The correlation between angio-IMR and thermodilution-based IMR in patients with ischemia and non obstructive coronary arteries

Abstract Background The diagnostic dilemma of angina with no obstructive coronary lesions (INOCA) poses remarkable challenges in clinical practice, and presents as a significant disease burden affecting up to 4 million people annually. Additionally, standard diagnostic tests such as angiography, do not reveal microvascular dysfunction despite clinical symptoms being present. Since the current Gold Standard of functional assessment is based on guidewire dependent measurements (i.e. CFR, IMR). As an invasive method, it is associated with an increased risk of adverse events such as arterial damage. Therefore new modalities are being introduced to improve patient safety, specifically, an angio-IMR (QMR, calculated based on angiography), shows a substantial promise as a potential diagnostic tool for INOCA patients. Purpose The aim of this study is to assess correlation between angio-IMR and thermodilution-based invasively measured IMR in INOCA patients. Methods In a group of INOCA patients who had undergone coronary angiography with concomitant thermodilution-based assessment of index of microcirculatory resistance (IMR) an additional angio-based IMR calculation was performed. The INOCA group consisted of 92 patients ranging in age from 49 to 80 years old, with a median age of 66 years. The majority of the patients were female (59.3%), predominantly with arterial hypertension (87%) and dyslipidemia (100%). Diabetes was present in 27% of cases. Angio-IMR (QMR) was determined by a qualitative angiography software using information about aortic pressures registered during angiography. Coronary microcirculatory dysfunction (CMD) was diagnosed according to current guidelines when IMR ≥ 25 or CFR < 2.0 were present. Results Increased IMR values were detected in 26% of patients. Median calculated value of angio-IMR value was 29 [IQR: 22,46], whereas the invasively measured IMR median value was 17 [IQR: 13,26]. A significant correlation between angio-IMR and invasive-IMR values was observed, Spearman Rho 0.29, p<0.001. Detailed scatterplot with histograms is presented in the figure. Conclusions Noninvasive methods, such as the Angio-IMR, represent a shift towards reducing the need for additional invasive procedures while still providing valuable diagnostic insights. Angio-IMR is significantly correlated with invasively measured IMR. When evaluated along with the clinical presentation, noninvasive approaches may therefore help mitigate certain risks and healthcare costs associated with invasive techniques.Figure.Correlation angio-IMR vs MR