Bicuspidalization of the Native Tricuspid Aortic Valve: A Porcine in Vivo Model of Bicuspid Aortopathy

Objective: To examine early histologic changes in the aorta exposed to bicuspid flow. Material and Methods: A porcine bicuspid aortopathy model was developed by suturing aortic cusps. Of nine pigs, eight underwent sham surgery (n=3) or bicuspidalization (n=5); one was used as an intact control. Wall shear stress (WSS) was assessed by computational fluid dynamics (CFD). Animals were exposed to normal or bicuspid flow for 48 h and were then euthanized for histologic examinations. Results: No animal died intraoperatively. One animal subjected to bicuspidalization died of respiratory failure during postoperative imaging studies. Echocardiography showed the aortic valve area decreased from 2.52 +/- 1.15 to 1.21 +/- 0.48 cm(2) after bicuspidalization, CFD revealed increased maximum WSS (10.0 +/- 5.2 vs. 54.0 +/- 25.7Pa; P=0.036) and percentage area of increased WSS (>5 Pa) in the ascending aorta (30.3%+/- 24.1% vs. 81.3%+/- 13.4%; P=0.015) after bicuspidalization. Hematoxylin-eosin staining and transmission electron microscopy showed subintimal edema and detached or degenerated endothelial cells following both sham surgery and bicuspidalization, regardless of WSS distribution. Conclusion: A bicuspid aortic valve appears to increase aortic WSS. The endothelial damage observed might have been related to non-pulsatile flow (cardiopulmonary bypass). Chronic experiments are needed to clarify the relationship between hemodynamic stress and development of bicuspid aortopathy.