Ann Thorac Surg 1996;61:1759-1763
© 1996 The Society of Thoracic Surgeons
Original Article: Cardiovascular
Autologous Tissue Cardiac Valve for Aortic Valve Replacement: Technical Aspects and Early Results
Christoph Gross, MD,
Paul Simon, MD,
Rudolf Mair, MD,
Rudolf Puschmann, MD,
Kurt Sihorsch, MD,
Robert Hofmann, MD,
Peter Brücke, MD
Departments of Surgery I and Cardiology, General Hospital, Linz, Austria
Accepted for publication February 7, 1996.
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Abstract
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Background. The known complications of heterograft bioprostheses and homograft valves have renewed the interest in the use of autologous material. A new technique to construct a tissue prosthesis for aortic valve replacement using the patient's pericardium harvested at the time of operation was developed. The glutaraldehyde-tanned pericardium is mounted on a stent requiring no suturing. Intraoperative testing assures adequate valve function.
Methods. The autologous tissue cardiac valve was implanted in 50 patients in the aortic position between March 1994 and May 1995. Echocardiograms were performed in all patients before hospital discharge, at 3 months (41 patients), and at the end of first postoperative year (12 patients). The mean age was 69.8 ± 5 years (range, 58 to 82 years). Eighty-four percent of patients presented with aortic stenosis and 16% had a combined lesion. Additional cardiac procedures were performed in 21 patients.
Results. Aortic cross-clamp time was 72 ± 19 minutes, and bypass time was 97 ± 28 minutes. There were three in-hospital deaths, and 2 patients died within the first postoperative year. Predischarge echocardiography demonstrated excellent hemodynamics, with a mean gradient of 20 ± 8 mm Hg and no or trivial aortic insufficiency in 45 patients. One patient had moderate aortic insufficiency. At first follow-up 36 patients (90%) were in New York Heart Association class I and 4 patients were in class II. Echocardiography showed no evidence of valve failure or degeneration (mean gradient, 17 ± 5 mm Hg; aortic insufficiency = grade 0 [trivial] in 35 patients, grade II in 3 patients, and grade III in 1 patient). Similarly, no degeneration or valve failure with increasing aortic insufficiency was seen in the patients studied at the end of the first postoperative year.
Conclusions. These results demonstrate that an autologous tissue cardiac valve can be manufactured in the operating room without significant additional operating time. Intraoperative testing minimizes the risk of primary failure with aortic insufficiency. Short-term results are encouraging, with good hemodynamic performance of the valve and no signs of degeneration. However, long-term durability needs to be demonstrated.
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Introduction
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Surgical efforts have been aimed toward the use of autologous material for aortic valve replacement [1, 2], which is more appealing than homologous and heterologous material. However, the advantage of a nonimmunogenic material has been offset by the inability to produce such a valve in the operating theater within a short time in a safe and reproducible way. Love and associates [3] developed a method to rapidly construct intraoperatively a stent-mounted, glutaraldehyde-fixed autologous pericardial valve in a standardized fashion (Autogenics, Newbury Park, CA). After successful in vitro and in vivo experimental testing [4, 5], the first clinical trials were started in 1992 [6]. However, reported patient numbers were small and only one valve size was available during the initial phases. Three valve sizes (21, 23, and 25 mm) with some modifications of the sewing ring and valve assembly kit became available in January 1994.
We report in this article a series of 50 consecutive patients undergoing aortic valve replacement with the autologous tissue cardiac valve between March 1994 and May 1995. Technical aspects of valve construction, hemodynamic performance, and short-term results up to 1 year are presented.
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Material and Methods
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Valve Construction
The autologous tissue cardiac valve is assembled in the operating room under sterile conditions. This process requires usually a maximum of 10 minutes. A piece of the patient's own pericardium is briefly tanned in glutaraldehyde and mounted on two mating stents. The tissue is clamped between the inner and outer stent, and no suturing is involved.
PREPARATION OF THE PERICARDIUM.
After the chest is opened the pericardium is thoroughly cleaned of fat and carefully inspected for fibrous thickening in situ. A 5 x 10-cm piece of pericardium is excised and immersed in 0.625% glutaraldehyde buffered to pH 7.4 for 10 minutes. Thereafter the tissue is rinsed in three serial washes of physiologic saline solution at room temperature.
MOUNTING THE VALVE.
