INTRODUCTION

The subcutaneous implantable cardioverter-defibrillator (S-ICD™ System, SQ-RX Model 1010, Boston Scientific) is a novel therapy for primary and secondary prevention of sudden cardiac death due to ventricular tachyarrhythmias. The lack of vascular access needed for the procedure mitigates complications of transvenous devices such as lead failure and infection. In the IDE trial for the S-ICD, there were 18 total suspected or confirmed infections, of which 14 (4.4% of the total study cohort) were managed without explantation of the device.¹ Importantly, none of the infections were systemic, but rather, were localized to the incision or pocket. The lack of endovascular infections is in stark contrast to transvenous defibrillators, which have a 22-54% rate of lead-related endocarditis.^2,3 There are clear guidelines for management of transvenous pocket and lead associated infections, which often necessitate device extraction. Management of subcutaneous defibrillator-related pocket infections are yet unclear. In this article, we review our experience with three subcutaneous defibrillator-related pocket infections, and offer potential management strategies as well as methods to reduce infection rates.

PATIENT EXPERIENCE

Patient #1: A 26-year-old obese female with a history of hypertension presented with longstanding non-ischemic cardiomyopathy. Her ejection fraction (EF) declined to 20% despite guideline-directed medical therapy. She was offered a subcutaneous ICD due to her young age and lack of pacing indication. She underwent a standard three-incision implantation technique. Seventeen days later, she presented with pain around her inframammary device pocket. On examination, the pocket was erythematous and tender to palpation (Figure 1). Her two sternal incisions did not appear infected. Intravenous antibiotics were initiated due to an elevated WBC count. Initially, her WBC count improved along with the erythema around her incision; however, her WBC count began to rise again and she began to develop pocket pain on day 8 of her admission. Exploration of the device pocket revealed serosanguineous fluid. An intraoperative Gram stain of the pocket was negative. The pocket was power irrigated with a vancomycin solution. An antibiotic pouch (TYRX™ Antibacterial Envelope, Medtronic, Inc.) was then cut open to accommodate the larger S-ICD can and placed around the device before pocket closure. There was no evidence of recurrent erythema or infection 5 months post discharge (Figure 2).

Patient #2: A 57-year-old male with HIV on anti-retroviral therapy, cutaneous T-cell lymphoma, stroke, and non-ischemic cardiomyopathy presented for evaluation. His most recent absolute CD4 count was 3167. After a pre-operative discussion with his HIV physician and dermatologist, he underwent implantation of a subcutaneous ICD with a two-incision technique. One month later, he presented for evaluation due to pain at the incision site and drainage at the superior margin of the wound with an associated ruptured pustule (Figure 3). His sternal incision did not appear infected. Of note, his cutaneous T-cell lymphoma had flared after implantation. He was admitted, blood cultures were drawn, IV vancomycin initiated, and the infectious disease service was consulted. His initial WBC count was normal. Over the course of four days with IV antibiotics, his pustule formed a scab and his drainage stopped. Superficial cultures of the drainage from his incision grew methicillin-sensitive S aureus. All of his blood cultures showed no growth. He was discharged on a course of oral antibiotics.

Patient #3: A 46-year-old obese female presented with a family history of cardiomyopathy, syncope, heart failure, non-sustained ventricular tachycardia, and a non-ischemic cardiomyopathy with an EF of 25%. She underwent implantation of a subcutaneous ICD with a two-incision technique. On her initial two-week postoperative follow-up visit, she appeared well with no pain at the pocket and no signs of infection. Thirty-seven days post implant, she presented with erythema, tenderness of her pocket, and a low-grade fever. Her single sternal incision appeared normal. She was noted to have an elevated WBC count on admission. She was initiated on IV vancomycin, which resulted in normalization of her WBC count, but the patient continued to have device pocket tenderness. Pocket exploration revealed yellow exudate under high pressure. Intraoperative Gram stain revealed no organisms. The parasternal pocket was also explored, and did not reveal any evidence of infection. The device and lead were removed given the obvious evidence of active infection. The pocket was debrided and closed with a Jackson-Pratt drain in place. Postoperative wound cultures grew methicillin-sensitive S aureus. Blood cultures showed no growth. She was treated with IV antibiotics and discharged home.

DISCUSSION

The incidence of postoperative device infections is not uncommon with the subcutaneous ICD, with rates ranging from 1.4-9.9%.⁴ Indeed, it appears that the rate of pocket infections is greater with the subcutaneous ICD than with traditional transvenous systems.⁴ Management can vary based on the unique characteristics of each case. Factors associated with increased rates of infection include the early learning curve related to implantation resulting in longer operative times, pockets being created too tightly around a bulkier device risking erosion, and selection bias since patients at high risk for blood-borne infections may be more frequently referred for the subcutaneous ICD. However, a two-year follow-up of over 800 implanted patients has reported no incidence of blood-borne infections.⁵  

Possible methods that may prevent infection include adopting the two-incision technique,⁶ reducing total procedure times, placing an antibiotic impregnated gauze in the device pocket while creating the sternal incision(s), and avoiding too small of a device pocket that may result in device erosion. As two of our infections were in obese patients, we believe that postoperative attention to keeping the inframammary incision clean and dry may help reduce infectious risk.  The use of a commercially available antibiotic pouch in select high-risk patients may result in lower rates of pocket infections as well. However, larger pouches capable of housing the larger subcutaneous ICD unit would have to be created.

Postoperative infection management may also vary. There are many successful cases of pocket infections treated with antibiotics only without the need to open the device pocket.^1,4,5 Certainly, a course of IV antibiotics may be considered as an initial strategy in a patient with an erythematous pocket. Early pocket exploration may be entertained in cases where the patient does not clinically respond to therapy, remains febrile, has persistent elevation of the WBC count, or if the patient remains in pain. Device removal should be considered in situations where the pocket is clearly infected with exudate or if an intraoperative Gram stain reveals persistent bacteremia despite antibiotic therapy. It is unclear as to whether a subcutaneous ICD device may be re-implanted after completing antibiotic therapy in the same pocket with an antibiotic pouch.

Summary

The subcutaneous ICD provides protection against sudden cardiac death. Amazingly, no blood-borne infections have been reported after implantation to date. However, the device pocket(s) may become infected. Often, conservative antibiotic therapy is effective, but sometimes, pocket revision with or without device removal is required. The antibiotic pouch may offer an additional protective measure preventing device infection. ■

Disclosures: Outside the published work, Dr. Sanghvi has served on the speaker’s bureau for St. Jude Medical, Medtronic, Boston Scientific, and Boehringer Ingelheim. Dr. Patel has no conflicts of interest to report regarding the content herein.

References

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