 The purpose of this early feasibility study is to investigate the outcome of selected patients with ascending aortic pathologies including type A aortic dissection, retrograde type A aortic dissection, who are suitable for endovascular repair with the Valiant PS-IDE Stent Graft device. The investigators propose to study patients with Dissections affecting the aorta between the Sinus of Valsalva and the innominate artery orifice with no involvement of aortic valve. In these patients, the ascending aorta will be repaired using the stent graft. For patients with type A aortic dissection, the investigators expect to reroute the blood to the true lumen by covering the proximal tear. In patients with retrograde type A aortic dissection, there might or might not be additional tears in the ascending aorta. If they are tears in ascending aorta, these dissections behave similarly like a type A aortic dissection, in which all the tears in the ascending aorta need to be covered. If the proximal tear is only in the descending thoracic aorta, these patients will require coverage in the ascending aorta with the stent graft along with coverage of proximal tear in the descending thoracic aorta using Valiant stent graft. 