Ann Thorac Surg 2009;87:1951-1952. doi:10.1016/j.athoracsur.2008.10.050
© 2009 The Society of Thoracic Surgeons
Case Reports
Morphologic Findings of the Aortic Homograft Implanted in the Tricuspid Position
Iki Adachi, MDa,
Siew Yen Ho, PhD, FRCPatha,*,
Karen P. McCarthy, BSa,
Michael Mullen, MDb,
Hideki Uemura, MD, FRCSc
a Cardiac Morphology Unit, National Heart and Lung Institute, Imperial College London, London, United Kingdom
b Adult Congenital Heart Unit, Royal Brompton and Harefield NHS Trust, London, United Kingdom
c Department of Cardio-Thoracic Surgery, Royal Brompton and Harefield NHS Trust, London, United Kingdom
Accepted for publication October 21, 2008.
* Address correspondence to Dr Ho, Cardiac Morphology Unit, National Heart and Lung Institute, Imperial College London, Guy Scadding Bldg, Dovehouse St, London, SW3 6LY, United Kingdom (Email: yen.ho{at}imperial.ac.uk).
 |
Abstract
|
|---|
We present histologic findings of the aortic homograft mounted in a woven Dacron (C.R. Bard, Haverhill, PA) tube, which had been in the tricuspid position for 68 months in a patient with Ebstein anomaly. Although the layered architecture of leaflets was relatively well preserved, prominent calcification was observed in the sinus wall that had been in direct contact with the surrounding fabric. This sinus stiffness might have contributed to worsening of the valvar function.
|
Introduction
|
|---|
Replacement of the tricuspid valve using homograft has been an appealing alternative to biologic or mechanical prostheses. In contrast to a recent trend toward the use of "mitral" homograft for this purpose, semilunar valves were exclusively utilized in the initial experiences reported in the early 1970s [1]. Despite such a long history, the fate of this particular usage has been rarely reported.
A 34-year-old woman with Ebstein malformation was scheduled to undergo redo surgery for her tricuspid lesion because of increased fatigue. Five years earlier, her native tricuspid valve had been replaced with an aortic homograft after an attempted valvar repair with plication of the atrialized right ventricle 3 weeks earlier. The homograft implanted was 25 mm in diameter and mounted in a woven Dacron (C.R. Bard, Haverhill, PA) tube with a pericardial collar at its proximal side [2]. Postoperatively, warfarin sodium had been continued for 1 year and then switched to aspirin. The first echocardiography at 1 year postoperatively demonstrated the presence of mild tricuspid stenosis with a peak flow velocity of 2.0 m/s. The degree of stenosis, however, had not changed thereafter, whereas valvar incompetence had gradually progressed to moderate degree. Nevertheless, the valvar leaflets themselves had been mobile throughout the period. This was confirmed with serial catheterizations performed at 3 and 5 years postoperatively. A mean pressure gradient across the tricuspid valve was 7 mm Hg and 5 mm Hg, respectively. During the second catheterization, the tricuspid valvar area and cardiac index was calculated as 0.8 cm2 and 2.0 L · min–1
· m–2, respectively. In view of recent deterioration in her exercise capacity along with worsening of the valvar function, replacement of the homograft was indicated.
Through a median sternotomy, cardiopulmonary bypass was initiated. Upon opening the right atrium, the valvar leaflets were soft and pliable, whereas the orifice appeared distorted. The proximal end of the conduit was located at the tricuspid annulus, with the rest of the conduit bulging into the ventricular cavity. A Carpentier-Edwards bioprosthesis (no. 29; Edwards Lifesciences, Irvine, CA) was implanted in the para-annular position. The first and second valvar replacements were performed by different surgeons, and prosthetic materials were selected according to their own preference. Our surgeon (H.U.) chose the Carpentier-Edwards valve rather than another homograft, because such a prosthesis is much more commonly used and hence is better tested. The patient showed uneventful postoperative recovery.
