asymptomatic disease. People with symptoms suggestive of thoracic aortic dissection should be routinely evaluated "to establish a pretest risk of disease that can then be used to guide diagnostic decisions." People diagnosed with Marfan syndrome should immediately have an echocardiogram to measure the aorta and followed up six months later to check for aortic enlargement. Treatment The size cut off for aortic aneurysm is crucial to its treatment. A thoracic aorta greater than 4.5 cm is generally defined as aneurysmal, while a size greater than 6 cm is the distinction for treatment, which can be either endovascular or surgical, with the former reserved for pathology at the descending aorta. Indication for surgery may depend upon the size of the aneurysm. Aneurysms in the ascending aorta may require surgery at a smaller size than aneurysms in the descending aorta. Treatment may be via open or via endovascular means. Epidemiology Each year in the United States, some 45,000 people die from diseases of the aorta and its branches. Acute aortic dissection, a life-threatening event due to a tear in the aortic wall, affects 5 to 10 patients per million population each year, most often men between the ages of 50 and 70; of those that occur in women younger than 40, nearly half arise during pregnancy. The majority of these deaths occur as a result of complications of thoracic aneurysmal disease References External links Diseases of the aorta Vascular diseases