Hahn VS, Yanek LR, Vaishnav J, et al. - This research prospectively assessed endomyocardial biopsies in patients with heart failure with preserved ejection fraction (HFpEF) to distinguish histopathologic phenotypes and their correlation with clinical characteristics. Between August 2014 and September 2018, individuals with HFpEF (EF ≥ 50%) referred to the Johns Hopkins HFpEF Clinic were included for a right heart catheterization and endomyocardial biopsy. They ascertained clinical features, echocardiography, hemodynamics, and tissue histology and correlated with controls (unused donor hearts) and HF with reduced EF (HFrEF). A total of 108 patients were included in the study. The data demonstrate that myocardial fibrosis and hypertrophy were common, CD68+ inflammation was increased, and CA prevalence was 14% in this large, prospective myocardial tissue analysis of HFpEF. In HFpEF, tissue analysis might improve precision therapies by distinguishing relevant myocardial mechanisms.