PRAETORIAN-DFT: Safe to Forgo Defibrillation Testing for S-ICD Implant

CHICAGO, IL—Defibrillation testing (DFT) is not always necessary in patients receiving a subcutaneous implantable cardioverter defibrillator (S-ICD) when using a scoring system that assesses the correct position of the device on a postimplant chest X-ray, according to findings from the randomized PRAETORIAN-DFT trial.

The rate of failed first shocks for spontaneous ventricular arrhythmias—the primary endpoint—was 1.7% among patients in the no-DFT group and 2.3% in the DFT group, a difference that met criteria for noninferiority with a 3% margin (P < 0.001). There was no difference in mortality between the trial arms, with fewer complications in the no-DFT group.

Reinoud Knops, MD, PhD (Amsterdam University Medical Centre, the Netherlands), reported the data recently at Heart Rhythm 2026.

“Defibrillation testing can be safely omitted after S-ICD implantation when guided by the PRAETORIAN score,” Knops concluded, adding that the strategy “simplifies the procedure, potentially increasing S-ICD adoption.”

The findings were published simultaneously online in Circulation.

PRAETORIAN-DFT

Trials like SIMPLE and NORDIC ICD have shown that defibrillation testing after implantation of transvenous ICDs “has largely become obsolete,” Knops said. He noted that DFT requires sedation or general anesthesia, “which is a logistical burden and potential risk.”

The Heart Rhythm Society, the European Heart Rhythm Association, and others strongly recommend DFT after implantation of S-ICDs, which have been shown to carry lower risks of lead-related and major complications compared with transvenous devices in trials like PRAETORIAN and ATLAS S-ICD.

“We still test because effective S-ICD defibrillation highly depends on implant positioning,” Knops said.

His group previously developed the PRAETORIAN score, which reflects the positioning of the device as seen on a postimplant chest X-ray, as a potential alternative to DFT. A low score (below 90) has been shown to predict defibrillation success with more than 99% accuracy.

The PRAETORIAN-DFT trial, conducted at 37 centers in Europe, the United States, and Israel, compared a no-DFT strategy guided by the PRAETORIAN score with routine DFT in patients receiving de novo ICD implants. Patients randomized to no DFT only underwent such testing if their PRAETORIAN score was 90 or higher; 95% ultimately had a score below that threshold.

Investigators enrolled 965 patients (mean age 54 years; 24% women) and followed them for a median of 41 months. Overall, 45% had ischemic cardiomyopathy and 35% had nonischemic cardiomyopathy; about one-third had a secondary prevention indication for ICD therapy. Mean LVEF was 40%.

The primary endpoint was failed first shocks for spontaneous ventricular tachycardia or fibrillation (VT/VF) episodes. The rate observed in the DFT group was “a very reassuring low number in a group of patients that you want to protect from sudden cardiac death,” with an even lower rate in the no-DFT arm, Knops said.

In both groups, all failed shocks were followed by a successful shock or self-termination of the arrhythmia. The proportion of patients with appropriate shocks in response to VT/VF was 12.6% in the no-DFT group and 15.8% in the DFT group, a nonsignificant difference.

This has potential medicolegal implications, and so these guidelines absolutely need to be updated. Andrea Russo

All-cause death occurred at similar rates in the no-DFT and DFT arms (7.2% vs 8.1%; HR 0.9; 95% CI 0.6-1.4), with only one and three arrhythmic deaths, respectively, in the two groups. None of the deaths were related to ineffective S-ICD therapy, Knops reported.

In terms of safety, potential DFT-related complications occurred in 1.7% of patients randomized to routine DFT and none of those randomized to the no-DFT strategy (P < 0.01). Composite complications within the first 30 days were less frequent in the no-DFT arm (1.7% vs 4.8%; HR 0.36; 95% CI 0.16-0.80).

Although not all of those complications are related to DFT, the main drivers of the difference—like unplanned stays in the intensive care unit and cardiac decompensation—could be, which “underscores the potential harm of DFT testing,” Knops said.

Practice-Changing Results

Discussant Andrea Russo, MD (Cooper Medical School of Rowan University, Camden, NJ), noted that despite recommendations from professional societies, many S-ICD patients do not undergo DFT and instead have lead placement guided by fluoroscopy and/or impedance testing. “This has potential medicolegal implications, and so these guidelines absolutely need to be updated,” Russo said.

She said PRAETORIAN-DFT is a well-conducted study that “addresses a really important gap in our knowledge . . . and should change our practice.”

Still, there are many unanswered questions, Russo added, pointing to issues around implant technique in the patients with high PRAETORIAN scores, device repositioning in the no-DFT group, the potential role of impedance measurement, generalizability of the results to a broader swath of S-ICD implanters, details on DFT performed during the trial, and more.