Ann Thorac Surg 1996;61:883-887
© 1996 The Society of Thoracic Surgeons
Original Articles: Cardiovascular
Pathologic Aspects of Polytetrafluoroethylene Sutures in Human Heart
Kenji Minatoya, MD,
Hitoshi Okabayashi, MD, PhD,
Ichiro Shimada, MD,
Nobuhisa Ohno, MD,
Takeshi Nishina, MD,
Tadaaki Yokota, MD, PhD,
Mutsuo Takahashi, MD,
Tokuhiro Ishihara, MD,
Eddie L. Hoover, MD
Divisions of Cardiovascular Surgery and Pathology, Kokura Memorial Hospital, Fukuoka, Japan.
Accepted for publication November 18, 1995.
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Abstract
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Background. Polytetrafluoroethylene (PTFE) sutures have been widely used as a mitral chord substitute. We present the cases of 4 patients who underwent mitral valve repair with chordal replacement by PTFE sutures and these required another operation. This gave us the chance to examine the PTFE sutures.
Methods. Structural analysis of the PTFE sutures was performed 26 to 378 days postoperatively. The specimens were examined grossly, microscopically, and by scanning or transmission electron microscopy or both.
Results. The PTFE suture in 1 patient was found to be completely covered with endothelial cells 154 days postoperatively. There was no calcification, and the flexibility and pliability of the PTFE sutures was preserved. Even though the PTFE sutures seemed uncovered on visual inspection, there was a thin lining of collagen and fibrin on the surface. Endothelial cells were seen in areas that looked clear in one specimen 26 days postoperatively.
Conclusions. We think that the new layer of collagen could be promising in terms of durability and that the endothelial layer will resemble normal tissue in its anticoagulant properties.
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Introduction
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In recent years, mitral valve repair has been widely used because of the theoretical advantages over replacement with artificial devices. Chordal substitution is considered a technical extension of mitral valve repair and is used to maintain the continuity between the papillary muscles and the mitral annulus [1]. Since the report of Vetter and associates [2], many instances of use of expanded polytetrafluoroethylene (PTFE) sutures as artificial mitral chordae tendineae have been reported [3]. In a sheep model in which PTFE stents were used to simulate chordae tendineae, the PTFE sutures were completely covered by a sheath of tissue with a collagen matrix and an endothelial surface [4]. Only a few reports [5, 6] have presented the histologic aspect of PTFE sutures in the human heart. It is important to prove the anticoagulability and durability of PTFE suture by surface endothelialization to determine the efficacy of its use over time.
We present the cases of 4 patients who had mitral valve repair with chordal replacement by PTFE sutures. The need of a second operation presented an opportunity to perform structural analysis of the sutures 26 to 378 days postoperatively. This report is intended to present only the pathologic findings observed; the clinical results and the merits of the procedure itself are beyond the scope of the study.
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Material and Methods
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Between January 1990 and July 1994, chordal replacement with PTFE sutures was performed in 15 patients as a part of mitral valve reconstruction in Kokura Memorial Hospital, Fukuoka, Japan. We used CV-4 or CV-5 Gore-Tex sutures (W.L. Gore & Associates, Inc, Flagstaff, AZ). The operative technique was based on the method of David and co-workers [5]. We were able to examine specimens from 4 patients who required reoperation (Table 1
). The duration of implantation was 26 days, 154 days, 168 days, and 378 days.
At reoperation, we obtained a sample of the PTFE suture from patients 1, 2, and 3. The suture from patient 4 was preserved. A piece of each specimen was fixed in 10% formalin solution and embedded in paraffin for light microscopy. Paraffin sections were stained with hematoxylin and eosin and were immunohistochemically reacted to anti-biotin-peroxidase complex. Von Kossa staining was also done to determine if calcium deposits were present. The remaining specimens were fixed in 1% glutaraldehyde solution followed by dehydration through a graded ethanol series to a critical drying point. They were then coated with gold-platinum for scanning electron microscopy. Part of each specimen was postfixed in 1% osmium tetroxide, covered with ultrathin silver, and embedded in Epon 812. Semithin sections were stained with toluidine blue, and ultrathin sections were stained with uranyl acetate and lead citrate for transmission electron microscopy.
