Myocardial Composition in Light-Chain Cardiac Amyloidosis More Than 1 Year After Successful Therapy

OBJECTIVES: The goals of this study were to characterize myocardial composition during the active and remission phases of light-chain (AL) cardiac amyloidosis. BACKGROUND: Cardiac dysfunction in AL amyloidosis is characterized by dual insults to the myocardium from infiltration and toxicity from light chains during the active phase and by infiltration alone in the remission phase. METHODS: Prospectively enrolled subjects with cardiac AL amyloidosis (21 remission AL amyloidosis; age: 63.4 ± 7.3 years; 47.6% male; and 48 active AL amyloidosis; age: 62.5 ± 7.4 years; 60.4% male) underwent contrast-enhanced cardiac magnetic resonance with T(1) and T(2) mapping and measurement of extracellular volume (ECV). By definition, serum free light-chain levels were normal for at least 1 year following successful AL therapy in the remission group and abnormal in the active group. RESULTS: Myocardial ECV was similarly expanded in the remission and active AL amyloidosis groups (0.488 ± 0.082 vs 0.519 ± 0.083, respectively; P = 0.15). However, myocardial T(2) relaxation times (47.7 ± 3.2 ms vs 45.5 ± 3.0 ms; P = 0.008) as well as native T(1) times (1,368 ms [IQR: 1,290–1,422 ms] vs 1,264 ms [IQR: 1,203–1,380 ms]; P = 0.024) were significantly higher in the remission compared to the active AL amyloidosis group. CONCLUSIONS: Myocardial ECV is substantially expanded in the active AL and remission AL cardiac amyloidosis groups, but native T(1) values were higher, suggesting a different myocardial composition. There is no evidence of myocardial edema in active AL cardiac amyloidosis. Future phenotyping studies of AL cardiac amyloidosis need to consider complementary myocardial markers that define the interstitial milieu in addition to changes in extracellular volume. (Molecular Imaging of Primary Amyloid Cardiomyopathy; NCT02641145)