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Ann Thorac Surg 2004;78:2150-2152
© 2004 The Society of Thoracic Surgeons

New technology

Replacement of the Aortic Valve and Ascending Aorta With an Extended Root Stentless Xenograft

Wolfgang B. Hemmer, MD, PhDa,*, Cornelius A. Botha, FCS SA (cardio)a, Jürgen O. Böhm, MDa, Tobias Herrmann, MDa, Christoph Starck, MDa, Joachim-Gerd Rein, MD, PhDa

a Department of Cardiac Surgery, Sana Herzchirurgische Klinik, Stuttgart, Germany

Accepted for publication September 23, 2003.

* Address reprint requests to Dr Hemmer, Sana Herzchirurgische Klinik, Herdweg 2, 70174 Stuttgart, Germany
w.hemmer{at}sana-herzchirurgie.de


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PURPOSE: We present an early series to determine the technical feasibility of simultaneous aortic valve and complete ascending aortic replacement using a longer stentless aortic xenograft, harvested with an extended root.

DESCRIPTION: The stentless xenograft valved conduits commercially available are too short for complete ascending aorta replacement, and usually a prosthetic tube graft is required distally.

EVALUATION: To avoid this extra prosthetic conduit distally a number of stentless aortic xenografts with extended conduit were obtained from a supplier (Medtronic Inc). They were inserted in 6 elderly patients (67.8 ± 7.1 years) who all required aortic valve and ascending aorta replacements owing to pathologic dilation.

CONCLUSIONS: In all cases an extra prosthetic conduit was avoided, and the length of the available biological conduit comfortably allowed total ascending aortic replacement without tension. The advantages therefore were one less suture line, cost saving regarding the prosthetic conduit, shorter cross-clamping time, and possibly shorter time spent on hemostasis.


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Studies have suggested that stentless prostheses for aortic valve replacement have superior hemodynamic results when compared with stented prostheses. This advantage over stented prostheses is even more pronounced when the stentless prosthesis is implanted as a root replacement rather than in an inclusive technique in the subcoronary position [1–3]. Stentless aortic valve xenograft prostheses were originally developed as a readily available substitute for the scarce aortic homografts or pulmonary autografts, and all approximate the anatomy and physiology of the natural aortic root more closely than stented composite conduit alternatives.

During the period of 100 months from January 1995 to April 2003, aortic root replacement surgery was performed in 779 patients with aortic valve disease in our clinic. It has been our practice to offer the Ross procedure (performed as a root replacement) as first choice aortic valve replacement for patients up to the age of about 60 years. After this age and when the patient's life expectancy begins to approximate the expected durability of aortic homografts or stentless conduits, either of these options is then offered to the patient [4]. For destroyed or badly disrupted aortic roots due to infective endocarditis, in all age groups the versatility of an aortic homograft still has many advantages in our hands.

In the elderly, the replacement of the aortic root with a stentless conduit is particularly attractive for the ectatic, poststenotic aorta or the inherently dilated aortic root, as remarked on by various authors [5, 6]. Aortic homografts with added length, often harvested to include even the aortic arch, are scarce. In common with these latter authors, we have also tended to replace all of the dilated aortas with a short polyester Hemashield (Boston Scientific, Wayne, NJ) prosthetic graft above the stentless conduit, generally to the origin of the brachiocephalic artery, occasionally obliquely into the lesser curvature of any dilated aortic arch. The poststenotic dilated aorta seldom extends further, and rarely is more than 2 to 3 cm of prosthetic conduit required. Thus, with this in mind, a longer stentless conduit, which would obviate the cost of an additional prosthetic conduit as well as one extra suture line, was desirable. The producer of the Freestyle stentless aortic valve prostheses, Medtronic Inc (Minneapolis, MN), was approached to supply us with a limited number of extended root prostheses for selected patients on a case-by-case basis. They have, though, not subsequently agreed to provide these extended root conduits commercially, apparently owing to cost and constraints of regulation and packaging.


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Extended Root Freestyle Prostheses
The production of the extended root prostheses proceeded in the same manner as standard length Freestyle stentless conduits, except that up to 2 cm more of the ascending aorta was harvested in suitable donor animals and processed (Fig 1). The function of the valve should therefore be unchanged. Six Freestyle extended root prostheses were supplied, two each of the sizes 25 mm, 27 mm, and 29 mm.



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  		Fig 1. Stentless xenograft conduit with extra root length clearly visible.

