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Eur J Cardiothorac Surg 2002;21:27-31
© 2002 Elsevier Science NL

Extensive use of polytetrafluoroethylene artificial grafts for prolapse of bilateral mitral leaflets

Yukihiro Tomita*, Hisataka Yasui, Ryuji Tominaga, Shigeki Morita, Munetaka Masuda, Kazuhiro Kurisu, Yosuke Nishimura

Department of Cardiovascular Surgery, Faculty of Medicine, Kyushu University, 3-1-1 Maidashi, Higashi-ku, Fukuoka 812-8582, Japan

Received 9 March 2001; received in revised form 24 August 2001; accepted 5 September 2001.

* Corresponding author. Tel.: +81-92-6425557; fax: +81-92-6425566
e-mail: tomita{at}heart.med.kyushu-u.ac.jp


   Abstract
Top
 Abstract
1. Introduction
 2. Patients and methods
 3. Results
 4. Discussion
 References
 
Objectives: There are an increasing number of reports concerning mitral valve repair by reconstruction of the chordae tendinae with the use of expanded polytetrafluoroethylene (PTFE) sutures. However, little information is available about the extended application or results of this technique for extended prolapse of bilateral mitral leaflets, which is considered to be difficult to repair. Methods: Between October 1993 and May 1998, 17 patients (age range 16–74 years) who had from moderate to severe mitral regurgitation as the result of a prolapse of bilateral leaflets underwent mitral valve repair by reconstruction of artificial chordae with CV-4 expanded PTFE sutures. Either bilateral or unilateral Kay's suture annuloplasty was also performed to correct annular dilatation in all patients. Results: No operative death or late mortality was observed. Before discharge, immediate postoperative echocardiography showed less than moderate mitral regurgitation in 16 of 17 patients. The follow-up was completed in all cases by a clinical examination and serial echocardiograms, and the median follow-up period was 52 months (range 27–82 months). There was one failure that required re-operation because of worsening mitral regurgitation (elongation of the anchored side of papillary muscle). When the re-operated patient was excluded from the following data, the degree of mitral regurgitation, estimated by echocardiography performed at recent follow-up, was none in four patients, trivial in eight patients, and mild in four patients. The systolic and diastolic dimensions of the left ventricle decreased significantly (P<0.01). Conclusions: Because replacement of artificial chordae was not complicated and seemed to preserve fine relationships among leaflet tissues, chordae, and papillary muscles, we therefore suggest that the extensive use of PTFE artificial chordae appears to be a promising procedure for the repair of all kinds of mitral lesions causing mitral regurgitation.

Key Words: Mitral regurgitation • Mitral valve repair • Artificial chordae • Polytetrafluoroethylene


   1. Introduction
Top
 Abstract
 1. Introduction
2. Patients and methods
 3. Results
 4. Discussion
 References
 
Although degenerative disease of the mitral valve may involve the mitral annulus, the leaflets, and the chordae tendinae, mitral incompetence usually occurs because of prolapse of one or both leaflets as a consequence of chordal elongation or rupture [1,2]. In general, prolapse of the posterior mitral leaflet (PML) is more common than prolapse of the anterior mitral leaflet (AML), and mitral valve incompetence in these patients can be treated by resection of the prolapsing segment of PML followed by annuloplasty [3]. When the incompetence is due to the AML prolapse or prolapse of both mitral leaflets (BML), repair of the mitral valve is more complicated and sometimes not feasible because of inadequate chordal tissue. Similarly, patients with advanced rheumatic mitral valve disease may have excessively thickened and calcified chordae tendinae preventing satisfactory repair.

In 1989, David [4] demonstrated the possibility of the extended operative application for mitral valve prolapse by the method of chordal replacement with expanded polytetrafluoroethylene (PTFE) sutures. Since then, the effectiveness and reliability of this technique have been shown experimentally and clinically [5–8]. However, the successful repair of extended mitral valve prolapse of both the anterior and posterior leaflets still remains a challenge. We herein report our experience in performing artificial chordal reconstruction for BML prolapse.


   2. Patients and methods
Top
 Abstract
 1. Introduction
 2. Patients and methods
3. Results
 4. Discussion
 References
 
2.1. Patients
From September 1994 through May 1998, chordal replacement with PTFE sutures was attempted in 21 patients with BML prolapse, and successfully performed in 17 patients. There were 11 men and six women whose mean age was 59.1 years (range 16–75 years) (Table 1). The preoperative electrocardiogram revealed sinus rhythm in nine patients and atrial fibrillation in eight. Preoperative echocardiographic studies showed degenerative disease of the mitral valve in 15 of 17 patients. Two patients had had infective endocarditis. No patient had previously undergone cardiovascular procedures.


