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

Aim of the study was to compare long-term clinical outcomes of two propensity-matched cohorts of DT+ and DT- patients.

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.

Among 1290 patients, a total of 566 propensity-matched patients (n=283 DT+; n=283 DT-) served as study population. Over a median follow-up of 25.3 months, no significant differences in primary outcome event rates were found (n=10 DT+ vs n=14 DT-; p=0.404) as well as for ineffective shocks (n=5 DT- vs n=3 DT+; p=0.725). At multivariable Cox regression analysis, DT performance was neither associated with a reduction of the primary combined outcome, nor of ineffective shocks at follow-up. A high PRAETORIAN score was positively associated with both the primary outcome (HR=3.976 [1.339–11.802] p=0.013) and ineffective shocks alone at follow-up (HR=19.030 [4.752–76.203] p=0.003).

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