 
Technique
The surgical technique of aortic root replacement is standardized for all involved surgeons in our clinic: median sternotomy, normothermic extra corporeal circulation, arterial return through cannulation of either the aortic arch, femoral or subclavian artery, right atrial venous return, and a combination of intermittent ante and retrograde blood cardioplegia. The aorta is clamped below the origin of the brachiocephalic artery, the diseased aortic valve is excised, and both coronary arteries are mobilized on large buttons of aortic wall. Generous buttons may be advantageous in any reoperation with root calcification. All suture lines are performed in a continuous fashion, and the stentless conduit is anastomosed to the aortic annulus with 3-0 Prolene on a V5 needle for the added curvature thereof; the coronary artery buttons are sutured to a position on the side of the conduit where they best fit with 5-0 Prolene. Although we do not usually rotate the stentless conduit out of the normal anatomical orientation, the position of the porcine coronary ostia only occasionally match the generously mobilized coronary artery buttons. In most patients, the left or right coronary button requires repositioning, and on occasion either of the two may even fit the noncoronary sinus best. Finally, the distal aorta-to-conduit anastomosis is performed with 4-0 Prolene. If necessary, a short period of hypothermic arrest with a clampless distal anastomotic technique is utilized into the lesser arch. The intention is to remove all ectatic aorta; therefore, mismatch of the distal anastomoses is easily compensated for with an oblique section of the xenograft conduit.

Patient Group
Between September 1995 and November 2002, 6 male patients received this specially manufactured extended root bioprosthesis for aortic valve replacement. The procedure was explained thoroughly to the patients and informed consent was obtained, as is local practice for isolated cases. Involvement of a review board was waived. Average patient age was 67.8 ± 7.1 years (range, 56 to 76). One patient presented with isolated aortic stenosis, 4 presented with mixed aortic valve disease, (echocardiographically, {Delta} pmax = 62.3 ± 11.0 mm Hg), and the last patient had incompetence only. At surgery all native valves were found to be congenitally bicuspid. One patient required mitral valve repair and left atrial radio frequency ablation for chronic atrial fibrillation. All patients had aneurysmally dilated ascending aortas with a mean diameter of 49 ± 2.8 mm (range, 45 to 52). In all cases, the complete ascending aorta could be replaced with the extended root conduits and no extra length of prosthetic conduit was required.

The mean cardiopulmonary bypass time was 123 ± 25.4 minutes (range, 101 to 163), and the mean cross-clamp time was 94.8 ± 22.3 minutes (range, 76 to 130).

All patients recovered routinely from the operation, and discharge occurred between the seventh and 16th postoperative day. At discharge, the mean peak systolic gradient across the prosthetic valves was 7.6 ± 2.9 mm Hg (range, 3.5 to 10.9 mm Hg). None of the patients had significant valvular regurgitation.


   Comment
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The standard operation for aortic valve disease combined with ascending aortic root dilation is valve and root replacement with a composite mechanical prosthetic valve conduit, techniques originally described by both Bentall and De Bono [7]. Alternatives are biological stentless valve conduits, which not only obviate the need for lifelong anticoagulation, but also have hemodynamic properties that more closely approximate those of the native aortic valve or homograft. During 100 months from January 1995 to April 2003, we performed aortic root surgery in 779 patients. The different techniques employed in aortic root surgery are portrayed in Table 1. From this table the influence of patient age on our choice of conduit is evident, age and life expectancy being our primary concern in choosing between techniques for aortic root surgery [8, 9].


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  		Table 1. Relationship Between Age and Conduit Choice in 779 Aortic Root Replacements

 
Older patients, in particular, receive the stentless conduit valve when the durability of the stentless valve can be expected to exceed the life expectancy of the patient. The extended root option obviates an extra anastomosis, and is therefore a rapid and safe option in the older patient with aortic valve disease combined with ascending aortic pathology. Long-term anticoagulation is avoided. There have been no reports of aneurysm formation of portions of the conduit walls of stentless xenografts inserted as free-standing roots, and we see no reason for an extra centimeter or two of glutaraldehyde pretreated porcine aortic wall to make any difference to this fact. Previous studies of the durability and function of stentless bioprostheses support this contention [2, 3]. Although calcification of the porcine aortic wall is to be expected with time [10], we expect that the natural life expectancy of these older patients will make reoperation the exception rather than the rule. Valvular dysfunction in the future, although difficult, does allow several other options at reoperation, from repeat root replacement to stented prostheses placed at the original aortic annulus salvaging the porcine root. It remains to be seen what the implications of such reoperations will be. Concerning the elderly patient with a poststenotic aortic ectasia or aneurysm formation, we in common with other authors have found the conduit length of currently available stentless bioprostheses to be inadequate for complete ascending aortic replacement, and a short prosthetic substitution, generally no longer than 2 to 3 cm, is often required [5, 6]. It was possible in all of our cases to replace the complete ascending aorta to the origin of the brachiocephalic artery, with the advantages of one less suture line, shorter cross-clamp time, and less nonbiological material in the circulation, as well as saving the cost of the prosthetic conduit.

