Should Histologic Determination of Amyloid  Load Determine Management Decisions in Light-Chain Amyloidosis?

We read with interest the report of Kristen et  al.(1), in which the prognostic usefulness of histologic amyloid load quantification by endomyocardial biopsy was described. Although the investigators stated that no significant variation was observed between biopsy sites, this observation was not quantified. Our collective experience is that Congo red staining of different biopsy specimens from within the same organ in the same patient can vary greatly in the so-called amyloid load, reflecting the patchy nature of amyloid deposition, which is well described(2) and introduces the likelihood of sampling error. Furthermore, quantification of amyloid load from a single slide does not control for variation in sample size, because a true load would require normalization to total heart size as determined by myocardial mass. In addition, immunohistochemistry in light-chain (AL) amyloidosis is associated with both false negative and considerable background nonspecific staining, which potentially confounds quantification of amyloid burden by the method described. Because the investigators found no survival advantage with chemotherapy in AL amyloidosis in the context of higher levels of amyloid load (>20%), we are concerned that clinicians may choose to withhold life-extending chemotherapy treatment from patients with advanced cardiac AL amyloidosis because of perceived futility, when it remains clear that some such patients do undoubtedly benefit from it. Cardiac magnetic resonance (CM...
Source: Journal of the American College of Cardiology - Category: Cardiology Source Type: research