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J Thorac Cardiovasc Surg 2005;130:601-603
© 2005 The American Association for Thoracic Surgery

Brief Communication

New graft formulation and modification of the David reimplantation technique

Division of Cardiothoracic Surgery, Department of Surgery, Northwestern University Feinberg School of Medicine, Chicago, Ill

Received for publication February 1, 2005; accepted for publication February 15, 2005.

^_* Address for reprints: Thomas G. Gleason, MD, Northwestern University Feinberg School of Medicine, Galter 10-105, 201 East Huron St, Chicago, IL 60611-3056 (Email: tgleason{at}nmh.org).

Two controversies of the reimplantation technique ¹ for valve-sparing aortic root replacement are how to choose the graft size and the role of neosinuses. Dating back to the original David-Feindel formula that was based on an assumption that "the internal radius of the ventriculo-aortic junction (the annulus) ... is two thirds of the leaflet height," ¹ surgeons have had difficulty determining optimal graft size. David, in fact, has changed his graft formulation strategy at least 3 times. ² Part of the impetus for the modifications in technique was the recognition that recreating aortic sinus segments is important to minimizing stress on the aortic cusps during systole. Data suggest that the techniques currently used still cause undue stress (albeit improved) on the cusps, even with recreation of neosinuses. ³ The principal hypothesis of this report is that the formulations in use probably underestimate optimal sinus diameter. An alternative and simpler formula with modification of the reimplantation technique is presented.

Methods

The geometry and relative dimensions of the normal human aortic root were previously characterized, confirming a constant ratio of the dimensions of the sinus diameter, sinotubular junction, commissural heights, and cusp height relative to the annular diameter. ⁴ Extrapolating from these data for the purposes of graft size selection and subsequent graft tailoring, 2 important relationships are noted: and , where h is defined as average cusp height, d is defined as internal annular diameter, and d' is defined as external sinus diameter (Figure 1). At the time of root replacement, the average cusp height is the only relatively fixed measurement, and thus all other diameters can be tailored to accommodate this value. The annulus should be supported (encircled) by graft to recreate , and the graft size should be or for that given h. This formula for d' can then be simplified to , where the added 1 to 2 mm approximates the constant (0.73/0.7) for the range of cusp heights typically seen (13–18 mm), corresponding to a graft size of 28 to 38 mm (Figure 1).

View larger version (35K): [in this window] [in a new window]   Figure 1. Normal human aortic root dimensions relative to cusp height for the internal annular diameter and the external sinus diameter are depicted on the left. A tailored aortic root graft is depicted on the right.

The annulus is dissected out circumferentially, including some of its fibrous continuity. The valve is reimplanted with 2 suture lines: the first is a subcusp-annular suture line placed with horizontal mattress sutures in a coronet-shaped, 3-dimensional annular fashion, and the second is a running suture line placed supra-annularly, incorporating residual aorta, annulus, and graft (Figure 2). The graft circumferentially supports the annulus, the fibrous continuity of the ventriculoaortic junction, and the commissures.

View larger version (45K): [in this window] [in a new window]   Figure 2. Reimplantation of the aortic valve in the tailored aortic root graft with neosinus creation is depicted from the superior and anterior anatomic views, respectively.

Discussion

Conceptually, the reimplantation technique is an attractive operation because the native valve is spared and subsequent annular dilatation is completely prevented by circumferential graft support. The primary limitations are its technical demand and the potential for progressive aortic insufficiency caused by cusp stress, leading to cusp injury, fibrosis, or prolapse. In the largest reported series, the 5-year reoperation rate was 3.2%, but 6% had 3–4+ AR, and 32% had 1+ AR at last follow-up. ⁵ Creation of neosinuses by previously reported techniques has not eliminated cusp stress, and this, in part, might be due to the fact that the sinuses created were not large enough to restore normal geometric relationships to optimize laminar flow through the valve. ^3,4 This new graft formula presented is simple, predicts a larger graft size than previously reported, and is based on normal root dimensions. It will require continued analysis to prove that cusp stress has been adequately reduced. Dynamic imaging studies are currently underway to identify a better means of evaluating flow patterns and cusp stress.

References

1. David TE, Feindel CM. 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]
   
2. Miller DC. Valve-sparing aortic root replacement in patients with the Marfan syndrome. J Thorac Cardiovasc Surg. 2003;125:773-778.[Free Full Text]
   
3. Grande-Allen KJ, Cochran RP, Reinhall PG, Kunzelman KS. Re-creation of sinuses is important for sparing the aortic valve. a finite element study. J Thorac Cardiovasc Surg. 2000;119:753-763.[Abstract/Free Full Text]
   
4. Swanson M, Clark RE. Dimensions and geometric relationships of the human aortic valve as a function of pressure. Circ Res. 1974;35:871-882.[Abstract/Free Full Text]
   
5. Kallenbach K, Hagl C, Walles T, Leyh RG, Pethig K, Haverich A, et al. Results of valve-sparing aortic root reconstruction in 158 consecutive patients. Ann Thorac Surg. 2002;74:2026-2033.[Abstract/Free Full Text]
   

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