Clinical and prognostic implications of capillary density in patients with cardiac light chain amyloidosis

AIMS: Cardiac involvement is crucial factor determining outcomes of light chain (AL) amyloidosis. This study evaluated whether capillary density (CD) quantified from endomyocardial biopsy is associated with structural and functional parameters of amyloid heart. Also, we investigated whether capillary density improves the prognostic value of the current staging system in AL amyloidosis patients with cardiac involvement. METHODS AND RESULTS: A total of 67 patients with biopsy‐proven AL cardiac amyloidosis were prospectively enrolled in this study. All patients underwent transthoracic echocardiography and EBM at the time of diagnosis. Left ventricle global longitudinal strain was evaluated on two‐dimensional strain echocardiography. The primary endpoint was all‐cause mortality. Amyloid load and capillary density were calculated on endomyocardial biopsy stained immunohistochemically with antibody against amyloid P and CD31, respectively. Among the study population, 37 patients (55.2%) were classified as Stage IV, and the cumulative incidence of death at 1 year was 34% (23 patients). A total of 65 (97%) patients underwent chemotherapy. CD showed a significant correlation with left ventricle global longitudinal strain (r = 0.274, P = 0.025), log N‐terminal pro‐B type natriuretic peptide (r = −0.311, P = 0.005), and amyloid load (r = −0.438, P < 0.001). Patients with a CD ≤ 220/mm(2) were at significantly higher risk of death than those with a CD > 220/mm(2) (P = 0.026 by log‐rank test). A model based on the 2012 Mayo staging system and CD showed significantly better discrimination and reclassification ability than a model using the 2012 Mayo staging system alone (C‐index 0.582 vs.0.689, P for difference <0.001). CONCLUSIONS: Capillary density was significantly related to the severity of amyloid deposits in the myocardium and showed incremental prognostic value in addition to the 2012 Mayo staging system.