Experimental Study of Rupture Pressure and Elasticity of Abdominal Aortic Aneurysms Found at Autopsy

Abstract

Resistance and elasticity of normal and aneurysmal aorta walls are directly associated with this vessel's growth and rupture. This study aims to experimentally analyze the biomechanical behavior of aneurysmal specimens found at autopsy, comparing them with normal diameter aortas removed from age-matched donors. Thirty-eight human aortas (30 normal aortas; 8 infrarenal abdominal aortic aneurysms) were harvested during autopsy. An apparatus was built with a digital gauge, plastic tray, connections, and hoses that conducted fluid (air) from a pump through the system. Specimens were dissected, and a flexible balloon was introduced in each of them to avoid leakage. The specimens were fastened on the test tray, and activation of the air pump enhanced system pressure up to their rupture. All 8 aneurysms and all 30 normal aortas specimens evolved to rupture under inflation pressures above 590mm Hg (mean±standard deviation=1,035±375mm Hg) and 840mm Hg (mean±SD=1,405±342mm Hg), respectively. In the aneurysm group, 25% of specimens did not rupture in their most dilated region. Percentage of increment in diameter was higher in normal aortas (mean±SD=0.2106±0.144) than in aneurysms (mean±SD=0.093±0.070). In the present experiment, unruptured infrarenal abdominal aortic aneurysms could support high pressures nearly as much as nonaneurysmal abdominal aortas. In some specimens, the most dilated part of the aneurysm was not the most vulnerable under pressure. Normal aortas presented higher elasticity than aneurysms.