Developing imaging biomarkers for myocardial involvement in amyloidosis: challenge and opportunity.

SEE PAGE 50 W ith the increasing recognition of the heterogeneity of patients who have heart failure with preserved ejection fraction (HFpEF), assessing the underlying etiology has assumed substantial clinical importance. Large, randomized trials using broad treatment paradigms for HFpEF patients, such as those examining the role of aldosterone antagonists (1), have not proven positive, suggesting that a therapeutic approach needs to be more targeted. Thus, diagnostic strategies that may uncover a more directly treatable condition are of great interest. One underlying etiology that presents as the HFpEF syndrome is cardiac amyloidosis. The current understanding holds that cardiac amyloidosis is usually the expression of 1 of 3 diseases associated with the deposition of amyloid-type fibrils in the myocardium (2). Cardiac amyloid may be associated with expansion of a plasma cell clone resulting in deposition of immunoglobulin light chains in the myocardium, known as AL amyloid. Cardiac amyloid may also be the result of deposition of misfolded transthyretin (TTR), a transport protein synthesized by the liver. The TTR syndrome is divided into 2 categories: hereditary, or associated with misfolding of wild-type TTR (2). The latter appears to mostly be clinically manifest in older men. Recent evidence indicates that these 3 major types of cardiac amyloidosis may have distinct phenotypic and prognostic profiles (2). Treatment of AL amyloid is directed at the expanded plasma cell clone. However, there are also