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Ann Thorac Surg 2002;73:1029-1030
© 2002 The Society of Thoracic Surgeons

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Editorial

Aortic valve sparing operations

^a Toronto General Hospital, Toronto, Ontario, Canada

* Address reprint requests to Dr David, Toronto General Hospital, 200 Elizabeth St, Room EN13-219, Toronto, Ontario M5G 2C4, Canada
e-mail: tirone.david{at}uhn.on.ca

Aortic valve sparing operations are complex operative procedures because the surgeon has to have a sound knowledge of functional anatomy of the aortic valve; ability to recognize anatomically abnormal components of the aortic root; judgment to select appropriate surgical techniques; and technical skill to execute the operation. As in any operative procedure, the surgeon has to apply as much basic science principles as possible, but unfortunately, like most reconstructive procedures in cardiac surgery, the actual performance of the operation remains more art than science.

In this issue of The Annals, Morishita and colleagues [1] describe a study designed to verify the best method of estimating the diameter of the graft used for aortic root remodeling, a type of aortic valve sparing operation for patients with aortic root aneurysm. They made 127 casts of formaldehyde fixed aortic roots from Japanese and Caucasians cadavers. The casts were sectioned at the level of the sinotubular junction and various measurements obtained. These investigators would have made more accurate molds and measurements of the aortic roots if the dental impression material had been injected at physiologic pressures in fresh specimens rather than in formaldehyde fixed ones. Both the aortic wall and the aortic cusps are quite elastic (a feature that decreases with age) and fixation with formaldehyde shrinks the various components of the aortic root differently. Thus, the geometric relationships between the various components of the aortic root are not the same in the fresh and fixed specimens. Studies of this nature are important to enhance our knowledge on the geometry of the normal aortic root but they are useful only as guidelines during the performance of aortic valve sparing operations.

The authors’ definitions of "predicted diameter" of the sinotubular junction were the following: the Yacoub method as the "distance between the commissures," theirs as the diameter of the circle that contains a triangle made by the three commissures, and the David method as the average lengths of the free margins of the aortic cusps minus 10%. When they compared these "predicted diameters" with the "measured diameters" obtained from the aortic root casts, their method of determining the diameter of the sinotubular junction was the most accurate and mine was the least accurate. That is precisely what I would have expected from that study. Contrary to what the authors stated, I have never written or said that the diameter of the sinotubular junction of a normal aortic root is equal to the average lengths of the free margins of the aortic cusps minus 10% nor do I use this method regardless of the aortic valve operation I am performing. We studied the geometric relationships of the various components of the fresh aortic roots of humans several years ago [2]. The mean diameter of the sinotubular junction was 21.1 ± 1.0 mm and the mean length of the free margins of the aortic cusps was 32.4 ± 1.3 mm [2]. Thus, in the normal, fresh aortic root, the diameter of the sinotubular junction was approximately 30% less than the average length of the free margins of the aortic cusps and not 10%. The point those authors missed is that aortic valve sparing operations are not performed in patients with normal aortic root. These operations were developed to preserve the aortic valve in patients with aneurysm of the aortic root with or without aortic insufficiency. The diameter of the sinotubular junction is certainly important for normal valve function but determination of the size of the graft to reconstruct the aortic root is only a part of a far more complex operation. Two other components of the aortic root are equally important: the diameter of the aortic annulus and the size and shape of the aortic cusps. Although anatomic studies of the normal aortic root show that the diameter of the aortic annulus is 15% to 20% larger than the diameter of the sinotubular junction [2], after successful aortic valve sparing operations, those two diameters are either equal or the sinotubular junction is larger than the aortic annulus. Similarly, the lengths of the bases of normal aortic cusps are approximately one and one-half times longer than the lengths of their free margins. This relationship is seldom encountered in patients with aortic root aneurysms.

There are basically two types of aortic valve sparing operations for patients with aortic root aneurysm: remodeling of the aortic root and reimplantation of the aortic valve [3–6]. Remodeling of the aortic root consists in excising all three aortic sinuses, tailoring a tubular Dacron graft to create neosinuses, and suturing it to the aortic annulus. In the reimplantation procedure, the aortic annulus and cusps are resuspended inside a tubular Dacron graft. Clearly, sizing of the graft is different, depending on the technique used.

Yacoub and colleagues, who used the remodeling technique exclusively, described the selection of the size of the graft using the following method: "the three commissures are stretched in a vertical direction by the use of three horizontal mattress sutures placed just above the top of each commissure. The position of the aortic cusps and their ability to coapt without prolapsing is tested using a blunt instrument. The size of the Dacron tube is determined by measuring the distance between the commissures, which produces maximal coaptation of the cusps" [7]. This method slightly underestimates the diameter of the sinotubular junction because it measures only one of the sides of an imaginary triangle made by the three suspended commissures. The diameter of the circle that includes all three commissures is probably the correct one, and what Morishita and colleagues recommends. These techniques do not take into account the diameter of the aortic annulus and the relationship between the free margin and base of the aortic cusps. They both work well as long as the aortic cusps and aortic annulus are entirely normal, rare findings in patients with aortic root aneurysms.

