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J Thorac Cardiovasc Surg 1998;115:1219-1222
© 1998 Mosby, Inc.
BRIEF COMMUNICATIONS |
Boston, Mass.
From the Departments of Cardiac Surgery and Cardiology, Children'sHospital, and Department of Pediatrics, Harvard Medical School, Boston, Mass.
Received for publication Feb. 11, 1997. Accepted for publication Dec. 4, 1997. Address for reprints: Richard A. Jonas, MD, Children's Hospital,Department of Cardiac Surgery, 300 Longwood Ave., Boston, MA 02115.
Tunnel subaortic stenosis is often a component of Shone's syndrome andtherefore may be associated with mitral stenosis and hypoplasia of the mitralanulus.
1 It is also often,although not always, associated with valvular aortic stenosis. Patch enlargementof the ventricular septum, which forms the anterior wall of the left ventricularoutflow tract, with preservation of the aortic anulus and valve ("modifiedKonno procedure"), is a useful procedure for management of tunnelsubaortic stenosis when the aortic anulus and mitral anulus are of adequatesize. However, when the mitral anulus is hypoplastic and must be enlarged toaccommodate an adequate-sized prosthesis, an alternative approach can be used,as we describe in this report.
Method.
Moderately hypothermic bypass is established with the arterial cannula inthe ascending aorta and venous return through a right-angled cannula in the superiorvena cava and a straight cannula in the inferior vena cava. After the aorta hasbeen crossclamped, cardioplegic solution infused, and caval tourniquetstightened, a vertical incision is made in the right lateral aspect of theascending aorta (Fig. 1A). The incision is directed toward thecommissure between the left and noncoronary cusps. An oblique incision is madein the right atrial free wall and is extended across the roof of the rightatrium, across the atrial septum, and into the left atrium so as to meet theaortic incision. The atrial septal incision is extended inferiorly to theinferior margin of the left atrium. The stenotic and hypoplastic mitral valve isexcised. The aortic incision is carefully extended across the non-leftcommissure and completely through the subaortic fibrosa (Fig. 1B). The subaortic area is now completely openfor inspection. Any fibrous membranelike tissue can be excised with particularcare in the region of the membranous septum to avoid injury to the conductionbundle. A triangular patch of polytetrafluoroethylene is sutured, as shown inFig. 1C, to reconstitute the aorticvalve and to supplement the mitral anulus. The apex of the triangle is at thecommissure of the aortic valve, and the broad base of the patch will form partof the mitral anulus. Autologous pericardium treated with glutaraldehyde isuseful to extend the aortic valve cusps and to increase the area of aorticleaflet coaptation. A mitral prosthesis is sutured to the base of the prostheticpatch, as well as to the remainder of the mitral anulus. The length of thebase of the prosthetic patch determines the degree to which the mitral anulus isenlarged. The atrial septum and the roof of the left atrium are closedwith apolytetrafluoroethylene patch. The right atriotomy and aortotomy are closed,supplemented with patches if necessary. The heart is deaired in the usualfashion.
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PATIENT 1. A 15-year-old girl had beennoted at 7 years of age to have a primum atrial septal defect with severesubaortic stenosis. However, she was not referred for surgery until 9 years ofage. At that time the mitral valve, which was the primary cause of the outflowtract obstruction, was resected and replaced with a 23 mm St. Jude Medicalprosthesis (St. Jude Medical, Inc., St. Paul, Minn.). The primum atrial septaldefect was closed with a pericardial patch. Postoperatively, complete heartblock developed and necessitated pacemaker implantation. At the time ofpacemaker generator replacement, transesophageal echocardiography revealed a 100mm Hg gradient across the left ventricular outflow tract and mild aorticregurgitation. Cardiac catheterization showed a 65 mm Hg gradient, whichappeared to be due to a tunnel extending from the aortic valve to the level ofthe mitral prosthesis. A 4 to 6 mm Hg mean gradient was detected across themitral prosthesis.
At operation the aortic valve was noted to be tricuspid, although theleft cusp was half the size of the noncoronary cusp. The technique describedherein was applied. The mitral valve was again replaced with a 25 mm St. JudeMedical prosthesis. A collagen-impregnated Dacron patch was used to enlarge thesubaortic area and mitral anulus. The non-left aortic commissure of the aorticvalve was reconstituted. In this first patient, autologous pericardial leafletextenders were not used in the aortic valve reconstruction. The child toleratedthe procedure well and required no inotropic support. Intraoperativetransesophageal echocardiography revealed a residual Doppler gradient of 25 mmHg across the left ventricular outflow tract, no change in the mild aorticregurgitation present before the operation, and a mean gradient of 5 mm Hgacross the new mitral prosthesis. Both leaflets of the prosthesis moved freely.
At most recent follow-up 4 years after the operation, a 25 mm Hg gradientacross the left ventricular outflow tract and moderate aortic regurgitation weredetected by continuous-wave Doppler echocardiography. Inflow velocities were notsuggestive of significant stenosis of the mitral prosthesis. Symptomatically,she is well and has recently begun attending college.
