Aortic aneursym

Hi..diagnosed 3 weeks ago with an ascending thoracic aneurysm measuring 4.7cm. Twenty two years ago, at age 37, I had my aortic valve replaced with a St. Jude mechanical valve. I have done well except with the hassle of having to be on coumadin and the constant protimes that are required. Has anyone been diagnosed and been through surgery for this type of aneurysm?  I would appreciate any info as I am very nervous and scared about dealing with this. My cardiologist has prescribed ct scans every six months to check the growth. Surgery is required at 5.0-5.5 cm. At this time the valve will be replaced again. Thanks.