Thoracic Aortic Compliance as a Determinant of Rupture of Abdominal Aortic Aneurysms

The relative importance of collagen and elastin in formation, expansion, and rupture of abdominal aortic aneurysms (AAAs) has been investigated extensively. Aortic compliance, which is a relevant component of cardiac afterload, is also determined by the relative amount of media proteins in large arteries as well as by pathological arterial processes. The objective of this study was to determine if thoracic aortic compliance was different in patients with ruptured AAAs compared to those undergoing elective AAA repair. The study was carried out in 43 patients with infrarenal AAAs in the postoperative period. The first group (A) included 17 patients undergoing emergency ruptured AAA repair. The second group (B) included 26 patients operated on for an AAA who underwent elective repair. Patients were studied by a noninvasive Doppler echocardiography. Pulse wave velocity (PWV) was determined in the descending thoracic aorta. Results show that patients with electively repaired AAAs had an accelerated pulse wave transmission, typical of an atherosclerotic aorta with a Gaussian distribution (PWV 9.26 m/sec +/- 1.27). In contrast, patients with ruptured aneurysms presented in a distribution with three peaks. A striking increase in aortic compliance (41% of patients with PWV<6 m/sec in group A vs. 3% of group B) was observed in patients with ruptured AAAs.