The heart of the matter

Sandeep Arora and associates1 recommend extracardiac biopsy and other diagnostic modalities instead of heart biopsy for diagnosis of cardiac amyloidosis. However, endomyocardial biopsy remains an excellent method of demonstrating this problem, and false-negative results are uncommon in patients with heart failure.2

Immunohistochemical typing of the amyloid may be prognostic. Primary (amyloid light-chain [AL]) amyloidosis with resultant heart failure is associated with a poor prognosis, and up to 40% of such patients die of heart disease.3 In contrast, senile amyloidosis, which is common, is often uncomplicated, and treatment with cytotoxic agents may not be required.4^,5

Algorithms have been proposed to diagnose amyloidosis.5^,6 Depending on the amyloid type, the results of extracardiac staining may not accurately indicate the presence of cardiac amyloid.3 Furthermore, in a study of patients with AL-type amyloidosis who had positive results on endomyocardial biopsy, the extracardiac biopsy results were not always positive.3

In patients with severe heart failure, biopsy-proven extracardiac amyloid site, characteristic electrocardiographic findings and characteristic echocardiographic changes, most clinicians feel confident in attributing cardiac dysfunction to amyloidosis.3 However, doing so may underestimate or overestimate cardiac involvement, depending on the patient population. Endomyocardial biopsy may be the only way to diagnose amyloidosis if it is confined to the heart. Immunotyping of the biopsy specimen may add prognostic information. Heart biopsy is also useful in distinguishing restrictive myocardial abnormalities from constrictive pericardial disease.

John P. Veinot Pathology and Laboratory Medicine University of Ottawa Ottawa, Ont.