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.