Scans May Help Pin Down Tricky Diagnosis Of Cardiac Amyloidosis

"Clinically, this finding helps differential diagnosis and reducesthe risk of misdiagnosis between two conditions with very differenttherapeutic options," said Claudio Rapezzi, M.D. from the University ofBologna and S. Orsola-Malpighi Hospital in Bologna, Italy.

Clinicians have a difficult time distinguishing betweentransthyretin amyloidosis, which is often hereditary, and acquiredmonoclonal immunoglobulin light-chain amyloidosis, which is often aconsequence of multiple myeloma. Although the two forms of abnormalprotein deposition look similar and both stiffen the heart muscle,ultimately leading to heart failure; they require different treatments.Treatment of transthyretin amyloidosis can include livertransplantation, while bone marrow transplantation may be indicated foracquired monoclonal immunoglobulin light-chain amyloidosis.

This small trial is the first assessment of scintigraphy inpatients with cardiac amyloidosis. Intravenous solutions containing aradioactive isotope (99mTc-DPD) were given to 15 patients withtransthyretin amyloidosis and 10 patients with acquired monoclonalimmunoglobulin light-chain amyloidosis. Genotyping andimmunohistochemistry were used as the reference standards for thisstudy.

Detectors showed that the radioactive tracer was taken up bythe heart muscle tissue of the transthyretin amyloidosis patients, butnot by the hearts of the patients with acquired monoclonalimmunoglobulin light-chain amyloidosis.

"From a research perspective, the study also indicates thatetiology, the cause of a disease, is a third major cause, in additionto type of organ involved and tracer type, of scintigraphic variabilityin cardiac amyloidosis: this is a highly relevant consideration forfuture studies," Dr. Rapezzi said.

Dr. Rapezzi said this finding needs to be confirmed in larger groups of patients.

Myron C. Gerson, M.D., F.A.C.C., at the University of Cincinnatiin Cincinnati, Ohio, who was not connected with this study, noted thatcorrect classification of the disorder is essential to effectivetreatment.

"There has been no simple, widely available test fordistinguishing hereditary from immunoglobulin light-chain amyloid," Dr.Gerson said. "Although this is a small study requiring independentconfirmation, the findings suggest that 99mTc-DPD imaging may provide auseful step in the workup of the differential diagnosis oftransthyretin versus immunoglobulin light-chain (AL) etiology inpatients with documented cardiac amyloidosis."