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

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.