Ann Thorac Surg 2001;71:S353-S355
© 2001 The Society of Thoracic Surgeons
Autografts, allografts, and biological valves in children
Results of up to 9 years of high-temperature- fixed valvular bioprostheses in a young population
Alain J. Berrebi, MDa,
Sophie M. Carpentier, PhDa,
Phan Kim Phuong, MDb,
Nguyen Van Phan, MDb,
Sylvain M. Chauvaud, MDa,
Alain Carpentier, MD, PhDa
a Hôpital Européen Georges Pompidou, Paris, France
b Heart Institute, Ho Chi Minh City, Viet Nam
Address reprint requests to Dr Alain Carpentier, Department of Cardiovascular Surgery and Organ Transplantation, Hôpital Europeen Georges Pompidou, 20 Rue Leblanc, 75015 Paris, France
Presented at the VIII International Symposium on Cardiac Bioprostheses, Cancun, Mexico, Nov 3–5, 2000.
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Abstract
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Background. Bioprosthetic valve replacement in young patients remains a controversial issue due to a high rate of early calcification. Previous studies in our laboratory have shown that high-temperature fixation of glutaraldehyde preserved bioprosthesis (HTF) mitigates calcification. The first clinical application of this technique was started in 1991.
Methods. From January 1991 to September 1998, 50 patients in whom anticoagulants were contraindicated underwent single aortic valve replacement (n = 33) or mitral valve replacement (n = 17) using HTF bioprostheses. The age of the patients ranged from 7 months to 35 years (mean 22.7 ± 6.8 years). The mean New York Heart Association status was 2.4. Mean follow-up 4 years ± 1.8 for a total follow-up of 196 patient-years.
Results. There were no operative deaths and but there were two late deaths, one valve related. Structural failure occured in 4 patients (2%/patient-year) requiring a reoperation in 3 patients (1.5%/patient-year). No endocarditis or thromboembolic episodes were observed. At late examination (June 2000), 46 patients (92%) were in New York Heart Association class I or II, with a well functioning valve.
Conclusions. Replacement with HTF bioprostheses in young patients has demonstrated encouraging midterm results with a low incidence of structural failure
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Introduction
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Bioprosthetic valves were introduced in cardiac surgery in 1969 after the discovery of the beneficial effect of glutaraldehyde on tissue valve rejection and tissue degeneration [1]. The low rate of thromboembolism without anticoagulation made these valves particularly attractive in children and very young adults. Unfortunately early calcification leading to bioprosthetic valve failure in this age group restrained their use. In the past 20 years continuous efforts have been made to develop techniques that could mitigate calcification. In 1980 the introduction of a surfactant (Tween-80) associated with ethanol as a complementary step to glutaraldehyde fixation [2] led to improved results in the adult population but less significantly so in younger populations [3]. In 1989 the development of a new method of calcium mitigation using a technique of high-temperature fixation of the tissue was associated with promising experimental results [4]. These results led us to investigate this method clinically in the younger population, for which there is no satisfactory method of valve replacement.
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Material and methods
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From January 1991 to September 1998, 50 patients (32 female and 16 male) underwent single valve replacement with HTF in two institutions: Hôpital Broussais (Paris, France) and Saïgon Heart Institute (Ho Chi Minh City, Vietnam). Their ages ranged from 7 months to 35 years (mean 22.7 ± 6.8 years). The choice of this new valve was based on social, medical, and geographic contraindications to anticoagulants. The great majority of the patients (94%) were in sinus rhythm (n = 47). Valve replacement was performed in aortic (n = 23) or mitral (n = 17) position. The size of the valves used varied from 19 to 25 mm for the aortic position and 25 to 33 for the mitral position. A total of 30 patients (60%) had rheumatic valvular disease, 13 congenital valve anomalies (26%), 5 endocarditis, 1 traumatic lesion, and 1 postradic lesion. Preoperatively, 96% of the patients were New York Heart Association (NYHA) class II or III (average 2.4). The follow-up was complete and extended from 4 months to 9 years (average 4 ± 1.8 years). The total follow-up was 196 patients-years. Follow-up was obtained from local hospitals and from physicians who returned questionnaires. Data were reported and statistical analysis was conducted following the guidelines of the Council of the Society of Thoracic Surgeons. Actuarial survival curves were calculated according to the Kaplan-Meier method.
