Freestanding Root Technique for Implantation of the Stentless Medtronic Freestyle Valve

The operation is typically performed through a full median sternotomy, although an upper partial sternotomy may also be used. After opening the pericardium and exposing the heart and great vessels, the ascending aorta and main pulmonary artery are separated with sharp dissection. Standard cardiopulmonary bypass is instituted.

The ascending aorta has been replaced with a vascular graft, a procedure frequently required for concomitant aneurysmal or severe atherosclerotic disease. The ascending aorta is completely transected just superior to the sinotubular junction. Myocardial protection is usually maintained with retrograde cardioplegia. At this point, note should be made of the orientation of the right and left coronary arteries as well as their heights above the aortic annulus. This will facilitate orientation of the prosthesis.

The stentless porcine bioroot has coronary anatomy that differs from the typical human root configuration. In the porcine root, the coronary ostia are 90 to 110° apart (white arrows) compared with the usual human relationship of 120° to 140° apart. Additionally, the right coronary ostium is situated more distal to the aortic annulus, above a band of right ventricular muscle (black arrow).

Because of these differences, the stentless bioprosthesis is usually rotated 120° to facilitate coronary alignment. In this procedure, an opening is made in the noncoronary sinus of the prosthesis, which will serve as the site of reattachment of the human left coronary button. The porcine left coronary sinus then will become the site of reattachment of the human right coronary button, and the porcine right coronary artery is oversewn. This orientation usually suffices when the human coronaries are 120° to 160° apart and can be sufficiently modified in the situation of a bicuspid valve with coronaries 180° apart by placing the opening in the porcine noncoronary sinus slightly more to the right. However, if the ostia are located 90° to 110° apart, the native orientation may be maintained if the human right coronary is located relatively distal to the annulus or can be mobilized sufficiently to the meet the “high” porcine right coronary artery.

The right and left coronary ostia are mobilized on buttons of aortic tissue. Traction sutures are placed to facilitate orientation and mobilization. Excess aortic root tissue including the noncoronary sinus is removed.

Removal of the sinus tissue facilitates exposure and resection of the aortic cusps and debridement of the aortic annulus. Traction sutures are placed at the top of each commissure to facilitate exposure. When performing total aortic root replacement, liberal debridement of calcium and diseased annular tissue may be safely performed because the prosthesis can be sewn to the left ventricular outflow tract in most locations and not to the aortic annulus itself. However, care must be taken with debridement and suturing in the area of the membranous septum below the commissure of the right and noncoronary cusps because of the location of the His bundle.

The coronary buttons and base of the aortic root are then extensively dissected free from the pulmonary artery, right ventricle, and left atrial tissues. This will ease valve suture placement and coronary reattachment.

The valve is then sized. After identifying the largest sizer that will pass into the left ventricular cavity, the valve chosen should be one size larger so that the internal orifice of the prosthesis will match the left ventricular outflow tract diameter. Thus, the stentless bioprosthesis is “up-sized” by one size over the measured annulus. This will allow the entire orifice of the prosthesis to be exposed to the left ventricular outflow tract.

Valve sutures of 3-0 braided polyester are then placed in simple fashion through the left ventricular outflow tract and around a narrow (approximately 3 mm) felt strip, which helps with hemostasis. The typical number of valve sutures used usually varies between 28 and 32. Use of suture guides simplifies placement and organization.

The ventricular side of each valve suture is passed through the sewing ring of the bioprosthesis, which is then seated within the felt ring. The ring should remain at or above the level of the annulus to minimize chance of exposure to the bloodstream. The sutures are tied and cut.

The left coronary button is then sewn to the bioprosthesis using running 5-0 monofilament suture. An opening is then made in the porcine left coronary sinus for reattachment of the right coronary button, which is also sewn in running fashion taking care to maintain proper orientation. Excess tissue from the distal end of the bioprosthesis is removed, with more taken from the lesser curve of the ascending aorta to help reproduce its natural contour.

The native ascending aorta or vascular graft is then trimmed to appropriate bevel, and an end-to-end anastomosis is constructed using running monofilament suture.

The aortic cross-clamp is removed with an aortic vent in place to facilitate de-airing.