Simultaneous Assessment of Coronary Microvascular Dysfunction and Ischemia With Non-obstructed Coronary Arteries With Intracoronary Electrocardiogram and Intracoronary Doppler

Coronary Microvascular Dysfunction has been consistently shown to play a considerable role in pathophysiology of Ischaemia with non-obstructed coronary arteries (INOCA). While the both diagnoses are individually related to remarkably worse outcome, there is no available method to simultaneously determine INOCA-CMD endotypes in vessel level, during the invasive diagnosis. The investigators hereby hypothesize that, combined intracoronary electrocardiogram (IC-ECG) (considering the high sensitivity and specificity of IC-ECG for studied vessel-territory) and intracoronary doppler can simultaneously and successfully identify vessel specific coronary microvascular dysfunction and resulting ischemia, which may potentially enable immediate diagnosis and endotyping of CMD-INOCA subgroups during the invasive assessment of first ANOCA episode, obviating the need for further ischemia-studies such es SPECT, which have considerably higher costs and lower sensitivity. Major coronary arteries of patients aged between 18 - 75 without obstructing coronary artery disease who have previously documented ischemia with non-obstructed coronary arteries (INOCA) via coronary angiogram and myocardial perfusion scan will be evaluated simultaneously with IC-ECG and intracoronary Doppler during rest and under adenosine induced hyperaemia. Performance of the combined system to identify Coronary Microvascular Dysfunction with structural and functional subgroups as defined by abnormal Coronary Flow Reserve (CFR) and Hyperemic Microvascular Resistance (HMR) and Ischemia in downstream territories of same vessel area (as defined by perfusion scan) is intended to be determined. The investigators also intend to interrogate the possible relationship between dynamic changes in IC-ECG parameters and invasively obtained intracoronary hemodynamic data.