On standard cardiopulmonary bypass the diseased aortic valve is excised and the aortic annulus sized. A coresponding size-specific kit is opened at this point. Using a specifically designed cutting tool a precise geometric shape and eight 0.5-mm holes used to align the tissue on the inner stent are cut out of the pericardium (Fig 1
). Particular care is taken to use the thinnest and most homogeneous-appearing part of the tissue. The tissue is placed on the inner stent, aligning it by buttoning the tissue to two alignment stubs on each stent post. On one of them the two ends of the pericardium overlap. A shedding cap is put on the assembly mandrel to protect the tissue commissures while the outer stent is positioned (Fig 2). The expandable outer stent is distended with a spreading tool and lowered over the tissue-wrapped inner stent (Fig 3). The shedding cap is removed, and valve construction is complete.
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Fig 2. . The pericardial tissue is wrapped around the inner stent and buttoned to each stent post. A shedding cap is placed over the commissural areas to protect the tissue while the expanded outer stent is being placed over the inner stent.
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Fig 3. . The outer stent is expanded before it can be lowered over the inner stent holding the pericardial tissue.
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Three size-specific kits are currently available to manufacture a 21-, 23-, or 25-mm valve. All tools are disposable. The stents are made of thermoplastic Delrin (Autogenics) and are covered with Dacron fabric by a process of thermal molding [7]. The expandable outer stent contains a garter spring at its base.
VALVE TESTING.
A disposable test device is used to examine the valve before implantation. In this device the valve is cycled at a closing pressure of 85 mm Hg. Exact coaptation of the leaflet edges can be observed and leaflet prolapse and valvular regurgitation ruled out. In our experience this relatively crude testing of the valve appears to be satisfactory to ensure adequate valve function. Minor relative prolapse of one leaflet does not appear to influence valve competence, and implanted valves with minor prolapse did not demonstrate increased insufficiency on postoperative echocardiograms. If valve function is suboptimal with major prolapse or wrinkling of a leaflet and valve incompetence, another valve can be constructed from the 5 x 10-cm piece of pericardium. In this series all valves were manufactured by one surgeon (P.B.).
Patients
Between March 1994 and May 1995 the autologous tissue cardiac valve was implanted in 50 consecutive patients suitable for bioprosthetic valve replacement. All patients gave informed consent and agreed to participate in follow-up at 3 months and 1 year after operation and yearly thereafter. Complete clinical and echocardiographic evaluation was performed before hospital discharge and at follow-up. Patients were placed on oral anticoagulation for the first 3 months.
There were 25 male and 25 female patients with a mean age of 69.8 ± 5.0 years (range, 58 to 82 years). Indication for operation was aortic stenosis in 84% of patients and a combined valvular lesion in 16%. Seventy-eight percent of patients were in New York Heart Association (NYHA) functional class III and 12% were in class IV before operation. The main symptoms were angina pectoris in 48% of patients, heart failure in 44%, and syncope in 14%. There were no patients with prior or active endocarditis or cardiac reoperation. Associated diagnoses included diabetes in 16% of patients, hypertension in 10%, coronary artery disease in 34%, and carotid artery disease in 8%. Preoperative cardiac catheterization data were as follows: ejection fraction, 0.57 ± 0.16; peak-to-peak gradient, 105 ± 23 mm Hg; mean gradient, 70 ± 18 mm Hg; and orifice area, 0.6 ± 0.1 cm2.
Statistical Analysis
Data are expressed as means ± standard deviation where appropriate. Student's t test was applied to test for differences in hemodynamic parameters between valve sizes.
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Results
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In 16 patients (32%) a 21-mm valve was implanted, 23 patients (46%) received a 23-mm valve, and 11 patients (22%) a 25-mm prosthesis. Additional coronary artery bypass grafting was performed in 14 patients (28%), and carotid endarterectomy in 2 patients (4%). In 7 patients (14%) aortic root enlargment using a pericardial patch plasty technique was performed to accommodate a larger valve: 21 mm in 3 patients and 23-mm in 4. Extracorporeal circulation times and aortic cross-clamp times are shown in Table 1. In patients with isolated aortic valve replacement the mean aortic cross-clamp time was 64 ± 15 minutes. This is slightly longer than with both mechanical valves and other bioprostheses. However in our institution in most cases the surgeon constructing the valve was also implanting it.
