Subcutaneous implantable cardioverter-defibrillator (S-ICD) therapy could be continued after intervention in a majority of patients with a complication, according to a recent study published in the Journal of the American College of Cardiology: Clinical Electrophysiology.

Although conventional transvenous ICDs have been shown to increasesurvival, approximately 10% to 15% of patients experience implant-related or long-term complications. The S-ICD was introduced to reduce harm associated with transvenous leads, which can cause thrombotic events, cardiac perforation, and lead endocarditis.

The researchers sought to assess outcomes of S-ICD therapy after implant-related complications in order to avoid switching to transvenous ICD therapy.


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Study end points included complications related to the implantation of the S-ICD system, such as infection, hematoma, or skin erosion, requiring surgical intervention such as reposition or device extraction.

The study included 123 patients who had received an S-ICD at a median age of 40 years. Underlying diagnoses included ischemic cardiomyopathy (16%) and nonischemic cardiomyopathy (19%), genetic arrhythmia syndromes (58%), congenital heart disease (4%), or a family history of sudden cardiac death and non-sustained ventricular tachycardias (3%).

Complication-free survival at 1 year was 91.8% (95% confidence interval [CI], 86.5%-97.0%) and at 2 years, 90.6% (95% CI, 84.6%-96.3%). There were 8 cases that required surgical intervention due to infectious complications: 5 from device infection and 3 from pocket erosion. The S-ICD systems were extracted and were later re-implanted. A wearable cardioverter defibrillator (WCD) was used as bridge therapy, lasting from 6 weeks to 3 months.

In addition, 6 patients had presumed infections: 5 patients had symptoms of superficial infection and 1 had a swollen pocket with elevated infection biomarkers; those patients were treated with antibiotics. There were also 2 acute non-infectious complications that required intervention: 1 case with defibrillation threshold test (DF-test) failure due to malposition of device and 1 case of lead displacement.

One patient experienced an inappropriate shock approximately 2 months after implantation due to oversensing of myopotential. A chest x-ray revealed the tip of the lead had migrated in a caudal direction and the proximal part of the coil toward the pulse generator. After the lead was repositioned, the oversensing resolved.

Another patient failed both the peri-procedural DF-test and a second DF-test the day after implantation. The researchers noted that this discovery underscores the importance of positioning the pulse generator directly on the fascia of the chest wall centered in the mid-axillary line.

“Although the sample size of this cohort was too small to provide a precise estimate of the complications rate,” the researchers wrote, “it was similar to the large S-ICD cohort published study by Burke et al which reported 9.6% complications at 2 years follow-up.”

“Our study provides several insights regarding complications of S-ICD therapy In 9 out of the 10 patients with a complication, S-ICD therapy could be continued after intervention. In these 9 patients, conversion to transvenous ICD therapy was an option, but not decided.”

Reference

Brouwer TF, Driessen AHG, Nordkamp Olde LRA, et al. Surgical management of implant related complications of the subcutaneous implantable defibrillator. JACC Clin Electrophysiol. 2015;doi:10.1016/j.jacep.2015.09.011.