Tracking Treatment Response in Cardiac Light-Chain Amyloidosis With Native T1 Mapping

Importance: Cardiac magnetic resonance (CMR) imaging-derived extracellular volume (ECV) mapping, generated from precontrast and postcontrast T1, accurately determines treatment response in cardiac light-chain amyloidosis. Native T1 mapping, which can be derived without the need for contrast, has demonstrated accuracy in diagnosis and prognostication, but it is unclear whether serial native T1 measurements could also track the cardiac treatment response. Objective: To assess whether native T1 mapping can measure the cardiac treatment response and the association between changes in native T1 and prognosis. Design, Setting, and Participants: This single-center cohort study evaluated patients diagnosed with cardiac light-chain amyloidosis (January 2016 to December 2020) who underwent CMR scans at diagnosis and a repeat scan following chemotherapy. Analysis took place between January 2016 and October 2022. Main Outcomes and Measures: Comparison of biomarkers and cardiac imaging parameters between patients with a reduced, stable, or increased native T1 and association between changes in native T1 and mortality. Results: The study comprised 221 patients (mean SD age, 64.7 10.6 years; 130 male 59%). At 6 months, 183 patients (mean SD age, 64.8 10.5 years; 110 male 60%) underwent repeat CMR imaging. Reduced native T1 of 50 milliseconds or more occurred in 8 patients (4%), all of whom had a good hematological response; by contrast, an increased native T1 of 50 milliseconds or more occurred in 42 patients (23%), most of whom had a poor hematological response (27 68%). At 12 months, 160 patients (mean SD age, 63.8 11.1 years; 94 male 59%) had a repeat CMR scan. A reduced native T1 occurred in 24 patients (15%), all of whom had a good hematological response, and was associated with a reduction in N-terminal pro-brain natriuretic peptide (median IQR, 2638 913-5767 vs 423 128-1777 ng/L; P < .001), maximal wall thickness (mean SD, 14.8 3.6 vs 13.6 3.9 mm; P = .009), and E/e' (mean SD, 14.9 6.8 vs 12.0 4.0; P = .007), improved longitudinal strain (mean SD, -14.8% 4.0% vs -16.7% 4.0%; P = .004), and reduction in both myocardial T2 (mean SD, 52.3 2.9 vs 49.4 2.0 milliseconds; P < .001) and ECV (mean SD, 0.47 0.07 vs 0.42 0.08; P < .001). At 12 months, an increased native T1 occurred in 24 patients (15%), most of whom had a poor hematological response (17 71%), and was associated with an increased N-terminal pro-brain natriuretic peptide (median IQR, 1622 554-5487 vs 3150 1161-8745 ng/L; P = .007), reduced left ventricular ejection fraction (mean SD, 65.8% 11.4% vs 61.5% 12.4%; P = .009), and an increase in both myocardial T2 (mean SD, 52.5 2.7 vs 55.3 4.2 milliseconds; P < .001) and ECV (mean SD, 0.48 0.09 vs 0.56 0.09; P < .001). Change in myocardial native T1 at 6 months was independently associated with mortality (hazard ratio, 2.41 95% CI, 1.36-4.27; P = .003). Conclusions and Relevance: Changes in native T1 in response to treatment, reflecting a composite of changes in T2 and ECV, are associated with in changes in traditional markers of cardiac response and associated with mortality. However, as a single-center study, these results require external validation in a larger cohort.