Defibrillation testing (DFT) during subcutaneous implantable cardioverter-defibrillator (S-ICD) implantation is recommended to confirm effective shock delivery but carries procedural risks. In a multinational randomized trial conducted across 37 centers, omission of DFT guided by the PRAETORIAN score was noninferior to routine testing for first-shock efficacy after S-ICD implantation. A total of 965 patients were randomized to DFT (n=482) or no DFT (n=483). Results were published in Circulation.

In the no-DFT group, the PRAETORIAN score, derived from chest radiography, was assessed before discharge to estimate defibrillation success. The primary endpoint was failed first shock for spontaneous ventricular arrhythmias, analyzed with a prespecified noninferiority margin of 3% absolute risk. Secondary endpoints included all-cause mortality, arrhythmic death, DFT-related complications, and device revisions.

Over a median follow-up of 41 months, failed first shock occurred in 1.7% of the no-DFT group compared with 2.3% in the DFT group (absolute difference, −0.6%; 95% confidence interval [CI], −2.6 to 1.4; p<0.001 for noninferiority).

All-cause mortality was comparable between groups (hazard ratio [HR], 0.9; 95% CI, 0.6–1.4), as was arrhythmic death (HR, 0.4; 95% CI, 0.04–3.4). DFT-related complications occurred in 1.7% of patients undergoing testing. Device revisions due to inadequate positioning were infrequent and identical across groups (n=2 each).

PRAETORIAN score-guided omission of DFT met noninferiority criteria for first-shock efficacy. Avoiding routine DFT reduced procedural risk without increasing device revisions.