Myocardial Contraction Fraction by M-Mode Echocardiography Is Superior to Ejection Fraction in Predicting Mortality in Transthyretin Amyloidosis

Background: Transthyretin amyloidosis (ATTR) is often associated with cardiac involvement manifesting as conduction disease as well as restrictive cardiomyopathy causing heart failure and death. Myocardial contraction fraction (MCF), the ratio of left ventricular stroke volume (SV) to myocardial volume (MV), is a volumetric measure of myocardial shortening that is superior to ejection fraction (EF) in predicting mortality in patients with primary amyloid light chain cardiac amyloidosis. We hypothesized that MCF would be an independent predictor of survival in TTR-CA. Methods and Results: MCF was derived from 2-dimensional echocardiography-guided M-mode data for 530 subjects in the Transthyretin Amyloidosis Outcomes Survey (THAOS) database: age 61 ± 16 years, 74% male, 158 wild-type (ATTRwt) and 372 mutant (ATTRm), follow-up 1.5 ± 1.7 years. Using multivariate Cox proportional hazard regression models, MCF <25% was highly associated with survival (hazard ratio [HR] 8.5, 95% confidence interval [CI] 4.8–14.9,-P <.0001), which was stronger than the association of EF dichotomized at 50% (HR 2.8, 95% CI 1.8–4.4; P <.0001). MCF <25% remained significantly predictive of survival in a multivariate model that included systolic blood pressure, estimated glomerular filtration rate <65 mL·min ⁻¹ ·m ⁻² , New York Heart Association (NYHA) functional class, and health status based on the EuroQol-5D-3L questionnaire (area under the receiver operating characteristic curve [AUC] = 0.83, 95% CI 0.78–0.89). Conclusions: MCF was superior to EF in predicting mortality in patients with ATTR. A predictive model combining MCF with systolic blood pressure, renal function, NYHA functional class, and health status was strongly associated with survival in patients with ATTR. ClinicalTrials.gov identifier: NCT00628745