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  		Table 1. Patient profilesa

 
Mitral regurgitation (MR) was assessed by transthoracic color Doppler echocardiography. MR was graded according to the percentage of regurgitant jet area to the left atrial area (mild, <20%; moderate, between 20 and 40%; and severe, >40%) [9]. The calculations were based on an average of three sequential cardiac cycles in patients with normal sinus rhythm and five sequential cycles in those with atrial fibrillation. Preoperative MR showed moderate in two patients and severe in the other 15 patients (Table 2). Preoperative cardiac catheterization was performed in all patients. Preoperative left ventriculography showed grade 3/4 MR in three patients and 4/4 in 14 patients.


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  		Table 2. Pre- and postoperative MR evaluated by echocardiography

 
One patient was in New York Heart Association (NYHA) functional class I, ten were in class II, four were in class III, and two were in class IV.

2.2. Operative technique
The approach to the heart was by means of a midline sternotomy, and the mitral valve repair was performed with cardiopulmonary bypass with moderate hypothermia (28–30°C) [10,11]. Myocardial protection was provided by topical cooling and intermittent cold crystalloid cardioplegic solution (Kyushu University Solution).

The approach to the mitral valve was by a superior transseptal approach. The entire mitral valve apparatus was carefully inspected, and prolapsed legions were identified. The main cause of prolapse was chordal elongation in 12 patients, and torn chordae in four patients. The prolapsed area was described as the proportion of AML and/or PML. Subsequently, we reconstructed the chordae tendinae with CV-4 expanded PTFE sutures according to the method of David [4,7]. Briefly, the double armed suture is passed twice through the fibrous portion of the papillary muscle head that anchors the elongated or ruptured chordae and is tied down (seven or eight knots are needed for this suture material). The two arms of the suture are then brought up to the free margin of the leaflet and passed through the point where the original chorda was attached (thickened portion of the leaflet). The needle is brought from the ventricular side of the leaflet to its atrial side and then passed once more through the leaflet. The length of the expanded PTFE chordae is adjusted by approving the coating area of the opposite leaflet [10,11]. When the opposite leaflet was also prolapsed, the lengths of the PTFE chordae were adjusted to align the edge of the leaflets with the level of the mitral annulus. Great care was taken to maintain the predetermined distance between the annulus and the left ventricular apex. We determined the distance by measuring the diastolic distance between the apex and the mitral annulus by means of a preoperative echocardiographic examination. Once the length is adjusted, both ends of the suture are passed through the leaflet again and tied together on the ventricular side. We did not use any pledgets. When the prolapsed portion was wide, another PTFE suture was placed in the same fashion. Bilateral (eight patients) or unilateral (nine patients) Kay's suture annuloplasty was added according to the dilation of the mitral annulus.

Cold cardioplegic solution was then injected into the left ventricular cavity to evaluate residual MR. The repair was considered acceptable when the regurgitation was less than trivial during testing. Following the cardiopulmonary bypass, residual MR was reevaluated by the intraoperative transesophageal echocardiography. When the regurgitant area was less than 3 cm2, the repair was considered acceptable, and when the area was more than 3 cm2, the repair was unacceptable and mitral valve replacement was chosen.

A representative mitral repair is illustrated in Fig. 1 (patient no. 2). Preoperative transesophageal echocardiography showed a floppy mitral valve where all of the chordae were elongated, and whole portions of AML and PML were severely prolapsed (Fig. 1a). On inspection, the mitral annulus was markedly enlarged, both AML and PML were redundant and mildly thickened, and allo chordae were elongated (not torn) (Fig. 1b). Elongated chordae were replaced with 13 strands (pairs; six AML, seven PML) (Fig. 1c,d). Bilateral suture annuloplasty was added. An intraoperative regurgitation test showed trivial MR (Fig. 1e). Postoperative recovery in this patient was uneventful. He was reviewed and has been well for 5.6 years after operation. Residual MR was tiny in transesophageal echocardiography and absent in left ventriculography at discharge. Recent transsternal echocardiography showed trivial MR.



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  		Fig. 1. Preoperative transesophageal echocardiography and intraoperative findings of patient 2. Preoperative transesophageal echocardiography showed a floppy mitral valve where all of the chordae were elongated, and whole portions of AML and PML were severely prolapsed (a). On inspection, mitral annulus was markedly enlarged, both AML and PML were redundant and mildly thickened, and allo chordae were elongated (not torn) (b). The double armed suture is passed twice through the fibrous portion of the papillary muscle head that anchors the elongated chordae (c). Then, sutures were passed through the edge of the bilateral leaflets. Elongated chordae were replaced with 13 strands (pairs; six AML, seven PML) (d). Bilateral suture annuloplasty was added. An intraoperative regurgitation test showed trivial MR (e).

 
Five patients had other associated procedures (see Table 1).

2.3. Follow-up
All patients had a postoperative transsternal and transesophageal echocardiographic study before discharge from the hospital. Studies were repeated at 3 and 6 months and annually thereafter. All patients received warfarin sodium after the operation. In the anticoagulation therapy, the International Normalized Ratio (INR) was kept at 2.0–2.5. Anticoagulation was controlled. Anticoagulation was discontinued after 3 months except in patients who were in atrial fibrillation.

