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

Aims This study aimed to study the prognostic value of myocardial oxygen consumption (MVO 2 ) and myocardial external efficiency (MEE) from 11 C‐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 11 C‐acetate PET and echocardiography. MVO 2 , forward stroke volume (FSV), and left ventricular mass (LVM) were derived from 11 C‐acetate PET and used to calculate MEE. CA patients were followed for survival and the prognostic impact of clinical, echocardiographic, and 11 C‐acetate PET parameters was analysed. MVO 2 and MEE were reduced in CA compared with controls, but without significant difference between deceased and surviving CA patients. The ratio of 11 C‐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 11 C‐acetate PET parameters FSV/LVM and MEE were the strongest prognostic factors. Of the 11 C‐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 < 0.001), also when separating AL‐ and ATTR‐CA. Conclusions Reduced MEE was associated with shorter survival in CA patients, but FSV/LVM was the strongest survival predictor and the only independently prognostic 11 C‐acetate PET parameter in multivariate analysis.