Gross examination of the extracted homograft revealed barely any pannus deposition, and the supporting fabric cuff was uncovered (Fig 1). The valve had three semilunar leaflets of fairly equal sizes. All the leaflets were pliable, and could be opened and closed easily. There were no calcific masses or any perforations in the leaflets. Nodular deposits of calcium were present in the walls of the aortic sinuses, affecting in particular one of the sinuses with one of the nodules bordering on the semilunar attachments of one leaflet. Even so, that leaflet remained mobile. Histologic examination of the leaflets showed a cellular but irregular layered architecture reminiscent of atrialis, fibrosa, and ventricularis.
View larger version (62K):
[in this window]
[in a new window]
|
Fig 1. (A) An internal aspect of the resected homograft mounted in a woven Dacron (C.R. Bard, Haverhill, PA) tube. Although three leaflets remained pliable, the shape of the valvar annulus was distorted. (B) Hematoxylin-eosin staining of one of the valve leaflets showed the layers as being compact in parts but slightly increased in thickness in others (arrow). (C) Elastic–Van Gieson staining of the aortic sinus wall showed nodular deposits of calcium (arrows). (Magnification x5 in B and C.)
|
|
|
Comment
|
|---|
In the past, there was an enthusiasm for the use of semilunar homograft for tricuspid valve replacement [1]. Despite its long history, long-term outcomes have been reported only sporadically [3]. Furthermore, no article has mentioned histologic changes of homograft tissue. This paucity of information is in marked contrast to the extensive investigations on the fate of semilunar valves at the right ventricular outflow, both histologically and physiologically. Nevertheless, knowledge regarding the latter situation cannot be applied to the inlet position, because the hemodynamic influence on the valve is completely different.
Histologic findings were consistent with gross observations, and the leaflets would have been capable of normal movement. Any restriction in movement could only be attributed to the sinusal stiffness due to calcification. These findings are in line with a report from Kawauchi and coworkers [3] describing a case having aortic homograft in the tricuspid position functioning 28 years after implantation, with echocardiographic evidence of well-mobile leaflets. Such longevity is probably due to less mechanical stress on the leaflets in the tricuspid position. In terms of total valvar function, however, leaflet motion is not a sole determinant. Rather, the hemodynamic property of semilunar valves depends on the coordinative interaction between leaflets and Valsalva sinuses [4].
In this regard, the use of semirigid fabric could have a negative impact on the sinus function. In fact, severe degeneration was found in the aortic sinus wall that had been in direct contact with the fabric. Loss of integrity and distortion of the sinus wall might have played important roles in the disorganization of valvar interaction in our case. Furthermore, distortion of valvar annulus must also have adversely affected valvar function, because competency of a semilunar valve is dependent on its circular shape. Deviation from a circle seems inevitable in this setting as the native tricuspid junction is not a perfectly circular structure and its shape changes with cardiac cycle. That would also be the case when a semilunar valve is used for the mitral junction, as seen in the so-called Ross II operation [5].
In conclusion, a semirigid fabric may not be the optimal material, because it can also affect the maintenance of valvar circularity at the inherently noncircular atrioventricular junction.
|
References
|
|---|
- Ross D, Somerville J. Surgical correction of Ebstein's anomaly Lancet 1970;2:280-284.[Medline]
- McKay R, Sono J, Arnold RM. Tricuspid valve replacement using an unstented pulmonary homograft Ann Thorac Surg 1988;46:58-62.[Abstract/Free Full Text]
- Kawauchi M, Saigusa M, Furuse A, Takamoto S. Aortic homograft valve functioning for twenty-eight years in the tricuspid position J Thorac Cardiovasc Surg 1999;118:384-385.[Free Full Text]
- Bellhouse BJ, Bellhouse FH. Mechanism of closure of the aortic valve Nature 1968;217:86-87.[Medline]
- Ross DN. Replacement of aortic and mitral valves with a pulmonary autograft Lancet 1967;2:956-958.[Medline]
Top
Abstract
Introduction
