Subcutaneous Cardioverter-defibrillator Implantation after Cardiac Surgery and Endocardial Device Infection

Case description

The patient was a 52-year-old man with no relevant family history of cardiovascular disease. He led a sedentary lifestyle, had grade I obesity, and was a former smoker.

His cardiovascular history began in 2021 with exertional angina and dyspnea. Transthoracic echocardiography revealed chamber dilation, severe mitral regurgitation (Carpentier I), systolic dysfunction with a reduced LVEF of 22%, moderate tricuspid regurgitation, high probability of pulmonary hypertension, and generalized hypokinesia.

A comprehensive workup for cardiomyopathy was initiated, including viral serologies, TORCH profile, antibodies against Trypanosoma cruzi (Chagas disease), and an autoimmune panel, all of which were negative. Thyroid studies demonstrated subclinical hypothyroidism.

The patient was admitted to the hospital and, as part of the diagnostic evaluation, underwent invasive coronary angiography. This demonstrated three-vessel coronary artery disease: the left main coronary artery was free of significant lesions; the proximal left anterior descending artery showed total functional occlusion with bifurcation disease involving the first diagonal branch, as well as a mid-segment stenosis of 70%; the intermediate ramus presented an ostial 80% stenosis; the dominant circumflex artery was totally occluded proximally; and the dominant right coronary artery had a proximal 90% lesion, a mid-segment stenosis of 80%, multiple distal tandem lesions, and a chronically occluded posterior descending artery. The calculated SYNTAX score was 55 points.

Given the complexity of the coronary anatomy and the coexistence of severe mitral and moderate tricuspid regurgitation, the case was presented at a multidisciplinary heart team conference, where surgical intervention was recommended. The patient underwent mitral valve replacement with a 29 mm mechanical prosthesis, tricuspid annuloplasty with a 34 mm ring, and myocardial revascularization with a left internal mammary artery graft to the left anterior descending artery and a reversed saphenous vein graft to the intermediate ramus. Due to technical limitations, grafting to the obtuse marginal and posterior descending arteries was not feasible. The postoperative course was uneventful, and the patient was discharged on guideline-directed medical therapy and referred to the outpatient clinic.

Follow-up echocardiography demonstrated normal prosthetic mitral valve function, severely reduced LVEF (18%), decreased right ventricular systolic function, dilation of all four chambers, and mild tricuspid regurgitation with high probability of pulmonary hypertension.

An exercise stress test was subsequently performed to assess functional capacity. Using a modified Bruce protocol, the patient achieved only 55% of his age-predicted maximum heart rate, and the test was terminated due to fatigue. The energy expenditure was 3.6 METS. The test was negative for ischemia but revealed poor exercise tolerance (NYHA class III).

Based on these findings, the cardiology team determined the patient was a candidate for primary prevention ICD. An endocardial device was implanted in the left subclavian region without complications. However, during follow-up, he developed device exposure and was hospitalized with a diagnosis of cardiac implantable electronic device infection. Transesophageal echocardiography excluded vegetations or intracavitary thrombi, and complete device extraction was performed. After negative blood cultures and clinical improvement, he was discharged with the plan for later reimplantation (Figure 1).

Figure 1: Temporal evolution and relevant facts of the condition.Timeline showing the date of onset of symptoms, diagnostic approach, evolution, and date of ICD implantation. Note: Figure created by Daniel Ruiz Domínguez, 2025.

The patient was subsequently evaluated at the electrophysiology clinic and deemed a candidate for subcutaneous ICD implantation. In late 2023, he was readmitted and underwent successful implantation of an EMBLEM™ S-ICD (Boston Scientific). Figure 2 illustrates ventricular tachycardia induction, arrhythmia detection, shock delivery, and restoration of sinus rhythm. Figure 3 depicts the fluoroscopic image of the implanted device.

Figure 2: Tracing of ventricular tachycardia induction and successful device shock. Tracing recorded by the device, where in the line corresponding to second 0 (0.0 s) sinus rhythm is seen. Subsequently, in the tracing corresponding to second 6 (6.0 s), induction of tachycardia is shown (isoelectric line). In the line of second 12 (12.0 s), the tracing corresponding to established ventricular tachycardia is seen. In the line of second 24 (24.0 s), the device senses the tachycardia ending at the line of second 30 (30.0 s) with a shock (indicated by a lightning bolt icon at the bottom of the line), and subsequently sinus rhythm is evidenced in the line corresponding to second 36 (36.0 s). S (Sensing); T (Tachycardia); ϟ (Shock/Discharge).

Figure 3: Post-implant fluoroscopy of ICDs. Image obtained by fluoroscopy immediately after implantation performed in the electrophysiology room, where the coil and generator are seen in adequate position, in addition to the valve prosthesis and the sternal cerclage.

At present, the patient remains free of complications and has experienced no inappropriate discharges. He is asymptomatic with respect to angina and is in NYHA functional class II under optimal pharmacologic therapy, consistent with guideline-directed management for chronic coronary syndromes, valvular disease, and heart failure.

