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Ann Thorac Surg 2005;80:642-646
© 2005 The Society of Thoracic Surgeons

Original article: Cardiovascular

Redo Mitral Valve Replacement in Children

Kirk R. Kanter, MD * , Joseph M. Forbess, MD, Paul M. Kirshbom, MD

Division of Cardiothoracic Surgery, Department of Surgery, Emory University School of Medicine, and Children’s Healthcare of Atlanta at Egleston, Atlanta, Georgia

Accepted for publication February 14, 2005.

* Address reprint requests to Dr Kanter, Division of Cardiothoracic Surgery, Emory University School of Medicine, 1365 Clifton Road, Atlanta, GA 30322 (Email: kkanter{at}emory.edu).

Presented at the Fifty-first Annual Meeting of the Southern Thoracic Surgical Association, Cancun, Mexico, Nov 4–6, 2004.


   Abstract
Top
 Abstract
Introduction
 Patients and Methods
 Results
 Comment
 Discussion
 References
 
BACKGROUND: Despite excellent results with current techniques of mitral valve repair, some children still require mitral valve replacement (MVR). Of necessity, a certain percentage of these children need valve rereplacement (redo MVR).

METHODS: Of 82 MVRs at our institution since 1988, 22 were redo MVRs in 21 children aged 1.4–21 years (mean 9.8 ± 5.6 years). Interval from initial MVR was 1 month to 18 years (mean 5.8 ± 4.9 years). Reoperation indication was primarily stenosis in 13 (usually pannus formation), regurgitation in 4, valve thrombosis or embolism in 4, and endocarditis in 1. The initial valve was mechanical in 18 and xenograft in 4.

RESULTS: During redo MVR, 8 of 22 (36%) patients had additional procedures including left ventricular outflow tract obstruction relief or aortic valve replacement in 4 and tricuspid valve repair in 2. The new mitral valve was mechanical in 20 and xenograft in 2. Median valve size increased from 21 mm to 25 mm although 7 valves were not upsized on rereplacement (average valve size increase was 3.3 ± 1 mm). Only 2 patients (9%) needed a new pacemaker. There were no hospital deaths. Six children developed end-stage heart failure and underwent successful cardiac transplantation 3 to 32 (mean 12.1 ± 10.0) months, postoperatively. On follow-up of 1 month to 7.7 years (mean 2.5 ± 2.3 years) there has been only one late death of an unrecognized coronary artery anomaly.

CONCLUSIONS: Redo MVR in children can be performed safely with low morbidity and mortality. A larger prosthesis can often be placed in these children. A surprisingly high percentage of patients eventually require transplantation, perhaps reflecting unnecessary delay in referral for redo MVR.


   Introduction
Top
 Abstract
 Introduction
Patients and Methods
 Results
 Comment
 Discussion
 References
 
The current standard of care for treatment of children with mitral valve abnormalities is to attempt a mitral valve repair. Unfortunately there are certain children in whom a successful mitral valve repair cannot be accomplished, and therefore will need mitral valve replacement (MVR). As times goes on, some of these children will require repeat mitral valve replacement due to a variety of reasons such as outgrowth of the valve, deterioration of a bioprosthetic valve, or pannus formation. As this population of children undergoing repeat mitral valve replacement grows, we felt that it would be useful to review our experience with repeat mitral valve replacement in children to determine its safety and efficacy. This is the basis of our report.


   Patients and Methods
Top
 Abstract
 Introduction
 Patients and Methods
Results
 Comment
 Discussion
 References
 
Patient Population
Since 1988, of 82 mitral valve replacements performed at our institution, there were 22 repeat mitral valve replacements in 21 children. Children undergoing repeat combined aortic and mitral valve replacements were excluded from this report. The clinical characteristics of the patients including the initial diagnosis are shown in Table 1. The average age at the time of first mitral valve replacement was 3.9 ± 3.0 years. The age at redo mitral valve replacement was 9.8 ± 5.6 years. The interval from initial mitral valve replacement to redo mitral valve replacement ranged from one month to 18 years (mean 5.8 ± 4.9 years). The indication for reoperation was mitral stenosis in 13 (either outgrowth of the valve or pannus formation), mitral regurgitation in four, valve thrombosis or embolism in four, and endocarditis in one. The initial mitral valve replacement was bioprosthetic in four and mechanical in 18. Because our preference for mechanical valve choice changed over time, a variety of mechanical valves were utilized including Bjork-Shiley (Shiley, Inc, Irvine, CA), St. Jude (St. Jude Medical, St. Paul, MN), and Carbomedics (Carbomedics, Austin, TX) mechanical valves.


