Background
Subcutaneous implantable cardioverter-defibrillators (S-ICDs) have emerged as a vital tool in preventing sudden cardiac death (SCD) in high-risk patients. Unlike traditional transvenous ICDs, S-ICDs avoid intravascular lead complications but require precise subcutaneous positioning to ensure effective defibrillation. Historically, defibrillation (DF) testing has been recommended post-implantation to verify shock efficacy. However, DF testing carries risks, including hemodynamic instability and, in rare cases, death. The PRAETORIAN score, derived from chest X-ray analysis, was developed to predict DF success without the need for invasive testing. The PRAETORIAN-DFT trial aimed to validate this approach.
Study Design
This multinational, randomized controlled trial enrolled 965 patients from 37 centers, randomizing them into two groups: one undergoing standard DF testing (n=482) and the other omitting DF testing (n=483). In the latter group, the PRAETORIAN score was evaluated pre-discharge to ensure adequate device positioning. The primary endpoint was the rate of failed first shocks for spontaneous ventricular arrhythmias, tested for non-inferiority with a 3% absolute risk margin. Secondary endpoints included mortality rates, DF testing-related complications, and S-ICD revisions due to positioning issues.
Key Findings
After a median follow-up of 41 months, the No-DF testing group exhibited a first-shock failure rate of 1.7%, compared to 2.3% in the DF testing group (-0.6%, 95% CI [-2.6 to 1.4]; p<0.001), meeting the non-inferiority criteria. All-cause mortality (HR 0.9 [95% CI 0.6-1.4]) and arrhythmic death (HR 0.4 [95% CI 0.04-3.4]) showed no significant differences between groups. Importantly, potential DF testing-related complications occurred in 1.7% of the DF testing group, highlighting the procedural risks avoided in the No-DF testing arm. Postoperative S-ICD revisions due to inadequate positioning were identical between groups (n=2 each).
Expert Commentary
The results of the PRAETORIAN-DFT trial align with growing clinical evidence advocating for the omission of routine DF testing in S-ICD implantation. The trial’s findings suggest that the PRAETORIAN score reliably predicts DF success, reducing procedural risks without compromising patient outcomes. Limitations include the surrogate nature of the primary endpoint, though the long-term follow-up strengthens the clinical relevance of the findings. Future studies could explore the broader applicability of this approach, particularly in diverse patient populations.
Conclusion
The PRAETORIAN-DFT trial provides robust evidence supporting the omission of DF testing in S-ICD implantation when guided by the PRAETORIAN score. This approach reduces procedural risks and maintains shock efficacy, offering a safer alternative for high-risk patients. Further research is warranted to validate these findings in broader clinical settings.
Funding and ClinicalTrials.gov
The PRAETORIAN-DFT trial was funded by Boston Scientific. The trial registration number is available on ClinicalTrials.gov.