Non-invasive cardiac imaging in patients with systemic amyloidosis: a practical approach with emphasis on clinical contribution of bone-seeking radiotracers

Cardiac amyloidosis is a rare and still underdiagnosed disease leading a poor prognosis. We reviewed the literature regarding non-invasive imaging of cardiac amyloidosis (i.e., echocardiography, magnetic resonance, and nuclear medicine imaging) with special attention to the clinical contribution of bone-seeking radiotracers. We performed a PubMed and Scopus literature search using keywords related to imaging of cardiac involvement in systemic amyloidosis. In particular, a review of studies published in the English literature between 2002 and 2017 dealing with clinical contribution of in vivo nuclear medicine imaging using bone-seeking radiotracers has been performed; studies that do not clearly report final diagnoses have been excluded. Interest for cardiac amyloidosis imaging has raised in the last years; in particular, about 20 recent studies evaluating imaging with bone-seeking radiotracers have been considered for the review. Echocardiography represents the first imaging approach, although its sensitivity (in the early stage) and specificity are limited. Magnetic resonance imaging can show highly suggestive signs for cardiac amyloidosis. Imaging with bone-seeking radiotracers has high accuracy in revealing cardiac amyloidosis etiology-both sensitivity and specificity reach 100% in selected groups of patients-and performs better than other imaging modalities in revealing the early cardiac amyloidosis. PET radiotracers' contribution is still under investigation. Imaging can aid in differentiating cardiac amyloidosis from other diseases providing prognostic information. Bone-seeking radiotracers can establish the type of amyloidosis, even without performing biopsy, in a large part of patients, and are able to early detect cardiac involvement in subjects with transthyretin gene mutations.