Native T1 and Extracellular Volume in Transthyretin Amyloidosis

This study evaluated the prognostic potential of native myocardial T1 in cardiac transthyretin amyloidosis (ATTR) and compared native T1 with extracellular volume (ECV) in terms of diagnostic accuracy and prognosis.

ATTR is an increasingly recognized cause of heart failure that has an overlapping clinical phenotype with hypertrophic cardiomyopathy (HCM). Native T1 mapping by cardiac magnetic resonance (CMR) is useful for diagnosis in cardiac amyloidosis but its prognostic potential has never been assessed.

A total of 134 patients with wild-type ATTR (ATTRwt) (122 men; age 76 ± 7 years), 81 patients with hereditary-type ATTR (ATTRm) (60 men; age 69 ± 11 years), 44 patients with HCM (32 men; age 51 ± 13 years), and 12 asymptomatic mutation carriers (4 men; age 47 ± 10 years) were studied. All subjects underwent CMR with T1 mapping and ECV measurement. ATTR patients also underwent ^99mTc-3,3-diphosphono-1,2-propanodicarboxylic acid (^99mTc-DPD) scintigraphy.

Native T1 and ECV were elevated in ATTR compared with HCM (p < 0.001) and were both associated with a high diagnostic accuracy (area under the curve [AUC]: 0.87; 95% confidence interval [CI]: 0.82 to 0.91) for T1 and an AUC of 0.91 (95% CI: 0.87 to 0.94) for ECV. No significant difference in native T1 and ECV was found between ATTRwt and ATTRm, and ECV correlated well with ^99mTc-DPD scintigraphy. During follow-up of a mean of 32 ± 17 months, 55 ATTRwt and 40 ATTRm patients died. Native T1 and ECV predicted death (T1: hazard ratio [HR]: 1.225 for each 59-ms increase; 95% CI: 1.010 to 1.486; p < 0.05; ECV: HR: 1.155 for each 3% increase; 95% CI: 1.097 to 1.216; p < 0.001), but only ECV remained independently predictive after adjustment for age, N-terminal pro-B-type natriuretic peptide, left ventricular ejection fraction, E/E', left ventricular mass index, DPD grade, and late gadolinium enhancement.

Native T1 mapping and ECV are good diagnostic techniques for cardiac ATTR that are associated with prognosis. Both parameters correlated with mortality, but only ECV remained independently predictive of prognosis, suggesting that it is a more robust marker in cardiac ATTR.