Funding Acknowledgements Type of funding sources: None. On Behalf of MiniFellows Research Group CLINICAL AND IMAGING VARIABLES IN MICROVASCULAR ANGINA. A 13N-AMMONIA MPI APPROACH Background Patients with typical angina may have no obstructive artery disease1 and 2/3 may present microvascular dysfunction(MVD)2 which is associated with poor prognosis3,4,5. In 2017 the Coronary Vasomotion Disorders International Study Group (COVADIS) included it as a criteria of MVA6; later, included in MINOCA ESC 2020 guidelines.7 For diagnosis6,7: symptoms of ischemia; absence of relevant epicardial CAD (<50% diameter reduction or FFR >0.80); myocardial ischemia; impaired coronary microvascular function (CFR < 2 or <2.5 depending on methodology). Our aim was to identify clinical and imaging variables in patients with MVA due to 13N-ammonia Positron Emission Tomography/Cardiac Tomography(PET/CT) and Cardiac Computed Tomography Angiography(CCTA) in a cardiovascular imaging referral center. Methods.Retrospective, cross-sectional study of patients with suspected CAD. For inclusion: ischemia quantitation (summed stress score,SDS < 3) and obstruction <50% in all vessels. Exclusion criteria: previous infarction, intervention, or incomplete study. Clinical data was assessed. Both studies performed on the same day. Frequencies and percentages to report categorical variables; x2 and Fisher´s exact tests to compare them. Mean (+/-DE) or median (interquartile range) to report continuous variables according to their distribution, and T student or Wilcoxon test to compare them. Results 274 patients included: Group A (CFR <2) and group B (CFR 2)(108vs166). Difference for systemic hypertension(p <0.001), type 2 diabetes mellitus(p <0.001), dyslipidemia(p = 0.019), smoking(p <0.001). Group B presented higher incidence for mild ischemia(p = 0.004) while MVA for severe ischemia(p = 0.002). Difference between groups for EDV and ESV at rest (p = 0.002), EDV at stress(p = 0.03) and at rest(p < 0.001), LVEF at rest and stress(p < 0.001) and for a negative change of LVEF(p < 0.001). Also, reduced Calcium Score(SC)(p < 0.001) Discussion With a higher prevalence reported in women8,9, no difference for women in both groups. Presentation been reported as atypical 3,6,10, as in our study. Traditional risk factors may affect the microvascular circulation earlier in the disease. Regarding mild and severe ischemia, CFR´s may be lower in defect perfusion zones and presence of both ischemia and MVD has worse prognosis11 suggesting ischemia could had already developed in this group. LVEF drop supports the relation between CFR and ventricular function12. Finally, MVA group had a reduced CS, associated with CAD and worse prognosis, suggesting it also affects the microvasculature function. Conclusions 13N-ammonia PET/CT MPI with CCTA is a great combination to diagnose MVA, whose main component is microvascular dysfunction. Recognizing the risk factors associated with this pathology allows making opportune detections, implementing early treatment strategies, controlling symptoms and avoiding the disease"s evolution