Prevalence and imaging spectrum of coronary artery anomalies by coronary computed tomography angiography (CCTA) among patients with failed coronary artery catheterization; A single center cross-sectional study in Egyptian population Abstract Background: Anatomic variations and abnormalities of coronary arteries could affect the blood supply of the heart, hemodynamic characteristics and could be a risk of atherosclerosis. Knowledge about the variations of coronary artery origin and its course provides a valuable guide to Cardiothoracic Surgeons and Physicians and be useful for choosing the appropriate devices for such variant anatomical structures. The aim of the study was to estimate the prevalence of coronary artery anomalies among patients with failed coronary artery catheterization using CCTA to prevent misdiagnosis and reduce mismanagement of such anomalies. Methods: One hundred MDCT coronary angiography examinations were done using a 128-detectors (Philips Healthcare Ingenuity) scanner for patients who had previously failed coronary artery catheterization. Dedicated software and post processing techniques were used for precise evaluation and description of the coronary artery tree to be a road map for future interventional procedures. Results: Class A coronary artery anomalies were found in 53.2% of the detected anomalies (25 / 47 anomalies) in 20% of the included patients while class B coronary artery anomalies were recorded in 46.8% of the detected anomalies (22 / 47 anomalies) in 19% of the included patients. No cases showed class C anomalies in our cohort. Significant coronary artery disease (CAD) had no significant association with the presence of coronary artery anomalies. Conclusions: Detection of different coronary artery anomalies among patients with previous failed coronary artery catheterization can help the cardiologists for better planning for the interventional procedures and better patient outcome. Keywords: Coronary artery; Non-invasive; Origin; Coronary computed tomography angiography; Course.