Subcutaneous ICDs reduce complications without compromising shock effectiveness

Implantation of subcutaneous implantable cardioverter defibrillators (S-ICDs) results in fewer perioperative, lead-related complications without offsetting the effectiveness of ICD shocks, reveals a study. However, S-ICDs lead to more early postoperative pain and inappropriate shocks.

Researchers included 544 patients with a primary or secondary prevention indication for an ICD, aged <60 years, who had a cardiogenetic phenotype or prespecified risk factors for lead complications in this randomized, multicentre trial.

Participants were electrocardiographically screened, leading to 503 to be randomly assigned to either S-ICD (n=251) or transvenous ICD (TV-ICD; n=252). Mean follow-up was 2.5 years.

A statistically significant decrease was observed in perioperative, lead-related complications: one patient (0.4 percent) with an S-ICD and 12 (4.8 percent) with TV-ICD (‒4.4 percent, 95 percent confidence interval [CI], ‒6.9 to ‒1.9; p=0.001).

Moreover, a trend appeared for more inappropriate shocks with the S-ICD (hazard ratio [HR], 2.37, 95 percent CI, 0.98‒5.77), but there was no rise in failed appropriate ICD shocks (HR, 0.61, 95 percent CI, 0.15‒2.57).

Patients on S-ICD reported more ICD site pain, measured on a 10-point numeric rating scale, on the day of implant (4.2 vs 2.9; p<0.001) and 1 month later (1.3 vs 0.9; p=0.035).

Of note, the trial was underpowered to detect differences in clinical shock outcomes, but an extended follow-up is ongoing.

“ICDs improve survival in patients at risk for cardiac arrest but are associated with intravascular lead-related complications,” the researchers said. “The S-ICD, with no intravascular components, was developed to minimize lead-related complications.”