Myocardium From Patients With ATTR Amyloidosis Produces Less Force Secondary to Increased Fibrosis.

Amyloid transthyretin cardiac amyloidosis is one of the most common infiltrative cardiomyopathies. Contractile, biochemical, and histological assays were performed on myocardium from patients with and without amyloid transthyretin amyloidosis. Force was reduced in amyloidosis, but calcium sensitivity was increased. The change in calcium sensitivity may reflect dephosphorylation of troponin I. The proportion of stiffness attributable to the extracellular matrix was larger in amyloidosis. Septal fibrosis and amyloid burden correlated with measurements from LV samples. Technetium pyrophosphate scans may detect increased microcalcifications in amyloidosis myocardium. Replacement of myocytes with extracellular matrix is the most important factor depressing contractile force in amyloidosis myocardium.