Abstract
Background99mTc-labelled bisphosphonates are used for imaging assessment of patients with transthyretin cardiac amyloidosis (ATTR). Present study evaluates whether quantitative SPECT/CT measurement of absolute myocardial 99mTc-labelled 3,3-diphosphono-1,2-propanodicarboxylic acid (Tc-DPD) uptake can diagnose patients with suspected ATTR.MethodsTwenty-eight patients (25 male, age 80.03 ± 6.99 years) with suspected ATTR referred for Tc-DPD imaging had planar and SPECT/CT imaging of the chest. Three operators independently obtained Tc-DPD myocardial SUVmax and SUVmean above threshold (SMaT) (20, 40 and 60% of SUVmax), using a semi-automated threshold segmentation method. Results were compared to visual grading (0–3) of cardiac uptake.ResultsTwenty-two patients (78%) had cardiac uptake (2 grade 1, 15 grade 2, 5 grade 3). SUVmax and SMaT segmentation thresholds enabled separating grades 2/3 from 0/1 with excellent inter- and intra-reader correlation. Cut-off values 6.0, 2.5, 3 and 4 for SUVmax, SMaT20,40,60, respectively, separated between grades 2/3 and 0 /1 with PPV and NPV of 100%. SMaT20,40,60(cardiac)/SUVmean (liver) and SMaT20,40,60(cardiac)/SUVmean(liver/lung) separated grades 2 and 3.ConclusionQuantitative SPECT/CT parameters of cardiac Tc-DPD uptake are robust, enabling separation of patients with grades 2 and 3 cardiac uptake from grades 0 and 1. Larger patient cohorts will determine the incremental value of SPECT/CT quantification for ATTR management.
Highlights
Cardiac amyloidosis is characterized by protein misfolding and myocardial deposition mainly of monoclonal light chain (AL) or transthyretin (ATTR), resulting in restrictive cardiomyopathy and heart failure [1, 2]
99mTechnetium (Tc)-labeled bisphosphonates used for bone scintigraphy including 99mTc-3′3-diphosphono-1,2propanodicarboxylic acid (DPD), pyrophosphate (PYP) and hydroxy-dimethylene diphosphonate (HDP) localize
Present study assesses the potential of SPECT/CT quantification of Tc-DPD myocardial uptake in patients with suspected cardiac amyloidosis. Patients This retrospective two center international study includes 30 consecutive patients with cardiomyopathy and suspected cardiac amyloidosis based on symptoms, monoclonal protein studies, echocardiography and/or MRI
Summary
Cardiac amyloidosis is characterized by protein misfolding and myocardial deposition mainly of monoclonal light chain (AL) or transthyretin (ATTR), resulting in restrictive cardiomyopathy and heart failure [1, 2]. ATTR amyloidosis may be acquired, associated with wild-type transthyretin (TTR), or hereditary, associated with TTR gene variants. Cardiac ATTR amyloid deposits are present in up to 25% elder individuals [3], more common among patients with heart failure and preserved ejection fraction (HFpEF) [4]. A sensitive and accurate method to quantify amyloid burden is needed to evaluate treatment response. Quantification of myocardial Tc-DPD uptake may overcome shortcomings of planar studies in borderline cases and may improve the diagnostic performance, monitor the amyloid burden over time and determine ATTR treatment response
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