Journal Article

4D flow CMR analysis comparing patients with anatomically shaped aortic sinus prostheses, tube prostheses and healthy subjects introducing the wall shear stress gradient: a case control study

Huellebrand, Markus, Oechtering, Thekla Helene, Scharfschwerdt, Michael, Barkhausen, Joerg, Frydrychowicz, Alex, Sievers, Hans-Hinrich, Wegner, Franz, Sieren, Malte Maria, Fujita, Buntaro, Schultz, Victoria

2020

Overview

Background Anatomically pre-shaped sinus prostheses (SP) were developed to mimic the aortic sinus with the goal to preserve near physiological hemodynamic conditions after valve-sparing aortic root replacement. Although SP have shown more physiological flow patterns, a comparison to straight tube prosthesis and the analysis of derived quantitative parameters is lacking. Hence, this study sought to analyze differences in aortic wall shear stress (WSS) between anatomically pre-shaped SP, conventional straight tube prostheses (TP), and age-matched healthy subjects) using time-resolved 3-dimensional flow cardiovascular magnetic resonance (4D Flow CMR). Moreover, the WSS gradient was introduced and analyzed regarding its sensitivity to detect changes in hemodynamics and its dependency on the expression of secondary flow patterns. Methods Twelve patients with SP (12 male, 62 ± 9yr), eight patients with TP (6 male, 59 ± 9yr), and twelve healthy subjects (2 male, 55 ± 6yr) were examined at 3 T with a 4D Flow CMR sequence in this case control study. Six analysis planes were placed in the thoracic aorta at reproducible landmarks. The following WSS parameters were recorded: WSS avg (spatially averaged over the contour at peak systole), max. WSS seg (maximum segmental WSS), min. WSS seg (minimum segmental WSS) and the WSS Gradient, calculated as max. WSS seg – min. WSS seg . Kruskal-Wallis- and Mann-Whitney-U-Test were used for statistical comparison of groups. Occurrence and expression of secondary flow patterns were evaluated and correlated to WSS values using Spearman’s correlation coefficient. Results In the planes bordering the prosthesis all WSS values were significantly lower in the SP compared to the TP, approaching the physiological optimum of the healthy subjects. The WSS gradient showed significantly different values in the four proximally localized contours when comparing both prostheses with healthy subjects. Strong correlations between an elevated WSS gradient and secondary flow patterns were found in the ascending aorta and the aortic arch. Conclusion Overall, the SP has a positive impact on WSS, most pronounced at the site and adjacent to the prosthesis. The WSS gradient differed most obviously and the correlation of the WSS gradient with the occurrence of secondary flow patterns provides further evidence for linking disturbed flow, which was markedly increased in patients compared to healthy sub jects, to degenerative remodeling of the vascular wall.

• Publisher: BioMed Central,BioMed Central Ltd,Elsevier
• Subject: 4D flow MRI / Adult / Aged / Analysis / Angiology / Aorta / Aorta, Thoracic - diagnostic imaging / Aorta, Thoracic - physiopathology / Aorta, Thoracic - surgery / Aortic aneurysms / Aortic arch / Aortic tube prosthesis / Aortic Valve - diagnostic imaging / Aortic Valve - physiopathology / Blood Vessel Prosthesis / Blood Vessel Prosthesis Implantation - instrumentation / Cardiac-Gated Imaging Techniques / Cardiology / Case-Control Studies / Coronary vessels / Correlation coefficients / Electrocardiography / Female / Flow velocity / Hemodynamics / Humans / Imaging / Implants, Artificial / Magnetic resonance / Magnetic Resonance Imaging / Male / Mathematical analysis / Medicine / Medicine & Public Health / Middle Aged / Parameters / Patients / Perfusion Imaging - methods / Physiological aspects / Physiology / Predictive Value of Tests / Prostheses / Prosthesis / Prosthesis Design / Prosthetics / Pulmonary arteries / Radiology / Regional Blood Flow / Secondary flow / Shear stress / Sinuses / Stress, Mechanical / Studies / Systole / Thoracic aortic aneurysm / Thorax / Three dimensional flow / Treatment Outcome / Valve-sparing aortic root replacement / Visualization / Vortices / VSARR / Wall shear stress / Wall shear stresses