Defibrillation testing may be omitted in most recipients of S-ICD

The majority of subcutaneous implantable cardioverter defibrillator (S-ICD) recipients may safely forgo defibrillation testing (DT) during implantation, suggests a study. However, selective DT may be considered in those at higher risk.

Of the 4,924 patients included in the study, 4,066 (82.6 percent) underwent DT, decreasing from 85.4 percent in 2012–2014 to 66.9 percent in 2019 (p<0.001).

Patients who omitted DT tended to be older (51.2 vs 49.6 years; p=0.007), had lower left ventricular ejection fraction (37.6 percent vs 43.3 percent; p<0.001), and were more frequently implanted for primary prevention (68.0 percent vs 62.4 percent; p=0.002) and structure heart disease (84.9 percent vs 76.8 percent; p<0.0001).

DT-related complications, including two deaths, occurred in 0.1 percent of patients. The failure rate was 1.0 percent, with corrective reinterventions done in 87.8 percent of S-ICD recipients. Elevated shock impedance (≥89 Ω; odds ratio [OR], 4.60, 95 percent confidence interval [CI], 2.32–9.66; p<0.001) and obesity (BMI ≥30 kg/m2; OR, 2.17, 95 percent CI, 1.01–4.55; p=0.007) each predicted DT failure.

After adjustment, DT omission did not lead to higher risks of overall mortality (hazard ratio [HR], 1.17, 95 percent CI, 0.86–1.61; p=0.313), cardiovascular mortality (HR, 1.04, 95 percent CI, 0.70–1.56; p=0.846), sudden cardiac death (HR, 0.27, 95 percent CI, 0.04–1.72; p=0.167), and appropriate (HR, 1.10, 95 percent CI, 0.78–1.30; p=0.945) or inappropriate shocks (HR, 0.98, 95 percent CI, 0.78–1.23; p=0.865).

Additionally, the combined rates of ineffective shocks or undetected ventricular arrhythmias were comparable (0.05 vs 0.06 per 100 person-years).

This nationwide, ongoing observational study included all S-ICD recipients in France (2012–2019). The investigators centrally adjudicated 5-year endpoints and compared outcomes by DT status using propensity score-weighted analyses.