Discussion

Sudden cardiac death accounts for approximately 50% of all cardiovascular mortality in developed nations [1]. The implantable cardioverter-defibrillator (ICD), introduced into clinical practice nearly three decades ago, has consistently demonstrated its ability to reduce mortality both in primary and secondary prevention [2], regardless of whether the underlying etiology is coronary or non-coronary. It significantly improves survival in patients with a history of ventricular arrhythmias and reduced ejection fraction [3].

Over the years, ICD technology has undergone significant evolution. Initially, devices were implanted via thoracotomy with epicardial leads. Subsequently, endocardial approaches were developed, adding pacing capabilities. Despite these advances, transvenous implantation carries risks such as hemopericardium, pneumothorax, systemic infection, vascular occlusion, and lead displacement or dysfunction—the latter two considered the Achilles’ heel of transvenous systems [4-11]. Long-term data indicate mechanical complication rates as high as 25% at 10 years [6]. In contrast, complications associated with subcutaneous ICDs (S-ICDs) tend to be less severe, with up to 92% of patients free from adverse events at six months post-implant [10]. Moreover, the S-ICD has been shown to reduce moderate or severe lead-related complications by over 90% compared with transvenous devices [12].

The need to avoid vascular access, prevent intravascular mechanical stress leading to lead dysfunction, and reduce the complexity of device extraction spurred the development of the S-ICD. Since 2010, accumulating evidence has demonstrated the clinical utility of S-ICDs [6]. Early support was derived primarily from non-randomized studies [7,8], but in 2020, the pivotal PRAETORIAN trial established non-inferiority of the S-ICD versus the transvenous ICD with respect to inappropriate shocks and complications, while underscoring its main limitation—lack of pacing support.

Compared with endocardial devices, S-ICDs are associated with fewer complications, most commonly minor bleeding, superficial infection, generator displacement, or local tissue injury [9,10]. Large registries and clinical trials have confirmed their efficacy and safety. The IDE and EFFORTLESS registries demonstrated high first-shock success rates and acceptable complication profiles, forming the basis for real-world adoption. The PRAETORIAN trial confirmed equivalence in outcomes compared with transvenous ICDs, with fewer lead-related complications. The UNTOUCHED study showed particularly low rates of inappropriate therapy in patients with reduced left ventricular function under optimized programming, supporting the avoidance of routine defibrillation testing in most cases. More recently, the ATLAS trial corroborated these findings in younger patients, highlighting a lower incidence of lead-related complications without loss of efficacy.

Technological refinements have also improved outcomes. Intermuscular generator placement has enhanced comfort and cosmetic results while reducing erosion. Simplified two-incision techniques and radiographic scoring tools, such as the PRAETORIAN score, facilitate optimal positioning and reduce oversensing. Programming innovations—including dual-zone detection, high-rate cutoffs, and algorithms such as SMART Pass—have significantly lowered the incidence of inappropriate shocks related to T-wave oversensing. Collectively, these advances have aligned the performance of S-ICDs with that of the best transvenous systems.

Current clinical practice shows increasing adoption of S-ICDs among populations at elevated risk for complications from intravascular hardware. These include younger patients with a long expected device lifespan, individuals on chronic hemodialysis, and patients requiring reimplantation after systemic infection. Growing use is also seen in adults with congenital heart disease, where anatomical complexity often precludes transvenous placement. Although the lack of antitachycardia pacing remains a limitation in those with frequent monomorphic ventricular tachycardia, integration with leadless pacing systems may expand the candidate population. Furthermore, emerging platforms such as the extravascular ICD may offer hybrid solutions by combining pacing and defibrillation without the need for traditional venous access.

In Mexico, where the first S-ICD was implanted in 2008, national experience remains limited, and long-term outcome data are scarce. Efforts to establish a national registry are underway, though the timeline for publication is uncertain. Regarding cost, S-ICD implantation remains expensive, with a total cost of approximately USD 25,000 when including device, hospitalization, and supplies, though this may be reduced by around USD 5,000 in public institutions.

In summary, the S-ICD has transitioned from a niche therapy to a robust alternative to transvenous ICDs in appropriately selected patients. Evidence consistently supports its safety and efficacy, particularly its reduction of lead-related complications. As integration with leadless pacing technologies advances, the clinical utility of the S-ICD will likely continue to expand, consolidating its role in the long-term prevention of sudden cardiac death.

Conclusion

In patients with an established indication for ICD placement—whether for primary or secondary prevention—yet in whom endocardial device implantation is not feasible, referral to a tertiary center for multidisciplinary evaluation should be strongly considered. In such scenarios, implantation of a subcutaneous ICD represents a viable and effective alternative.

Ethics

This study was approved by the institutional ethics committee, and informed consent was obtained from the patient.

Key learning points

This case highlights the importance of recognizing the limitations of transvenous devices and the clinical scenarios in which a subcutaneous ICD should be considered as an appropriate alternative.