Invasive Assessment of Coronary Microvascular Dysfunction in Patients With Wild-Type Transthyretin Amyloid Cardiomyopathy

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BACKGROUND: Coronary microvascular dysfunction (CMD) is frequently observed in patients with wild-type transthyretin amyloid cardiomyopathy (ATTRwt-CM). We aimed to investigate the prevalence of CMD and identify factors associated with CMD in patients with ATTRwt-CM by using an intracoronary pressure-temperature wire. METHODS: Patients with cardiac hypertrophy, defined as an interventricular septum ≥12 mm, who were undergoing invasive CMD assessment by the use of a pressure wire, were evaluated in a prospective, multicenter study conducted between August 2022 and April 2025. CMD was defined as coronary flow reserve (CFR) <2.0 or index of microvascular resistance (IMR) ≥25. RESULTS: A total of 64 patients (ATTRwt-CM, n = 32; left ventricular hypertrophy (LVH), n = 32) were analyzed. A similar prevalence was observed in the 2 groups (ATTRwt-CM: 68.8%; LVH: 59.4%; P = 0.434). In patients with ATTRwt-CM, CFR and IMR were significantly correlated with troponin T (r = -0.503; P = 0.004, and r = 0.483; P = 0.006, respectively), while such correlations were not observed in the LVH group (r = -0.128; P = 0.501; r = 0.130; P = 0.493, respectively). Multivariable linear regression analysis demonstrated that troponin T was significantly associated with CFR (β = -0.011; P = 0.007); and IMR (β = 0.177; P = 0.010) in patients with ATTRwt-CM. CONCLUSIONS: CMD was highly prevalent in patients with ATTRwt-CM. The modest association among CFR, IMR, and cardiac biomarkers was observed only in patients with ATTRwt-CM compared with those with LVH. This may suggest the pathophysiological role of CMD in myocardial injury among patients with ATTRwt-CM.

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