A study of valve incompetence that developed in an experimental model of venous hypertension.

Surgical treatment of venous valve incompetence should be aimed at restoring the underlying valve defect. For a better definition of the structural anatomical defects in acquired valve incompetence, an experimental study was performed with 40 rats. Venous valves were subjected to hemodynamic stress by creating femoral arteriovenous fistulas. The resulting valve incompetence was studied by using descending phlebography and a casting technique, which allowed for an accurate description of leaking valves when the scanning electron microscope was employed. A three-dimensional insight of the morphology of incompetent venous valves was obtained. A description of short- and long-term (two to four months) changes in valve architecture was also obtained; initially, there was retrograde passage of fluid through a separation of the cusps' free border. The cusps' bulgings were still clearly defined after two months, and, at this stage, commissures had started to widen. After a four-month period, commissures were lost and no recognizable valve sinus was present.