Outcome prediction by myocardial external efficiency from 11C‐acetate positron emission tomography in cardiac amyloidosis

Abstract Aims This study aimed to study the prognostic value of myocardial oxygen consumption (MVO2) and myocardial external efficiency (MEE) from 11C‐acetate positron emission tomography (PET) in cardiac amyloidosis (CA) patients. Methods and results Forty‐eight CA patients, both transthyretin (ATTR) and immunoglobulin light chain (AL) amyloidosis, and 20 controls were included. All subjects were examined with 11C‐acetate PET and echocardiography. MVO2, forward stroke volume (FSV), and left ventricular mass (LVM) were derived from 11C‐acetate PET and used to calculate MEE. CA patients were followed for survival and the prognostic impact of clinical, echocardiographic, and 11C‐acetate PET parameters was analysed. MVO2 and MEE were reduced in CA compared with controls, but without significant difference between deceased and surviving CA patients. The ratio of 11C‐acetate PET‐derived FSV and LVM was also reduced in CA and significantly lowered in deceased patients compared with survivors. In univariate analysis, New York Heart Association class, N‐terminal pro‐brain natriuretic peptide, and the 11C‐acetate PET parameters FSV/LVM and MEE were the strongest prognostic factors. Of the 11C‐acetate PET parameters, FSV/LVM was the strongest survival predictor with hazard ratio of 0.56 per 0.1 mL/g (95% confidence interval 0.39–0.81, P = 0.002) and independently prognostic in a multivariate model. MEE significantly separated deceased from surviving CA patients with the cut‐off of 15.7% (P = 0.032). Survival was significantly shorter with FSV/LVM below 0.27 mL/g (P