1. The congenitally bicuspid aortic valve: how does it function
The congenitally bicuspid aortic valve: how does it function? Why does it fail? 
Francis Robicsek, MD, PhD, Mano J Thubrikar, PhD, Joseph W Cook, MD, Brett Fowler, RT 
The Annals of Thoracic Surgery 
Volume 77, Issue 1, Pages (January 2004)
DOI: /S (03)

2. Fig 1
Schematic drawings of the geometry of the three bicuspid aortic valves studied. Numbers in parentheses represent either the length of the free edge or the height of each leaflet in millimeters. Numbers without parentheses represent abnormalities in the respective valves. Valve A: (1) free edge of the leaflet is attached to the sinotubular ridge away from the commissure; (2) hole in the leaflet in the coaptation surface; (3) a raphe in the leaflet; (4) the line of attachment is almost flat; (5) the line of attachment is skewed. Valve B: (1) very tiny third leaflet; (2) very thick cordal structure; (3) considerably increased leaflet height; (4) very wide commissure. Valve C: (1) very thick raphe; (2) very long free edge; (3) flat attachment line; (4) very thick leaflet free edge; (5) thickened free edge region.
The Annals of Thoracic Surgery  , DOI: ( /S (03) )

3. Fig 2
Valve A: views in closed (a) and (b) open positions in a pulse duplicator. In the open position, the attachment of the free edge to the sinotubular ridge, away from the commissure, produces the appearance of two triangular “curtains.” A prominent raphe and the arrangement of collagen cords also may be noted. In the open valve, the leaflet separation is much less than the diameter of the aorta. (c) Silicone mold prepared at a pressure of 80 mm Hg shows the geometry of the sinuses, presence of raphe, orientation of collagen cords, configuration of the line of closure, curve in the leaflet surface, the contour of the line of leaflet attachment, and the protrusive nature of the leaflet surface. (d–i) Photographs taken at a high speed (500 fps) during the valve opening. The change in topography of the leaflet surface can be appreciated. (a) The leaflet with raphe in the closed valve. (d–i) Its surface is curved upward, indicating that a circumferentially oriented fold (wave) is traveling from the base to the free edge.
The Annals of Thoracic Surgery  , DOI: ( /S (03) )

4. Fig 3
Valve A: short-axis intravascular ultrasound images show cross-section of the aortic root. (a) Curved line of closure is evident. (b and c) Smaller leaflet separation is restricted at the free edge compared with that towards the base. (c) The raphe causes the base at 7 to 8 o'clock to appear thick. (d–f) Long-axis views show the leaflets during opening. Folds and kinks are clearly visible. (e and f) The open channel is dome-shaped.
The Annals of Thoracic Surgery  , DOI: ( /S (03) )

5. Fig 4
Valve B: (a and b) aortic views in the pulse duplicator reveal a third rudimentary leaflet (located at 5 o'clock). The closure line is straight in a. (c) Silicone mold prepared at a pressure of 80 mm Hg. (c) Ventricular aspect of the mold of valve. Note the elliptical shape of the aortic root and the extensive folding and creasing of the leaflet belly present even under diastolic pressure. Note the bulbous protrusion in the leaflet surface. (d-i) Photographs from the aortic aspect taken at a high speed (500 fps) during the valve opening. (e-g) During opening, the leaflet surface is curved upward even before the valve opens. Circumferentially oriented fold (wave) travels through the leaflet surface from the base towards the free edge. A bubble-like protrusion is visible in the leaflet surface at 11 o'clock, corresponding to the similar but inverted protrusion in the mold. (i) Fully open valve.
The Annals of Thoracic Surgery  , DOI: ( /S (03) )

6. Fig 5
Valve B: (a) short-axis intravascular ultrasound images show a straight line of closure and a wide commissure. (b) Opening is restricted at the free edge and (c) increases towards the base. (a) The aortic root is elliptical. (d) Long-axis views show coaptation surface as well as (e and f) folds and kinks in the leaflet as the valve opens. (f) The open channel is dome-shaped.
The Annals of Thoracic Surgery  , DOI: ( /S (03) )

7. Fig 6
Valve C: (a and b) aortic views in the pulse duplicator. (a) The contour of the closure line and the overall appearance is more like that seen in the trileaflet valve. (a) In the conjoined leaflet, enhanced thickness of the free edge and of the raphe can be noted. Also, a central hole is visible. (b) In the open valve, the raphe near the base of the leaflet appears to produce a partitioning membrane. The orifice of the valve is highly elliptical. (b) One leaflet moves well whereas the other moves only a little. (c) Silicone mold prepared at a pressure of 80 mm Hg. The valve has a central hole and silicone leaking through the hole may be noted. The raphe is prominent, and makes one of the sinuses look like two separate ones. The mold appears as if it is of a trileaflet valve with regurgitation. (d–i) Photographs from the aortic aspect taken at a high speed (500 fps) during the valve opening. Closed valve showing a hole at the center. Also, leaflet fusion, thick raphe, and thickened free edge of one leaflet is obvious. There is limited leaflet folding because one leaflet is very stiff and the other somewhat thicker and stiffer than those of valves A and B.
The Annals of Thoracic Surgery  , DOI: ( /S (03) )

8. Fig 7
Valve C: (a) short-axis intravascular ultrasound images reveal two unequal sinuses. (b) Leaflet separation is restricted near the free edge and (c) increases towards the base. (b) Increased thickness in the free edge of the leaflet at 4 o'clock. (d) Long axis views show the valve shut. (e and f) With the valve open, only one leaflet could be seen.
The Annals of Thoracic Surgery  , DOI: ( /S (03) )

9. Fig 8
(A) Digital modeling of a cusp of a bicuspid valve. (B) The stress distribution on the leaflets of the eccentric bicuspid valve. Because of asymmetrical geometry of the open valve, the blood flow path is forced toward the left by the leaflets. It resulted in an uneven stress distribution in the two leaflets. A high stress is present in one leaflet only. This is because the leaflet on the right needs to provide the force to alter the flow path. Such a high stress is seldom present in a normal trileaflet valve.
The Annals of Thoracic Surgery  , DOI: ( /S (03) )

10. Fig 9
(A) Flow and (B) stress patterns of an eccentric bicuspid valve. The valve opening is tilted to the left. The commissure attachment is 5 mm off from the center of the valve. Valve dimensions: annulus, 20 mm; sinotubular junction, 20 mm; leaflet height, 16 mm; leaflet free-edge length, 26 mm. The area of the orfice is approximately 50% of that in the nonstenotic valve. For the stenotic valve, the left ventricle needs to contract harder and, as a result, the blood may carry a higher momentum (energy, velocity) into the aorta. Consequently, the aortic arch needs to provide a larger force to turn the flow path into the descending aorta. This causes a higher and uneven stress distribution in the ascending aorta.
The Annals of Thoracic Surgery  , DOI: ( /S (03) )

11. Fig 10
Digital modeling of bicuspid valve 1 in a closed position. Note the extensive wrinkling and folding.
The Annals of Thoracic Surgery  , DOI: ( /S (03) )

12. Fig 11
Folding and unfolding of the free edge of the leaflets is necessary for opening and closure of the normal tri leaflet (left) as well as for the bicuspid aortic valve (right). Note that whereas the former fully unfurls at both full opening and full closure, the maximum folding of the bicuspid valve occurs at full closure. The degree of folding is illustrated below.
The Annals of Thoracic Surgery  , DOI: ( /S (03) )