The Primary Research Of Wall Motion And Mechanical Properties Of Abdominal Aortic Aneurysms With Ultrasound Technique

BackgroundAbdominal aortic aneurysm(AAA) is defined as a permanent localized dilation of aorta having at least a 50% increase in diameter compared with the expected normal diameter. AAA becomes more dangerous for its rupture risk. The modern opinions consider the etiology of AAA was the combination action of genetics, circumstance, biochemistry, anatomy and haemodynamics rather than single factor. Ultrasound technique can undirectly provide individual AAA wall stress distribution by wall motion and show the mechanical properties of artery wall. Can these interesting information give us some new way to investigate the rupture risk of AAA?Materials and Methods1. The measurement of abdominal aortic wall motion in mammalian species(dog, pig, human) by M-mode ultrasound.2. The measurement of intraluminal thrombus of AAA by Integrated Backscatter technique.3. The measurement of velocity, strain, strain rate of abdominal aortic wall in control and AAA group by velocity vector imaging (VVI) technique.4. Illustration to the reason of AAA occurs to human mostly combined ultrasound information and haemodynamics.5. A new variation to measure the rupture risk of AAA.Results1. The ratios of wall displacement to diastolic diameter were similar for the anterior and posterior walls among species. Anterior wall displacement was greater than posterior among the species studied. Wall displacement increases linearly with the diameter of aortic artery.2. Control group: The systolic maximum velocity(Vs) had no significant difference, except anterior and posterior wall. The Vs of anterior wall was higher than posterior wall. The same with maximum strain (Smax) and maximum strain rate (SRmax).Vs, Smax, SRmax of walls localized at inlet segment and outlet segment were higher than those of maximum diameter segment of AAA. Vs, Smax, SRmax of walls were higher in the control group than those in AAA group.3. Reflow blood in infrarenal aorta was observed in human group, not in pig group. Vs, Smax, SRmax of infrarenal aorta wall were higher than those of common carotid artery and common femoral artery. Reflow blood was observed in intrarenal aorta and common femoral artery, not in common carotid artery.4. A new variation :X=Smax/Vs. X value of posterior wall was higher than lateral and posterior walls in control group. X value can be used in special wall point of AAA.Conclusion1. Aortic wall motion may help explain why human AAAs initially develop anteriorly. It should be considered when developing endovascular devices and follow-up to those patients receiving endovascular aorta repair.2. Integrated backscatter, as new ultrasound technique, can be used on evaluation intraluminal thrombus of AAA.3. Velocity vector imaging technique can calculate velocity, strain and strain rate of aorta wall. It is very important to draw the outline of wall accurately.4. Higher wall circumferential stress in aorta than in peripheral artery and persistent shear stress change in furcation of aorta can explain why aneurysms develop in abdominal aorta than other arteries.5. X value can explain the special point of AAA wall which may rupture pronely. It needs to be verified at clinical research in the future.