Patient 1
A 52-year-old man had mitral regurgitation (MR) caused by posterior chordal rupture from degenerative disease and anterior leaflet prolapse. We performed quadrangular resection of the ruptured chordal area of the posterior leaflet and implantation of PTFE suture (CV-4 Gore-Tex) as an artificial chorda for the anterior leaflet. The PTFE suture was anchored to the papillary muscle with small Teflon felt pledgets and sutured at the leaflet from the ventricular side to the atrial side and again to the ventricular side. The tie was made at the edge of the leaflet in the ventricular side. The annulus plication was also performed with Teflon felt.
Postoperatively, the regurgitation was minimal, but major hemolysis necessitated mitral valve replacement 168 days after the first operation. The hemolysis was thought to be secondary to the regurgitant jet striking the Teflon felt used for the annuloplasty. After this operation, we began using pericardium instead of Teflon and have not seen this complication in subsequent patients. However, we cannot rule out the possibility that the uncovered PTFE surface may have caused or contributed to the hemolysis.
Patient 2
A 68-year-old man had mitral leaflet prolapse caused by degenerative disease. At the first operation, artificial chordae (CV-5 Gore-Tex) were used to reconstruct the anterior and posterior leaflets. The placement of sutures was the same as in patient 1. A few days after the first operation, the patient again showed severe MR on echocardiography and underwent the second operation 26 days later. The fixed point of the PTFE suture at the edge of the anterior leaflet was avulsed, thus creating the regurgitation.
Patient 3
A 65-year-old woman had undergone implantation of a pacemaker when she was 54 years old because of Wolff-Parkinson-White syndrome combined with sick sinus syndrome. Mitral regurgitation caused by prolapse of the anterior leaflet developed. We performed implantation of PTFE suture (CV-4 Gore-Tex) as an artificial chorda for the center of the anterior leaflet and a Kay annuloplasty for the anterolateral commissure. Postoperatively there was mild regurgitation on the echocardiogram. The patient experienced frequent paroxysmal supraventricular tachycardia attacks 2 weeks after discharge from the hospital and manifested progressive MR. Catheter ablation was unsuccessful, and she underwent reoperation for mitral valve replacement and accessory pathway ablation 154 days after the first procedure. The cause of the regurgitation was a new degenerative lesion of the anterior leaflet.
Patient 4
A 42-year-old woman had Bland-White-Garland syndrome and moderate MR. We performed a modified Takeuchi operation and mitral chordal plastic repair with CV-4 Gore-Tex suture and a Kay annuloplasty. Later we found a leak from the pulmonary artery conduit. Because of severe MR, the patient required reoperation after 378 days. We repaired the leaking point and performed mitral valvoplasty again. The cause of the regurgitation was the new prolapsing segment in the anterior leaflet. It was repaired using another artificial chorda with PTFE at the point of leakage and remodeling with a Carpentier ring.
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Results
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Macroscopically, the PTFE suture material in patient 2 at 26 days was almost the same color as when it was placed. Patient 1 at 168 days and patient 3 at 154 days showed both completely covered and some incompletely covered PTFE suture. In patient 4, the suture was almost its natural color, and a tiny fibrin mass had adhered to the center of the suture. The completely covered PTFE suture was nearly impossible to distinguish from the natural chordae by gross examination (Fig 1). Flexibility and pliability were preserved.
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Fig 1. . (Patient 3.) A pair of polytetrafluoroethylene sutures. One is completely covered and is nearly impossible to distinguish from natural chordae by gross examination (arrow), whereas the other is covered only at the ends.
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At histologic examination, the suture material in patient 2 showed protein deposits not only at the surface but also in the inner space. The porous microstructure, which is characteristic of PTFE suture, was filled with plasma protein, but no lymphocytes, fibroblasts, or macrophages were observed. In the material in patients 1 and 3, only serum protein stained pink by hematoxylin and eosin, was observed, as in patient 2. Even though it could not be seen with visual inspection, there was a thin lining of collagen and fibrin on the surface of the PTFE suture. The sheath covering the surface of the suture was made primarily of collagen (Fig 2). In general, its thickness was proportional to the duration of implantation, and it was thicker closer to the native tissue. In patient 2, there was a small cluster of endothelial cells on the surface that were stained for factor VIII (Fig 3). This specimen had been implanted for 26 days, and this is the portion that did not have a new lining by visual inspection. There was no calcification in any of the specimens.
