Dissectometer - a new device for tensile strength testing of the vascular wall.

OBJECTIVES: The underlying mechanisms leading to aortic dissection are poorly understood. The present paper describes a unique device for aortic wall testing during open heart surgery which allows to directly predict the risk of aortic dissection. MATERIAL AND METHODS: Samples of the aortic wall were taken during surgery of the aortic valve and ascending aorta in 35 patients. Disruption of the samples was performed by using the dissectometer (patent pending). The output signal of the actuator was visualized by a "tensile strain curve". Seven destinctive curve parameters were compared by parametric or nonparametric evaluation with regard to the results of the normality test. RESULTS: Variations of all seven parameters in each patient differed not significantly; however, significant differences could be observed between the 35 patients. All parameters proved to be consistent and reproducible intra-individually. Histological analysis showed the integrity of the surface and localization of dissection in the external layer of tunica media. CONCLUSIONS: The dissectometer proved to be a suitable device to predict aortic wall consistence intraoperatively. Statistical analysis confirmed that a single sample of aorta is sufficient for assessment of aortic wall quality. A valid statistical discrimination between "healthy" and pathological aortas could only be assumed by generation of a large database of patients.

Ascending aortic wall cohesion: comparison of bicuspid and tricuspid valves.

Objectives. Bicuspid aortic valve (AV) represents the most common form of congenital AV malformation, which is frequently associated with pathologies of the ascending aorta. We compared the mechanical properties of the aortic wall between patients with bicuspid and tricuspid AV using a new custom-made device mimicking transversal aortic wall shear stress. Methods. Between 03/2010 and 07/2011, 190 consecutive patients undergoing open aortic valve replacement at our institution were prospectively enrolled, presenting either with a bicuspid (group 1, n = 44) or a tricuspid (group 2, n = 146) AV. Aortic wall specimen were examined with the "dissectometer" resulting in nine specific aortic-wall parameters derived from tensile strength curves (TSC). Results. Patients with a bicuspid AV showed significantly more calcified valves (43.2% versus 15.8%, P < 0.001), and a significantly thinner aortic wall (2.04 ± 0.42 mm versus 2.24 ± 0.41 mm, P = 0.008). Transesophageal echocardiography diameters (annulus, aortic sinuses, and sinotubular junction) were significantly larger in the bicuspid group (P = 0.003, P = 0.02, P = 0.01). We found no difference in the aortic wall cohesion between both groups as revealed by shear stress testing (P = 0.72, P = 0.40, P = 0.41). Conclusion. We observed no differences of TSC in patients presenting with tricuspid or bicuspid AVs. These results may allow us to assume that the morphology of the AV and the pathology of the ascending aorta are independent.