Increasing Extracellular Volume Fraction on Coronary CTA in Patients With Coronary Microvascular Dysfunction

Coronary computed tomography angiography (CCTA) could evaluate myocardial fibrosis as well by estimating extracellular volume fraction (ECV). While coronary microvascular dysfunction (CMD) has been increasingly recognized as an important pathophysiological mechanism underlying chest pain, the association between CMD in angina with nonobstructive coronary artery disease (ANOCA) and CCTA-derived ECV remains to be elucidated. We sought to evaluate the association between CCTA-derived ECV and CMD in patients with ANOCA.

We retrospectively analyzed 57 patients with ANOCA from a single center who underwent CCTA on ECV protocol with subtraction method (including precontrast and 7-minute delayed postcontrast) and invasive functional testing using pressure-temperature sensor-tipped wire. Patients with significant epicardial stenosis (fractional flow reserve ≤0.80 or stenosis on computed tomography ≥50%), prior history of revascularization, known myocardial infarction, or heart failure were excluded. CMD was defined as a coronary flow reserve of <2.5 in any of the vessels evaluated. Standard transthoracic echocardiography assessed diastolic dysfunction (DD).

Among the 57 patients included, 26 (45.6%) were diagnosed with CMD. CMD was significantly associated with age, NT-proBNP (N-terminal pro-B-type natriuretic peptide) level, calcium score, DD, and higher ECV. In a multivariable logistic regression analysis, a CCTA-derived ECV >31.9% (the optimal cutoff value derived from receiver operating characteristic curve analysis) was independently associated with CMD (odds ratio, 10.50 [95% CI, 2.34-47.40]; P=0.002). DD also emerged as an independent predictor (odds ratio, 17.90 [95% CI, 2.53-127.00]; P=0.004). The addition of elevated ECV to a clinical model including DD significantly enhanced the discrimination efficacy for CMD (area under the receiver operating characteristic curve, 0.742 versus 0.854; P=0.019).

In patients with ANOCA with CMD, ECV was significantly elevated, alongside a higher prevalence of DD. These findings suggest that ECV and DD may serve as pivotal markers for personalized management strategies in patients with CMD with ANOCA.