Noninvasive anatomical assessment for ruling out hemodynamically relevant coronary artery anomalies in adults - A comparison of coronary-CT to invasive coronary angiography: The NARCO study design.

Background Anomalous aortic origin of a coronary artery (AAOCA) is a rare congenital heart disease, potentially leading to myocardial ischemia and adverse cardiac events. As the sole presence of AAOCA does not always imply a revascularization, a detailed anatomical and functional analysis is crucial for clinical decision-making. Currently, invasive coronary angiography is the gold-standard method for a thorough hemodynamic assessment of AAOCA. However, due to its invasive nature, the development of noninvasive diagnostic alternatives is desired. Methods In the NARCO trial, patients with AAOCA will undergo coronary computed tomography angiography (CCTA) to assess anatomical high-risk features followed by a vessel-based (i.e. invasive measurement with fractional flow reserve and intravascular imaging under a dobutamine-volume challenge) and a myocardium-based (i.e. nuclear imaging) ischemia testing. Comparison of noninvasive and invasive imaging will be performed. Additionally, explorative analysis of post-processing advanced computational fluid dynamics (CFD) and 3D printing will be performed to unravel the pathophysiologic mechanism of myocardial ischemia in AAOCA. Aims Our primary aim is to define characteristics of anatomical high-risk features (using CCTA) to rule out noninvasively hemodynamically relevant anomalous vessels in AAOCA patients. The secondary aim is to investigate the underlying pathophysiology of AAOCA-related hemodynamic relevance using advanced techniques such as CFD and 3D printing. Conclusions The NARCO trial will help to optimize AAOCA patient selection for revascularization by improving risk stratification and ruling out hemodynamic relevance noninvasively and, therefore, preventing unnecessary downstream testing and/or costly interventions in patients with AAOCA.