All patients referred electively to a participating investigator for the evaluation of their ascending aortic aneurysm will be screened for study eligibility. Patients between the age of 18 and 79 with an asymptomatic ascending aortic aneurysm between 5.0 cm and 5.4 cm in maximal diameter are entered into the randomization study. Patients with ascending aortic aneurysm with a diameter of 4.5 cm - 4.9 cm will be observed with serial CT, and will be considered for enrollment into the trial once the aneurysm reaches 5.0 cm.

When the patient is first assessed in clinic, a pre-randomization evaluation will be completed. Baseline information of the patient, including demographics, past medical history, family history, medications, smoking habits, and the characteristics of the aneurysm, is collected. Measurements including weight, height, heart rate, blood pressure in both arms, is recorded. Basic blood work, including hemoglobin, white cell count, platelets, electrolytes, creatinine, random blood sugar, HbA1c, and cholesterol profile is taken for analysis. An electrocardiograph, chest X-ray, and a CT scan from the surgeon's institution is also obtained. SF-36, the quality of life questionnaire, will be completed by the patient. Those patients that are suitable for the trial based on inclusion and exclusion criteria will then be randomized en-site through a computer-generated randomization program.

For the patients randomized to elective surgery group, the surgery is scheduled within 10-12 weeks of randomization. In the interim, the patient will be placed on maximal medical therapy for their aneurysm, including beta-blocker, statin, and blood pressure control, and the doses of these medication will be individualized based on each patient's own physiological response. The types of surgery (ascending aortic replacement, Bentall procedure, valve-sparing root replacement, etc.) will be at the discretion of the surgeon. The details of the surgery and the patient's course of postoperative hospital stay is recorded. The patient will be managed postoperatively according to routine hospital care. After discharge, patients will be seen at 1 months for their routine postoperative follow up, then annually counting from their index clinic visit before the surgery. At the first postoperative clinic visit, weight, height, heart rate, blood pressure in both arms, is recorded. Basic blood work, including hemoglobin, white cell count, platelets, electrolytes, creatinine is taken for analysis. An electrocardiograph and chest X-ray will be obtained. All subsequent clinic visits can be done in person or by phone conducted by a study coordinator. A CT scan will be obtained at all subsequent clinic visits. Mortality status and occurrence of acute aortic event or stroke in the previous year will be assessed at every annual clinic visit. Quality of life assessment by SF-36 questionnaire will be completed by the patient in person or by phone at 1 year and 2 years follow-up. Annual follow-up will continue until either the patient dies or the trial ends. Patients who are randomized to the surveillance group will be placed on maximal medical therapy for their aneurysm, including beta-blocker, statin, and blood pressure control. The doses of these medication will be individualized based on each patient's own physiological response. The patients will undergo a CT scan of the chest at the first clinic visit then annually for the duration of the study. All CTs will be uploaded to a core CT imaging lab where the image will be reviewed by a Radiologist. If the aneurysm grows beyond 5.5 cm or the patient develop symptoms, the surgeon will consider the patient for surgery. At all clinic visits, in addition to CT, weight, height, heart rate, blood pressure in both arms, an electrocardiograph, and a chest X-ray will be obtained. The surveillance visits continue until either the patient dies, the trial ends, or surgery is considered. If the patient is no longer considered a suitable candidate for surgery or refuse surgery, follow-up will continue, and the patient will no longer be a part of the trial and will only be registered in the side arm.