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Fig 2. . The sheath covering the surface of the polytetrafluoroethylene suture was composed mainly of collagen and showed surface endothelial cells. (x40 before 42% reduction.)
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Fig 3. . (Patient 2.) A small section (arrow) of endothelial cells on the surface was stained black for factor VIII. (x400 before 42% reduction.)
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Scanning electron microscopy confirmed the results of the histologic examination in demonstrating that thickness was proportional to duration of implantation. This layer became progressively thinner as distance from the native tissue increased (Fig 4). At the site of the tie, the surface layer completely covered the junction, which also showed a smooth surface (Fig 5). The surface had a wavelike lining similar to the inner surface of the endothelial layer of the PTFE graft (Fig 6). In the electron microscopic observations, the specimens that were already covered with ultrathin silver were embedded in Epon 812 and stained with toluidine blue to identify surface endothelial cells. Although this procedure may influence the real structure of the specimen to some extent, it shows the continual disposition of cellular nuclei on the surface just under the silver layer.
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Fig 4. . (Patient 3.) A pair of polytetrafluoroethylene sutures at electron microscopy. One is completely covered, and in the other, the layer gradually decreases toward the end. (x40 before 42% reduction.)
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Fig 5. . (Patient 1.) At the site of the tie, the surface layer covered the junction completely, and the junction also showed a smooth surface. (x40 before 42% reduction.)
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Fig 6. . The surface had a wavelike lining that looked like the inner surface of the endothelial layer of the polytetrafluoroethylene graft. (x1,000 before 42% reduction.)
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With transmission electron microscopy, the nuclei that stood out from the surface had the characteristics of endothelium (Fig 7). Other possibilities included macrophages and fibroblasts, but macrophages have more lysosomal dense bodies, and fibroblasts should demonstrate the existence of rough endoplasmic reticulum. We also recognized Weibel-Palade body-like structures, which are the essential structure of endothelial cells. Therefore, we concluded that the cellular surface consisted of endothelial cells even though the basement membrane was not clear.
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Fig 7. . With transmission electron microscopy, the nuclei (arrows) that stood out from the surface had the characteristics of endothelium. (x3,000 before 42% reduction.)
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Comment
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Since Vetter and associates [2] reported the reconstruction of chordae tendineae with PTFE suture, many instances of its use for mitral valve repair have been presented. Revuelta and co-workers [4] discussed the results of mitral chordal replacement in 30 sheep. The suture was completely covered by a sheath of tissue with a collagen structure remarkably similar to that of a native chorda. In contrast, David and associates [5] reported the case of a patient in whom there was no cellular covering for any of the prosthetic chordae 9 months postoperatively. The PTFE chordae had only plasma protein in the interstices. Maurer and Bernhard [6] found that in 1 patient 21 days postoperatively, there were lymphocytes, fibroblasts, and macrophages in the interstices of the PTFE sutures and fibrin deposits at the surface of the sutures. Zussa and associates [3, 7] reported the case of a patient in whom 18 months after the chordae had been replaced with PTFE, the suture material was free from any biologic layer. However, as there was some covering at the ends of the suture, they predicted that the entire synthetic chordae would eventually be covered.
The PTFE chordae in all of our patients had only plasma protein in the PTFE interstices, but a portion of the suture was completely covered with collagen tissue. In patient 3 particularly, the PTFE suture was wholly covered with collagen tissue and endothelial cells after 5 months. Patients 1 and 2 had similar surface structure (wavelike lining), a finding that may indicate that the surface of the PTFE suture will, in time, be covered with cellular components. Although no change was seen by visual inspection, a wavelike lining consisting of fibrin and collagen tissue covered the surface of the suture. Patient 2 also had the presence of endothelial cells on the surface. We think this layer will grow into an endothelial monolayer over time.
Hanel and colleagues [8] reported endothelialization of PTFE grafts only adjacent to the anastomoses. This phenomenon is common in prosthetic grafts. We think that the probability of coverage with fibrous tissue is partially influenced by the length of the suture. The wholly covered PTFE was recognized in short-length segments that initially were longer than the visible area but were buried in leaflet tissue with fibrous neointima. We think that eventually the entire PTFE suture will become covered and possibly also become smooth if the distance to the native tissue is not great. The fibrin deposits will start the progression of endothelialization of the surface. The case of patient 4 may also suggest that endothelialization could start at the center of the sutures.
