Utility of (99 m)Tc-Pyrophosphate Scintigraphy in Diagnosing Transthyretin Cardiac Amyloidosis in Real-World Practice

Background: Amyloid transthyretin (ATTR) cardiac amyloidosis has now been recognized as one of the major causes of heart failure, especially in elderly patients. The purpose of the present study was to validate the usefulness of technetium-99 m ((99 m)Tc)-pyrophosphate ((99 m)Tc-PYP) scintigraphy in the screening diagnosis for ATTR amyloidosis in daily clinical practice. Methods and Results: Ninety-eight patients underwent (99 m)Tc-PYP scintigraphy in the previous 3 years (PYP positive/negative, 18/80), of whom 29 underwent concomitant endomyocardial biopsy (ATTR positive/negative, 9/20). The sensitivity and specificity of (99 m)Tc-PYP scintigraphy for the diagnosis of biopsy-proven ATTR amyloidosis were 0.889 and 0.950, respectively. Age, gender, N-terminal prohormone of brain natriuretic peptide (NT-proBNP) level, or electrocardiogram findings did not differ significantly between PYP-positive and PYP-negative patients. Left ventricular (LV) wall thickness was significantly greater in PYP-positive than in PYP-negative patients, but LV ejection fraction or prevalence of atrial fibrillation was similar between groups. In the PYP-positive patients, higher uptake of PYP correlated with younger age and lower NT-proBNP. Conclusions: (99 m)Tc-PYP scintigraphy was useful, with high sensitivity and specificity in the screening diagnosis for ATTR cardiac amyloidosis, which is difficult to diagnose on clinical characteristics alone. (99 m)Tc-PYP scintigraphy should be considered to elucidate the underlying causes of heart failure, especially in elderly patients based on the higher prevalence of ATTR cardiac amyloidosis in this population.