Ann Thorac Surg 2008;86:1033-1035. doi:10.1016/j.athoracsur.2008.01.017
© 2008 The Society of Thoracic Surgeons
How To Do It
A Novel Technique of Supra-Annular Mitral Valve Replacement
Si Chan Sung, MDa,*,
Yun Hee Chang, MDa,
Hyoung Doo Lee, MDb,
Jong Soo Woo, MDc
a Department of Thoracic and Cardiovascular Surgery, Medical Research Institute, Busan, South Korea
b Department of Pediatrics, Pusan University National Hospital, Busan, South Korea
c Department of Thoracic and Cardiovascular Surgery, Dong-A University Hospital, Busan, South Korea
Accepted for publication January 4, 2008.
* Address correspondence to Dr Sung, Department of Thoracic and Cardiovascular Surgery, Medical Research Institute, Pusan National University Hospital, 1-10, Ami-dong, Seo-gu, Busan, 602-061, South Korea (Email: scsung21{at}hanmail.net).
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Abstract
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We describe a new technique of mitral valve replacement in an 11.5-month-old, 5.5 kg baby whose native mitral annulus was only 14 mm. We successfully implanted a 16-mm mechanical valve in the supra-annular position by sewing it into a short polytetrafluoroethylene graft that was then sutured to the native annulus.
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Introduction
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Mitral valve replacement in small infants is very difficult when the smallest available prosthetic valve is too large for the native mitral annulus. When sufficiently small mechanical valves are not available for infants, and the urgency of disease presentation does not allow adequate time for the infant heart to grow, a method must be used in which a prosthesis can be accommodated despite the valve–annulus size mismatch. An infant with a history of aortic coarctation repair underwent a supra-annular mitral valve replacement with a 16-mm mechanical valve (CarboMedics prosthetic valve; Carbomedics Inc, Austin, TX) at the age of 5.5 months after a failure of an attempted valve repair. The patient continued to have heart failure because a substantial fraction of the left ventricular ejection volume flowed retrogradely into the sizable portion of the left atrium lying between the prosthesis and the mitral valve annulus, causing systolic expansion of the atrium. This valve also compressed and obstructed the left main bronchus. The mechanical valve was replaced by a porcine valve modified from a 14-mm extracardiac valved conduit (Capentier-Edwards bioprosthetic valved conduit; Edwards Lifesciences LLC, Santa Ana, CA), but the valve struts caused left ventricular outflow obstruction with a 40 to 50 mm Hg pressure gradient. This outflow obstruction progressed with time causing significant left ventricular hypertrophy, and we were again forced to replace the valve at the age of 11.5 months and at a body weight of 5.5 kg.
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Technique
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The smallest commercially available mitral mechanical valve in our country is 16 mm. At operation, the measured diameter of the patient's mitral annulus was 14 mm. The operation was carried out using cardiopulmonary bypass at moderate hypothermia. Prior to making a skin incision, we prepared the mechanical valve to be implanted at the small annulus. We inserted the valve metal housing (16-mm ATS mitral valve; ATS Medical Inc, Minneapolis, MN) into the short-segment polytetrafluoroethylene tube graft (18 mm in diameter, 8 mm in length; W. L. Gore & Associates, Flagstaff, AZ) and attached the graft to the sewing ring of the valve with a continuous polytetrafluoroethylene suture (W. L. Gore & Associates) (Figs 1A and 2). The previous valve was removed and 14 pledgeted, everting, horizontal mattress sutures were placed in the mitral valve annulus. The outflow margin of the polytetrafluoroethylene tube graft was then threaded onto the valve sutures (Fig 1B). Short longitudinal incisions were then made in the polytetrafluoroethylene tube graft between the two limbs of each mattress suture to allow the tube to conform to the smaller annulus as the sutures were tied (Figs 1B and 1C). The motion of the mechanical valve leaflets was not hampered by the circumferentially narrowed subvalvular tube graft. The patient was weaned from bypass without any problems. Transesophageal echocardiography showed good functioning of the mechanical mitral valve without left ventricular outflow obstruction. Warfarin anticoagulation has been used to maintain the International Normalized Ratio between 2 and 3. Transthoracic echocardiography at 4 months after the operation showed normal ventricular function without any significant mechanical valve stenosis, regurgitation, or paravalvular leak (Fig 3).
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Fig 1. Schematic drawings of a novel technique of supra-annular mitral valve replacement. (A) The valve metal housing was inserted into the short-segment polytetrafluoroethylene (PTFE) tube graft, which was then attached to the sewing ring of the valve with a continuous PTFE suture. (B) The outflow margin of the PTFE tube graft was then threaded onto the valve sutures (B, C) and short longitudinal incisions were made in the PTFE tube graft between the two limbs of each mattress suture to allow the tube to conform to the smaller annulus as the sutures were tied.
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Fig 2. Photograph of the 16-mm mechanical mitral valve attached to the polytetrafluoroethylene tube graft.
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Fig 3. Postoperative two-dimensional echocardiographic scan showing supra-annular location of mechanical mitral valve (arrow). (AO = aorta; LA = left atrium; LV = left ventricle; RV = right ventricle.)
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Comment
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Valve replacement in the small baby is still challenging. A mechanical or bioprosthetic valve of the appropriate size for the small mitral valve is not commercially available. The 16-mm mechanical valve is the smallest valve available in our country.
Supra-annular implantation of the mechanical valve has been used to compensate for the size mismatch between annulus and prosthesis in pediatric patients with a small mitral annulus [1, 2]. However, unless the valve is implanted near the native mitral annulus, the large volume of ventricularized atrium can lead to heart failure through a pathophysiology similar to severe mitral regurgitation. We think that this phenomenon is unavoidable in patients with a large valve–annulus size mismatch. Implantation of a pulmonary autograft in the mitral position, as described by Ross [3], could be another option for the small mitral valve. However, this technique is technically demanding and has no growth potential. It also requires a right ventricular outflow conduit that is an additional big problem for small babies.
With conventional valve suturing techniques, the implantation of a 16-mm mechanical valve in the mitral position requires an annular diameter measured in the arrested heart of 20 mm. Our novel technique enables the implantation of a 16-mm mechanical valve into a 14-mm mitral valve annulus.
Two advantages of our technique are its technical reproducibility and its absence of direct insertion of a rigid mechanical ring into a small and friable annulus. We believe that our technique can also be applied in the adult patient with a small mitral annulus or left ventricular outflow obstruction.
One theoretical disadvantage of this technique, in addition to need for Coumadin (Warfarin; Bristol-Myers Squibb, Princeton, NJ) with a mechanical valve, is the creation of stagnant flow in the recess space around the valve in the left atrium, which might enhance the probability of left atrial thrombus formation. Precise control anticoagulation therapy should ameliorate this risk. Our patient has not had a thrombotic complication so far, although a long-term follow-up study is mandatory.
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Acknowledgments
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We appreciate the efforts of Dr Hon Chi Suen in the preparation of this article.
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References
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- Schaffer MS, Clarke DR, Campbell DN, Madigan CK, Wiggins JW, Wolfe RR. The St. Jude Medical cardiac valve in infants and children: role of anticoagulation therapy J Am Coll Cardiol 1987;9:235-239.[Abstract]
- Kadoba K, Jonas RA, Mayer JE, Castaneda AR. Mitral valve replacement in the first year of life J Thorac Cardiovasc Surg 1990;100:762-768.[Abstract]
- Ross DN. Replacement of aortic and mitral valves with a pulmonary autograft Lancet 1967;290:956-958.
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Abstract
Introduction