There were three in-hospital deaths. All three patients died suddenly during uneventful recovery. At autopsy severe left ventricular hypertrophy was found in all cases, and no specific cause of death could be identified. In particular, the autologous tissue valve appeared normal and unrelated to the fatal events. Perioperative complications included need for implantation of a permanent pacemaker in 3 patients (6%) and transitory cerebral ischemic attack in 1 patient (2%).
Forty-seven patients were discharged from the hospital in good condition at a mean of 11.9 ± 3.7 days (range, 7 to 24 days) after operation. Predischarge echocardiograms showed excellent hemodynamic performance of the autologous tissue valve. The mean gradient was 20 ± 8 mm Hg. All but 1 patient had none or trivial aortic insufficiency. See also Table 2 for details. One patient had moderate aortic insufficiency due to a paravalvular leak.
Follow-up at 3 months is available in 40 patients and at the end of the first postoperative year in 11 patients. One patient was lost to follow-up. There were two deaths during this follow-up period, one at 2 months and one at 6 months. Both deaths were sudden after an uneventful postoperative course and appeared unrelated to the autologous pericardial valve. However, no autopsy was performed in these patients. One patient who had had moderate aortic insufficiency at discharge was reoperated on after 6 months. At reoperation a paravalvular leak as well as leaflet prolapse were found to cause aortic insufficiency. The patient received a 27-mm valve, whereas the explanted autologous tissue valve was 25 mm. It may be postulated that undersizing of the valve due to the lack of larger valve sizes may have contributed to the development of the paravalvular leak.
At a mean follow-up of 3.6 ± 1.8 months (median, 3 months) 36 patients (90%) were in NYHA class I and 4 patients (10%) were in NYHA class II. At the end of the first postoperative year all 11 patients were in NYHA class I or II. There were no valve-related complications during the follow-up period. In particular, there was no prosthetic endocarditis or thromboembolism. The hemodynamic performance of the autologous tissue cardiac valve remained stable. At 3 months 35 patients (88%) had no or trivial aortic insufficiency. Three patients (8%) had mild aortic insufficiency. There were no signs of valvular failure or structural degeneration at 3 months and the end of the first postoperative year.
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Comment
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Early attempts to use autologous material for valve replacement all failed because of shrinkage of the fresh untreated tissue, lack of standardized construction methods, and a high incidence of endocarditis [8, 9]. However Senning [10] noted that a few patients who had these valves implanted were alive 12 to 20 years with minimal valve degeneration, a durability result surpassed only by autologous pulmonary valves transplanted in the aortic postion [11].
Introduction of glutaraldehyde fixation of heterologous tissue greatly reduced its immunogenicity and made the use of heterologous tissue for valve prosthesis construction possible [12]. Modern heterograft valves have demonstrated good midterm to long-term durability, especially in the older age group [13]. However, calcific degeneration remains the primary mode of failure of heterologous tissue valves. Experimental work has elucidated that immunogenicity is reduced but not completely eliminated after glutaraldehyde treatment [12, 14]. The immune response may at least in part contribute to the degenerative process. The excellent results of Chauvaud and associates [15, 16] using briefly glutaraldehyde tanned autologous pericardium in mitral valve repair suggested that pretreated pericardium is superior to fresh tissue because the abnormal cell metabolism is stopped and furthermore indicated that pretreated autologous pericardium is superior to heterologous tanned pericardium because of the absence of residual antigenicity. Similarly, autologous glutaraldehyde-tanned pericardium was used by Duran and colleagues [17] in aortic valve reconstruction with good results. It is of particular interest that they used their method of aortic valve reconstruction with autologous tanned pericardium in a young age group who shows generally poor results with bioprostheses. Although these results cannot be considered ultimate proof of the superiority of glutaraldehyde-treated pericardium over tanned xenograft pericardium they are certainly remarkable.
