Placement of aortic valve bioprostheses in sheep via a left thoracotomy. Implantation of stentless porcine heterografts.

ABSTRACT

Juvenile sheep provide a good model for assessing the efficacy of antimineralization techniques because of their rapid calcification of bioprosthetic valves. Stentless bioprosthetic valves are under evaluation for possible improved durability as aortic valve replacements. A left thoracotomy approach for aortic valve implantation, which facilitates intraoperative and postoperative hemodynamic data collection, has been developed and refined in 13 sheep. A critical feature of this technique is a partial rib resection that creates a soft tissue acoustic window to improve postoperative transthoracic echocardiographic examination. This allows both quantification of valvular gradients and qualitative assessment of valve leaflet motion and calcification. Excellent correlation was observed between the intraoperative invasive valvular gradients and the postoperative echocardiographic gradients available in four animals (mean gradient r = 0.96, p = 0.003; peak gradient r = 0.98, p = 0.0004). This is an excellent technique for serial postoperative noninvasive evaluation of valve prostheses implanted in the aortic position.