Bicuspid Aortic Valve: Four-dimensional MR Evaluation of Ascending Aortic Systolic Flow Patterns
Abstract
By using four-dimensional flow MR imaging, we have provided evidence that markedly abnormal helical flow is evident in the ascending thoracic aorta of patients with a bicuspid aortic valve, including those without aneurysm or aortic stenosis.
Purpose
To use time-resolved three-dimensional phase-contrast magnetic resonance (MR) imaging, also called four-dimensional flow MR imaging, to evaluate systolic blood flow patterns in the ascending aorta that may predispose patients with a bicuspid aortic valve (BAV) to aneurysm.
Materials and Methods
The HIPAA-compliant protocol received institutional review board approval, and informed consent was obtained. Four-dimensional flow MR imaging was used to assess blood flow in the thoracic aorta of 53 individuals: 20 patients with a BAV, 25 patients with a tricuspid aortic valve (TAV), and eight healthy volunteers. The Fisher exact test was used to evaluate the significance of flow pattern differences.
Results
Nested helical flow was seen at peak systole in the ascending aorta of 15 of 20 patients with a BAV but in none of the healthy volunteers or patients with a TAV. This flow pattern was seen both in patients with a BAV with a dilated ascending aorta (n = 6) and in those with a normal ascending aorta (n = 9), was seen in the absence of aortic stenosis (n = 5), and was associated with eccentric systolic flow jets in all cases. Fusion of right and left leaflets gave rise to right-handed helical flow and right-anterior flow jets (n = 11), whereas right and noncoronary fusion gave rise to left-handed helical flow with left-posterior flow jets (n = 4).
Conclusion
Four-dimensional flow MR imaging showed abnormal helical systolic flow in the ascending aorta of patients with a BAV, including those without aneurysm or aortic stenosis. Identification and characterization of eccentric flow jets in these patients may help identify those at risk for development of ascending aortic aneurysm.
© RSNA, 2010
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Article History
Received August 4, 2009; revision requested September 17; revision received September 30; accepted October 15; final version accepted October 28.Published online: Mar 10 2010
Published in print: Apr 2010