Love and associates [3] have consequently revitalized the concept to use autologous material, which would eliminate the problem of immunogenicity and also the possibility of viral transmission, a major concern in the modern era, especially in human transplants. It is the merit of this group to develop a method to construct an autologous glutaraldehyde-fixed tissue valve in the operating room in a simple, standardized, and expedient fashion. The patient's pericardium is used as autologous material. In vitro testing has demonstrated the autologous tissue cardiac valve to function normally beyond 800 million cycles, the equivalent of 20 years of use [5, 18]. The juvenile sheep model was used to further evaluate calcific degeneration of this valve experimentally [5]. Typically in this model bioprostheses become heavily calcified within 5 months [19]. However, the autologous tissue valves showed no signs of degeneration and no evidence of thickening or shrinkage when explanted after 5 months. Roentgenographic examination showed only minimal focal calcification at the commissures. These findings were confirmed by histopathologic examination. Based on these encouraging results clinical implantations were started in a few centers in well-controlled studies.
In our series one surgeon made all valves to reduce operator variability. Our data confirm that the method to produce the valve proposed by Love and associates is reproducible. A fully functional valve can be manufactured in the operating room usually within 10 minutes. Intraoperative testing can be performed and ensures adequate leaflet coaptation and minimizes the risk of aortic insufficiency. This crude testing appears in our experience to be adequate to rule out implantation of a malfunctioning valve. The basic concept of valve construction is the use of concentric mating stents, which substitutes clamping for sewing, making the manufacturing highly standardized. Aortic cross-clamp time was only marginally longer than with other types of prostheses and can be further shortened if a second surgeon places the sutures after the native valve is excised while the autologous tissue valve is being constructed. Predischarge and follow-up data up to 1 year demonstrate good clinical condition of the patients and good hemodynamic performance of the valve. Eight percent of our patients were judged to have mild aortic regurgitation based on color-flow Doppler echocardiography, which is highly sensitive. The amount of insufficiency did not exceed the regurgitation that can be seen in other normally functioning bioprostheses, and was certainly less than in mechanical valves. No signs of degeneration or increase in aortic insufficiency due to leaflet tear were seen. One patient had to be reoperated on for increasing aortic insufficiency, which was due to a paravalvular leak. Undersizing of the prosthesis at the primary implantation was thought to be responsible for the development of the paravalvular leak. Valve size can be a problem because there are only three sizes-21, 23, and 25 mm-available presently. Gross and microscopic pathologic examination of the explanted valve confirmed normal valve leaflets with no major prolapse and tears or rupture seen. There were in particular no signs of inflammation, calcification, or infection. The leaflets were partially covered with a cellular monolayer.
In our series construction of the autologous tissue valve failed eight times, and introperative testing demonstrated major prolapse with significant valve insufficiency in all. In 3 patients a second valve was manufactured successfully and implanted; 5 patients received a heterologous bioprosthesis. Several factors have contributed to these failures. First, placement of the outer stent over the inner stent caused wrinkling of the tissue in some cases. A change in the design of the spreading device has eliminated this risk. Second and most important, technical factors related to the preparation of the pericardium have to be emphasized. The cleansing of the pericardium should be performed in situ because the stretched tissue facilitates this process best. Cleansing the pericardium of all fatty tissue and fibrous bands should be done very thoroughly with gauze. One can actually observe two distinct layers during preparation, with the small vessels of the individual layers shifting in different directions during respiration. The top layer has to be removed completely. The pericardium should be inspected very carefully after excision, and the thinnest, most homogeneous part should be used for valve construction (Fig 4). We believe that in case of reoperation the pericardium is unsuitable because of scar formation and thickening. The importance of these technical aspects cannot be overemphasized because residual fibrous bands or nonhomogeneous tissue may cause wrinkling and prolapse of the tissue when it is mounted on the stents. We have observed minor prolapse of leaflets in some patients, which did not interfere with leaflet coaptation, and no increased amount of aortic insufficiency was noted.
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Fig 4. . A piece of pericardial tissue unsuited for valve construction is shown. Dense fibrous strands are easily identified. These may cause wrinkling of the tissue during valve manufacture and subsequently lead to leaflet prolapse.
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Even though we are encouraged by the in vitro, experimental, and initial clinical data demonstrating good results of this new device, we need to remain cautious. The number of implants is still small: in our series, 50 patients, worldwide, about 400 implants. The follow-up period is still short, and no assumptions about long-term durability can be made. In particular, it is known that immunogenicity is not the only factor in valve degeneration, but mechanical factors also may play a significant role. How this will affect the durability of this new device in humans needs to be demonstrated. We therefore feel strongly that at present implantation should be restricted to a few highly experienced centers until well-controlled studies demonstrate at least comparable long-term result of this device with other biological heart valve prostheses.
