Early diastolic dysfunction in patients with ischemia and no obstructive coronary artery disease: a prospective study on hybrid positron emission tomography-magnetic resonance imaging.

BACKGROUND: Coronary microvascular dysfunction (CMD) has been proposed to be one of the pathological mechanisms underlying heart failure with preserved ejection fraction (HFpEF) and left ventricular (LV) diastolic dysfunction. This study aimed to clarify the relationship between CMD and LV early diastolic function in patients with ischemia and no obstructive coronary artery disease (INOCA). METHODS: Consecutive patients with INOCA treated at The First Affiliated Hospital of University of Science and Technology of China between August 2024 and March 2026 were prospectively recruited. LV strain rates, myocardial flow reserve (MFR), and peak filling rate (PFR) were acquired via positron emission tomography-magnetic resonance imaging (PET/MRI). Linear regression analysis was performed to identify independent associations between LV early diastolic strain rates and CMD. RESULTS: A total of 73 patients (mean age 55±10 years; 49.3% females) with INOCA were ultimately enrolled and divided into a CMD group and a non-CMD group based on global MFR assessment. Compared with the non-CMD group, the CMD group exhibited significantly lower radial peak early diastolic strain rate (PEDSR), circumferential PEDSR, and longitudinal PEDSR (all P values <0.001). However, no significant differences were observed in LV global strain rate parameters. Multivariate regression analysis revealed that the factors independently associated with global MFR were radial PEDSR [standardized β (95% CI) = -0.250 (-0.494 to -0.006); P=0.044] and circumferential PEDSR [standardized β (95% CI) = 0.464 (0.194 to 0.734); P=0.001]. Additionally, multivariate analysis confirmed CMD to be an independent predictor of all three directions of PEDSR (radial, circumferential, and longitudinal) (all P values <0.001). Notably, the independent predictors of radial PEDSR were PFR [standardized β (95% CI) = -0.356 (-0.523 to -0.190); P<0.001] and extracellular volume [standardized β (95% CI) = 0.289 (0.139 to 0.439); P<0.001]. CONCLUSIONS: Despite normal LV ejection fraction in patients with INOCA, CMD was significantly associated with subclinical LV early diastolic dysfunction. These physiological findings provide a mechanistic basis for future prospective studies investigating the prognostic significance of these diastolic abnormalities in patients with INOCA.