Homocysteinemia is a risk factor for aortic dissection

There are significant associations between moderate increases in serum homocysteine and three cardiovascular diseases: ischemic heart disease, deep vein thrombosis and pulmonary embolism, and stroke. An association between the presence of abdominal aortic aneurysm and elevated homocysteine plasma levels has been indicated. Although chronic systemic hypertension is the most common factor predisposing the aorta to dissection, homocysteinemia has never been known as the risk for aortic dissection except for that with Marfan syndrome. Homocysteinemia is suggested to be the risk for aortic dissection in Marfan syndrome and spontaneous cervical artery dissection. Reduced fibrillin-1 deposition into the extracellular matrix is found not only in Marfan syndrome but also in isolated ascending aortic aneurysm and dissection. The reduced matrix deposition produces a mild form of weakness of elastic tissue, which predisposes to ascending aortic aneurysm and dissection in patients who do not have the Marfan syndrome. The defect in fibrillin-1 leads to: (1) formation of elastin that is abnormally aggregated and more easily degraded by matrix metalloproteinases than is normal elastin; (2) upregulation of the synthesis of matrix metalloproteinases; (3) progressive destruction of connective tissue by these enzymes; (4) development of thoracic aortic aneurysms. Homocysteine causes premature breakdown in the arterial elastic fibers by activation of the elastolytic activities. Irreversible homocysteinylation of long-lived proteins should lead to cumulative damage and progressive clinical manifestations, and fibrillin-1 is seen as the paradigm of extracellular connective tissue proteins that are specially susceptible to homocysteine (and presumably homocysteine thiolactone) attack. The authors hereupon propose a novel hypothesis that homocysteine plays an important role in development of aortic dissection and that homocysteinemia is one of the risk factors for aortic dissection.