Abstract Body (Do not enter title and authors here): Background:
Reduced ejection fraction in the setting of transthyretin cardiac amyloidosis (ATTR-CA) is associated with a poor prognosis. Based on current left ventricular ejection fraction (LVEF) based guidelines, patients with ATTR-CA and a persistent LVEF ≤35% should receive an implantable cardioverter-defibrillator (ICD) for primary prevention of sudden cardiac death (SCD). However, no studies to date have shown a survival benefit with primary prevention ICD in ATTR-CA cardiomyopathy.

Objective:
To investigate the effect of ICD placement on outcomes in patients with ATTR-CA.

Methods:
This retrospective study was conducted utilizing TriNetX, a claims and electronic health records based multicenter database. Patients diagnosed with ATTR-CA and an LVEF ≤35% based on their most recent echocardiogram, without documented prior ventricular arrhythmias, were identified. Patients with light-chain cardiac amyloidosis were excluded. Differences in mortality and ventricular tachycardia (VT) between ATTR-CA patients with and without ICD placement were evaluated. Propensity score matching (PSM) was performed using clinical parameters associated with SCD.

Results:
A total of 94 patients with ATTR-CA had an ICD placed, while 353 patients with ATTR-CA and an LVEF ≤35% did not have an ICD. When comparing the ATTR-CA and ICD group to ATTR-CA without ICD group, Kaplan-Meier analysis of 5-year survival from death was 41.0% v. 32.5% (p=0.121) and 1-year survival from death was 77.15% v. 65.58% (p=0.157). No diagnoses of VT were recorded in either cohort. Significant differences between the cohorts existed, which were balanced using PSM, yielding 82 patients in each group. Tafamidis usage was similar in both cohorts (12.2% vs 12.2%, p=1.00).

Conclusion:
In patients with ATTR-CA and reduced LVEF, primary prevention ICD placement did not demonstrate statistically significant differences in mortality or VT compared to a PSM cohort without ICDs. Further research is needed to develop more precise criteria for identifying ATTR-CA patients who would benefit from primary prevention ICD beyond LVEF measurement.