Dual perfusion imaging with integrated positron emission tomography-magnetic resonance imaging for the detection of coronary microvascular dysfunction in patients with ischemia with no obstructive coronary artery disease: a study on myocardial perfusion imaging and T1 mapping

Background: Coronary microvascular dysfunction (CMVD) is a common cause of ischemia with no obstructive coronary arteries (INOCAs), a condition previously considered benign but now recognized to confer an increased risk of adverse cardiovascular events. The aim of this study was to compare the diagnostic performance of T1 mapping and myocardial perfusion reserve index (MPRI) in detecting CMVD in patients with INOCA, with positron emission tomography (PET) serving as the reference standard.

Methods: Sixty-six patients with INOCA (mean age 55±9 years; 50% female) were prospectively enrolled from August 2024 to February 2026 and underwent an integrated 3.0-T PET-magnetic resonance imaging (MRI) examination. MRI-derived left ventricular function, native T1, postcontrast T1, extracellular volume (ECV), T2 mapping, and regadenoson stress/rest MPRI were obtained and compared between the CMVD group and the non-CMVD group. CMVD was defined as a PET-derived myocardial flow reserve (MFR) <2.0.

Results: Patients with CMVD (n=28), as compared with patients without CMVD (n=38), exhibited higher native T1 (1,239±23 vs. 1,205±17 ms; P<0.001) and a lower MPRI (1.66±0.36 vs. 2.15±0.38; P<0.001), while no significant intergroup differences were observed in left ventricular ejection fraction (LVEF) or ECV (all P values >0.05). MFR was correlated with both native T1 (r=−0.513; P<0.001) and MPRI (r=0.577; P<0.001), which were identified as independent predictors of impaired MFR (P=0.015 and P=0.002, respectively). At a cutoff of 1,225 ms, native T1 yielded a sensitivity of 75%, a specificity of 100%, and an accuracy of 89.39%, while MPRI, at a cutoff <1.8, yielded a sensitivity of 75%, a specificity of 81.58%, and an accuracy of 78.79%.

Conclusions: Native T1 and MPRI showed nonsignificant differences in their ability to detect CMVD, with consistent and complementary diagnostic value. As a contrast-free method, native T1 may serve as a potential initial screening option, particularly for patients with renal dysfunction.