A stent-graft prosthesis includes a generally tubular outer PTFE layer, a generally tubular helical stent, a generally tubular inner PTFE layer, and a suture or fabric support strip. The outer PTFE layer defines an outer layer lumen. The helical stent is disposed within the outer layer lumen and defines a stent lumen. The inner PTFE layer is disposed within the stent lumen and defines an inner layer lumen. The suture includes a suture first end coupled to a stent first end and a suture second end coupled to a stent second end, with the suture disposed between the outer PTFE layer and the inner PTFE layer. Alternatively, the fabric support strip is disposed between the outer and inner PTFE layers. The suture or fabric support strip may include a plurality of sutures or fabric support strips and may be spaced equally around a circumference of the inner PTFE layer.