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

Aims This study aimed to study the prognostic value of myocardial oxygen consumption (MVO2) and myocardial external efficiency (MEE) from C-11-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 C-11-acetate PET and echocardiography. MVO2, forward stroke volume (FSV), and left ventricular mass (LVM) were derived from C-11-acetate PET and used to calculate MEE. CA patients were followed for survival and the prognostic impact of clinical, echocardiographic, and C-11-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 C-11-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 C-11-acetate PET parameters FSV/LVM and MEE were the strongest prognostic factors. Of the C-11-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 C-11-acetate PET parameter in multivariate analysis.