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. 2023 Dec 1;13(12):7973-7986.
doi: 10.21037/qims-23-183. Epub 2023 Oct 27.

Comparison of aortic blood flow rotational direction in healthy volunteers and patients with bicuspid aortic valves using volumetric velocity-sensitive cardiovascular magnetic resonance imaging

Affiliations

Comparison of aortic blood flow rotational direction in healthy volunteers and patients with bicuspid aortic valves using volumetric velocity-sensitive cardiovascular magnetic resonance imaging

Sebastian Ebel et al. Quant Imaging Med Surg. .

Abstract

Background: The rotational direction (RD) of helical blood flow can be classified as either a clockwise (RD+) or counter-clockwise (RD-) flow. We hypothesized that this simple classification might not be sufficient for analysis in vivo and a simultaneous existence of RD+/- may occur. We utilized volumetric velocity-sensitive cardiovascular magnetic resonance imaging (4D flow MRI) to analyze rotational blood flow in the thoracic aorta.

Methods: Forty volunteers (22 females; mean age, 41±16 years) and seventeen patients with bicuspid aortic valves (BAVs) (9 females; mean age, 42±14 years) were prospectively included. The RDs and the calculation of the rotating blood volumes (RBVs) in the thoracic aorta were performed using a pathline-projection strategy.

Results: We could confirm a mainly clockwise RD in the ascending, descending aorta and in the aortic arch. Furthermore, we found a simultaneous existence of RD+/RD-. The RD+/--volume in the ascending aorta was significantly higher in BAV patients, the mean RD+/RD- percentage was approximately 80%/20% vs. 60%/40% in volunteers (P<0.01). The maximum RBV always occurred during systole. There was significantly more clockwise than counter-clockwise rotational flow in the ascending aorta (P<0.01) and the aortic arch (P<0.01), but no significant differences in the descending aorta (P=0.48).

Conclusions: A simultaneous occurrence of RD+/RD- indicates that a simple categorization in either of both is insufficient to describe blood flow in vivo. Rotational flow in the ascending aorta and in the aortic arch differs significantly from flow in the descending aorta. BAV patients show significantly more clockwise rotating volume in the ascending aorta compared to healthy volunteers.

Keywords: Volumetric velocity-sensitive cardiovascular magnetic resonance imaging (4D flow MRI); aortic blood flow; bicuspid aortic valve (BAV); helical blood flow; rotating blood volume (RBV); rotational direction (RD).

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Conflict of interest statement

Conflicts of Interest: All authors have completed the ICMJE uniform disclosure form (available at https://qims.amegroups.com/article/view/10.21037/qims-23-183/coif). AA was supported by an ESOR/ESCR 2019 cardiac fellowship. The other authors have no conflicts of interest to declare.

Figures

Figure 1
Figure 1
Three examples for the determination of the rotation direction in the cross-sectional plane. The lines from the blue point (first) to the red point (second) are pathline segments that are projected into a plane. (A) The successive points are in the first and second quadrant (Q1 and Q2), they represent a right-handed segment. (B) The successive points are in the fourth and third (Q4 and Q3) quadrant, they represent a left-handed segment. (C) The points are in diagonal quadrants (Q1 and Q4), in this case they represent a right-handed segment.
Figure 2
Figure 2
Visualization of a RD map on the surface of the thoracic aorta and as pathlines. Please note that in the volunteer the aortic arch counter-clockwise flow aligns at the outer surface of the vessel, while clockwise flow aligns at the inner surface of the aorta, while there is no such alignment in the patient. In the ascending and descending aorta clockwise and counter-clockwise flow are not separated. In the volunteer the pathlines on the outer surface of the aortic arch seems to go predominantly into the supraaortic vessels. Volunteer: 29 years old female. Patient: 27 years old female, BAV type L-R. BAV, bicuspid aortic valve; L-R, left coronary-right coronary; RD, rotational direction.

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