110 Delayed remodelling in severe LVSD, does this reduce the need for primary prevention ICDs? Ideal-HF feasibility study

Introduction Heart failure with reduced ejection fraction (HFrEF) increases the risk of sudden cardiac death (SCD). ESC and NICE guidelines recommend primary prevention implantable cardioverter-defibrillator (ICD) for HFrEF patients with an LVEF ≤35% despite 3 months of optimised medical therapy (OMT). Recommendations are primarily based on data from MADIT II and SCD-HeFT. However, OMT in these trials was suboptimal by current standards. Further, several studies have shown improvements in LVEF with longer OMT. If LVEF improves with newer/longer OMT, ICD implantation may be avoidable for many patients. Consideration must be given to the safety of delaying ICD implantation. However, the absolute risk reduction of mortality in MADIT II and SCD-HeFT was only 1% at 12 months (0% for patients with DCM). We assessed the impact of longer duration OMT on LV function and ICD therapy rates in patients who have already undergone guideline-directed ICD implantation. Methods This is a multi-centre, observational study enrolling adults with HFrEF. Patients had to have been treated with OMT for ≥3 months at the time of ICD implantation, and for between 12 and 24 months at the time of reassessment. Patients with cardiac resynchronisation therapy or an indication for RV pacing were excluded. Approval was obtained from local and national ethics committees. Two timepoints were compared, baseline (3 months of OMT) and follow-up (12–24 months of OMT). Main outcomes proportion of participants with LVEF >35% after ≥12 months of OMT appropriate and inappropriate ICD therapy complications secondary to ICD implantation Results Since January 2022, 26 patients have been recruited. Baseline characteristics are shown in table 1. The mean duration of OMT at follow-up was 547 days (122). At baseline, mean LVEF was 28.4% (4.7) (figure 1). At follow-up, mean LVEF increased to 33.9% (5.8) (figure 1) and 8 patients (31%) had an LVEF of >35%. 1 patient required a lead revision for RV lead displacement. 1 patient had their ICD explanted due to suspected infection. Only 1 patient received appropriate therapy from their ICD, receiving anti-tachycardia pacing (ATP) for VT 583 days post-implant. 1 patient received both an inappropriate shock and inappropriate ATP. 1 patient received an inappropriate shock and 1 patient received inappropriate ATP. Conclusions We found that 31% of patients no longer met the indications for a primary prevention ICD after a longer duration of OMT. If ICD implantation were delayed many patients could avoid ICD implantation altogether. Further, rates of appropriate ICD therapy were low; within the first 12 months after ICD implant no patients received appropriate therapy from their device. This suggests that the risk of ventricular arrhythmias is low and it may be safe to delay primary prevention ICD implantation until patients have been on OMT for a longer duration. However, our study is limited by small numbers. We plan to continue recruitment to reach target of 50 patients. Conflict of Interest None