Defibrillation Testing at ICD Implantation: Are We Asking the Wrong Question?

ICD implantation without intraoperative testing does not increase the rate of system modifications and does not impair defibrillation efficacy tested in follow-up

AIM

The need for implantable cardioverter-defibrillator (ICD) defibrillation testing (DT) and subsequent intraoperative system modifications is discussed controversially. The study's goal was to prove that consequent abdication of intraoperative DT does not impair defibrillation efficacy and does not increase the rate of postoperative system revisions.

METHODS

In a prospective single-center observational study, 609 out of 648 consecutive patients underwent transvenous ICD implantation (left-sided, active can, dual coil lead, and biphasic shock waveform) waiving intraoperative DT. Defibrillation efficacy was validated prior to hospital discharge (PHD) by applying two 10 J safety margin (SM) shocks.

RESULTS

Following "schockless" implantation 580 out of 609 patients (95.2 %) met a 10 J SM with default programming. Shock path reversal provided 10 J SM in 13 out of 29 cases with initially failed DT. In four patients (0.7 %) maximum energy shocks were ineffective. There was no morbidity or mortality related to DT. The total rate of surgical ICD revisions was 1.8 %.

CONCLUSION

Routine ICD implantation without intraoperative DT does not lead to an increased rate of postoperative system modifications and does not decrease defibrillation efficacy as tested PHD.

Clinical evaluation of defibrillation testing in an unselected population of 2,120 consecutive patients undergoing first implantable cardioverter-defibrillator implant

OBJECTIVES

The purpose of this study is to assess the effectiveness of defibrillation testing (DT) in patients undergoing implantable cardioverter-defibrillator (ICD) insertion.

BACKGROUND

Although DT is considered a standard procedure during ICD implantation, its usefulness has not been definitively proven.

METHODS

The SAFE-ICD (Safety of Two Strategies of ICD Management at Implantation) study is a prospective observational study designed to evaluate the outcome of 2 strategies: performing defibrillation testing (DT+) versus not performing defibrillation testing (DT-) during de novo ICD implants. No deviation from the centers' current practice was introduced. In all, 2,120 consecutive patients (836 DT+ and 1,284 DT-) age ≥18 years were enrolled at 41 Italian centers from April 2008 to May 2009 and followed up for 24 months until June 2011. The primary endpoint was a composite of severe complications at ICD implant and sudden cardiac death or resuscitation at 2 years.

RESULTS

The primary endpoint occurred in 34 patients: 12 intraoperative complications (8 in DT+ group; 4 in DT- group) and 22 during follow-up (10 in DT+ group; 12 in DT- group). Overall, the estimated yearly incidence (95% confidence interval) was DT+ 1.15% (0.73 to 1.83) and DT- 0.68% (0.42 to 1.12). The difference between the 2 groups was negligible: 0.47% per year (-0.15 to 1.10). Mortality from any cause was similar at 2 years (adjusted hazard ratio: 0.97 [0.76 to 1.23], p = 0.80).

CONCLUSIONS

In this large cohort of new ICD implants, event rates were similar and extremely low in both groups. These data indicate a limited clinical relevance for DT testing, thus supporting a strategy of omitting DT during an ICD implant. (Safety of Two Strategies of ICD Management at Implantation [SAFE-ICD]; NCT00661037).

Randomized comparison of defibrillation thresholds from the right ventricular apex and outflow tract

BACKGROUND

Implantable cardioverter-defibrillator (ICD) leads are traditionally placed in the right ventricular apex (RVA), in part because this is considered the preferred vector for minimizing defibrillation threshold (DFT). However, if adequate DFT safety margins are attainable, ICD leads placed in the right ventricular outflow tract (RVOT) might confer advantages if frequent ventricular pacing is anticipated.

OBJECTIVE

The purpose of this study was to compare RVA with RVOT transvenous ICD lead position on DFT.

METHODS

This was a prospective, randomized, crossover study of RVA versus RVOT DFT in 33 patients undergoing left pectoral ICD placement. A binary search algorithm was used to measure DFT, with initial lead position tested in randomized order. The relationship between RVOT position and DFT was assessed by evaluation of the distance between RVA and RVOT.

RESULTS

The study population had a mean age of 59 ± 12 years and ejection fraction of 33% ± 14%. Mean DFT in the RVA was 9.8 ± 7.3 J versus 10.8 ± 7.2 J in the RVOT (P = .53), with no correlation between RVOT location and DFT.

CONCLUSION

The study found no evidence that ICD lead placement in the RVOT is associated with significantly higher DFT than lead placement in the RVA.