Elsevier

Heart Rhythm

Volume 18, Issue 12, December 2021, Pages 2072-2079
Heart Rhythm

Clinical
Subcutaneous implantable cardioverter-defibrillator and defibrillation testing: A propensity-matched pilot study

https://doi.org/10.1016/j.hrthm.2021.06.1201Get rights and content

Background

To date, only a few comparisons between subcutaneous implantable cardioverter-defibrillator (S-ICD) patients undergoing and those not undergoing defibrillation testing (DT) at implantation (DT+ vs DT–) have been reported.

Objective

The purpose of this study was to compare long-term clinical outcomes of 2 propensity-matched cohorts of DT+ and DT– patients.

Methods

Among consecutive S-ICD patients implanted across 17 centers from January 2015 to October 2020, DT– patients were 1:1 propensity-matched for baseline characteristics with DT+ patients. The primary outcome was a composite of ineffective shocks and cardiovascular mortality. Appropriate and inappropriate shock rates were deemed secondary outcomes.

Results

Among 1290 patients, a total of 566 propensity-matched patients (283 DT+; 283 DT–) served as study population. Over median follow-up of 25.3 months, no significant differences in primary outcome event rates were found (10 DT+ vs 14 DT–; P = .404) as well as for ineffective shocks (5 DT– vs 3 DT+; P = .725). At multivariable Cox regression analysis, DT performance was associated with a reduction of neither the primary combined outcome nor ineffective shocks at follow-up. A high PRAETORIAN score was positively associated with both the primary outcome (hazard ratio 3.976; confidence interval 1.339–11.802; P = .013) and ineffective shocks alone at follow-up (hazard ratio 19.030; confidence interval 4.752–76.203; P = .003).

Conclusion

In 2 cohorts of strictly propensity-matched patients, DT performance was not associated with significant differences in cardiovascular mortality and ineffective shocks. The PRAETORIAN score is capable of correctly identifying a large percentage of patients at risk for ineffective shock conversion in both cohorts.

Introduction

In the last decade, the subcutaneous implantable cardioverter-defibrillator (S-ICD) has become an established alternative to the transvenous implantable cardioverter-defibrillator (TV-ICD) among patients without indications for pacing or resynchronization therapy.1 Although i the past defibrillation testing (DT) was required at the time of TV-ICD implantation, this practice is no longer routinely recommended.1 As the S-ICD is a more recent technology, DT is deemed to be necessary in these patients. The predominant role of DT is related to the assessment of appropriate sensing of ventricular arrhythmias as well as the assurance of adequate defibrillation energy requirements needed for effective termination of ventricular tachycardia and ventricular fibrillation (VF), thereby testing system integrity at implant, which is crucial for delivery of effective defibrillation. The clinical utility of DT during ICD implantation has gradually been questioned.2 Arguments against DT include the risks of DT-related complications and mostly the inability to predict shock efficacy and long-term outcomes.3, 4, 5 Indeed, the safety margin of an 80-J S-ICD has been suggested to be largely superior to that of a 40-J DT in nearly 90% of patients, thus questioning the role of DT per the manufacturer’s recommendation.6 The latest consensus statement recommends the use of DT in patients undergoing S-ICD implantation,1 whereas after the SIMPLE (Shockless IMPLant Evaluation)7 and NORDIC-ICD (NO Regular Defibrillation testing In Cardioverter Defibrillator Implantation) trials,8 implantation of a TV-ICD without performing DT is considered standard clinical practice in most patients.

Recent studies have shown that a new risk stratifying tool (the PRAETORIAN score [PS]) may help to identify patients with S-ICD at high risk for conversion failure,9 and that DT seems not to impact the safety of defibrillation therapy and overall patient survival.10 Therefore, the need for routine DT implementation in S-ICD systems has been further questioned, even if the lack of association between DT and effective defibrillation, as well as long-term survival outcomes, reflects findings derived only from registries or nonrandomized studies.10, 11, 12 This study aims to present long-term outcomes of 2 multicenter, propensity-matched cohorts of patients implanted with an S-ICD, based on performance of DT.

