A case report of an uncommon presentation of 99mtechnetium pyrophosphate scintigraphy in transthyretin cardiac amyloidosis: A potential diagnostic pitfall, pseudo-positive or pseudo-negative?

99mTechnetium pyrophosphate (99mTc-PYP) scintigraphy has shown utility for diagnosis of transthyretin (ATTR) cardiac amyloidosis with a high sensitivity and specificity. However, in clinical practice, a protocol and a method of analysis of this modality are not yet unified. We present a case of ATTR cardiac amyloidosis showing a positive cardiac uptake in planar imaging but no myocardial uptake in single-photon emission computed tomography/computed tomography (SPECT/CT) fusion imaging on 99mTc-PYP scintigraphy. We considered this tracer accumulation in the cardiac blood pool to be an inconclusive study. In this report, we focus on an inconclusive study case as a potential pitfall of 99mTc-PYP scintigraphy and discuss the interpretation of 99mTc-PYP scintigraphy findings with using both planar and SPECT/CT imaging for improvement of diagnostic accuracy for ATTR cardiac amyloidosis. <Learning objective: The present report describes the importance of distinguishing myocardial uptake from the cardiac blood pool by both planar and single-photon emission computed tomography/computed tomography fusion imaging on 99mtechnetium pyrophosphate (99mTc-PYP) scintigraphy for diagnosis of transthyretin cardiac amyloidosis. To improve diagnostic accuracy, the 99mTc-PYP scintigraphy protocol including the method of evaluation and interpretation of the findings should be unified.>.