Volume 11, Issue 3 , Pages 166-172, Autumn 2006
Freestanding Root Technique for Implantation of the Stentless Medtronic Freestyle Valve
Article Outline
Over the past decade, aortic valve replacement with stentless porcine bioprostheses has become an accepted technique for routine treatment of aortic valve and root diseases. Compared with traditional stented biological and mechanical prostheses, advantages of stentless valves include better hemodynamics, improved regression of left ventricular mass, less risk of patient–prosthesis mismatch in the small aortic root, and possibly improved long-term patient survival. Most of these advantages appear to be maximized with implantation using a total root replacement technique, which also is associated with less risk of late valve failure.
Operative Technique
Figure 1.
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.
Figure 2.
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.
Figure 3.
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).
Figure 4.
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.
Figure 5.
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.
Figure 6.
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.
Figure 7.
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.
Figure 8.
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.
Figure 9.
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.
Figure 10.
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.
Figure 11.
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.
Figure 12.
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.
Figure 13.
The aortic cross-clamp is removed with an aortic vent in place to facilitate de-airing.
Conclusions
The expected postoperative course of patients following stentless aortic root replacement is similar to those undergoing other types of aortic valve operations. With attention to detail, excess bleeding risks should be minimal despite more suture lines exposed to the pericardial space. On echocardiography, flow patterns are purely laminar in the ascending aorta, and mean pressure gradients are typically less than 10 mm Hg for all sizes except the 19-mm prosthesis, which averages 12 mm Hg.
Since 1992, we have performed over 700 aortic root replacements with stentless porcine valves. A recent review of this data revealed an operative mortality of 3.9% in a series in which over half also underwent coronary artery bypass graft and/or multivalve procedures. Freedom from structural valve degeneration has been 97% at 10 years follow-up. This exceptional durability may be explained by the creation of natural, laminar flow patterns, which are universally observed with the total root technique.
PII: S1522-2942(06)00059-6
doi:10.1053/j.optechstcvs.2006.06.004
© 2006 Elsevier Inc. All rights reserved.
Volume 11, Issue 3 , Pages 166-172, Autumn 2006
