Medical Therapy Approach for Treating Abdominal Aortic Aneurysm

Abstract

Abdominal aortic aneurysm (AAA) is a common and deadly problem. The aortic diameter increases in association with a complex remodeling process that includes changes in the structure and content of key proteins, elastin and collagen. As these changes occur, the tissue mechanical properties also change. The natural history of AAA is progressive enlargement to a point of mechanical tissue failure, typically followed by death. Currently, the marker used to predict the risk of impending rupture is the largest transverse diameter. After reaching a diameter threshold of 5.5 cm, the aneurysm is surgically repaired. This criterion does not consider any patient-specific information or the known heterogeneity of the aneurysm that may, in some cases, lead to rupture before the aneurysm reaches the standard intervention threshold. Conversely, in many patients, continued observation beyond this threshold is safe. Although no medical treatment is yet approved, doxycycline has been shown to greatly reduce aortic aneurysm growth in animal models and has been shown to slow growth in several small clinical trials. Although larger prospective randomized trials are needed, one unknown is what effect doxycycline has on the structural integrity of the aortic wall. That is, does slowed aneurysm growth by doxycycline treatments, in fact, prevent rupture, or does the wall continue to weaken and the aneurysm instead ruptures at a smaller diameter? Research has begun to answer these questions before a large clinical trial begins.