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  		Table 1. Patient Characteristics
 
Patient follow-up was determined by periodic cardiology visits, by review of hospital and clinic records, as well as our cardiac surgery database. This retrospective study was approved by the Institutional Review Board of Emory University School of Medicine.


   Results
Top
 Abstract
 Introduction
 Patients and Methods
 Results
Comment
 Discussion
 References
 
At the time of redo mitral valve replacement (MVR), eight of the 22 operations (36%) had additional procedures as shown in Table 2. These procedures included relief of left ventricular outflow tract obstruction or a new aortic valve replacement in four patients and tricuspid valve repair or annuloplasty in two patients.


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  		Table 2. Concomitant Procedures (n = 8)
 
Mechanical valves were used for all redo MVRs except for two patients who received bioprosthetic valves. Both of these patients originally had mechanical valves. One had ongoing severe hemolysis from her mechanical prosthetic valve; it was felt that she would benefit from replacement with a bioprosthetic valve. The other patient was the only patient in the series who received three mitral valves. She was born with an unbalanced complete atrioventricular septal defect with a mildly hypoplastic left ventricle. Initially she underwent a successful biventricular repair but two months later developed severe mitral stenosis. She initially underwent supraannular replacement with a 17-mm St Jude mechanical valve. Five and a half months later she thrombosed one of the leaflets of the valve and again underwent supraannular rereplacement of her mitral valve with a 17-mm St Jude valve. One month after this she again had evidence of clotting of one of her valve leaflets. It was felt that she would have ongoing problems with thrombosis with another mechanical valve; therefore, a second redo MVR was performed with a 19-mm bioprosthetic valve in the supraannular position.

Fifteen of the 22 redo mitral valves were larger in size than the original MVR (Fig 1 ). The median valve size of the original valve replacement was 21 mm and size of the redo MVR was 25 mm for an average valve size increase of 3.3 ± 3.1 mm. Seven valves that did not have an increase in size at the time of redo MVR. In four instances, this was due to redo valve replacement within a year of the initial operation. For two of the other three instances, the original valve was 31 mm in size as was the new mitral valve.



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  		Fig 1. Valve size in millimeters plotted against age in years at each valve replacement. Each line represents a single patient with the left side of the line representing the age and prosthetic valve size at the time of initial mitral valve replacement (MVR) and the right side of each individual line representing the age and prosthetic valve size at the time of the redo MVR.

 
In only two of the 22 redo MVRs was there a new onset of complete atrioventricular block requiring placement of a new pacemaker. One of these children had a modified Konno procedure for relief of recurrent subaortic obstruction during the same operation. One other child who had normal atrioventricular conduction had prophylactic placement of a biventricular pacemaker system because of severe preoperative ventricular dysfunction. Interestingly, two patients had placement of pacemakers after hospital discharge for redo MVR. One had a pacemaker placed six weeks postoperatively for an out of hospital syncopal episode. An electrocardiogram showed rare episodes of second-degree heart block and, therefore, a pacemaker was placed although the relationship between the syncope and heart rate were never clearly defined. The other patient had a pacemaker placed seven months later to allow higher amiodarone dosing for arrhythmias related to her end-stage cardiomyopathy.

All patients survived hospitalization in this series. On follow-up from one month to 7.7 years (mean 2.5 ± 2.3 years), there was one late death in a patient with an unsuspected coronary artery anomaly. This was the patient who had unexplained syncope with rare episodes of second-degree heart block for which a pacemaker had been placed after hospital discharge from her redo MVR. Six patients developed severe heart failure and underwent successful cardiac transplantation between 2.5 months and two and one-half years after redo MVR (mean 12.1 ± 10.2 months). All patients had a normally functioning prosthetic heart valve at the time of transplantation.


