Treatment in Thoracic Aortic Aneurysm: Surgery vs Surveillance

Inclusion Criteria: 1. Patients between the age of 18 and 79 inclusive. 2. Ascending aortic aneurysm between 5.0cm and 5.4cm in maximal diameter as measured by CT with contrast. 3. 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. Exclusion Criteria: 1. Patients who refused to be randomized 2. Patients with symptomatic attributable to ascending aortic aneurysms 3. Patients who are unable to provide informed consents 4. Patients who are unable to attend for regular follow-up/ remain compliant with protocol 5. Previous cardiac surgery 6. Patients whose primary indication for cardiac surgery is non-AsAA related 7. Known AsAA expansion rate exceeding 0.5 cm/year during the past 5 years 8. Arch aneurysms with no ascending aorta involvement (no aneurysmal segments before the innominate artery) 9. Ascending aortic and arch aneurysm with descending thoracic aorta involvement 10. Patients with known connective tissue disease (E.g. Marfan syndrome, Loey-Dietz syndrome, Turner syndrome etc) syndrome, etc.) 11. Patients with possible genetic aortopathies (eg known family history of aortic aneurysms/premature aortic dissections/ruptures) 12. Patients with inflammatory arteritis (e.g. takayasu's arteritis, syphilitic arteritis, etc.) 13. Female patients who are pregnant or planning to become pregnant 14. Patients who have a history or presence of a medical condition or disease or psychiatric condition that in the investigator's assessment would render the subject ineligible for study participation. 15. Patients who, in the opinion of the investigator, are deemed unfit for surgery for reasons that may include: * Severe pulmonary disease * Cr = 250umol/L * Child Pugh Class B or C * NYHA III or IV * MI within the last 6 months * Major surgical procedure or angioplasty within 3 months * Expected survival less than 5 years because of other disease (e.g. invasive cancer)