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Ann Thorac Surg 1998;66:849-852
© 1998 The Society of Thoracic Surgeons

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Original articles: Cardiovascular

Homograft replacement of mitral valve in children¹

^a Division of Cardiovascular and Thoracic Surgery, University of Illinois College of Medicine and Children’s Hospital of Illinois at St Francis Medical Center, Peoria, Illinois, USA
^b Section of Cardiology, Department of Pediatrics, University of Illinois College of Medicine and Children’s Hospital of Illinois at St Francis Medical Center, Peoria, Illinois, USA

Accepted for publication April 13, 1998.

Address reprint requests to Dr Plunkett, Pediatric Cardiac Surgery, Illinois Cardiac Surgery Associates, 515 NE Glen Oak, Suite 202, Peoria, IL 61603
e-mail: (plunk{at}ilcardiac.com)

	Abstract

Top Footnotes Abstract Introduction Patients and methods Results Comment References

 
Background. Recent reports have demonstrated successful early outcomes using mitral valve homografts in adults. We report our early results after homograft mitral valve replacement in 4 children with previous atrioventricular septal defects, previous placement of a prosthetic valve, and rheumatic valvular disease.

Methods. Between May 1996 and June 1997, 4 children (ages 5, 11, 13, and 15 years) underwent mitral valve replacement with cryopreserved mitral valve homografts at our institution. Preoperative echocardiography confirmed moderately severe to severe mitral regurgitation, stenosis, or both in all 4 patients.

Results. Successful homograft valve replacement was achieved in all 4 patients. Based on symptoms, physical examinations, and echocardiographic follow-up, all four homograft mitral valves are functioning well with normal hemodynamics. None of these patients are receiving warfarin. Follow-up has been limited to 10 months.

Conclusions. In children requiring mitral valve replacement, the use of mitral valve homografts offers advantages over prosthetic valves, such as the avoidance of complications associated with thrombosis and anticoagulation. Homograft mitral valve replacement is technically feasible in children with congenital and rheumatic heart disease and previous prosthetic valves.

	Introduction

Top Footnotes Abstract Introduction Patients and methods Results Comment References

 
The traditional approach for pediatric mitral valve operations, which are usually performed for congenital or rheumatic heart disease, has generally been to attempt mitral valve repair. If repair is unsuccessful, the valve is usually replaced with a bioprosthetic or mechanical valve. The use of bioprosthetic valves in children is generally associated with reduced durability and early valve failure. Although a mechanical mitral valve prosthesis is generally durable and functions well, there is a significant risk of morbidity and mortality owing to thrombosis or hemorrhagic complications resulting from anticoagulation. In addition, anticoagulation is often difficult to manage in children. In patients whose mitral valve cannot be repaired, the alternative to a mitral valve prosthesis is replacement with a cryopreserved homograft mitral valve. The potential advantages of using a homograft tissue valve include the avoidance of anticoagulation and preservation of the subvalvar apparatus and its role in ventricular function [1].

For the past several decades, experimental studies have shown the successful transplantation of homograft mitral valves in dogs and sheep using cryopreserved valves [2–5]. Initial attempts at homograft replacement of the mitral valve in humans were not generally successful. Early failures were attributed to inadequate preservation methods or operative technical problems. However, owing to an improved understanding of mitral valve function gained from experience in mitral valve reconstruction, as well as improved imaging techniques for preoperative assessment, there has been a resurgence of interest in this procedure [6]. Recently, the operative techniques have been modified and successful early results have been reported in adults [7–9]. Acar and others [6, 10–12] presented significant data illustrating mitral valve replacement using cryopreserved homograft mitral valves in patients presenting with acute endocarditis, rheumatic stenosis, systemic lupus endocarditis, and marasmic endocarditis. They concluded that in a particular group of patients, using mitral valve homografts significantly extended the limitations of mitral valve reparative surgery.

