Factors; D014693:Ventricular Fibrillation / Q000175:diagnosis / Q000453:epidemiology / Q000628:therapy
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