In conclusion, the autologous tissue cardiac valve can be manufactured in a standardized fashion expediently in the operating room. Short-term results up to 1 year are promising, with no valve failure or degeneration observed, and demonstrate the feasibility of this concept. However, the number of patients is still small and long-term durability needs to be demonstrated.
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Footnotes
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Address reprint requests to Dr Gross, Department of Surgery I, General Hospital, Krankenhausstr 9, A-4020 Linz, Austria.
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References
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- Senning A. Fascia lata replacement of aortic valves. J Thorac Cardiovasc Surg 1967;54:465–70.[Medline]
- Björk VO, Hultquist G. Teflon and pericardial aortic valve prostheses. J Thorac Cardiovasc Surg 1964;47:693–701.
- Love JW, Calvin JH, Phelan RF, Love CS. Rapid intraoperative fabrication of an autologous tissue heart valve: a new technique. In: Bodnar E, Yacoub M, eds. Proceedings of the Third International Symposium on Cardiac Bioprostheses. New York: Yorke Medical, 1986:691-8.
- Love CS, Love JW. The autologous tissue heart valve: current status. J Cardiac Surg 1991;6:499–507.[Medline]
- Love JW, Schoen FJ, Breznock EM, Shermer SP, Love CS. Experimental evaluation of an autologous tissue heart valve. J Heart Valve Dis 1992;1:232–41.[Medline]
- Love CS, Willems PW, Love JW. An autologous tissue bioprosthetic heart valve. In: Gabbay S, Frater RWM, eds. New horizons and the future of heart valve bioprostheses. Austin, TX: Silent Partners, Inc, 1994:135-41.
- Love CS. An alternative method for applying a Dacron cover to a Delrin bioprosthetic heart valve stent. In: Sheppard LC, ed. Biomedical engineering III: recent developments. New York: Pergamon, 1984:30-7.
- Edwards WS. Late results with autologous tissue heart valves. Ann Thorac Surg 1971;12:385–90.[Medline]
- Silver MD, Hudson REB, Trimble AS. Morphologic observations on heart valve prostheses made of fascia lata. J Thorac Cardiovasc Surg 1975;70:360–6.[Abstract]
- Senning A. Alterations in valvular surgery: biological valves. In: Cohn LH, Gallucci V, eds. Cardiac bioprostheses. Proceedings of the Second International Symposium on Cardiac Bioprostheses. New York: Yorke Medical, 1984:140-53.
- Ross DN. Replacement of the aortic and mitral valve with a pulmonary autograft. Lancet 1967;2:956–8.[Medline]
- Carpentier A, Lamaigre CG, Robert L, Carpentier S, Dubost C. Biological factors affecting long term results of valvular heterografts. J Thorac Cardiovasc Surg 1969;58:467–83.[Medline]
- Perier P, Mihaileanu S, Fabiani JN, et al. Long-term evaluation of the Carpentier-Edwards pericardial valve in the aortic position. J Cardiac Surg 1991;6(Suppl):589–94.[Medline]
- Bajpai PK, Salgaller ML. Immune response to glutaraldehyde treated xenografts. In: Szicher M, ed. Biocompatible polymers, metals, and composites. Lancaster, PA: Technomic Publishing Co, 1983:373-94.
- Chauvaud S, Jebara V, Chachques JC, Perier P, Carpentier A. Valvular extension with autologous pericardium preserved with glutaraldehyde: results in mitral valve repair. In: Bodnar E, ed. Surgery for heart valve disease (Proceedings of the 1989 Symposium). London: ICR, 1990:370-4.
- Chauvaud S, Jebara V, Chachques JC, et al. Valve extension with glutaraldehyde preserved autologous pericardium. J Thorac Cardiovasc Surg 1991;102:171–8.[Abstract]
- Duran C, Kumar N, Gometza B, Al Halees Z. Indications and limitations of aortic valve reconstruction. Ann Thorac Surg 1991;52:447–54.[Abstract]
- Love CS, Love JW. The autogenous tissue heart valve: current status. J Cardiac Surg 1991;6:499–507.
- Barnhart GR, Jones M, Ishihara T, Rose DM, Chavez AM, Ferrans VJ. Degeneration and calcification of bioprosthetic cardiac valves. Am J Pathol 1982;106:136–9.[Medline]
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Abstract
Introduction
