99mTc-Pyrophosphate Scintigraphy: History, Evolution, and Role in Cardiac Amyloidosis

Abstract Cardiac amyloidosis is an important cause of heart failure, particularly among the elderly population. It manifests as restrictive cardiomyopathy resulting from myocardial infiltration of misfolded amyloid fibrils (light chain or transthyretin), leading to heart failure with preserved ejection fraction. The two main forms of cardiac amyloidosis are amyloid light chain and transthyretin-related (ATTR). There has been a notable increase in the prevalence of cardiac amyloidosis due to advances in diagnostic methods and effective treatment for ATTR amyloidosis after the discovery of tafamidis. We aim to discuss the interesting history and evolution of the pyrophosphate scan, which plays an important role in the diagnosis of ATTR amyloidosis.