Blood flow helical pattern in type III arch configuration as a potential risk factor for type B aortic dissection

Abstract OBJECTIVES Abnormal helical flow (HF) in the aortic arch has been proposed as a causative factor for aortic dilatation and aortic dissections (ADs). Patients with type B AD present a high prevalence of type III arch configuration, which comprises recognized anatomic AD risk factors. Our aim was to assess whether the type III arch configures a consistent secondary HF pattern. METHODS We employed computational fluid dynamics to compare HF features associated with type I–III arches. The intra-aortic blood flow pattern was regionally assessed through the Modified Arch Landing Areas Nomenclature (MALAN) for planning endovascular aortic repair. Aortic flow pathlines were extracted from the systolic aortic velocity field and objectively characterized through intrinsic shape indices of absolute curvature |κ| and absolute torsion |τ|. Absolute local normalized helicity was computed and mapped on aortic flow pathlines. RESULTS The tendency of aortic flow pathlines to bend and rotate exacerbated in the isthmus of type III arch (MALAN 3/III), where the highest |κ| values (P < 0.0001) were paralleled by the lowest |τ| values (P = 0.010), demonstrating the persistence of a high rotational HF heavily insisting on 3/III. In 3/III area, local normalized helicity was higher than both 3/I and 3/II (P = 0.053). CONCLUSIONS Type III arch configuration is associated with a specific, consistent and abnormal secondary HF pattern, which may account for its high prevalence in patients with type B AD. The presence of a helical blood flow pattern in the aortic arch is a well-established phenomenon, which represents a physiological response to the specific anatomical features of this aortic tract, namely torsion, branching, curvature and taper.