Funding Acknowledgements Type of funding sources: None. Introduction Implantable cardioverter defibrillator (ICD) is gold standard therapy for primary and secondary prevention of sudden cardiac death (SCD) and ventricular tachyarrhythmias. While reducing arrhythmic mortality in patients with left ventricular dysfunction of various causes, inherited primary arrhythmia syndromes and after aborted SCD, these devices can have serious adverse effects including inappropriate shocks and device-related infection. Purpose The aim of this study was to create an institutional ICD registry and to examine the major complications after ICD implantation. Methods We analysed the data concerning all newly implanted ICDs in our institution from 2011 to 2017. All patients received periprocedural antibiotic prophylaxis according to relevant guidelines. Follow-up data was collected from hospital electronic medical records. Results Total number of implanted ICDs was 507 (85.4% male, 57.6 ± 14.0 years-old) and mean follow-up was 34.3 ± 23.8 months. Major complications (infection, large haematoma/hemorrhage, lead displacement/dysfunction) occurred in 18 (3.6%) patients. In 9 (1.8%) cases patients were diagnosed with ICD infection (8 surgical wound/pocket infections and 1 confirmed endocarditis of the lead). Device was explanted in 5 cases (1.0%) while the rest were treated only with antibiotic therapy (empirically or according to swab/blood culture results). All of the infections were successfully resolved and no relapses were noted. Eventually, 3 of 5 devices were reimplanted. One death was recorded 5 month after the explanation. Second most common complication was lead displacement/dysfunction which occurred in 5 (1.0%) patients and was successfully repaired in all cases. Large haematoma and/or hemorrhage at the implantation site were present in 5 (0.8%) patients (2 required surgical revision and transfusion while 2 were managed by needle aspiration). Pneumothorax (2 cases, 0.4%) had to be drained in one patient. There was one case of subclavian vein thrombosis which was treated by anticoagulation. Conclusion Despite appropriate antibiotic prophylaxis, the rate of ICD infections in our institution was relatively higher than the one reported in similar registries. The prevalence of other major complications, including lead dysfunction was quite low. Institutional registries could help monitor and plan actions to resolve ICD-related complications to improve patient outcomes.

Funding Acknowledgements Type of funding sources: None. Introduction Implantable cardioverter defibrillator (ICD) is an effective therapy for primary (PP) and secondary prevention (SP) of sudden cardiac death (SCD). ICD adverse events include inappropriate shocks (IS), device infection and failure.  Methods We analysed the data concerning all newly implanted ICDs in our institution from 2011 to 2017. Follow-up data was collected until the end of 2019. Results In total, 507 ICDs were implanted (85.4% male, 57.6 ± 14.0 years-old), 375 (74.0%) for PP and 132 (26.0%) for SP. The mean follow-up was 34.3 ± 23.8 months. ICD delivered therapy in 42.4% of SP and in 28.8% of PP patients (p = 0.15). In PP, shocks were delivered in 25.7% of non-ischaemic heart disease (NIHD) and in 17.6% ischaemic heart disease (IHD) patients (p = 0.81). IS were significantly more common in NIHD patients (13.8% vs 2.4% in IHD group, p < 0.0001). PP patients with NIHD also had a higher shock burden (average of 8.0 ± 17.4 shocks compared to 2.7 ± 3.0 in the IHD group). However, it failed to reach the level of statistical significance (p = 0.052). In SP, the rate of ICD activation and that of IS were similar in both groups (IHD and NIHD). In total, 32.6% of SP patients received appropriate shock (AS) and 5.3% of them received at least one IS (average number of AS and IS being 8.7 ± 11.5 and 1.1 ± 0.4 respectively). Mortality was significantly higher in SP than in PP (34.8% vs 13.9%, p < 0.001). In PP, significantly more deaths occurred among IHD than NIHD patients (18.8% vs 10.0%, p < 0.001).  Conclusion The prevalence of AS and IS was relatively higher than reported elsewhere. Same was true for mortality. Interestingly, the rate of IS was somewhat higher in NIHD than in IHD, which was unexpected. ICD outcomes Primary prevention Secondary prevention Total IHD NIHD Total IHD NIHD Patients, n 375 165 210 132 88 44 Patients with ICD activation, n (%) 108 (28.8) 46 (27.9) 62 (29.5) 56 (42.4) 33 (37.5) 22 (50.0) Patientns with AS, n (%) 60 (16.0) 27 (16.4) 33 (15.7) 43 (32.6) 29 (33.0) 14 (31.8) Patientns with IS, n (%) 33 (8.8) 4 (2.4) 29 (13.8) 7 (5.3) 5 (5.7) 2 (4.5) AS delivered (mean ± SD) 5.6 ± 13.3 2.7 ± 3.0 8.0 ± 17.4 8.7 ± 11.5 9.9 ± 12.2 9.7 ± 17.6 IS delivered (mean ± SD) 3.2 ± 5.1 1.2 ± 0.5 3.5 ± 5.4 1.1 ± 0.4 1.0 ± 0 3.2 ± 5.2 Deaths, n (%) 52 (13.9) 31 (18.8) 21 (10.0) 46 (34.8) 32 (36.4) 14 (31.8) Time to death (months, mean ± SD) 20.3 ± 13.9 19.9 ± 12.6 21.1 ± 16.5 27.1 ± 25.7 28.9 ± 24.9 22.6 ± 28.1 ICD, implantable cardioverter defibrillator; IHD, ischemic heart disease; NIHD, non-ischemic heart disease; AS, appropriate shock; IS, inappropriate shock