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Results
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Mortality
There were no operative deaths but there were two late deaths (1%/patient-year). A 6-year-old child died 4 months after the operation from a recurent hemothorax due to disseminated intravascular coagulopathy, and a 3-year-old child died from a low cardiac output after a reoperation performed 31 months after the first operation. At reoperation the valve was found to be calcified. The actuarial survival at 9 years was 95% ± 3.6% for the whole series, 100% for aortic valve replacement (AVR), and 85% ± 10.2% for mitral valve replacement (MVR) (Fig 1).
Valve failure and reoperations
Valve failure occured in 4 patients, for an overall rate of 2%/patient-year. The 4 patients were aged 7 months, 9 years, 9 years, and 30 years at the time of the first operation. Valve failure was observed respectively at 31 months, 31 months, 34 months, and 60 months after the operation. There were two failures in the aortic position and two in the mitral position. The dysfunction in all cases was due to a valve stenosis assessed by echocardiography.
A reoperation was carried out in 3 patients for an overall rate of 1.5%/patient-year. Figure 2 shows 87.6% ± 7.1% freedom from reoperation at 9 years for the whole series (91.7% ± 8% for AVR and 80% ± 12.6% for MVR).
Other complications
In this series there were no prosthetic endocarditis and no thromboembolic events, despite the fact that the patients were not subjected to long-term anticoagulation. Figure 3 shows the actuarial freedom of all valve-related complications: 85.8% ± 7.1% at 9 years (2%/patient-year) for the whole series, 91.7% ± 8% for AVR, and 75.6% ± 12.7% for MVR. At late examination (June 2000) of the 45 patients who were followed-up, 92% were in New York Heart Association class I/II. All were in sinus rhythm with no clinical or echocardiographic signs of significant dysfunction (either leak or stenosis).
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Fig 3. Freedom from all valve-related complications for patients studied. (Cum. Freedom = cumulative freedom.)
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Comment
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In the early 1970s, the introduction of the glutaraldehyde-preserved bioprosthesis raised new hopes because anticoagulation was not needed [1]. In the following 5 years, however several studies began to report early structural valve failure in children due to primary dystrophic calcification [5–7]. Geha and colleagues [5] reported the results of 25 patients between 17 months and 16 years of age. 20% required a reoperation 18 to 45 months after implantation. Williams and associates [6] reported a series of 212 patients less than 15 years of age with an incidence of structural failure due to early calcification of 45.9% 37.2 ± 14.5 months after implantation. The mean age of patients in these series was younger than that in our series. Antunes and Santos [8], however reported a series more comparable to our own. There were 289 patients whose age averaged 25.8 years (versus 22.7 years in our series) who had had a mitral replacement with currently available porcine valve bioprostheses. The valve failure rate was 11.1%/patient-year versus 1.1%/patient-year in our study; however, the mean follow-up was 5 years versus 4.1 years in our series, so it is difficult to make a valuable comparison.
Whenever a valve repair is not possible, the best techniques of valve replacement in children are use of the homograft valve and the Ross operation; however, these can only be used for aortic valve replacement. The use of the homograft mitral valve, although associated with promising early results, requires a longer follow-up to assess its value [9]. Whatever the position—aortic or mitral—the problem of procurement of homograft valves limits their use, particularly in developing countries. Another alternative to bioprosthetic valve replacement is mechanical valve replacement. This technique is the most frequently used today for mitral valve replacement in young patients, but it is associated with a high incidence (as much as 3%/patient-year) of anticoagulant-related and thromboembolic complications [10]. A recent study by Lupinetti and coworkers [11] reported a high incidence of reoperation with aortic bileaflet mechanical valves in young patients (mean 11.6 years); only 75% were free from reoperation at 3 years, mainly due to pannus formation in the subvalvular region of the left ventricule. Moreover, only 49% were free from all valve-related complications at 3 years. For patients 15 to 35 years of age, the results of mechanical valves are better, but the need for long-term anticoagulation is a burden that must not be underestimated. For all of these reasons, a continuous search for more durable bioprosthetic valves is mandatory. The introduction of unstented aortic valve bioprostheses has been regarded as a step forward in this respect because this valve "mimics" the aortic valve homograft. Our experience with unstented bioprostheses, which goes back to 1968, showed that the more difficult surgical operation with an unstented bioprosthesis overides the advantage of a better hemodynamics [1]. In addition it should be kept in mind that the main difference between the homograft and the bioprosthesis is not so much the stent but the fact that the homograft is living human tissue and the bioprosthesis is glutaraldehyde-treated animal tissue. Therefore it remains to be seen whether this purely mechanical factor (ie, the absence of a stent) will make a significant biological difference in the long term.
