Dissociation between PET-derived amyloid burden and CMR extracellular volume in transthyretin cardiac amyloidosis
A Venkateshvaran, S Arvidsson, B Pilebro, J Axelsson, P LindqvistAbstract
Background
Cardiac magnetic resonance (CMR)–derived extracellular volume (ECV) is a validated marker of disease severity and prognosis in transthyretin cardiac amyloidosis (ATTR-CM).1 Amyloid-binding positron emission tomography (PET) tracers have been proposed to directly quantify myocardial amyloid burden and enable early disease detection.2 However, the relationship between molecular PET tracer signal and CMR tissue characterization (ECV) remains poorly defined.
Methods
Sixteen patients with ATTR-CM (14 hereditary V30Met, 2 wild type) underwent simultaneous hybrid PET-CMR using 18F-flutemetamol (18F-FLUTE) for amyloid deposition and 18F-sodium fluoride (18F-NaF) for microcalcification. Fourteen of the patients were DPD positive. Myocardial tracer uptake was quantified using SUV metrics and tissue-to-blood pool ratios (TBR). Patients were stratified by CMR ECV (<35% vs ≥35%). PET parameters, echocardiographic indices, ECG markers, and bone scintigraphy grade were compared between groups.
Results
ECV displayed no association with TBR using either of tracers (Figure 1). No differences in sex, ECG parameters, echocardiographic measures of wall thickness, ejection fraction or global longitudinal strain were observed between groups (p > 0.05 for all comparisons). No differences in Perugini score were observed. Myocardial uptake of 18F-FLUTE and 18F-NaF (SUVmean, SUVmax, and TBRmax) did not differ between ECV groups (Figure 2).
Conclusion
In a pilot PET-MR study including well-defined ATTR-CM, ECV and myocardial PET uptake appear largely unrelated. This suggests that interstitial expansion may reflect not only amyloid burden but also other pathologies such as fibrosis, oedema and local inflammation beyond fibrillar deposition alone. Hybrid PET-CMR might provide complementary insights into disease biology, offering potential for early diagnosis, improved phenotyping and therapy monitoring. However, this needs to be tested in larger cohorts.For image description, please refer to the figure legend and surrounding text.For image description, please refer to the figure legend and surrounding text.