Aortic valve graft implantation in rats: a new functional model

Allograft heart valves used in cardiac surgery often fail at an unacceptable rate. Immune mechanisms contribute to this failure, but adequate and functional small-animal valve models to characterize this phenomenon are lacking. The objective of this study was to create native aortic valve insufficiency in recipient rats to provide for a functional abdominal aortic valve graft implant.

Lewis recipient rats underwent single-leaflet injury of their native aortic valve through a right carotid catheter injury. Animals were allowed to recover for 28 days, at which time a Lewis aortic valve graft was implanted infrarenally. Echocardiography with color flow Doppler scanning was performed before aortic injury, 1 week after aortic injury, and after abdominal implantation of a valve graft in animals with native aortic insufficiency.

After aortic valve injury, all animals had moderate-to-severe aortic insufficiency with a significant increase in diastolic and systolic left ventricular dimensions. Color flow Doppler scanning revealed diastolic aortic flow reversal from the aortic valve extending to the infrarenal abdominal aorta. Aortic valve grafts were then implanted infrarenally in animals with created aortic valve insufficiency and resulted in 100% patency and preservation of leaflets at 4 weeks after implantation. Leaflet motion of the abdominal graft was visualized by means of M-mode echocardiography.

Compensated native aortic insufficiency results in aortic diastolic flow reversal distal to the infrarenal aorta, thus allowing normal motion of the infrarenal allograft leaflets. This functional model will provide an opportunity to investigate the role of immunologic valve injury in the failure of valve allografts.