J Thorac Cardiovasc Surg 1998;115:961-963
© 1998 Mosby, Inc.
Early failure of freehand aortic stentless xenograft valves
Mark F. O'Brien, FRACS, FRCS
To the Editor:
Luciani, Bertolini, and Mazzucco
1 report two cases of supposed early (<12 months) failure with the O'Brien-Angell stentless porcine xenograft aortic valve (now the CryoLife-O'Brien model 300 composite aortic stentless xenograft; CryoLife, Inc., Marietta, Ga.), which they label as structural failures. The first patient required reoperation for aortic valve replacement at 8 months. A large periprosthetic dehiscence of the valve from the host "for a length of about 1 cm at the level of the native noncoronary cusp" had occurred. The authors published a photograph of the explanted valve, which they said was originally implanted with a technique described by O'Brien. 2 As the author of this technique and of the composite stentless valve, I respond and offer an entirely different interpretation. This is not structural valve failure. It is incorrect surgical technique of implantation leading to nonstructural failure of the device. The method published and recommended is quite specific and must be used with this valve, because of the unique single suture line technique and minimal xenograft aortic wall. It combines a supraannular implantation with this single-layer continuous 3-0 Prolene suture (Ethicon, Inc., Somerville, N.J.), which must incorporate virtually all of the xenograft wall. It is clearly illustrated in the manufacture's brochure 3 and in the technical article referenced. 2 The explant photograph shows that only a small portion of the xenograft wall has been incorporated in the suture. This incorrect modification would be totally inadequate to hold the xenograft in place. The xenograft would be more likely to tear away, which is precisely the event that occurred. In addition, this would lead to an unwanted space below the valve on the ventricular side (Fig. 1). If the surgeon as well places the valve at anulus level, then unsatifactory hemodynamics would eventuate (Fig. 2). A perfect implantation must finish with virtually all of the xenograft wall securely pinned against the supraannular aortic wall above the radically excised valve anulus (Fig. 3).
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Fig. 1. Suturing only a small rim of the xenograft aortic wall (as in case 1 of Luciani, Bertolini, and Mazzucco) gives inadequate fixation of the xenograft to the host and a space under the unsupported xenograft wall.
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Fig. 2. Annular implantation encroaches on or reduces and lessens the effective valve orifice, compromising hemodynamics.
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Luciani, Bertolini, and Mazzucco failed to implant the valve correctly, and thus a second operation for their patient was necessary. This is a technical error and not structural failure of the implant. In a series of 199 patients treated over 5 years, I have had no structural failures, and in a larger series of more than 250 patients, Hvass shares the same experience (U. Hvass, Bichat Hopital, Paris; personal communication). Therefore 449 patients have not shown intrinsic structural valve failure over a maximum of 6 years (minimum 1 month).
For the readers of this letter, three simple technique diagrams are included to illustrate the correct and incorrect methods of implantation (Figs. 1
to 3). The technique is simple and safe if done correctly, but like many things in surgery, most advantages of this stentless valve are lost if the technique is not followed exactly.
The second patient may be somewhat different. Eleven months after aortic valve implantation, severe stenosis of the prosthetic stentless xenograft valve occurred, with a peak pressure gradient of 82 mm Hg. At reoperation the aortic root and valve leaflets were found to be extensively covered and distorted by fibrous tissue overgrowth (Fig. 2 from the Luciani article). The scarring was so extensive that a Nicks root enlargement was necessary before the insertion of a size 23 Hancock II valve (Hancock Extracoporeal Inc., Anaheim, Calif.). The unanswered question is this: Will the same extensive fibrous pannus return? Pannus has led to reoperation in stented xenografts and mechanical valves in both the aortic and mitral positions, yet it is not at all a common phenomenon with the free subcoronary or root replacement allograft aortic valve. I believe that the stentless xenograft per se, and particularly the CryoLife-O'Brien model 300, because of the lack of Dacron backing, should yield a very low incidence of pannus ingrowth.
Because of the extent of the fibrosis in patient 2, one wonders (and Luciani, Bertolini, and Mazzucco do suggest) that there may be in this particular patient "the involvement of biologic reactions in the host." Nevertheless, Luciani, Bertolini, and Mazzucco do inject a note of caution that pannus ingrowth has occurred in one patient of a cohort of 40 patients. In my own series of patients, closely monitored echocardiographically at 6- to 12-month intervals over the 5 years, I have seen no evidence of increasing obstruction. In fact, gradients from the left ventricle to the aorta drop markedly as left ventricular regression occurs.
In conclusion, I do not accept structural failure as the correct interpretation in the first patient described by Luciani, Bertolini, and Mazzucco. I do accept excessive fibrous tissue overgrowth of causes unknown that have led to structural device failure and the need for reoperation in the second patient.
Department of Cardiac SurgeryThe Prince Charles HospitalBrisbane North Region, Rode Rd., Chermside,
Brisbane 4032, Australia12/8/88050
References
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Luciani GP, Bertolini P, Mazzucco A. Early failure of freehand aortic stentless xenograft valves. J Thorac Cardiovasc Surg 1997;113:1109-10.
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O'Brien MF. The CryoLife-O'Brien composite aortic stentless xenograft: surgical technique of implantation. Ann Thorac Surg 1995;60:S410-22.
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The CryoLife-O'Brien model 300 composite stentless porcine aortic xenograft technique brochure. Kennesaw (GA). CryoLife International Inc.
