Transverse histological section of the aortic wall (A and D) with details (B and E). eNOS: endothelial nitric oxide; TA: tricuspid valve without dilatation; TAD: tricuspid valve with dilatation; BA: bicuspid valve without dilatation; BAD: bicuspid valve with dilatation. *P < 0.05, **P < 0.01, scale bar (A and D 50 µm; B and E, 10 µm).