Bone scintigraphy with 99mtechnetium-hydroxymethylene diphosphonate allows early diagnosis of cardiac involvement in patients with transthyretin-derived systemic amyloidosis

Objective: To assess the usefulness of bone scintigraphy with (99m)Technetium-hydroxymethylene diphosphonate (Tc-99m-HDP) for the detection of cardiac involvement in a group of patients with ATTR amyloidosis in different phases of disease, to relate the findings to echocardiography, ECG and cardiac biomarkers, and to evaluate different bone scintigraphic techniques and calculation methods for quantification of the cardiac uptake and for correlation with echocardiographic features and cardiac biomarkers. Methods: Forty-one patients underwent clinical examinations, echocardiography, ECG, measurement of cardiac biomarkers and bone scintigraphy (planar imaging and SPECT-CT) and were subsequently subdivided into three groups: (1) carriers of an amyloidogenic TTR mutation, n=11, (2) proven ATTR amyloidosis without echocardiographically-defined (mean wall thickness 412 mm) cardiac amyloidosis (AC), n=19, and (3) ATTR amyloidosis with echocardiographically-defined cardiac amyloidosis, n=11. Planar and SPECT-CT images were analyzed visually according to a routine scoring system (grade 0-3) and semiquantitatively by heart-to-whole body (H/WB) and heart-to-skull (H/S) ratio on planar images and by a left ventricle-blood pool ratio on SPECT-CT images. Results: All patients with ATTR and echocardiographically-defined AC and none of the carriers showed high cardiac uptake on bone scintigraphy. Furthermore, 8 out of 19 patients with ATTR without echocardiographically-defined AC showed high cardiac uptake. Highest correlations were found between H/S ratio on planar bone scintigraphy with troponin T (r = 0.76, p < 0.0001) and H/WB ratio with left ventricular mass index (r = 0.73, p < 0.0001). Conclusions: Bone scintigraphy with Tc-99m-HDP may detect cardiac involvement in patients with ATTR amyloidosis prior to echocardiographic evidence of cardiac involvement. Cardiac uptake on bone scintigraphy correlates with severity of cardiac involvement using echocardiography, ECG and cardiac biomarkers. Visual grading and calculation of H/S ratio on planar imaging are the preferred methods to assess cardiac uptake.