Cochran and Kunzelman [9] reported that PTFE appears to be the best synthetic alternative for chordal replacement because of its limited viscoelastic properties. The lining on the surface of the suture might possibly alter the characteristics of the suture. Historically for chordal substitution, materials such as silk, Teflon, nylon, autologous pericardium, and bovine pericardium have been used [10–15]. Bovine pericardium occasionally showed calcification. In our experience, we have not identified calcification or early evidence of suture degeneration.
We believe that the new layer consisting mainly of collagen could be promising in terms of durability and that the endothelial layer is promising in terms of anticoagulant properties. However, these data were obtained after a rather limited period in a small group of patients. Definitive conclusions must await long-term follow-up of large cohorts of patients who undergo operation using this material.
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Acknowledgments
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We are indebted to Hiroaki Yoshioka, MD, for his assistance in the preparation of the manuscript.
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Footnotes
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Address reprint requests to Dr Minatoya, c/o Dr Hoover, Department of Surgery, Erie County Medical Center, 462 Grider St, Buffalo, NY 14215.
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References
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- Okita Y, Miki S, Ueda Y, et al. Replacement of chordae tendineae using expanded polytetrafluoroethylene (ePTFE) sutures during mitral valve replacement in patients with severe mitral stenosis. J Cardiac Surg 1993;8:567–78.[Medline]
- Vetter HO, Burach JH, Factor SM, et al. Replacement of chordae tendineae of the mitral valve using the new expanded PTFE suture. In: Bodnar E, Yacoub M, eds. Biologic and bioprosthetic valves. 1st ed. New York: Yorke Medical Books, 1986:772-85.
- Zussa C, Polesel E, Col UD, Galloni M, Valfre C. Seven-year experience with chordal replacement with expanded polytetrafluoroethylene in floppy mitral valve. J Thorac Cardiovasc Surg 1994;108:37–41.[Abstract/Free Full Text]
- Revuelta JM, Garcia-Rinaldi R, Gaite L, et al. Generation of chordae tendineae with polytetrafluoroethylene stents. Results of mitral valve chordal replacement in sheep. J Thorac Cardiovasc Surg 1989;97:98–103.[Abstract]
- David TE, Bos J, Rakowski H. Mitral valve repair by replacement of chordae tendineae with polytetrafluoroethylene sutures. J Thorac Cardiovasc Surg 1991;101:495–501.[Abstract]
- Maurer I, Bernhard A. PTFE sutures for mitral valve reconstruction: histological findings in man. Thorac Cardiovasc Surg 1991;39:73–5.[Medline]
- Zussa C, Frater RWM, Polesel E, Galloni M, Valfré C. Artificial mitral valve chordae: experimental and clinical experience. Ann Thorac Surg 1990;50:367–73.[Abstract]
- Hanel KC, McCabe C, Abbott WM, et al. Current PTFE grafts: a biomechanical scanning electron, and light microscopic evaluation. Ann Surg 1982;195:456–63.[Medline]
- Cochran RP, Kunzelman KS. Comparison of viscoelastic properties of suture versus porcine mitral valve chordae tendineae. J Cardiac Surg 1991;6:508–13.[Medline]
- January LE, Fisher JM, Ehrenhaft JL. Mitral insufficiency resulting from rupture of normal chordae tendineae. Circulation 1962;26:1329–33.[Abstract/Free Full Text]
- Kay JH, William S, Egerton WS. The repair of mitral insufficiency associated with ruptured chordae tendineae. Ann Surg 1963;157:351–60.[Medline]
- Morris JD, Penner DA, Brandt RL, et al. Surgical correction of ruptured chordae tendineae. J Thorac Cardiovasc Surg 1964;48:772–80.[Medline]
- Marchand P, Barlow JB, Du Plessis LA, et al. Mitral regurgitation with rupture of normal chordae tendineae. Br Heart J 1966;28:746–58.[Free Full Text]
- Rittenhouse EA, Davis CC, Wood SJ, et al. Replacement of ruptured chordae tendineae of the mitral valve with autologous pericardial chordae. J Thorac Cardiovasc Surg 1978;75:870–6.[Abstract]
- Frater RWM, Gabbay S, Shore D, Factor S, Strom J. Reproducible replacement of elongated or ruptured mitral valve chordae. Ann Thorac Surg 1983;35:14–28.[Abstract]
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Top
Abstract
Introduction
