A population-based method for the estimation of defibrillation energy requirements in humans. Assessment of time-dependent effects with a transvenous defibrillation system.
BACKGROUND
A weighted logistic regression analysis was developed to allow pooling of patient data for the study of the stability of defibrillation energy requirements with a new nonthoracotomy lead defibrillation system.


RESULTS
One hundred twenty patients were prospectively studied with a single-model nonthoracotomy implantable cardioverter defibrillator (ICD) system at the time of implant and at 3 months. The pooled data of all shocks delivered to all patients were fitted to a logistic function to construct a defibrillation voltage/energy dose-response relationship. The crude logit curve was weighted in quartiles according to the average shock energy delivered per patient. Shocks at implant (n = 802; 6.6 +/- 2.5 shocks/patient) and follow-up (n = 292; 2.4 +/- 1.2 shocks/patient) were analyzed. The modeled voltage/energy required for 50% successful defibrillation (95% CI) in the pooled data was 367 V (273, 461) and 9.8 J (6.7, 12.9) at implant and 338 V (264, 412) and 10.5 J (8, 13.0) at follow-up. The conventional measure of lowest successful voltage/energy (95% CI) was 430 V (411, 449) and 12.1 J (11, 13.2) at implant and 415 V (391, 439) and 11.3 J (10, 12.6) at follow-up. There were no statistically significant differences between implant and follow-up energy requirements with either method.


CONCLUSIONS
The nonthoracotomy lead system used in this study demonstrated stability of defibrillation energy requirements at implant and 3-month follow-up. A new technique for the estimation of the defibrillation energy dose-response relationship was derived by using a weighted logistic regression analysis.
Newman
D
D
Division of Cardiology, St. Michael's Hospital, University of Toronto, ON, Canada. newmand@SMH.Toronto.on.ca
Barr
A
A
Greene
M
M
Martin
D
D
Ham
M
M
Thorne
S
S
Dorian
P
P
D000368:Aged; D004554:Electric Countershock / Q000295:instrumentation* / Q000379:methods; D017097:Electric Impedance; D004560:Electricity; D004867:Equipment Design; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D016015:Logistic Models; D008297:Male; D008875:Middle Aged; D011446:Prospective Studies; D013997:Time Factors