HEMODYNAMICS AND ANEURYSM DEVELOPMENT IN VASCULAR ALLOGRAFTS

Purpose: Mechanical and immunologic factors may play a role in the dev elopment of native arterial and biologic graft aneurysms. We developed an experimental rat aortic allograft aneurysm model in which segments of infrarenal aorta were transplanted between hypertensive and normot ensive rats to study these factors in this model. Methods: Aortic allo grafts and autografts were inserted into spontaneously hypertensive (S HR) and normotensive Wistar. Kyoto (WKY) rats. Effects of immunologic and antihypertensive therapy were evaluated. Graft diameters were foll owed up with magnetic resonance imaging and at harvest. Direct-pressur e measurements were taken and dp/dt(max) (force of ventricular contrac tions) was calculated before harvest. Results: Autografts remained iso diametric and maintained their histologic architecture. Aneurysmal dil ation of transplanted segments occurred in SHR host allografts but not in WKY host allografts. Histologic examination of ah allograft specim ens noted a rejection reaction characterized by inflammatory cell infi ltration and medial smooth muscle cell loss. Antigenic enhancement acc elerated aneurysm development in SHR hosts but had no significant effe ct on WKY hosts. Rates of allograft enlargement and final allograft di ameters were similar in antihypertensive treated and untreated SHR hos ts. The dp/dt(max) in untreated SHR hosts was greatest and differed si gnificantly from that in the WKY rats but only marginally from that in treated SHR hosts. Conclusions: Immunologic rejection but not abnorma l hemodynamics is necessary for development of allograft aneurysm in t his model.