Invasive assessment of coronary microvascular dysfunction in patients with wild-type transthyretin amyloid cardiomyopathy

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 using intracoronary pressure-temperature wire.Methods: Patients with cardiac hypertrophy, defined as interventricular septum 12 mm, undergoing invasive CMD assessment using pressure wire were evaluated in the 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, LVH: n=32) were analyzed.A similar prevalence was observed between the 2 groups (ATTRwt-CM: 68.8%, left ventricular hypertrophy [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 (=-0.011,P=0.007) and IMR (=0.177,P=0.010) in patients with ATTRwt-CM.Conclusions: CMD was highly prevalent in patients with ATTRwt-CM.Modest association between CFR, IMR and cardiac biomarkers observed only in patients with ATTRwt-CM compared with those with LVH may suggest the pathophysiological role of CMD in myocardial injury among patients with ATTRwt-CM.