False-Positive 99mTc-Pyrophosphate Uptake Due to Myocardial Calcification from Prior Viral Myocarditis

Area of Science:

• Nuclear medicine
• Cardiology
• Radiology

Background:

• Cardiac amyloidosis diagnosis relies on imaging techniques.
• 99mTc-pyrophosphate (PYP) scintigraphy is used to detect amyloid deposition.
• Myocardial calcifications can mimic PYP uptake, leading to false positives.

Purpose of the Study:

• To highlight the role of SPECT/CT in differentiating cardiac amyloidosis from myocardial calcifications.
• To present a case study illustrating a false-positive PYP uptake scenario.

Main Methods:

• A patient with suspected cardiac amyloidosis underwent 99mTc-PYP planar imaging and SPECT/CT.
• Cardiac MRI was used previously to document myocardial fibrosis post-myocarditis.

Main Results:

• Planar PYP imaging showed diffuse uptake in the left ventricle.
• SPECT/CT revealed these areas corresponded to extensive myocardial calcifications, not amyloid.
• The patient had a history of severe myocarditis with fibrosis.

Conclusions:

• SPECT/CT correlation is crucial for accurate interpretation of 99mTc-PYP imaging in suspected cardiac amyloidosis.
• Dystrophic myocardial calcifications can cause false-positive PYP uptake, mimicking amyloidosis.
• Clinical history and multimodal imaging are essential for correct diagnosis.