Abstract
ObjectivesCardiac MR is widely used to diagnose cardiac amyloid, but cannot differentiate AL and ATTR subtypes: an important distinction given their differing treatments and prognoses. We used PET/MR imaging to quantify myocardial uptake of 18F-fluoride in ATTR and AL amyloid patients, as well as participants with aortic stenosis and age/sex-matched controls. MethodsIn this prospective multicenter study, patients were recruited in Edinburgh and New York and underwent 18F-fluoride PET/MR imaging. Standardized volumes of interest were drawn in the septum and areas of late gadolinium enhancement to derive myocardial standardized uptake values (SUV) and tissue-to-background ratio (TBRMEAN) after correction for blood pool activity in the right atrium. Results53 patients were scanned: 18 with cardiac amyloid (10 ATTR and 8 AL), 13 controls, and 22 with aortic stenosis. No differences in myocardial TBR values were observed between participants scanned in Edinburgh and New York. Mean myocardial TBRMEAN values in ATTR amyloid (1.13 ± 0.16) were higher than controls (0.84 ± 0.11, P = .0006), aortic stenosis (0.73 ± 0.12, P < .0001), and those with AL amyloid (0.96 ± 0.08, P = .01). TBRMEAN values within areas of late gadolinium enhancement provided discrimination between patients with ATTR (1.36 ± 0.23) and all other groups (e.g., AL [1.06 ± 0.07, P = .003]). A TBRMEAN threshold >1.14 in areas of LGE demonstrated 100% sensitivity (CI 72.25 to 100%) and 100% specificity (CI 67.56 to 100%) for ATTR compared to AL amyloid (AUC 1, P = .0004). ConclusionQuantitative 18F-fluoride PET/MR imaging can distinguish ATTR amyloid from other similar phenotypes and holds promise in improving the diagnosis of this condition.
Highlights
Systemic amyloidosis represents a spectrum of conditions characterized by disordered protein folding and fibrils formation
Other data have indicated that patients with aortic stenosis and concurrent cardiac amyloidosis have an adverse prognosis despite aortic valve replacement
While patterns of late gadolinium enhancement tend to differ between patients with amyloidosis transthyretin (ATTR) and aortic stenosis, we have demonstrated that 18F-fluoride PET/MR can too provide excellent discrimination between ATTR and aortic stenosis
Summary
Systemic amyloidosis represents a spectrum of conditions characterized by disordered protein folding and fibrils formation. Some studies have suggested that cardiac amyloidosis is present in 6% to 29% of patients with significant aortic stenosis.[5,6,7] Other data have indicated that patients with aortic stenosis and concurrent cardiac amyloidosis have an adverse prognosis despite aortic valve replacement. It is, important to identify aortic stenosis patients with co-existent amyloidosis both in terms of predicting prognosis and because it influences interventional treatment decisions
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