Ann Thorac Surg 1998;66:2127-2131
© 1998 The Society of Thoracic Surgeons
How To Do It
Mitral valve replacement with homograft
Donald B. Doty, MDa,
Christophe Acar, MDb
a Division of Thoracic and Cardiovascular Surgery, Department of Surgery, LDS Hospital, Salt Lake City, Utah, USA
b Hôpital Bichat, Paris, France
Accepted for publication July 11, 1998.
Address reprint requests to Dr Doty, 324 Tenth Ave, Salt Lake City, UT 84103
e-mail: (ldddoty{at}ihc.com)
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Abstract
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The technique for replacement of the mitral valve with a mitral valve homograft is described. Principles include side-by-side approximation of the papillary muscles using multiple stitches of fine monofilament suture, direct attachment of the annulus of the mitral homograft to the annulus of the patient, and support of the repair by remodeling annuloplasty ring.
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Introduction
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Replacement of the mitral valve with a mitral valve homograft is appealing because it uses natural tissues and a valve designed specifically for the purpose of withstanding the full contractile force of the ventricle while providing unobstructed flow from atrium to ventricle. Anticoagulant medications should not be required provided there is normal atrial contraction. Many previous attempts at transplantation of the natural mitral valve to the mitral position have been tried both experimentally and clinically. Operations have been limited by the ability to attach the papillary muscles securely. Mitral valve replacement with a homograft mitral valve can be performed reproducibly by using the techniques described by Acar and associates [1]. The crux of the method is the attachment of the papillary muscles of the graft to the native papillary muscles by using a side-by-side attachment of the papillary muscles which appears to be secure. The valve replacement is supported by an annuloplasty ring.
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Operative technique
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The operation is performed through a median sternotomy. The Carpentier-Delacroix retractor system is used to obtain exposure. Cardiopulmonary bypass is established using two right angle venous uptake cannulae. One cannula is placed directly in the superior vena cava, the other is passed through the right atrial wall into the inferior vena cava. Oxygenated blood is returned through a cannula in the ascending aorta. The aorta is occluded and myocardial protection is provided during the period of ischemia by infusion of hypothermic cardioplegia solution retrograde through a cannula placed in the coronary sinus. A vent catheter is placed in the left atrium. The left atrium is opened on the right side through the interatrial groove.
The mitral valve is removed by incision of the valve circumferentially (Fig 1A). The incision is placed near the fibrous annulus of the valve. The chordae tendineae are removed from the tips of the papillary muscles (Fig 1B). Retraction of the papillary muscles exposes the muscular trabeculations (bands) that attach the papillary muscles to the ventricular wall (Fig 1B, inset). These trabeculations are divided to create space in which the graft papillary muscles can be deeply embedded.
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Fig 1. (A) The mitral valve is resected circumferentially. (B) The chordae tendineae are resected from the tips of the papillary muscles. (Inset) Trabeculations joining the base of the papillary muscles to the left ventricular wall are divided.
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The size of the homograft is determined by measurements taken from the echocardiogram. The most important dimension is the height of the anterior leaflet measured in the diastole. A slightly larger homograft (+3 mm) than the natural valve is desired. After the valve is thawed, it is trimmed. The myocardium of the atrium and the ventricle is cut away from the annulus of the valve, leaving just enough tissue to allow needle penetration without entering leaflet tissue (Fig 2A). The papillary muscles are shortened, leaving 15 mm of muscle below the chordal attachments (Fig 2B). The implantation is started with fixation of the papillary muscles. The posterior papillary muscles are implanted first. Two mattress stitches are placed at the base of the papillary muscles (Fig 2B). The suture material is 5-0 Cardionyl, a monofilament suture chosen because of its flexibility, knot security, and fine needle.
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Fig 2. (A) The atrial and ventricular myocardium is trimmed from the mitral homograft. (B) Papillary muscles of the graft are shortened to 15 mm. Two mattress stitches are placed through the base of the posterior papillary muscle.
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The two mattress stitches are placed in the graft papillary muscle and then passed through the patient papillary muscle (Fig 3A). The stitches are placed low at the base of the papillary muscle so that the homograft papillary muscle is slightly lower than the recipient papillary muscle when it is drawn into place between the papillary muscle of the recipient and the ventricular wall. Exposure is enhanced by placing a retraction stitch through the papillary head that supports the commissure, which is invariably at the apex of the patient papillary muscles. The stitches are tied with attention to the tension placed on them so as to securely approximate the muscular tissues without weakening or cutting through the papillary muscles.
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Fig 3. (A) The mattress stitches are placed through the base of the patient posterior papillary muscle so as to approximate the papillary muscles in side-by-side fashion. (B) Two simple stitches join the papillary muscles anteriorly. (C) Two more simple stitches are placed posteriorly at the edge of the papillary muscles. The tips of the papillary muscles are approximated by multiple simple stitches to complete the papillary muscle attachment. The anterior papillary muscle of the graft is attached to the anterior papillary muscle of the patient in an identical fashion.
