Myocardial blood flow changes assessed by dynamic CZT-SPECT in patients with transthyretin amyloid cardiomyopathy treated with Tafamidis: Correlation With [99mTc]-PYP Scintigraphy and CMR

Objectives To quantify myocardial blood flow (MBF) and myocardial flow reserve (MFR) using dynamic thallium-201 cadmium-zinc-telluride single-photon emission computed tomography (²⁰¹Tl CZT-SPECT), characterise microvascular dysfunction in transthyretin amyloid cardiomyopathy (ATTR-CM) versus individuals without obstructive coronary artery disease (CAD), and examine associations with disease markers. Post-tafamidis flow changes were explored secondarily. Materials and Methods Thirty-three participants were included (19 ATTR-CM, 14 without obstructive CAD). Dynamic ²⁰¹Tl CZT-SPECT quantified MBF and MFR. Flow parameters were correlated with extracellular volume (ECV), biomarkers, echocardiographic indices, and ⁹⁹ᵐTc-pyrophosphate (PYP) uptake. Twelve patients underwent follow-up imaging after tafamidis. Results Patients with ATTR-CM showed significantly reduced MBF and MFR, inversely correlated with ECV, N-terminal pro-B-type natriuretic peptide (NT-proBNP), and the E/e′ ratio (all p < 0.05), but not with PYP uptake. After tafamidis, PYP uptake decreased at the group level, whereas MFR changes were heterogeneous: seven patients showed no reduction, while five showed a reduction. Patients with reduced MFR had greater increases in ECV, NT-proBNP, and E/e′ ratio. Relative changes in stress MBF and MFR were inversely associated with changes in ECV and E/e′ ratio, whereas relative changes in MFR were also inversely associated with changes in NT-proBNP (all p < 0.05). Conclusions Dynamic CZT-SPECT demonstrated reduced MBF and MFR in ATTR-CM and associations with multimodality markers. Post-tafamidis findings were heterogeneous and exploratory, warranting larger prospective studies. Advances in Knowledg This is the first study to apply dynamic ²⁰¹Tl CZT-SPECT for MBF quantification in ATTR-CM and to relate myocardial flow impairment to multimodality markers of disease burden.