Patients with aortic root aneurysms frequently have more than just dilated sinotubular junction. Actually, aneurysmal dilation begins in the aortic sinuses and progresses in all directions affecting the sinotubular junction and often the aortic annulus and aortic cusps, which lose their original shapes; the scalloped shape of the aortic annulus tends to become more flattened along the fibrous components of the left ventricular outflow tract and the free margins of the aortic cusps become slightly elongated. Surgical correction of the sinotubular junction and remodeling of the aortic sinuses may be an inadequate procedure in most patients with aortic root aneurysms, particularly if they have the Marfan syndrome or its forme frusta. Indeed, in Yacoub’s experience with the remodeling procedure, the freedom from reoperation at 10 years was 89%, and "mild to moderate" aortic insufficiency was present in one-third of the patients [7]. In patients with the Marfan syndrome the freedom from reoperation at 10 years was 82.7%, and 22.4% had moderate aortic insufficiency at the time of that report [8]. Although those investigators did not address the issue of valve failure after remodeling of the aortic root, my bet is that it was caused by dilation of the aortic annulus or cusp prolapse. My rationale for this assumption is that aortic root aneurysms are caused by connective tissue disorders, often of genetic origin, and as such, the abnormalities in the various components of the aortic root do not occur at the same time. Thus, even if the aortic annulus is normal at the time of surgery, chances are it will dilate with time. For all these reasons I believe that an aortic annuloplasty is necessary in patients with aortic root aneurysm [5, 6].

After more than a decade of experience with aortic valve sparing operations in over 200 patients, I firmly believe that the technique of reimplantation of the aortic valve is more appropriate than the remodeling of the aortic root for patients with aortic root aneurysms [9]. The aortic annulus cannot dilate after securing it inside of a tubular Dacron graft. In addition, once the valve is resuspended, the diameter of the sinotubular junction can be easily adjusted by plicating the graft or cutting the graft immediately above the commissures and suturing a smaller one, and spacing the commissures according to the lengths of their free margins. Both techniques create neo-aortic sinuses. Moreover, reimplantation of the aortic valve offers an opportunity to precisely assess the coaptation level of the aortic cusps, an important element in the durability of these repairs [10]. Elongated cusps can be shortened by central plication or even reinforced by weaving a double layer of a fine expanded polytetrafluoroethylene suture along the free margins [5]. These techniques expand the indications of aortic valve sparing operations to patients with prolapse of the aortic cusps [5, 9]. To do all this, the surgeon has to know far more than how to suspend the three commissures and determine the diameter of the circle that contains them to estimate the diameter of the sinotubular junction. That is where the notion of the average lengths of the free margins of the aortic cusps is very useful. Since the free margin of each aortic cusp extends from one commissure to approximately the center of the aortic orifice to other commissure when the valve is closed, its length must exceed that of the diameter of the aortic orifice. Actually, the average lengths of the free margins must exceed the diameters of the sinotubular junction and aortic annulus because the aortic cusps are semilunar. Using these geometric principles, and the knowledge of functional anatomy of the aortic root, one can reconstruct the aortic valve and correct all its abnormal components. The technique of reimplantation of the aortic valve may be facilitated by the use of grafts with aortic sinuses [11] but the estimation of the diameters of the aortic annulus and sinotubular junction remains more art than science.

References

1. Morishita K., Murakami G., Koshino T., et al. Aortic root remodeling operation: how do we tailor a tube graft?. Ann Thorac Surg 2002;73:1117-1121.[Abstract/Free Full Text]
2. Kunzelman K.S., Grande K.J., David T.E., Cochran R.P., Verrier E.D. Aortic root and valve relationships. Impact on surgical repair. J Thorac Cardiovasc Surg 1994;107:162-170.[Abstract/Free Full Text]
3. David T.E., Feindel C.M. An aortic valve-sparing operation for patients with aortic incompetence and aneurysm of the ascending aorta. J Thorac Cardiovasc Surg 1992;103:617-622.[Abstract]
4. David T.E., Feindel C.M., Bos J. Repair of the aortic valve in patients with aortic insufficiency and aortic root aneurysm. J Thorac Cardiovasc Surg 1995;109:345-352.[Abstract/Free Full Text]
5. David T.E. Surgery of the aortic valve. Curr Probl Surg 1999;36:42-504.
6. David T.E. Remodeling of the aortic root and preservation of the native aortic valve. Op Tech Card Thorac Surg 1996;1:44-56.
7. Yacoub M.H., Gehle P., Chandrasekaran V., Birks E.J., Child A., Radley-Smith R. Late results of a valve-preserving operation in patients with aneurysms of the ascending aorta and root. J Thorac Cardiovasc Sur 1998;115:1080-1090.[Abstract/Free Full Text]
8. Birks E.J., Webb C., Child A., Radley-Smith R., Yacoub M.H. Early and long-term results of a valve-sparing operation for Marfan syndrome. Circulation 1999;100(Suppl II):29-35.
9. David T.E., Armstrong S., Ivanov J., Feindel C.M., Omran A., Webb G. Results of aortic valve-sparing operations. J Thorac Cardiovasc Surg 2001;122:39-46.[Abstract/Free Full Text]
10. Harringer W., Pethig K., Hagl C., Meyer G.P., Haverich A. Ascending aortic replacement with aortic valve reimplantation. Circulation 1999;100(Suppl II):24-28.
11. De Paulis R., De Matteis G.M., Nardii P., et al. One-year appraisal of a new aortic root conduit with sinuses of Valsalva. J Thorac Cardiovasc Surg 2002;123:33-39.[Abstract/Free Full Text]

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