Detection of Hypoxia in Human Thoracic Aorta Using Pimonidazole Hydrochloride

The proposed study is designed to identify the level of tissue hypoxia in patients presenting with ascending aortic aneurysm. Ascending aortic aneurysms affect approximately 15,000 people in the United States each year, and represent a serious clinical problem because there is a known, but unspecified risk of aortic rupture or dissection. Despite progress made in the surgical management of ascending aortic aneurysms, the molecular and cellular mechanisms involved remain elusive. However, indirect evidence of tissue hypoxia have recently been described in the literature. This pilot study will use pimonidazole-HCl, a compound that is retained by hypoxic cells and that has been used for detection of tissue hypoxia in human since the early 2000s. This pilot study will involve twenty patients who are candidates for aortic replacement due to aneurysm and twenty non-aneurysmal patients undergoing coronary artery bypass graft (controls). Patients will be administered pimonidazole-HCl orally in a single dose (0.5g/m2) 24 hours prior to scheduled surgical time. During surgery, the resected aneurysmal aortic specimens (for patients undergoing aortic replacement) or aortic punch (for patients undergoing coronary artery bypass graft) will be harvested. Tissue hypoxia will be qualitatively and quantitatively assessed in the investigator's research laboratory. Based on previous toxicological animal studies and previous use in human studies, the anticipated risk of severe or serious side effect will be relatively minimal.