The importance of SPECT cardiac reconstruction for accurate 99m Tc-pyrophosphate interpretation in TTR amyloidosis
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Seymour, Paul, and Gloria Milstein Division of Cardiology, Department of Medicine, Columbia University Irving Medical Center, New York, NY Section of Cardiovascular Medicine, Department of Medicine, Boston University School of Medicine, Boston Medical Center, Boston, MA Department of Radiology, Columbia University Irving Medical Center, New York, NY
Received Oct 1, 2020; accepted Oct 1, 2020 doi:10.1007/s12350-020-02409-5
INTRODUCTION The diagnosis of transthyretin cardiac amyloidosis (ATTR-CA) could historically only be made by endomyocardial biopsy, a test that is invasive, expensive, and often only available in tertiary care transplant centers. Work over the last decade has shown that bone seeking radiopharmaceuticals such as technetium-99m pyrophosphate (99mTc-PYP) are specific for ATTRCA.1 Use of these tracers is now widespread for the diagnosis of ATTR-CA. This case is of interest because it highlights potential errors in cardiac scintigraphy interpretation for ATTR-CA. CASE SUMMARY A 76-year-old African American man with a past medical history of hypertension, atrial fibrillation, and heart failure with preserved ejection fraction (HFpEF) was referred to our institution for further care. ATTRCA was suspected as a possible cause for his heart disease, and 99mTc-PYP nuclear scintigraphy was performed. The patient was injected with 10 mCi of
Funding This study was funded by the SCAN-MP Study (National Institutes of Health Grant 5R01HL139671). Reprint requests: Andrew J. Einstein, MD, PhD, Seymour, Paul, and Gloria Milstein Division of Cardiology, Department of Medicine, Columbia University Irving Medical Center, 177 Fort Washington Ave, New York, NY 10032; [email protected] J Nucl Cardiol 1071-3581/$34.00 Copyright Ó 2020 American Society of Nuclear Cardiology.
99mTc-PYP and image acquisition was initiated 3 hours after administration, on a Philips Precedence SPECT/CT camera (Philips Healthcare, Guildford, United Kingdom). Anteroposterior and lateral planar images were acquired (Figure 1A) which were graded as visual score 2 using the Perugini scale.2 A circular region of interest was drawn over the heart and replicated in the contralateral chest, from which mean counts were measured and the heart-to-contralateral chest ratio (H:CL) determined (Figure 1B). The H:CL was calculated at 1.48, with previous publications suggesting that H:CL values greater than 1.3 may be consistent with ATTR-CA in scans taken 3 hours after injection.3 In accordance with ASNC guidelines recommending its routine use, SPECT imaging was performed.2 On analysis of the axial images, a crescent-shaped structure was seen to the left of the sternum that was initially thought to be left ventricular myocardium (Figure 2). Cardiac reconstruction images were made by an experienced nuclear technologist to create short axis images (Figure 3). On evaluation of these images, right ventricular and left ventricular tracer blood pooling is clearly identified without myocardial uptake, creating a ‘‘mimic’’ of the left ventricular myocar
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