Intraoperative testing of the implantable cardioverter-defibrillator: how much is enough?
BACKGROUND
Defibrillation testing of the implantable cardioverter-defibrillator (ICD) is considered a standard and required practice at the time of implantation. How much testing, if any in some cases, should be performed, however, remains unknown.


RESULTS
Included in this retrospective analysis were 835 patients (77% men; age 65 +/- 13 years) who received transvenous ICDs between January 1996 and December 2003. One hundred twenty-nine (15.5%) had intraoperative defibrillation threshold (DFT) testing, 503 (60.2%) had limited defibrillation safety margin testing, and 203 (24.3%) had no defibrillation testing. We compared the outcome (success of ICD therapies against spontaneous VT/VF events and survival) of the three groups of patients, who in some respects had important clinical differences. The success of the first delivered shocks against VT/VF was similar for DFT (91%), safety margin testing (91%), and no-testing (92%) groups; and the second shocks terminated the remaining episodes in all three groups. Sudden-death-free survival rates were similar in the three groups, however, the overall long-term survival rate was significantly lower in the no-testing group (58%) than in the DFT (74%) and safety margin testing (69%) groups (P < 0.0005). Multivariate analysis found no strong predictors of sudden death, but there were several independent predictors of overall mortality including lack of ICD testing (HR: 2.031, CI: 1.253-3.290, P = 0.004).


CONCLUSIONS
In this select patient cohort, success of ICD therapies and sudden-death-free survival were similar in patients who had DFT, safety margin testing, and no testing, but overall survival was significantly lower in the no-testing group. Thus in the absence of prospective mortality data, a minimum of safety margin ICD testing should remain standard practice.
Pires
Luis A
LA
Heart Rhythm Center and the Division of Cardiology, Department of Medicine, St. John Hospital and Medical Center, Detroit, Michigan 48236, USA. luis.pires@stjohn.org
Johnson
Katrina M
KM
D000368:Aged; D017147:Defibrillators, Implantable / Q000592:standards*; D005260:Female; D006801:Humans; D007432:Intraoperative Period; D008297:Male; D012189:Retrospective Studies; D015996:Survival Rate; D013610:Tachycardia / Q000628:therapy; D016896:Treatment Outcome; D014693:Ventricular Fibrillation / Q000628:therapy