PATIENT2. A 12-year-old boy had been noted inthe neonatal period to be in congestive failure. Cardiac catheterizationrevealed mitral stenosis resulting from a mitral arcade. When the boy was 7weeks of age the mitral valve was replaced with a 17 mm Björk-Shileyprosthesis (Shiley, Inc., Irvine, Calif.). At 14 months the prosthesis wasreplaced with a 17 mm prosthesis because of pannus ingrowth. When the boy was 6years of age a third prosthetic valve replacement was performed with a 19 mm St.Jude Medical prosthesis. A progressive left ventricular outflow gradient wasnoted to develop after the operation. At catheterization when the boy was 11years old, there was a 40 mm Hg gradient across the left ventricular outflowtract and a 10 mm Hg mean gradient across the mitral prosthesis. At operationthe aortic valve was noted to be tricuspid, with some thickening of the leafletsbut no commissural fusion. The subaortic outflow area was tunnel-like. Leftventricular outflow obstruction was exacerbated by projection of the mitralprosthesis into the outflow tract.By means of the technique described herein, the subaortic area was laidopen. The mitral prosthesis was excised and was replaced with a 21 mm St. JudeMedical prosthesis. After reconstitution of the aortic valve at theleft-noncommissure, a leaflet extender of autolo-gous pericardium treated withglutaraldehyde was sutured to the free edge of the noncoronary cusp to improveleaflet apposition. The child tolerated the procedure well and required noinotropic support. By simultaneous pressure catheter measurement there was a 10mm Hg residual outflow tract gradient and by echocardiography trivial to mildaortic regurgitation. No gradient could be measured across the mitralprosthesis.
At the most recent follow-up catheterization 2 years after the operation,there was a 25 to 30 mm Hg gradient across the left ventricular outflow tractand mild to moderate aortic valve regurgitation. The mitral valve area wascalculated at 1.3 cm2/m2. Pulmonary artery pressure was onethird systemic pressure. He is free of symptoms and in sinus rhythm.
Discussion.
Although several procedures have been described for enlargement of theaortic anulus, such as the Nicks, Manougian, and Konno procedures, 2 there are very few options forenlargement of the mitral anulus. This is because of the presence of thecircumflex coronary artery, membranous ventricular septum, and conduction bundleand the aortic valve, which encircle the mitral anulus. In the past we haveperformed supraannular mitral valve replacement when the mitral anulus has beeninadequate to accept an adequate-sized mitral prosthesis. Supraannular mitralvalve replacement involves insertion of the prosthesis entirely within the leftatrium, thereby creating a ventricularized portion of the left atrium. Althoughthe early results of this procedure were encouraging, the late survival and latehemodynamic results have been disappointing. 3 The technique described in thisreport provides an alternative to supraannular mitral valve replacement and isparticularly appropriate in the setting of tunnel-like subaortic stenosis.
Rastan 4 and othershave described a procedure in which both the aortic and mitral anuli areenlarged with a single patch, but this procedure necessitates replacement ofboth valves. In growing children, we believe strongly in the principle ofminimizing the number of prostheses inserted. Therefore, even in a childwho has previously had a mitral valve replacement, we believe it is a worthwhilegoal to preserve the native aortic valve.
The modified Konno procedure has demonstrated the feasibility ofenlarging the immediate subaortic region without the need for replacement of theaortic valve. We have applied the same principle in the technique described inthis report. The patch that enlarges the mitral anulus is brought into thecommissure between the left and noncoronary cusps of the aortic valve, therebyalso enlarging the subaortic area. Although this procedure has the risk ofcausing some degree of aortic regurgitation and the ultimate need for aorticvalve replacement, nevertheless in a growing child it is useful to defer valvereplacement. A tolerable degree of aortic regurgitation will serve to acceleratethe growth of the aortic anulus. Aortic valvuloplasty techniques such as the useof leaflet extenders with autologous pericardium can limit the degree of aorticregurgitation to a tolerable degree. If an acceptablereconstruction of theaortic valve cannot be achieved, placement of a pulmonary autograft in theaortic position sutured to the patch enlarging the mitral anulus would seem tobe a reasonable option.
References
This article has been cited by other articles:
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  J. M. Caffarena, M. Rovirosa, and J. M. Gomez-Ullate Mitral annular and left ventricular outflow tract enlargement with autologous tissue: Extended application of the Ross-Konno procedure J. Thorac. Cardiovasc. Surg., February 1, 2003; 125(2): 423 - 425. [Full Text] [PDF]
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 M. Jahangiri, I. A. Nicholson, P. J. del Nido, J. E. Mayer, and R. A. Jonas Surgical management of complex and tunnel-like subaortic stenosis Eur J Cardiothorac Surg, June 1, 2000; 17(6): 637 - 642. [Abstract] [Full Text] [PDF]
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