Abstract Body (Do not enter title and authors here):
Background: Electroanatomic mapping (EAM) guidance for endomyocardial biopsies (EMB) has been suggested to be feasible and safe, but the diagnostic yield remains unclear for cardiomyopathies.

Objective: We aimed to evaluate the diagnostic efficacy of EAM and intracardiac echocardiography (ICE)-guided EMBs.

Methods: We retrospectively reviewed patients who underwent EMB from August 2018 to July 2024. EMB was guided by EAM using CARTO system (Biosense Webster, Irvine, CA), and ICE. After accessing the right femoral vein, samples (3-6 per suspected site) were collected using a disposable bioptome and steerable sheath. For left ventricular (LV) biopsies, we used a transseptal approach, and for atrial biopsies, we targeted the atrial septum. In cases of abnormal EAM, multiple samples were taken from the identified areas. When EAM was normal, biopsy targeting was guided by adjunctive imaging. EMB was considered positive if pathology demonstrated findings that directly corroborated the diagnosis.

Results: Of 87 patients who underwent EMB, the median age was 61 years, and 33% were female. EMB sites included the right ventricle (RV) and LV (15/87), RV only (27/87), LV only (38/87), right atrium (RA) and LV (3/87), and RA only (4/87). Pre-procedural imaging was common: cardiac MRI (80%), cardiac PET (65.6%), and/or pyrophosphate scan (8%). Mean LV ejection fraction was 44%, and mean scar burden was 11% on MRI. The overall diagnostic yield was 18%, encompassing a wide spectrum of pathologies (Figure 1A). Positive biopsy results were significantly associated with pre-procedural suspicion of amyloidosis (Odds Ratio {OR} 6.5, 95% CI 1.2-35.5), myocarditis (OR 6.5, 95% CI 1.2-35.5), or cardiac masses (OR 3.9, 95% CI 1.1-13.9), and sampling from both RA and LV (Figure 1B). EAM and ICE during EMB (Figure 1C) were used in 85% and 99% of cases, respectively. No procedural complications were observed.

Conclusions: In our cohort, EAM-guided EMB is a safe diagnostic tool with the best yield for pre-procedural suspicion of amyloidosis, myocarditis, or cardiac masses. Future studies investigating the role of potential tools to optimize biopsies for undifferentiated cardiomyopathies and cardiac sarcoidosis could significantly improve the potential value of EAM-guided EMB.