	Patients and methods

Top Footnotes Abstract Introduction Patients and methods Results Comment References

 
At our institution from May 1996 through June 1997, we performed homograft mitral valve replacements in 4 children (ages 5, 11, 13, and 15 years). Preoperatively, all patients were evaluated with two-dimensional Doppler echocardiograms to determine the need for mitral valve replacement and establish the dimensional and anatomic data necessary for proper selection of a mitral valve homograft. Two patients had previous atrioventricular defect repairs; one of these patient had previous placement of a prosthetic valve. Two patients had rheumatic valvular disease.

Patient 1
Patient 1 was a 13-year-old girl with an atrioventricular septal defect who at 11 months of age had undergone a complete repair. Four months later congestive heart failure developed secondary to severe mitral regurgitation, and the patient underwent mitral valve replacement with a 23-mm St Jude prosthesis valve (St Jude Medical, St Paul, MN). On postoperative day 9, her course was complicated by a cerebral hemorrhage while she was given warfarin therapeutic anticoagulation. She was subsequently managed on antiplatelet therapy (aspirin and dipyridamole) rather than warfarin.

At age 13 years, she presented with the sudden onset of congestive heart failure. A two-dimensional transthoracic echocardiogram revealed severe stenosis of the prosthetic mitral valve. She underwent mitral valve replacement using a 28-mm homograft mitral valve and a 28-mm Carpentier–Edwards annuloplasty ring (Carpentier; Baxter Healthcare Corp, Edwards Division, Santa Ana, CA), using the method of Acar and associates [10].

At operation, one of the leaflets of the prosthetic mitral valve was found to be thrombosed and immobile, resulting in severe valvular stenosis. The prosthetic valve was removed and the left ventricle was explored through the mitral valve annulus. The papillary muscles were identified and found to be located in normal positions within the ventricle. The papillary muscles were trimmed and the homograft papillary muscle was sutured to the patient’s papillary muscles. While this was being accomplished, a ventricular septal defect was identified anteriorly where the prosthetic valve had been removed and was repaired with a Gore-Tex patch (W.L. Gore & Assoc, Flagstaff, AZ). The homograft was then secured to the native annulus. Interrupted sutures were used anteriorly in the vicinity of the ventricular septal defect repair.

The patient had an uneventful postoperative course and an echocardiogram performed 7 months postoperatively (Table 1) revealed absence of mitral insufficiency and normal ventricular function. She is asymptomatic 10 months after her operation and is not receiving medication.

At operation, the homograft tissue was found to be partially detached from the native annulus. In addition, there was significant prolapse of the posterior leaflet. The posterior papillary muscle anastomosis was revised so that the homograft papillary muscle would sit farther within the ventricle. An incision was made between the native papillary muscle and the ventricle to allow for further insertion of the homograft papillary muscle. The homograft papillary muscle was then reanastomosed. This technique corrected the prolapse of the posterior leaflet. The annulus was reapproximated and a 24-mm Baxter Physio ring (Baxter Healthcare Corp, Santa Ana, CA) was placed. The defect in the ostium primum patch was then repaired.

The patient did very well postoperatively and was weaned from the ventilator without difficulty. Three months postoperatively, his activity, weight gain, and respiratory status were markedly improved. Echocardiography 6 months after the operation (see Table 1) demonstrated mild residual mitral stenosis with trace insufficiency.

Patient 3
Patient 3 was an 11-year-old girl with severe symptomatic mitral insufficiency due to previous rheumatic fever. The native mitral valve was found to be severely fibrotic and was not repairable. She underwent homograft replacement of the mitral valve using a 31-mm homograft valve and a 30-mm Carpentier–Edwards annuloplasty ring. She had an uncomplicated recovery and her symptoms dramatically improved. An echocardiogram 1 month after the operation (see Table 1) demonstrated normal left ventricular systolic function and no evidence of mitral insufficiency.

Patient 4
Patient 4 was a 15-year-old girl in whom severe symptomatic mitral insufficiency developed as a result of previous rheumatic fever. The native mitral valve was found to be severely fibrotic and not repairable. She underwent replacement of the mitral valve using a 32-mm homograft and a 28-mm Carpentier–Edwards ring. A postoperative transesophageal echocardiogram (see Table 1) revealed mild insufficiency and no evidence of stenosis.