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Two interrupted stitches are placed at the anterior margin of the papillary muscles to secure the side-by-side approximation of the muscles (Fig 3B). Two interrupted stitches are placed posteriorly on the muscles to finish aligning the muscles (Fig 3C). Multiple stitches are then placed to secure the tips of the papillary muscles (Fig 3C). Care is taken not to interfere with the chordae tendineae. Vertical mattress sutures might be required. The anterior papillary muscles are approximated similarly.
Sutures for mitral valve annuloplasty are placed around the perimeter of the mitral annulus (Fig 4A). The stitches for the anterior portion of the annulus can be placed earlier, during thawing of the valve. The suture material is 2/0 braided polyester. The mitral homograft annulus is attached to the mitral annulus using continuous stitches of 4-0 polypropylene suture (Fig 4B). The fibrous trigones of the graft are lined up with the patient’s fibrous trigones. Attention is given to distributing the graft leaflet tissues uniformly around the annulus. The replaced valve is supported by remodeling annuloplasty using a Carpentier classic ring. Size of the device is chosen to match the size of the graft anterior leaflet, as in standard mitral valve repair operations. The device is attached to the annulus by the previously placed sutures (Fig 4B, inset). Competence of the repair is tested by infusion of saline under pressure into the left ventricle and by echocardiography after closing the atrium and resuscitation of the heart.
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Fig 4. (A) Annuloplasty stitches are placed around the mitral annulus. (B) The mitral homograft is approximated to the mitral annulus by continuous stitches, taking care to line up the fibrous trigones. (Inset) A remodeling annuloplasty is attached to the annulus by the annuloplasty stitches to support the repair.
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Comment
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Modern replacement techniques of the mitral valve with a mitral valve homograft are an extension of mitral valvuloplasty techniques that have evolved over time. Robicsek [2] reviewed the historic experimental and clinical work that has preceded present success with the technique of mitral valve replacement with homograft. Successful replacement of the mitral valve with homograft revolves around achieving secure fixation of the graft papillary muscles to the papillary muscles of the recipient. Different methods have been tried, including direct end-to-end suture of the tip of the donor muscle to the tip of the recipient muscle, supported by pledgets on the muscle or with sutures brought to the outside of the ventricle where the suture is supported. Acar and associates [1], on the other hand, used a different approach and attached the papillary muscles in side-by-side fashion. Yankah and associates [3] reported success using mitral valve replacement with homograft, calling attention to fact that "the locus minoris resistentiae" was at the papillary muscle union site and recommending reinforcing that site.
It was generally thought that heavy, strong suture material supported with a pledget would most likely be successful. Acar and associates [1] took a different approach and recommended multiple stitches of 5-0 monofilament suture to attach the papillary muscles, to create less trauma to the delicate myocardium of the papillary muscles of both patient and graft and to distribute tension more evenly over the entire surface of the papillary muscles. This approach is akin to methods used by the Lilliputians to subdue and immobilize the giant Gulliver in Thomas Swift’s classic "Gulliver’s Travels, A Voyage to Lilliput."
"When I awaked, it was just about day-light. I attempted to rise, but was not able to stir: for, as I happened to lie on my back, I found my arms and legs were strongly fastened on each side to the ground; and my hair, which was long and thick, tied down in the same manner. I likewise felt several slender ligatures across my body, from my arm pits to my thighs."
A prosthetic ring is used systematically in all patients [1]. The size of the ring chosen was based on the measurement of the anterior leaflet of the homograft. Annuloplasty has the following advantages: the size of the annulus can be adapted precisely to that of the homograft; the semirigid structure of the ring absorbs some of the mechanical stress exerted by ventricular contraction and alleviates traction that otherwise would be applied directly on the valvular suture line; and ring annuloplasty allows a greater surface of leaflet coaptation, thereby lowering the tension on the subvalvular apparatus.
In summary, the operative technique for replacement of the mitral valve with mitral homograft is described. The crux of the operation is secure side-by-side approximation of the papillary muscles of the graft to those of the recipient by using multiple stitches of fine monofilament suture. The repair is routinely supported by remodeling annuloplasty ring.
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Footnotes
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A video clip of this procedure can be viewed on the Internet at http://www.sts.org/section/atsvideo/
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References
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Acar C., Tolan M., Berrebi A., et al. Homograft replacement of the mitral valve: graft selection, technique of implantation, and results in forty-three patients. J Thorac Cardiovasc Surg 1996;111:367-380.[Abstract/Free Full Text]
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Robicsek F. Homograft replacement of the atrioventricular valves. J Heart Valve Dis 1996;5:607-622.[Medline]
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Yankah A.C., Sievers H.H., Lange P.E., Bernhard A. Clinical report on stentless mitral allografts. J Heart Valve Dis 1995;4:40-44.[Medline]
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Abstract
Introduction
