Under the supervision of Scott A. LeMaire, M.D., director of research for the Division and Vice Chair for Research in the Department, the cardiac surgery research team pursues several research projects and maintains one of the world’s most extensive and well-cataloged aortic tissue banks. This core resource facilitates investigations into the causes and progression of aortic disease pursued by our researchers, as well as researchers from other academic institutions.
AKT2 confers protection against AAD
In this study, we examined the role of AKT2 in protecting the aorta from developing aneurysms and dissections. The AKT signaling pathway is involved in several cellular functions–including cell metabolism, survival, proliferation, and migration–and is known to have profound effects on the cardiovascular system. Our findings suggest that AKT2 may have a protective role against aortic disease in humans and raise the possibility that enhancing AKT2 signaling may be an effective strategy for preventing aneurysms and dissections.
On the cover (right), hematoxylin and eosin staining shows aortic dissection with a characteristic true lumen and false lumen in an Akt2-/- mouse challenged with angiotensin II infusion. Double staining for matrix metalloproteinase (MMP)-9 (green) and smooth muscle cell marker SM22α (red) shows increased MMP-9 expression in smooth muscle cells in the aorta of an Akt2-/- mouse challenged with angiotensin II infusion. Image courtesy Circulation Research © 2013. See related article.
Valve Sparing Approach to Aortic Repair
The division is active in presenting our experience regarding the outcomes of both standard and emerging surgical techniques for aortic repair. While the traditional approach toward repair of an aortic root aneurysm involves replacing it with a composite valve graft, an alternate approach—valve-sparing aortic root replacement—has increasingly become more widely used.
The valve-sparing approach maintains the superior hemodynamics of the native aortic valve and replaces the surrounding aneurysmal aorta with graft material. However, the primary advantage of valve-sparing repair is the avoidance of long-term anticoagulant therapy, which necessitates an often intolerable change in lifestyle.
In this illustration (right), valve-sparing aortic root replacement is demonstrated in a patient with an aortic root aneurysm (A). (B) The ascending aorta is opened and the diseased tissue is removed. (C) A graft is sewn to the aorta. (D) The aortic valve is prepared. (E) The replacement graft is brought down onto the native valve. (F-H) The aortic valve is secured to the graft. (I) The left main coronary artery is attached to the graft. (J) The top graft is attached to the bottom graft. (K) The right coronary artery is attached to the graft. (L) The completed repair is shown.
© Baylor College of Medicine.
Stanford Classification of Dissection
The Stanford Classification of aortic dissection categorizes dissection according to whether the ascending aorta is involved: type A dissection involves the ascending aorta, and type B dissection does not. Type B dissection generally begins with an intimal tear in the proximal descending thoracic aorta. This tear initiates separation of the vessel’s medial layer, resulting in a new channel—the false lumen—that progresses down the length of the descending thoracic aorta and often extends into the abdominal aorta.
The acute period of aortic dissection is defined as the first 14 days after the inciting intimal tear and separation of the aortic wall, which is generally heralded by the sudden onset of severe pain. Most patients with acute type B dissection stabilize upon receiving aggressive medical treatment consisting primarily of anti-impulse therapy and serial imaging. However, approximately 39 percent of patients with acute type B dissection present with or develop life-threatening sequelae and are categorized as having 'complicated dissection.'
The most feared complication is aortic rupture, which is caused by dilatation and disruption of the fragile, torn outer wall of the false lumen. Another major complication is malperfusion of organs—particularly the abdominal viscera and spinal cord—or the lower extremities. The true lumen and false lumen are separated by the dissecting membrane, a fragile boundary that oscillates within the aorta and can interfere with blood flow within the aorta and any of the branch arteries in either a static or a dynamic fashion. Impaired branch-vessel blood flow leads to organ ischemia—manifesting as paraplegia, bowel infarction, liver failure, or acute renal failure—or limb-threatening limb ischemia.