Operative technique
A median sternotomy incision was made and aortic and bicaval cannulation was performed in the usual manner. The patient was placed on cardiopulmonary bypass and cooled to 25°C. After the aorta was cross-clamped, antegrade cardioplegia was delivered into the aortic root and retrograde cardioplegia was delivered via the coronary sinus. A standard left atriotomy incision was made through the interatrial groove and the patient’s mitral valve was inspected. If the valve was not repairable, it was excised and an appropriately sized cryopreserved homograft mitral valve (CryoLife, Atlanta, GA) was prepared. The homograft was sized using the insert measurements which accompany the packaged homograft. The valve was then matched to the valve measurement as determined by preoperative echocardiography. Both annular diameter in systole and chordal lengths from the papillary muscles to the valve leaflets were used to determine the appropriate homograft. The patient’s subvalvar anatomy was then identified and traction sutures were placed in each papillary muscle. After the homograft had thawed, the excess atrial and ventricular tissue from the annulus were debrided and the homograft papillary muscles were trimmed. With interrupted horizontal mattress sutures of 5-0 Prolene (Ethicon, Sommerville, NJ), the posterior papillary muscle of the homograft was sutured to the posterior papillary muscle of the recipient in a side-to-side approximation. The anterior papillary muscle of the homograft was sutured to the anterior papillary muscle of the patient in a similar manner. The circumference of the homograft valve was then sutured to the annulus using either an interrupted or running 5-0 Prolene suture. The annulus of the homograft was sized with a Carpentier–Edwards ring sizer using the distance between the fibrous trigones. The ring was then secured to the annulus using 2-0 or 3-0 Ti-cron (Davis & Geck, Wayne, NJ) annuloplasty sutures. A catheter was placed through the valve to serve as a left ventricular vent. The left atriotomy was repaired using a running suture of 3-0 Prolene. After adequate deairing, the vent was removed and the aorta was unclamped.

	Results

Top Footnotes Abstract Introduction Patients and methods Results Comment References

 
Successful homograft mitral valve replacements were achieved in all 4 patients. Doppler transesophageal and transthoracic echocardiograms obtained within 10 months of the operation have demonstrated successful early results, including significant reductions in mitral regurgitation, and dramatic reductions in pulmonary artery pressures. All patients had mild residual gradients identified across the homograft valves (see Table 1).

	Comment

Top Footnotes Abstract Introduction Patients and methods Results Comment References

 
Two cases of mitral valve replacement with homografts in children were previously reported: the youngest was 11 years old [7]. Although our series is limited, our experience suggests that the use of homograft mitral valves is advantageous and successful short-term results can be achieved in children. Based on symptoms, physical examinations, and echocardiographic follow-up, all four homograft mitral valves are functioning well with normal hemodynamics. None of our patients are receiving warfarin.

The main advantage of using homograft valves instead of mechanical prosthetic valves for mitral valve replacement in children is the avoidance of risks and problems associated with anticoagulation. Maintaining consistent levels of anticoagulation is difficult and often problematic in children and adolescents. The use of bioprosthetic tissue valves also avoids the need for anticoagulation, but reduced durability and early valve failure discourages the routine use of these valves in children. Another distinct advantage of using mitral homograft valves is the preservation of the subvalvar apparatus, which can contribute significantly to systolic function of the left ventricle [1].

Our series demonstrates that mitral valve homografts can be used in children with atrioventricular septal defects, children with previous prosthetic mitral valve replacements, and children with rheumatic valvular disease. The operative techniques for implantation of mitral valve homografts in children may vary from currently described adult techniques. Because the papillary muscle orientation and septal geometry are not normal in some patients with congenital heart defects, replacing these mitral valves with normal homografts may be technically more difficult. Moreover, the implantation of homograft mitral valves may be more complex in children with remotely inserted prosthetic valves owing to abnormal papillary muscle development. The preoperative transesophageal echocardiogram should identify the annular size of the native mitral valve during systole to select the size of the homograft to be implanted. The height of the chordal attachments to the anterior and posterior leaflets should be assessed as accurately as possible to size the homograft in a similar manner. The anatomy of the papillary muscles should be defined as clearly as possible preoperatively. A single papillary muscle anatomy or abnormal papillary muscle location and development may obviate the use of a homograft because of resultant interference with leaflet coaptation or valvular competence. Careful evaluation and proper selection of the homograft are essential for successful implantation and function of the valve in children.

