Regionally heterogeneous tissue mechanics in cardiac amyloidosis.

OBJECTIVE: The goal of this study was to examine in vitro tissue stiffness and contractile performance in myocardial amyloidosis.
BACKGROUND: Primary systemic amyloidosis involves the deposition of amyloid protein in mesodermal tissues including the heart. Functional assessment of cardiac amyloidosis is usually performed using echocardiography. However, this technique does not involve assessment of preload-dependent contractile reserve (the Frank-Starling mechanism).
METHODS: At the time of heart transplantation, isolated myocardial trabeculae were dissected from the right ventricle of a patient with primary systemic amyloidosis. In vitro length-tension experiments were performed and trabeculae were subsequently fixed, sectioned and stained with crystal violet to determine amyloid deposition.
RESULTS: Among the nine trabeculae capable of generating force transients, various combinations of myocardial stiffness and contractile performance were observed including normal stiffness and contractility, severely increased stiffness with impaired contractility and hybrid patterns. Histological analysis demonstrated varying degrees of amyloid deposition among sampled trabeculae.
CONCLUSIONS: Our findings extend previous reports of functional heterogeneity among patients by demonstrating functional heterogeneity within a single patient's heart. Our findings also highlight the functional interdependence of passive stiffness and systolic performance in the diseased myocardium and demonstrate the value of dynamic assessments of myocardial performance.