The following is the summary of “Perioperative Safety and Early Patient and Device Outcomes Among Subcutaneous Versus Transvenous Implantable Cardioverter Defibrillator Implantations” published in the December 2022 issue of Internal medicine by Healey et al.

Patients at risk for cardiac arrest benefit from implantable cardioverter defibrillators (ICDs), however, they can have issues from the intravascular leads. The subcutaneous (S-ICD) was designed to reduce the risk of problems from leads because it is implanted subcutaneously. The purpose of this study is to evaluate the effectiveness of an implantable cardioverter defibrillator (ICD) by analyzing key ICD performance measures related to the delivery of ICD therapy, such as the number of inappropriate ICD shocks (shocks delivered in the absence of a life-threatening arrhythmia) and the number of failed ICD (which did not terminate ventricular arrhythmia).

Multi-site, randomized clinical trial design. Currently enrolling participants (NCT02881255)  503 patients were randomly assigned to S-ICD (251 patients) or transvenous ICD (TV-ICD) based on electrocardiographic screening results from 544 patients (141 female) with a primary or secondary prevention indication for an ICD who were younger than age 60 years, had a cardiogenetic phenotype, or had prespecified risk factors for lead complications (252 patients). The average duration of follow-up was 2.50 years (SD, 1.1). An average of 49 years of age (SD, 11.5). Lead-related significant complications during surgery were the primary outcome measure. One patient (0.4%) with an S-ICD and 12 patients (4.8%) with a TV-ICD experienced perioperative lead-related problems; this represents a statistically significant reduction in risk (4.4%; 95% CI, 6.9 to -1.9; P=0.001). In addition, the S-ICD was associated with a higher risk of inappropriate shocks (hazard ratio [HR], 2.37; 95% CI, 0.98 to 5.77) but no higher risk of failed acceptable ICD shocks (HR, 0.61]. (0.15 to 2.57). 

On the day of the implant (4.2 ± 2.8 vs. 2.9 ± 2.2; P<0.001) and 1 month later (1.3 ± 1.8 vs. 0.9 1.5; P=0.035), patients in the S-ICD group reported significantly higher levels of ICD site discomfort compared to those in the control group using a 10-point numeric rating scale. Although the ATLAS experiment is being followed up on for longer, it is currently underpowered to identify differences in clinical shock outcomes. There is an increase in early postoperative discomfort and a trend toward more inappropriate shocks, but the S-ICD lowers perioperative, lead-related problems without appreciably affecting the effectiveness of ICD shocks.