99mTc Bone-Avid Tracer Cardiac Scintigraphy: Role in Noninvasive Diagnosis of Transthyretin Cardiac Amyloidosis

Transthyretin cardiac amyloidosis (ATTR-CA) is an overlooked cause of heart failure, with substantial morbidity and mortality. The emergence of several novel therapies has fueled the interest in early and accurate diagnosis of ATTR-CA so that potentially life-saving pharmacologic therapy can be administered in a timely manner. The most promising imaging modality and biomarker is SPECT imaging with technetium 99m (Tc-99m)-radiolabeled bone-seeking tracers, which have high specificity in the diagnosis of ATTR-CA, potentially obviating biopsy. In this article, the authors provide a focused review on the use of Tc-99m pyrophosphate (PYP), 3,3-diphosphono-1,2-propanodicarboxylic acid (DPD), and hydroxymethylene diphosphonate (HMDP) for diagnosis of ATTR-CA, present a systematic approach to interpretation of the scans, and highlight several common pitfalls to illustrate important diagnostic principles for accurate interpretation of these images. The authors indicate when to use endomyocardial biopsy for the diagnosis of cardiac amyloidosis and conclude with a section on quantitation of Tc-99m-PYP/DPD/HMDP imaging. (c) RSNA, 2022

Automated summary

Transthyretin cardiac amyloidosis (ATTR-CA) is a frequently overlooked cause of heart failure with high morbidity and mortality. The emergence of novel therapies has increased interest in early and accurate diagnosis of ATTR-CA to facilitate timely administration of potentially life-saving pharmacologic therapy. SPECT imaging with technetium 99m (Tc-99m)-radiolabeled bone-seeking tracers is the most promising imaging modality with high specificity for the diagnosis of ATTR-CA, possibly eliminating the need for biopsy. This article provides a comprehensive review of the use of Tc-99m pyrophosphate (PYP), 3,3-diphosphono-1,2-propanodicarboxylic acid (DPD), and hydroxymethylene diphosphonate (HMDP) for the diagnosis of ATTR-CA, presents a systematic approach to interpreting the scans, and highlights common pitfalls to ensure accurate interpretation of these images. The authors also discuss the appropriate use of endomyocardial biopsy and provide insights into quantification of Tc-99m-PYP/DPD/HMDP imaging.