Use of CTFFR and CTCA to Diagnose and Triage Patients of INOCA: A Retrospective Study

Abstract

Objectives: INOCA (Ischemia in non- obstructive coronary arteries) has been recognized as a global health problem and poses a diagnostic challenge to establish the diagnosis which involves first ruling out obstructive coronary artery disease by the use of CT coronary angiography (CTCA) or an invasive angiogram. Second step involves the use of intracoronary pressure and Doppler monitoring which is not only costly, time consuming and lacks easy availability. CTFFR has emerged as frontline tool in the non invasive evaluation of patients with stable chest pain. This retrospective study was designed to evaluate the spectrum of findings of ischemia on CTCA and CT FFR in patients with stable chest pain to determine if this protocol can be used to identify patients with INOCA before they are subjected to invasive protocol. Methods: This was a retrospective study of 500 consecutive patients of stable chest pain with more than >1mm ST depression on resting EKG and or positive stress test who underwent CTCA along with CTFFR evaluation using a prescribed CT angiographic protocol. Post processing was done to reconstruct multiplanar angiographic views followed by CT FFR evaluation. All patients with no obstruction or stenosis less than 50% and with CT FFR of <0.80 were labeled as having INOCA. Subcategorisation of all INOCA patients was done based on Vessel tapering index (VTI), Plaque volume Index (PVI) into four subtypes- TypeI (vasospastic), Type II (site specific atherosclerotic), Type III (distal macrovascular dysfunction- DMD), Type IV (mixed). Results: Study showed 122 (34%) patients of stable chest pain had INOCA. Types I, III formed the largest group of patients 38% and 31% followed by the other two subtypes and showed significant differences in the VTI and PVI along with reduced FFR of <.80 in all these patients. Conclusion: Use of CTCA and CTFFR can be used as a first line tool to not only rule out obstructive coronary disease with ischemia but also to non invasively detect INOCA in patients with stable chest pain before subjecting these patients for further invasive protocols and can influence accurate management of such patients.