Abstract
2290
Introduction: Amyloid light-chain (AL) amyloidosis is the most common subtype forms of amyloidosis, which is characterized by multiple organ damage resulted from monoclonal protein. Cardiac amyloidosis (CA) deposition leads to cardiomyocyte necrosis and interstitial fibrosis. A recently developed PET tracer 68Ga-labeled fibroblast activation protein inhibitor (FAPI) presented great potential in specific detection and characterization of cardiac fibroblasts activation. The aim of this study is to evaluate the feasibility of 68Ga-FAPI PET in identifying and of AL-CA and explore the association between cardiovascular magnetic resonance (CMR) and PET/CT techniques.
Methods: Thirty AL amyloidosis patients confirmed by biopsy (age, 59.1±7.7 years; M/F, 20/10) were prospectively enrolled. Clinical parameters were collected including N-terminal pro–B-type natriuretic peptide (NT-proBNP), cardiac Troponin I (cTnI), difference between involved and uninvolved free light chains (dFLC) and Mayo 04 stage. All patients underwent 68Ga-FAPI-04 PET/CT and echocardiography, meanwhile 18 patients performed CMR. 68Ga-FAPI-04 images were acquired on a PET/CT scanner (Polestar m660, SinoUnion, China) 60 min after intravenous injection of 107.4±26.5 MBq. For semi-quantitative analysis of 68Ga-FAPI-04 PET/CT, the global and segemental mean standardised uptake values (SUVmean), maximum standardised uptake values (SUVmax) and metabolism volume (MV) of left ventricle (LV) were measured and further expressed as SUV ratio (SUVR) with descending thoracic aorta activity as background (MIM Software Inc, USA). Patients subsequently categorized as a positive group considering increased cardiac 68Ga-FAPI-04 activity than background and the negative group. The former included patchy and extensive group. For CMR, standard parameters of cardiac structure (LV end diastolic volume (LVEDV), LV end systolic volume (LVESV), cardiac output (CO), LV mass and left atrium (LA) volume with indexing for body surface area) were measured. In addition, native-T1 times, T2 times, and extracellular volume (ECV), global radial strain (GRS), global longitudinal strain (GLS), global circumferential strain (GCS) were quantitatively measured. In terms of echocardiography, interventricular septal (IVS) wall thickness, left ventricular ejection fraction (LVEF) and left posterior ventricular wall (LVPW) thickness, left ventricular diastolic diameter (LVDD) and left atrial diameter (LAD) were measured.
Results: Twenty-seven patients were diagnosed of AL-CA while three patients without cardiac involvement were assessed. 80% (24/30) of all the patients presented elevated signal on LV (patchy uptake group (n=4) vs. extensive uptake group (n=20)), whereas six (20%) patients did not show visible uptake. Of note, LV SUVR and MV of the extensive group were significantly higher than the patchy group (2.40 [1.96, 3.91] vs 1.28 [1.08, 2.23], P=0.045; 185.1 [152.2, 209.3] vs 131.6 [101.3, 150.5], P=0.005). Moreover, the correlation of PET/CT parameters with clinical, echocardiography and CMR parameters were depicted in Table S1. LV SUVmean, SUVmax and SUVR were all significantly correlated with Mayo 04 stage (Figure 1) and NT-proBNP (P<0.05). For echocardiography, LV SUVmean, SUVmax and MV were related with IVS (P<0.05). LV SUVmean and SUVmax were inversely related to the LVEF (P<0.05). Moreover, LV SUVmean, SUVmax and SUVR were all strongly correlated with LAD. In CMR analysis, LV SUVmean, SUVmax and SUVR were all significantly correlated with LVESV, LV mass, LV GCS and LV GLS (P<0.05). Of note, LV SUVmean, SUVmax and MV were related with LA volume (P<0.05). In addition, SUVmean and SUVmax were correlated with ECV (P<0.05).
Conclusions: Our study suggested 68Ga-FAPI-04 PET/CT was a promising tracer in AL-CA, which may provide complementary information of amyloidosis characterization, disease detection and staging examinations.