Blood flow characteristics in the ascending aorta after aortic valve replacement鈥攁 pilot study using 4D-flow MRI

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• 作者：Florian von Knobelsdorff-Brenkenhoff ; Ralf F. Trauzeddel ; Alex J. Barker ; Henriette Gruettner ; Michael Markl ; Jeanette Schulz-Menger
• 关键词：Aorta ; Hemodynamics ; Magnetic resonance imaging ; Surgery ; Valves ; 4D-flow
• 刊名：International Journal of Cardiology
• 出版年：1 January, 2014
• 年：2014
• 卷：170
• 期：3
• 页码：426-433
• 全文大小：1500 K

文摘

Background

Aortic remodeling after aortic valve replacement (AVR) might be influenced by the postoperative blood flow pattern in the ascending aorta. This pilot study used flow-sensitive four-dimensional magnetic resonance imaging (4D-flow) to describe ascending aortic flow characteristics after various types of AVR.

Methods

4D-flow was acquired in 38 AVR patients (m>nm> = 9 mechanical, m>nm> = 8 stentless bioprosthesis, m>nm> = 14 stented bioprosthesis, m>nm> = 7 autograft) and 9 healthy controls. Analysis included grading of vortex and helix flow (0-3 point scale), assessment of systolic flow eccentricity (1-3 point scale), and quantification of the segmental distribution of peak systolic wall shear stress (WSS_peak) in the ascending aorta.

Results

Compared to controls, mechanical prostheses showed the most distinct vorticity (2.7 卤 0.5 vs. 0.7 卤 0.7; m>pm> < 0.001), while stented bioprostheses exhibited most distinct helicity (2.6 卤 0.7 vs. 1.6 卤 0.5; m>pm> = 0.002). Instead of a physiologic central flow, all stented, stentless and mechanical prostheses showed eccentric flow jets mainly directed towards the right-anterior aortic wall. Stented and stentless prostheses showed an asymmetric distribution of WSS_peak along the aortic circumference, with significantly increased local WSS_peak where the flow jet impinged on the aortic wall. Local WSS_peak was higher in stented (1.4 卤 0.7 N/m²) and stentless (1.3 卤 0.7 N/m²) compared to autografts (0.6 卤 0.2 N/m²; m>pm> = 0.005 and m>pm> = 0.008) and controls (0.7 卤 0.1 N/m²; m>pm> = 0.017 and m>pm> = 0.027). Autografts exhibited lower absolute WSS_peak than controls (0.4 卤 0.1 N/m² vs. 0.7 卤 0.2 N/m²; m>pm> = 0.003).

Conclusions

Flow characteristics in the ascending aorta after AVR are different from native aortic valves and differ between various types of AVR.