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Ann Thorac Surg 2000;70:1004
© 2000 The Society of Thoracic Surgeons
a University Hospital of Geneva, Clinic for Cardiovascular Surgery, 1211 Geneva 14, Switzerland
e-mail: afksendyios.kalangos{at}hcuge.ch
To the Editor
I read with interest the paper by Uemura and colleagues and the invited commentary of Dr Kon [1]. Their case report clearly shows that using an aortic root bioprosthesis, which is favored for its hemodynamic advantages, can result in a hemodynamic disaster if some rules are not respected. I believe that the problems encountered in aortic valve replacement with stentless bioprostheses are mostly due to the tendency to apply the classical implantation techniques of stented bioprostheses or mechanical prostheses to that of a stentless bioprosthesis. Unfortunately, we sometimes completely neglect the fact that in aortic root bioprostheses such as the Freestyle valve (Medtronic, Inc, Minneapolis, MN) proper geometry is determined by the different elements of the aortic valve, which are the leaflets, commissures, sinuses of Valsalva with variable positions of the left and right coronary ostia, and the sinotubular and ventriculo-aortic junctions. Stented bioprostheses or mechanical prostheses strictly replace diseased aortic leaflets. Use of supraannular prostheses when coronary ostia are located close to the annulus or improper placement of a stent opposite a coronary ostium are avoided. The ability to implant an aortic root bioprosthesis depends on accommodating these various corresponding elements to each other. The angle between the left and right coronary ostia is key with respect to aortic valve replacement with an aortic root bioprosthesis, regardless of whether subcoronary, mini-inclusion, or root replacement is used. The great variability in the angle between the left and right coronary ostia and the disposition of both coronary ostia with respect to the commissures inclined us to modify the subcoronary implantation technique. One modification takes into account the spatial orientation of the patient’s coronary ostia rather than that of his commissures in an attempt to better match the porcine coronary ostia to the native ones.
We therefore conducted a clinical study in 50 consecutive patients who underwent aortic valve replacement using this technique. In these patients, the angle between both coronary ostia and the location of both coronary ostia with respect to the commissures were systematically measured and analyzed [2]. The angle between both ligated coronary arteries on the Freestyle bioprosthesis is 150° ± 5°. In only 16 of 50 patients, the angle between both coronary ostia corresponded to that of the Freestyle valve varying between 145° and 155°. Bicuspid aortic valve patients had significantly larger angles (162° ± 9°) than tricuspid aortic valve patients (143° ± 10°). In 16 of 50 patients, one or both coronary ostia were closer to a given commissure, rather than in the usual central position. These conditions allowed us to conclude that proper adjustment of the patient’s coronary ostia to those of the prosthesis should be achieved at the inflow insertion level. Further attempts to adjust them at the outflow insertion level can result in distortion of the commissures and thereby create leaflet immobilization, as in the reported case. This will reduce the inflow orifice area of the prosthesis and create turbulence, which can lead to early valve failure [3].
Moreover, we advocate that angles less than 130° and greater than 170°, constitute a major drawback for the subcoronary implantation technique with any kind of aortic root bioprosthesis. This creates crimping of the sewing skirt or of the native aortic annulus, or distortion of the prosthesis’ commissures or of coronary ostia when attempting to match the patient’s coronary ostia to those of the prosthesis at the inflow or outflow insertion level.
References
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