The current status of quantitative SPECT/CT in the assessment of transthyretin cardiac amyloidosis
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Nuclear Medicine and PET, Royal Brisbane and Women’s Hospital, Herston, QLD, Australia School of Medicine, James Cook University, Townsville, Australia Department of Medical Imaging, Princess Alexandra Hospital, Wooloongabba, QLD, Australia The University of Queensland, St Lucia, QLD, Australia
Received Oct 7, 2019; accepted Oct 7, 2019 doi:10.1007/s12350-019-01935-1
Nuclear medicine bone scans differentiate ATTR cardiomyopathy (ATTR-CM) from light chain cardiac amyloidosis and other myocardial disorders, helping to make the diagnosis without biopsy. Standard bone scans are not absolutely quantitative, so are assessed by comparing the heart to other tissues. The standard visual scoring system compares heart to bone. This accurately diagnoses ATTR-CM and has been validated in a multicenter study, but has limitations. Semiquantitative techniques including heart/contralateral thorax (H/CL) and heart/whole body ratio (H/WB) improve on visual scoring but still rely on extracardiac sites as comparators. Absolute quantitation of myocardial uptake using quantitative SPECT should help overcome these shortcomings. In ATTR-CM, this technique is practical, accurately makes the diagnosis and provides information that is not identical to visual scores. However, more work needs to be done. The reproducibility in ATTR-CM must be tested. Larger studies need to be undertaken to determine whether quantitative SPECT measurements can assess prognosis, disease progression or treatment response. As ATTR-CM is relatively uncommon multicenter trials will help recruit enough subjects to answer these questions. Accurate measurement techniques are needed in ATTR-CM to enable appropriate use of proven therapy and to conduct trials of new therapeutic agents. Quantitative bone scans offer a promising avenue. Key Words: Transthyretin cardiac amyloidosis Æ Bone scan Æ Quantitation
INTRODUCTION Transthyretin (ATTR) cardiac amyloidosis is associated with heart failure.1 Nuclear medicine bone scans differentiate ATTR cardiac amyloidosis from light chain (AL) cardiac amyloidosis and other myocardial
See related article, https://doi.org/10.1007/s12350-019-01893-8. Reprint requests: Stuart C. Ramsay, MBBS, MD, FRACP, FAANMS, DDU, Nuclear Medicine and PET, Royal Brisbane and Women’s Hospital, Herston, QLD, Australia; [email protected] J Nucl Cardiol 1071-3581/$34.00 Copyright Ó 2019 American Society of Nuclear Cardiology.
disorders with increased left ventricular wall thickness.2-4 In appropriately selected individuals, bone scans can diagnose ATTR cardiomyopathy (ATTR-CM) without endomyocardial biopsy.1,5 The technetium 99m (Tc) labeled phosphate-based agents hydroxymethylene diphosphonate (HMDP), pyrophosphate (PYP) and 3,3diphosphono-1,2-propanodicarboxylic acid (DPD) have equivalent diagnostic accuracy for detecting ATTRCM,2,6,7 though it is worth remembering that the images produced by these different agents are not identical.8 Given recent developments in bone scan imaging technology it is timely to consider how best to report cardiac
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