Subcutaneous ICDs Could Reduce Risk of Lead-Related Complications

Jeff Healey, MD

Results of the ATLAS trial demonstrate use of subcutaneous implantable cardioverter-defibrillator (S-ICD) was associated with a more than 90% reduction in major lead complications compared against transvenous implantable cardioverter-defibrillator (TV-ICD) in ICD-eligible patients

A randomized trial comparing use of S-ICD versus TV-ICD in a cohort of more than 500 ICD-eligible patients with cardiogenetic syndrome or considered to be at high risk for lead-related complications, results of the trial indicate use of the S-ICD, which is implanted under the skin just below the patient’s armpit, was associated with lower odds of the study’s primary outcome of major lead complications at 6 months, with no instances of pneumothorax, lead dislodgement, subclavian venous thrombosis, or significant tricuspid insufficiency occurring among those receiving S-ICD in the trial.

“The S-ICD greatly reduces perioperative, lead-related complications without significantly compromising ICD performance,” says Jeff Healey, a senior scientist at the Population Health Research Institute (PHRI) at McMaster University and Hamilton Health Sciences, in a statement. “The S-ICD is now an attractive alternative to the TV-ICD, particularly in patients at increased risk for lead-related complications.”

Led by Healey and colleagues at the PHRI, the Boston Scientific-funded Avoid Transvenous Leads in Appropriate Subjects (ATLAS) trial was designed as a multicenter, randomized, open-label, parallel-group trial with the intent of comparing use of a standard, single chamber TV-ICD against S-ICD for risk of preoperative and long-term complications. With this in mind, investigators enrolled patients aged 18-60 years of age with a primary or secondary indication for an ICD and randomized them to either TV-ICD or S-ICD, these patients were then followed for 12-48 months to assess outcome measures.

The primary outcome of interest was a composite of major lead-related preoperative complications at 6 months, which consisted of hemothorax or pneumothorax, cardiac perforation, tamponade, pericardial effusion, or pericarditis, lead dislodgement or loss of pacing/sensing requiring revision, new moderate-severe or severe tricuspid insufficiency, or ipsilateral upper-extremity deep venous thrombosis. The secondary outcome of interest for the trial was a safety composite that included all the primary outcome events and device-related infection requiring surgical revision, significant wound hematoma, myocardial infarction, stroke, and mortality.

Ultimately, 503 patients underwent randomization in the trial, with 251 randomized to S-ICD and 252 randomized to TV-ICD. This cohort had a mean age of 49 (SD, 11.5) years, 74.2% were men, 22.5% had a history of cardiac arrest, 78.5% reported beta-blocker use at baseline, and the mean follow-up time was 2.5 (SD, 1.1) years. Of the 251 in the S-ICD group, 247 underwent implantation. Of the 252 in the TV-ICD group, 246 underwent implantation.

Upon analysis, results indicated the risk of a primary outcome event was significantly reduced with S-ICD compared to TV-ICD (OR, 0.08 [95% CI, 0.00-0.55]; P=.003). Investigators pointed out just a single patient in the S-ICD arm of the trial experienced a patient had cardiac perforation, tamponade, pericardial effusion, or pericarditis, while a total of 12 primary outcome events occurred among patients in the TV-ICD arm. Further analysis indicated there were no statistically significant difference in the rate of secondary outcome events (4.4% vs 5.6%; OR 0.78; 95% CI 0.35-1.75), but Healey pointed out in his presentation that a numerically greater number of these events occurred when assessing any inappropriate shock among patients in the S-ICD arm compared against the TV-ICD arm.

“The S-ICD produces the first demonstration that there is a clear reduction in major lead-related complications of 92%. There is no significant loss in ICD performance; specifically, no reduction in shock efficacy and inappropriate shocks. Although numerically higher, it did not reach statistical significance and will be the subject of additional analyses,” Healey added during his presentation.

This study, “Subcutaneous Versus Transvenous Defibrillators: The Atlas Trial,” was presented at HRS 2022.