The purpose of this research study is to find out if AMDS is safe and effective in the treatment of acute dissection (sudden tear). For patients whose aortic anatomy is suitable for treatment with AMDS, the use of this device may promote healing of the aortic walls and possibly reduce the need for additional aortic surgeries. If conventional surgery, in combination with AMDS, is effective, it is believed that this could lead to improved aortic healing; an improvement in healing could reduce the risk of hospitalization and reoperation in the chest compared to conventional surgery alone.

Assess the safety and effectiveness of the ASG device in
the treatment of lesions involving the ascending aorta and
aortic arch.

To undertake the first prospective randomized controlled trial that compares early aortic surgery to aneurysm surveillance.

The purpose of the study is to compare different treatment plans for patients with abnormal aortas. Patients who have an abnormal aorta measuring at least 5.5cm will have surgery to replace the aorta. We do not know, however, whether patients with abnormal aortas that are not quite 5.5cm should have surgery or should be monitored to see if their aorta continues to grow. Therefore, through this registry and interventional study, the hope is to collect more data on which treatment is better for the patient. The interventional group will undergo surgery to repair their abnormal aorta, and the surveillance group will be closely monitored and medically managed per standard of care. Both groups will have data collected from their care and at the end of the study this data will be analyzed. The goal of this study is to determine if performing surgery earlier helps to prevent abnormal aortas below 5.5cm from tearing or bursting.