Thoracic aortic aneurysms rarely give symptoms, till they grow big. Many are incidentally discovered as a result of medical imaging for other conditions, by echocardiogram, CT scans, MRI's, or even plain X-rays of the chest.
If you are over 65 or over 55 with a relevant family history you should discuss with your doctor and have an echocardiogram. It is safe, fast and painless.