Hope this helps from Moonboy's post - From Google translation:

Given your history and the current size of your abdominal aortic aneurysm (AAA), the decision between surgery and ongoing monitoring depends on several factors, including your overall health, the rate of growth of the aneurysm, and potential surgical risks.

In general, an AAA of 5.1 cm is within the range where surgical intervention might be considered, especially if there is evidence of rapid growth or symptoms. However, given your age and cardiac history, it is essential to carefully consider the risks versus the benefits of surgery.

If the aneurysm has grown slowly over the past four years and you remain asymptomatic, ongoing monitoring with regular imaging might be appropriate. However, if there is concern about the stability of the aneurysm, or if you are experiencing symptoms such as abdominal or back pain, surgical intervention might be recommended.

I suggest discussing your case in detail with your cardiovascular surgeon and a vascular surgery specialist to determine the best course of action based on your specific situation.