Pathogenesis of anastomotic aneurysms.

Forty-two anastomotic aneurysms were encountered in 33 patients over a 13-year period. Thirty-six occurred after the use of prostheses, and six occurred after the the use of vein grafts. In the prosthetic group, 28 aneurysmal defects were repaired, and the cause was found in 25 cases. In 23 of these cases the defect was caused by the sutures that had pulled out of the arterial wall; suture failure was recorded in only two cases. There were no defects in any of the prostheses. The suture material was braided Dacron (Tevdek) in 25 anastomotic aneurysms, but it was not recorded in three cases. In the vein graft-related group the aneurysms occurred in the "juxta anastomotic position," with the suture lines intact. They were thus true aneurysms of the vein wall. This study shows that the predominant cause of an anastomotic aneurysm in weakness of the arterial wall and not the mechanical failure of the suture material (braided Dacron) or prosthesis. It would seem, however, that the prosthesis, by virtue of its undesirable physical characteristics-a compliant mismatch with the host artery and some dilatation with the passage of time-results in abnormal shear stress at the anastomosis, leading to disruption of the arterial wall and eventually to false aneurysm formation.