Different mechanisms have been proposed to explain the process of early calcification in children: primary collagen degeneration, discrete immunologic reaction, increased turnover of calcium, fatigue-induced lesions, and mechanical stress in the mitral position. The improved results observed in our series correlate with the improved experimental results observed in our laboratory [4–12]. They are thought to be due to a more efficient removal of lipids from the tissue and to structural changes that render the collagen fibers less attractive to calcium compounds.
In conclusion, although a longer follow-up is required, the data reported here seems to indicate a superior durability of high-temperature–fixed bioprostheses when compared to our large past experience with the currently available bioprosthetic porcine or pericardial valves in young patients. It is our policy today to propose that this valve be used in patients between 10 to 60 years of age who cannot receive a homograft or a mechanical valve, or who do not want to be subjected to long-term anticoagulation while accepting the need for a reoperation. It is hoped that, in the future, this technique will contribute to minimize the persistent dilemma raised by the choice between a tissue valve and a mechanical valve in young adults and children.
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References
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Carpentier A., Lemaigre G., Robert L., Carpentier S., Dubost C. Biological factors affecting long-term results of valvular heterografts. J Thorac Cardiovasc Surg 1969;58:467-483.[Medline]
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Carpentier A., Nashef A., Carpentier S., Goussef N., Ahmed A., Jones M. Techniques for prevention of calcification of valvular bioprostheses. Circulation 1984;70(Suppl 1):I165-I168.
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Jamieson W.R.E., Burr L.H., Tyers G.F.O., Munro A.I. Carpentier-Edwards standard and supra-annular porcine bioprostheses: 10 year comparison of structural valve deterioration. J Heart Valve Dis 1994;3:59-65.[Medline]
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Carpentier S., Carpentier A., Chen L., Shen M., Quintero L., Witzel T. Calcium mitigation in bioprosthetic tissues by iron pretreatment: the challenge of iron leaching. Ann Thorac Surg 1995;60:S332-S338.
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Geha A., Laks H., Stansel H., Jr, et al. Late failure of porcine valve heterografts in children. J Thorac Cardiovasc Surg 1979;78:351-364.[Abstract]
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Williams D., Danielson G., Mc Goon D., Puga F., Mair D., Edwards W. Porcine heterograft valve replacement in children. J Thorac Cardiovasc Surg 1982;84:446-450.[Abstract]
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Odell J., Gillmer G., Whitton I., Vythilingum S., Vanker A. Calcification of tissue valves in children: occurrence in porcine and bovine pericardial bioprostheses valves. Proceedings of the Third International Symposium. New York: Yorke Medical Books, 1986:259-270.
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Antunes M., Santos L. Performance of glutaraldehyde preserved porcine bioprosthesis as a mitral valve substitute in a young population group. Ann Thorac Sur 1984;37:387-392.
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Acar C., Tolan M., Berrebi A., Carpentier A. Homograft replacement of the mitral valve. Graft selection, technique of implantation, and results in forty-three patients. J Thorac Cardiovasc Surg 1996;111:367-378.[Abstract/Free Full Text]
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El Makhlouf A., Friedli B., Oberhansli I., Rouge J.C., Faidutti B. Prosthetic heart valve replacement in children. Results and follow up of 273 patients. J Thorac Cardiovasc Surg 1987;93:80-85.[Abstract]
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Lupinetti F., Warner J., Jones T., Herndon S. Comparison of human tissues and mechanical prostheses for aortic valve replacement in children. Circulation 1979;96:321-325.[Abstract/Free Full Text]
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Carpentier S., Chen L., Shen M., et al. A new method for preservation of bioprostheses. Ann Thorac Surg 1998;66:S264-S266.
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Abstract
Introduction
