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Ann Thorac Surg 1997;64:593-594
© 1997 The Society of Thoracic Surgeons
Department of Surgery, Dean Medical Center, 1313 Fish Hatchery Rd, Madison, Wi 53715
To the Editor:
Esper and associates [1] recently described 2 patients with late complications of retained mitral valve tissue after mitral valve replacement. In their second patient, left ventricular outflow tract obstruction developed with a peak gradient of 100 mm Hg due to anterior displacement of retained native anterior leaflet tissue after mitral valve replacement with a bioprosthesis. The patient was successfully reoperated on by removing the porcine bioprosthesis via a left atriotomy approach, resecting the anterior and most of the posterior leaflet, and replacing the valve with a St. Jude mitral prosthesis. Esper and associates cautioned that, although chordal preservation in mitral valve operations is important in maintaining left ventricular contractile function, performing mitral valve implantations "over unresected or not carefully mobilized mitral leaflets" was not indicated.
Their experience brought to our mind an 80-year-old female patient who underwent combined mitral valve replacement along with redo coronary artery revascularization, with retention of the entire native anterior mitral valve leaflet as well as the nonflail portion of the posterior leaflet of the mitral valve.
Approximately 1 week postoperatively, while the patient was awaiting discharge, recurrent congestive failure developed. Echocardiography demonstrated left ventricular outflow tract obstruction with a gradient up to 100 mm Hg caused by retained native anterior mitral leaflet tissue. The no. 29 bioprosthesis functioned satisfactorily without insufficiency, and the patient had moderate depression of her left ventricular ejection fraction.
The patient was returned to the operating room on the 12th postoperative day and, after a repeat sternotomy, was placed back on cardiopulmonary bypass with blood cardioplegic ischemic arrest. The aorta was opened with an incision below the proximal anastomoses from the coronary artery revascularization, and the normal native aortic valve leaflets were gently retracted. The anterior leaflet was grasped and an incision made in its midportion, several millimeters away from the annulus. When we passed through the leaflet, the stent of the bioprosthesis was immediately evident. With gentle retraction of the lower portion of the anterior leaflet, the incision was carried just below the annulus on each side to the mitral valve commissure, and the anterior leaflet then separated from the posterior leaflet at the commissures. The leaflet now was attached only by its chordae to the papillary muscle, and these were severed at their insertion and the specimen submitted. The aortotomy was closed, deairing performed, and the patient weaned from cardiopulmonary bypass without difficulty. The patient's postoperative echocardiogram demonstrated satisfactory bioprosthetic function and no significant subaortic gradient. Her subsequent recovery was uneventful.
Given this limited experience, we concur with Esper and associates that preservation of unresected anterior mitral leaflet tissue during mitral valve replacement may lead to left ventricular outflow tract obstruction in selected individuals and have abandoned this practice. In the event reoperation for such a patient becomes necessary, and if the mitral prosthesis is otherwise satisfactory, a transaortic approach through the native aortic valve, which does not require removal of the mitral prosthesis, may be possible for removal of the retained anterior leaflet without the additional operative risk of re-replacement of the mitral valve.
Reference
Division of Cardiac Surgery, University of Chicago Hospitals, Pritzker School of Medicine, 5841 S Maryland Ave, Mc5040, Chicago, Il 60637
Reply To the Editor:
The experience of Cowgill and Adamick reiterates the importance of carefully resecting anterior mitral leaflet tissue or performing chordal transfer of the unsupported portion of the anterior mitral leaflet before implantation of mitral valve prostheses. The routine use of this technique should avoid inflow or outflow tract ventricular obstruction in the postoperative period as demonstrated in our recent report. We were delighted with the proposed transaortic approach for resecting the mitral valve leaflet to relieve left ventricular outflow tract obstruction. However, as Cowgill and Adamick alluded, this route is feasible only if the device is otherwise satisfactorily implanted and if there is no other associated pathology. In 1 case encountered by us, left ventricular outflow tract obstruction was associated with a perivalvular mitral leak. In that situation, the transatrial approach should be used.
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