Section snippets

Methods

The ELISIR (Experience from the Long-term Italian S-ICD Registry) Project is a European, multicenter, open-label, independent, physician-initiated observational registry, currently involving 17 centers.10 This study was approved by the institutional review board and was drafted in accordance with the tenets of the Helsinki Declaration, as revised in 2013.

Baseline characteristics of the study population

From an overall registry population of 1290 patients, a total of 566 propensity-matched patients (283 DT+; 283 DT–) were extracted from the registry and enrolled in the current study to serve as the study population. After propensity matching, the 2 cohorts (DT+ and DT–) were comparable with regard to both matched and unmatched baseline data (median age 55 [46–64] years vs 56 [48–64] years, P = .273; male 78.1% vs 79.2%, P = .759; primary prevention 78.5% vs 77.4%, P = .761; respectively). No

Discussion

Our multicenter study presents long-term outcomes of 566 propensity-matched patients undergoing S-ICD implantation, with and without the performance of DT at the time of implant, extracted from the largest unsponsored S-ICD registry. Among an overall population of 1290 patients, propensity matching was performed for age, gender, arrhythmic substrate, left ventricular ejection fraction, and primary/secondary prevention for S-ICD placement.

The main results of the study were as follows. (1) Over

Conclusion

In 2 cohorts of propensity-matched patients, DT performance was not associated with a significant difference in the primary combined outcome of cardiovascular mortality and ineffective shocks over median follow-up of 25.2 months. PS was capable of correctly identifying a large percentage of patients at risk for ineffective shock conversion in both cohorts. Randomized controlled studies, with larger sample sizes and longer durations of follow-up, are needed to further validate these results.

References (18)

There are more references available in the full text version of this article.

Cited by (16)

  • The need for a subsequent transvenous system in patients implanted with subcutaneous implantable cardioverter-defibrillator

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    No specifics regarding shock energy and the use of general anesthesia or deep sedation for the procedure were given. The vast majority of patient received a 65-J shock and a small proportion underwent escalating low-energy defibrillation testing protocols, as previously described.16,17 When adequate postimplant imaging was available, PRAETORIAN score data was calculated from either a postprocedural 2-projection chest radiograph or from an intraprocedural fluoroscopic assessment,18,19 per each center’s practice, and patients were classified as having a low, intermediate, or high risk for conversion failure per the score definition.18

  • Age-related differences and associated mid-term outcomes of subcutaneous implantable cardioverter-defibrillators: A propensity-matched analysis from a multicenter European registry

    2022, Heart Rhythm
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    Another crucial aspect regarding S-ICD implantation is the role of defibrillation testing (DT) in assessing the appropriate sensing of ventricular arrhythmias and testing system integrity at implant. Forleo et al15 recently demonstrated that DT performance was not associated with significant differences in cardiovascular mortality and ineffective shocks. Interestingly, in our cohort, young patients were more likely to undergo DT at implant.

  • Evolution of Devices to Prevent Sudden Cardiac Death: Contemporary Clinical Impacts

    2022, Canadian Journal of Cardiology
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    Sometimes, delivery of a synchronized shock resulting in no VF induction will help to test the integrity of the defibrillating lead by measuring the high-voltage impedance. Trials are ongoing to assess the safety of no DSM for subcutaneous implants, as some registries showed the safety of this strategy and may, in the future, change the recommendation for DSM testing in this population.74-76 The components most likely to fail in an ICD system are transvenous leads.

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Funding sources: The authors have no funding sources to disclose.

Disclosures: Dr Santini is a consultant/speaker for Boston Scientific. Dr Tondo is a member of the Boston Scientific Advisory Board. Dr Steffel has received consultant and/or speaker fees Boston Scientific; and has received grant support through his institution from Boston Scientific. Dr Luigi Di Biase is a consultant for Boston Scientific. All other authors have reported that they have no relationships relevant to the contents of this paper to disclose.

1

Dr Giovanni B. Forleo and Dr Alessio Gasperetti share first co-authorship.

2

Dr Nicolas Badenco and Dr Mauro Biffi share last co-authorship. ClinicalTrials.gov Identifier: NCT0473876.

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