Surgeons versed in the use of aortic homografts for complicated aortic root diseases often value the versatility of an aortic homograft with the attached anterior mitral valve cusp. The anterior cusp can be fashioned individually to compensate for aortic annulus-to-conduit mismatch and can also be used in this way to cover an abscess or to help reconstruct the disrupted aortic root. A further development to the extended length stentless aortic root bioprostheses would be to process some of these conduits with the anterior leaflet of the porcine mitral valve left in situ, such as with aortic homografts. The polyester covering the proximal suture line of stentless xenografts is only essential for the weaker and friable muscle portion of the porcine root. Glutaraldehyde-treated aortomitral curtain tissue should supply adequate strength for secure sowing. These even more versatile bioprostheses could then be fashioned by the surgeon at the operating table to better manage complicated, destroyed, or infected aortic roots. We are in discussion with the manufacturers on what we believe to be the logical culmination of the development of stentless bioprostheses.

In conclusion, we see the stentless aortic xenograft conduit as a design still in evolution, and in this pilot study a clear advantage was observed for the extended root stentless bioprosthesis in older patients requiring aortic root and complete ascending aorta replacement.


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The Freestyle extended root stentless xenografts were supplied to our clinic at the same cost as the normal Freestyle prostheses. Medtronic, Inc, in no way financially supported the study or contributed in any other way. The authors had full control of the design of the study, methods used, outcome indicators, analysis of data, and production of the written report.


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The Society of Thoracic Surgeons, the Southern Thoracic Surgical Association, and The Annals of Thoracic Surgery neither endorse nor discourage use of the new technology described in this article.


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  1. Wendler O, Dzindzibadze V, Langer F, El Dsoki S, Schäfers HJ. Aortic valve replacement with a stentless bioprosthesis using the full-root technique. Thorac Cardiovasc Surg. 2001;49:361–364[Medline]
  2. Kon ND, Riley RD, Adair SM, Kitzman DW, Cordell AR. Eight-year results of aortic root replacement with the Freestyle stentless porcine aortic root bioprostheses. Ann Thorac Surg. 2002;73:1817–1821[Abstract/Free Full Text]
  3. Bach DS, Cartier PC, Kon ND, Johnson KG, Deeb GM, Doty DBFreestyle Valve Study Group. Impact of implant technique following Freestyle stentless aortic valve replacement. Ann Thorac Surg. 2002;74:1107–1114[Abstract/Free Full Text]
  4. Boehm JO, Botha CA, Hemmer W, et al. Older patients fare better with the Ross operation. Ann Thorac Surg. 2003;75:796–802[Abstract/Free Full Text]
  5. Byrne JG, Mihaljevic T, Lipson WE, Smith B, Fox JA, Aranki SF. Composite stentless valve with graft extension for combined replacement of the aortic valve, root and ascending aorta. Eur J Cardiothorac Surg. 2001;20:252–256[Abstract/Free Full Text]
  6. Markowitz A. Utility of the full root bioprosthesis in surgery for complex aortic valve-ascending aortic disease. Semin Thorac Cardiovasc Surg. 2001;13(Suppl 1):12–15[Medline]
  7. Bentall H, DeBono A. A technique for complete replacement of the ascending aorta. Thorax. 1965;23:338–339
  8. 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;103:617–621[Abstract]
  9. Sarsam MAI, Yacoub M. Remodelling of the aortic valve annulus. J Thorac Cardiovasc Surg. 1993;105:435–438[Abstract]
  10. Melina G, Rubens MB, Birks EJ, Bizzari F, Khaghani A, Yacoub MH. A quantitative study of calcium deposition in the aortic wall following Medtronic Freestyle compared with homograft aortic root replacement. A prospective randomized trial. J Heart Valve Dis. 2000;9:97–103[Medline]

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