Real-world outcomes of subcutaneous ICD implants: a single-centre experience

Background/Introduction

Subcutaneous implantable cardioverter-defibrillators (S-ICDs) avoid intravascular leads and reduce long-term lead-related complications when compared with transvenous systems.1,2 While large multicentre trials support their safety, outcomes from lower-volume, non-tertiary hospitals are less well characterised.

Purpose

To report real-world clinical outcomes following all S-ICD implantations at a single large district general hospital (DGH) in the United Kingdom and provide centre-level benchmarking against published trial data.

Methods

We retrospectively reviewed consecutive S-ICD implants performed at our centre between 2017–2025. Patients with no follow-up were excluded. The primary composite endpoint included the first occurrence of a device-related complication or an inappropriate shock. Time-to-event analyses used Kaplan–Meier (KM) methods. Crude proportions were compared with the PRAETORIAN S-ICD arm using Fisher’s exact test.3 A secondary time-to-first appropriate shock analysis was performed.

Results

There were 81 patients in the study cohort (mean age 50 years; 77% male). Reverse-KM median follow-up was 39.4 months. 16 patients (19.8%) met the primary composite endpoint. Components included 10 inappropriate shocks and device-related complications (1 infection, 1 lead fracture, 3 device extractions for device-related issues and 1 generator repositioning). There were 4 deaths, none attributed to the device.

The 36-month KM cumulative incidence of the primary composite endpoint was 20.1 % (95 % CI 8.9–29.9), increasing to 26.0 % (95 % CI 12.3–37.5) at 48 months. The event rate was 6.8 per 100 patient-years (95 % CI 3.9–11.1). Compared with the PRAETORIAN S-ICD cohort (68/426 [16%] patients met the primary endpoint), there was no statistically significant difference in crude event proportions (p = 0.42; RR 1.24 [95 % CI 0.76–2.02]).3

13 patients (16.0 %) received at least one appropriate shock during follow-up. The reverse-KM median follow-up for this analysis was 32.5 months, with a 48-month cumulative incidence of 23.3 % (95 % CI 9.1–35.3) and an event rate of 6.0 per 100 patient-years (95 % CI 3.2–10.3). When compared with the PRAETORIAN S-ICD arm, in which 83 of 426 patients (19.5 %) received an appropriate shock, there was again no statistically significant difference (p = 0.42; RR 0.82 [95 % CI 0.49–1.38]).3

Conclusion(s)

In this single-centre DGH experience, S-ICD implantation produced event rates and follow-up duration comparable to large trial data. The 4-year cumulative risk of device-related complication or inappropriate shock is clinically notable and underlines the importance of careful patient selection, procedural planning and structured follow-up pathways in DGH practice. Limitations of our study include the retrospective design and modest sample size; further multi-centre DGH data and pooled analyses would improve precision.KM Primary Composite EndpointKM Appropriate Shock