   Comment
Top
 Abstract
 Introduction
 Patients and Methods
 Results
 Comment
Discussion
 References
 
Although it is axiomatic that repair of the mitral valve in a child is superior to valve replacement, a certain percentage of these children will require prosthetic MVR. It is well known that xenograft valves in children will deteriorate with time with almost inevitable need for rereplacement [1, 2]. Others have reported rates for repeat MVR in patients with mechanical valves of 2.3% to 2.5% per patient-year in older children [3, 4]. Reports of ten-year freedom from valve failure or reoperation in children after mitral valve replacement ranges from 50% to 56% [5, 6]. Even with the newer bileaflet mechanical valves, Masuda and colleagues [7] reported a freedom from redo MVR at 15 years of only 54%. A recent multiinstitutional study from the Pediatric Cardiac Care Consortium [8] suggests that the median longevity for a prosthetic mitral valve in children aged five years or less undergoing mitral valve replacement is 12.7 years. This means that half of the mitral valves will be replaced by 12.7 years after initial MVR. We recently reported our 20-year experience with mitral valve replacement in children and found 12 percent who needed repeat MVR [9]. As results with initial mitral valve replacement improve, the proportion of children surviving to eventually require repeat MVR therefore will increase with time. We felt that it was reasonable to review our own series to determine the safety and efficacy of redo MVR at our institution.

Even after the first report of a redo MVR in a child by Robinson and Young in 1966 [10], there was concern that this reoperation would carry a high operative morbidity and mortality. It was felt that once the mitral valve annulus was "fixed" by the prosthetic valve sewing ring with initial placement of the valve, subsequent valve rereplacements would mandate the placement of a small prosthesis since, in growing children, there are no easily applied surgical techniques for enlarging the mitral annulus as there are for the aortic annulus. Most reports on this topic have been single institution series with low numbers (10 or fewer) of patients [2, 5–7, 11–16]. Although all of these series are small, in general, the mortality rates with redo MVR have been low. Furthermore, many of these series showed the feasibility of increasing the prosthetic valve size with redo MVR.

There have, however, been two single institution studies with relatively large numbers of MVRs. A report by Antunes [1] from Johannesburg, South Africa, reported 135 bioprosthetic MVRs in children, of which 62 were redo MVRs. There was a 17.2% early mortality with redo MVR. This series, however, consisted mostly of older children (mean age 13.7 years) operated on for rheumatic heart disease. Since the initial MVR was uniformly a bioprosthetic valve, the reoperation rate was high. The high operative mortality was attributed to delayed reoperation in that many of their patients underwent urgent or emergent reoperation. Alternatively, this high early mortality could be impacted by underlying myocardial dysfunction secondary to long standing valve disease or rheumatic heart disease.

A more recent study from Arkansas Children’s Hospital [17] reported 23 redo MVRs in 18 patients with no early deaths, but with three late deaths and five transplants. A multiinstitutional study [8, 18] from the Pediatric Cardiac Care Symposium reported on 32 redo MVRs with two early deaths and two late deaths.

The current series demonstrates that redo MVR can be done quite safely since there were no operative deaths in this series. In the early days of valve surgery, it was feared that placing a fixed sewing ring in the mitral annulus of a child would consign that child to a fixed annulus so that subsequent valve replacements would always be of similar size. We were able to upsize the redo mitral valve prosthesis in 15 of our 22 reoperations (Fig 1) with a median valve size increase from 21 mm to 25 mm. Despite increasing the valve size, only two patients in this series developed new onset of complete atrioventricular block requiring a pacemaker. The ability to increase the size of the mitral valve prosthesis at the time of rereplacement has been observed by others in smaller series [5, 6, 12–15, 17, 18].

Of concern is the fact that six of our 21 patients required cardiac transplantation within two and one half years of redo MVR. Two of these patients had cardiomyopathy before their MVR and the valve was replaced in hopes of delaying transplantation. The remaining four, however, appeared to be suffering from the ravages of ongoing valvular congenital heart disease. Eble and colleagues [17] from the Arkansas Children’s Hospital also found a high incidence of children requiring transplantation after redo MVR. Van Doorn and colleagues [6] from Great Ormond Street in London have shown that 41% of children after MVR have echocardiographic wall motion abnormalities, which certainly can contribute to ventricular dysfunction. It is difficult to determine the etiology of this abnormality, although there are several possible explanations. One is the deleterious effects of removing the tensor apparatus with the subvalvular tissue as is commonly necessary in pediatric MVR in order to place a larger prosthesis. Secondly, many of these children have underlying congenital heart disease with long standing heart failure or other lesions as is seen with Shone’s syndrome. A third explanation is abnormal conduction patterns in patients who have pacemakers after MVR, which can diminish ventricular function. Of interest is our one patient who required emergency MVR three weeks after repair of anomalous origin of the left coronary artery from the pulmonary trunk. This child had persistent left ventricular dysfunction after the coronary artery repair so it was elected to place a porcine valve at that time because of the child’s poor prognosis and poor ventricular function. However, at the time of redo MVR nine months later for bioprosthetic valve regurgitation, a biventricular pacemaker system was placed prophylactically in order to achieve electrical resynchronization. After this child’s redo MVR, her left ventricular ejection fraction over the course of four months has increased from 35% to 69% by echocardiography.