Acar and colleagues [10] maintained that an annuloplasty ring is a crucial element of the operation. Patient 2 of our group supported this notion because initially an annuloplasty ring was not used to allow for annular growth potential. Severe residual mitral insufficiency developed, however, which was corrected by placement of an annuloplasty ring. The use of an annuloplasty seems necessary in these patients, and all 4 of our patients received a Carpentier–Edwards annuloplasty ring, ranging from 24 to 30 mm. In sizing the homograft valves and the Carpentier–Edwards annuloplasty rings, the valves may not be identical, because the measurements to determine valve size (annular diameter and chordal lengths) are not the determinants of the ring size. Smaller-sized annuloplasty rings may, however, lead to earlier valve replacement in certain patients.

In conclusion, successful early results of homograft mitral valve replacements in children are possible, particularly in those with previous atrioventricular septal defects or previous placement of mitral valve prostheses, and in those with rheumatic valvular disease. Based on previous clinical experience using aortic and pulmonary valve homografts, there is likely to be limited growth potential with mitral homografts. Furthermore, there is a distinct possibility that these homografts may actually fibrose and develop calcifications over an extended period of time. Although our early results are encouraging and the use of homograft mitral valves in children offers potential advantages over prosthetic valves, long-term follow-up is clearly needed to determine the durability and long-term function of homograft mitral valves in children.

	Footnotes

Top Footnotes Abstract Introduction Patients and methods Results Comment References

 
This article has been selected for the open discussion forum on the STS Web site: http://www.sts.org/annals

	References

Top Footnotes Abstract Introduction Patients and methods Results Comment References

 

1. David T.E., Uden T.E., Strauss H.D. The importance of the mitral apparatus in left ventricular function after correction of mitral regurgitation. Circulation 1983;68(Suppl 2):76-82.[Free Full Text]
2. Rastelli G.C., Berghuis J., Swan H.J.C. Evaluation of function of mitral valve after homotransplantation in the dog. J Thorac Cardiovasc Surg 1965;49:459-474.
3. Hubka M., Siska K., Brozman M., Holec V. Replacement of mitral and tricuspid valves by mitral homograft. J Thorac Cardiovasc Surg 1966;51:195-204.[Medline]
4. Revuelta J.M., Cagigas J.C., Bernal J.M., Val F., Rabasa J.M., Lequerica M.A. Partial replacement of the mitral valve by homograft: an experimental study. J Thorac Cardiovasc Surg 1992;104:1274-1279.[Abstract]
5. Vliet P.D., Titus J.L., Berghuis J., et al. Morphological features of homotransplanted canine mitral valves. J Thorac Cardiovasc Surg 1965;49:504-510.
6. Acar C., Farge A., Ramsheyi A., Chachques J.-C., et al. Mitral valve replacement using a cryopreserved mitral homograft. Ann Thorac Surg 1994;57:746-748.[Abstract]
7. Dossche K., Vanermen H., Wellens F. Partial mitral valve replacement with a mitral homograft in subacute endocarditis. Thorac Cardiovasc Surgeon 1994;42:240-242.[Medline]
8. Kumar A.S., Trehan H. Homograft mitral valve replacement of the mitral valve—a case report. J Heart Valve 1994;3:473-475.
9. Pomar J.L., Mestres C.A. Tricuspid valve replacement using a mitral homograft: surgical technique and initial results. J Heart Valve Dis 1993;2:125-128.[Medline]
10. 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]
11. Acar C., Gaer J., Chauvaud S., Carpentier A. Technique of homograft replacement of the mitral valve. J Heart Valve Dis 1995;4:31-34.[Medline]
12. Acar C., Iung B., Cormier B., et al. Double mitral homograft for recurrent bacterial endocarditis of the mitral and tricuspid valves. J Heart Valve Dis 1994;3:470-472.[Medline]

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