BACKGROUND: Despite previous histopathologic evidence for its presence, the role of myocardial inflammation in the development and progression of cardiac transthyretin amyloidosis (ATTR-CA) remains insufficiently understood. Thus, this study sought to characterize the prevalence and potential prognostic implications of myocardial inflammation in ATTR-CA. METHODS: A retrospective observational study including patients with ATTR-CA diagnosed by endomyocardial biopsy was conducted. Myocardial inflammation was diagnosed through a review of routine endomyocardial biopsy reports. Baseline characteristics were compared using the Mann-Whitney RESULTS: A total of 103 patients with ATTR-CA (100 wild type
3 variant) were enrolled. Median follow-up was 18.2 (8.0-31.1) months. Myocardial inflammation was prevalent in 32% (n=33/103) of patients with ATTR-CA. Among evaluable patients with myocardial inflammation, 96% (n=26/27) and 31% (n=9/29) had elevated CD68 (clusters of differentiation 68)-positive macrophage and CD3 (clusters of differentiation 3)-positive T-cell counts, respectively. Overall survival ( CONCLUSIONS: Our findings affirm previous evidence that myocardial inflammation is present in approximately one-third of all patients with ATTR-CA. Moreover, we provide first data indicating that myocardial inflammation may be associated with a higher risk of death and heart failure hospitalizations in ATTR-CA.