The possibility, of course, exists that these children are referred for reoperation too late in their course. Understandably, there is reluctance to refer these patients for repeat mitral valve replacement for a variety of reasons. One thought is that the operative risk is too high; certainly this argument has been dispelled with our current results. A second possibility is that in an effort to place a larger, more appropriate valve size in a growing child, the risk of new onset heart block is worrisome. Again, since this occurred in only nine percent of our series, this concern too, has been lessened.

In summary, we feel that redo mitral valve replacement in children can be performed safely. In general, a larger prosthetic valve can be placed. There remains the concern for ongoing heart failure leading to transplantation. For these reasons, we recommend earlier referral for redo mitral valve replacement.


   Discussion
Top
 Abstract
 Introduction
 Patients and Methods
 Results
 Comment
 Discussion
References
 
DR CONSTANTINE MAVROUDIS (Chicago, IL): That was a very nice presentation and I think it speaks to the difficulty of placing a mitral valve in a child. I always thought that whenever a mitral valve is placed in a child, the long-term outcome can be measured in five and ten-year survival curves because of the intervening somatic growth problems and attendant complications. I think you have shown this. I don’t particularly think that there is an alarming incidence of cardiac transplantation in these patients. However, it is something that can be expected, and that these patients with multiple valve operations may have cardiac transplantation as a therapeutic option in their future.

Did you perform an actuarial survival of your patient population? I’m not sure about the estimation, but it seems to me that it is 60% 5-year survival or maybe 70% 5-year or 10-year survival. And if that is the case, and it probably is, I think your point about early referral, and also referral for cardiac transplantation, is a good one.

I would mildly disagree with your comment that this situation is alarming. I think this mode of therapy is to be expected. Proceeding with transplantation in selected cases gives these patients a better outlook, especially when ventricular dysfunction is unlikely to improve after a valve reoperation. I wonder if you can comment on this issue.

DR KANTER: Well, Gus, it is hard to develop an actuarial survival when we only had one death in the whole series. Now, if you look at failure, including transplant, then we could have constructed that graph. We previously have reported our entire mitral valve replacement series, and the actuarial survival at about 5 years is similar to that of other series, and you are right, it is in the 60 to 70% range. Placing the mitral valve in a child is not a benign process and the long-term outlook is not really terrific.

DR JOHN H. CALHOON (San Antonio, TX): Kirk, I very much enjoyed your presentation, thought it was well illustrated and well done. Could you describe a little bit, I have done a few redo mitral valves, how are you able to upsize them, where do you find the room, please?

DR KANTER: As all of us in the audience are aware, there are no good techniques applicable to the mitral valve annulus as there are for the aortic annulus like a Manougian or a Nicks or a Konno procedure. However, when we remove the prosthetic mitral valve, we are very careful to debride the annulus and to remove all the prosthetic material and fibrotic tissue. With that, without really making any extra incisions, we are surprised that that really increases the annulus, which is counterintuitive. I think that that in the past has been the reluctance to reoperate on these children because you feel that you are just going to be able to put in the same size valve. But as we have shown, without really doing anything special other than debriding the annulus and taking out all the scar tissue and prosthetic tissue, we are generally able to upsize from a median valve size of 21 to a median of 25.

DR D. GLENN PENNINGTON (Johnson City, TN): There were several patients who required replacement within a year or so. I wondered if you have had any experience with fibrinolytic treatment of these valves, particularly the mechanical valves, I guess the question would be, is that a worthwhile thing to do in this population?

DR KANTER: We actually reported a case series of three patients in the Journal of Thoracic and Cardiovascular Surgery that were successfully managed with thrombolytic therapy within the first few days of recognition of valve thrombosis. The few cases in our series that were replaced soon after implantation included one patient with endocarditis. There was one patient with that Silzone-impregnated St Jude valve that went in beautifully and had no leak. Four months later he had regurgitation. That particular valve has been withdrawn from the market for this problem with early regurgitation.

One disturbing patient was a small child where we put a St Jude valve in the supraannular position. About five months after implantation, one of the leaflets got stuck, and we took him back, replacing it with another St Jude valve. It worked great in the operating room. A month later it got stuck again, and we tried thrombolytic therapy, which worked for a week and then it got stuck again. We felt that in the supraannular position there was something about the morphology of her atrium that was catching the leaflet. We, therefore, put a bioprosthetic valve in her, and that has been a year now. So that pretty much accounts for the short interval redo replacements.


