Single center experience with subcutaneous ICD in combination with previously implanted endocardial or epicardial antibradycardia or cardiac resynchronization devices

FUNDING ACKNOWLEDGEMENTS: Type of funding sources: None. BACKGROUND: Subcutaneous ICD (S-ICD) is an established therapy for prevention of sudden cardiac death due to ventricular arrhythmias (VA). One major drawback of the S-ICD is the lack of antibradycardia pacing. Theroretically the S-ICD can be used in combination with endocardial or epicardial pacemaker (PM), or even cardiac resinchronization (CRT) devices, but recently there are only few case reports available on this topic. PURPOSE: To evaluate the feasibility and safety of concomitant use of endocardial or epicardial PM or CRT devices and S-ICD in a single center patient cohort. METHODS: Fifty-seven patients underwent S-ICD implantation in our center between 2017 and 2022. Based on individualized decision making-process, six out of these patients underwent the S-ICD implantation without explantation of previuosly implanted transvenous devices, or after epicardial PM or CRT implantation (group 1). The procedural and follow-up data of these patients were compared with data of the other 51 patients (group 2). All patients underwent successful S-ICD screening before implantation. Patients with previously implanted devices were screened either in bipolar pacing mode and either during intrinsic rhythm, if present. S-ICD implantations were performed under general anaesthesia (33 %) or under deep sedation with ultrasound guided regional nerve blocks (66 %) using intermuscular generator placement and two incision technique. Defibrillation threshold test was performed successfully in all the 57 patients. RESULTS: All S-ICD implantations were performed successfully without any procedural complications. There were no significant difference between group 1 and group 2 in terms of age (52,3±20 yrs vs. 37,7±18,5 yrs, p=0,75), ejection fraction (49,2±25,6 % vs. 46,5±21 %, p=0,77), procedure duration (57±9,7 min. vs. 52,2±15,5 min., p=0,46), and the mean follow-up duration (20,5±23,6 months vs. 25±18,8 months, p=0,59). During follow-up, one patient in group 1 (17%), and 10 patients in group 2 (19,6 %) experienced adequate ICD therapies due to VA. There were no inadequate ICD therapy in group 1, but eight patients (15,6 %) in group 2 suffered from inadequate ICD shocks caused by T wave oversensing (3/8), atrial fibrillation (2/8) myopotential oversensing (2/8,) and S-ICD lead fracture (1/8). In group 1, no interferences occured between the implanted devices, and no missed S-ICD therapy were observed during induced or spontaeous VA due to pacing artefact oversensing by the S-ICD caused by undersensing of the VA by the pacemakers. Non of the patients in group 2 experienced symptomatic bradycardia required antibradycardia pacing during follow up. CONCLUSION: Based on our observations, S-ICD implantation after previously implanted endocardial or epicardial pacemaker or CRT systems seems feasible and safe. After individualized decision-making, with careful screening and device programming the potential interference between the implanted devices can be prevented.