   References
Top
 Abstract
 Introduction
 Patients and Methods
 Results
 Comment
 Discussion
 References
 

  1. Antunes MJ. Bioprosthetic valve replacement in children—long-term follow-up of 135 isolated mitral valve implantations Eur Heart J 1984;5:913-918.[Abstract/Free Full Text]
  2. Williams DB, Danielson GK, McGoon DC, Puga FJ, Mair DD, Edwards WD. Porcine heterograft valve replacement in children J Thorac Cardiovasc Surg 1982;84:446-450.[Abstract]
  3. Antunes MJ, Vanderdonck KM, Sussman MJ. Mechanical valve replacement in children and teenagers Eur J Cardiothorac Surg 1989;3:222-228.[Abstract/Free Full Text]
  4. Milano A, Vouhe PR, Baillot-Vernant F, et al. Late results after left-sided cardiac valve replacement in children J Thorac Cardiovasc Surg 1986;92:218-225.[Abstract]
  5. Gunther T, Mazzitelli D, Schreiber C, et al. Mitral-valve replacement in children under 6 years of age Eur J Cardiothorac Surg 2000;17:426-430.[Abstract/Free Full Text]
  6. van Doorn C, Yates R, Tsang V, deLeval M, Elliott M. Mitral valve replacement in childrenmortality, morbidity, and haemodynamic status up to medium term follow up. Heart 2000;84:636-642.[Abstract/Free Full Text]
  7. Masuda M, Kado H, Tatewaki H, Shiokawa Y, Yasui H. Late results after mitral valve replacement with bileaflet mechanical prosthesis in childrennevaluation of prosthesis-patient mismatch. Ann Thorac Surg 2004;77:913-917.[Abstract/Free Full Text]
  8. Raghuveer G, Caldarone CA, Hills CB, Atkins DL, Belmont JM, Moller JH. Predictors of prosthesis survival, growth, and functional status following mechanical mitral valve replacement in children aged < 5 years, a multi-institutional study Circulation 2003;108(suppl II):II174-II179.[Medline]
  9. Erez E, Kanter KR, Isom E, Williams WH, Tam VK. Mitral valve replacement in children J Heart Valve Dis 2003;12:25-29.[Medline]
  10. Robinson G, Young D. Secondary implantation of a mitral valve prosthesis in a child Ann Thorac Surg 1966;2:208-212.[Free Full Text]
  11. Alexiou C, Galogavrou M, Chen Q, et al. Mitral valve replacement with mechanical prostheses in childrennimproved operative risk and survival. Eur J Cardiothorac Surg 2001;20:105-113.[Abstract/Free Full Text]
  12. Yoshimura N, Yamaguchi M, Oshima Y, et al. Surgery for mitral valve disease in the pediatric age group J Thorac Cardiovasc Surg 1999;118:99-106.[Abstract/Free Full Text]
  13. Zweng TN, Bluett MK, Mosca R, Callow LB, Bove EL. Mitral valve replacement in the first 5 years of life Ann Thorac Surg 1989;47:720-724.[Abstract/Free Full Text]
  14. Schaff HV, Danielson GK, DiDonato RM, Puga FJ, Mair DD, McGoon DC. Late results after Starr-Edwards valve replacement in children J Thorac Cardiovasc Surg 1984;88:583-589.[Abstract]
  15. Nudelman I, Schachner A, Levy MJ. Repeated mitral valve replacement in the growing child with congenital mitral valve disease J Thorac Cardiovasc Surg 1980;79:765-769.[Abstract]
  16. Friedman S, Edmunds Jr LH, Cuaso CC. Long-term mitral valve replacement in young children. Influence of somatic growth on prosthetic valve adequacy Circulation 1978;57:981-986.[Abstract/Free Full Text]
  17. Eble BK, Fiser WP, Simpson P, Dugan J, Drummond-Webb JJ, Yetman AT. Mitral valve replacement in childrennpredictors of long-term outcome. Ann Thorac Surg 2003;76:853-859.[Abstract/Free Full Text]
  18. Caldarone CA, Raghuveer G, Hills CB, et al. Long-term survival after mitral valve replacement in children aged < 5 yearsna multi-institutional study. Circulation 2001;104(suppl I):I143-I147.[Medline]



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