2.4. Statistical analysis
Computerized statistical analysis was performed with the StatView 5.0 for Macintosh statistical program (Abacus Concepts, Inc., Berkeley, CA). All values are expressed as the mean±standard deviation (SD). Student's t-test was used to analyze the data. To analyze the change of other variables, a paired t-test was used.


   3. Results
Top
 Abstract
 1. Introduction
 2. Patients and methods
 3. Results
4. Discussion
 References
 
No operative death or morbidity was observed. Before being discharged from hospital, echocardiography was performed in all patients. The results revealed no MR in five patients, trivial MR in seven patients, mild MR in four patients, and moderate MR in one patient (Table 2).

The follow-up on these patients extended from 27 to 82 months (median 52 months). In one patient the operation was unsuccessful (patient no. 15, Table 1). This patient showed whole AML prolapse and 1/3 PML prolapse on the posteromedial side. Elongated chordae were replaced with seven strands (pairs; six AML, one PML) of CV-4 PTFE grafts. This patient had an acceptable hemodynamic result from the mitral valve repair with only mild residual MR (evaluated by intraoperative transesophageal echocardiography). Unfortunately, however, the regurgitation was becoming worse to moderate MR by 1 week after operation. Because the MR advanced to severe after 8 months, this patient underwent successful mitral valve replacement. At re-operation, the several anchored sites of papillary muscles were elongated. We judged that the strength of these papillary muscles was not enough to sustain the anchored PTFE grafts.

There were no late deaths and no episodes of hemorrhage or thromboembolism. When the re-operated patient was excluded from the data, no progressive MR was observed that was more than mild, and the NYHA functional class, cardiothoracic ratio (CTR), left ventricle dimension during systole (LVDs), and left ventricle dimension during diastole (LVDd) in all patients based on the echocardiographic findings obtained during the follow-up period (Table 3).


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  		Table 3. Clinical results pre- and post-mitral valve repair

 

   4. Discussion
Top
 Abstract
 1. Introduction
 2. Patients and methods
 3. Results
 4. Discussion
References
 
Surgical repair for mitral valve insufficiency permits total preservation of the mitral valve apparatus and ventricular function, with only few valve-related complications [12,13]. Classically, Carpentier [3] reported excellent results using various repair techniques. Prolapse of PML and limited prolapse of AML and BML can be repaired in a straightforward manner by leaflet resection and suture. Many AML and BML prolapses are, however, difficult to repair and require the application of more complex techniques such as chordae shortening, chordal transposition or a flip-over technique [3,14,15]. Clinical results of their techniques are controversial [16] (our unpublished data).

The experimental evidence that expanded PTFE is a reliable material to replace mitral valve chordae has been confirmed by Cochran and Kunzelman [17], who compared the viscoelastic properties of natural mitral chordae with those of different sutures. Clinically, David et al. reported excellent mid-term results in 44 cases with chordal replacement, including leaflet resection followed by ring annuloplasty [7]. By May 1998, we had 31 patients with a single leaflet prolapse which were successfully repaired with this technique. The chordal replacement technique with PTFE is very attractive in that it offers the possibility of repairing all types of MR. Thus, we reconfirmed that PTFE sutures seem to be the suitable artificial chordae to extended operative application for BML prolapse, and started to accept this technique from 1991. The present results showed that the chordal replacement technique is applicable to repair all types of BML prolapse.

The major concern regarding artificial chordae is the long-term durability, as well as flexibility, of the material. Several authors summarized their recent findings relating to the use of PTFE suture as artificial chordae [5,18,19]. First, PTFE chordae had become covered by a host fibrosa and endothelium layer within a year. Second, PTFE sutures, after being covered by the host, had flexibility similar to that of natural chordae. On this point, however, Kobayashi et al. [20] described the mitral valve dysfunction resulting from thickening and stiffening of PTFE chordae. Third, no report has ever been made of PTFE chordae breakage, either early or late. Fourth, calcification had been found in an isolated PTFE chordae used experimentally, but had not otherwise been reported.

Mitral valve repair is associated with a low operative mortality, and the long-term survival is excellent [21–23]. Deloche et al. [23] reported an actuarial survival (excluding operative mortality) of 71±3% at 15 years in a group of 113 French patients operated on from 1972 to 1979. The survival rate at 8 years in that series was very similar to the recent report [24]. Many reports indicate that the actuarial survival at 5 years is around 90% [21–24]. More recently, 10 year surgical outcome with the chordal replacement technique clarified the similar late mortality to others [19]. We performed mitral valve plasty in 110 patients, which includes the present cases, in the last 10 years, resulting in no operative deaths or late mortality (Y. Tomita, unpublished data). This survival rate is higher than that observed after mitral valve replacement [25], and valve-related deaths are less common among patients who have mitral valve repair than in patients who have mitral valve replacement [22].

For the successful repair with the use of this technique, the most important factor is accurately determining the proper length of the reconstructed chordae. During this procedure, many surgeons tie the suture at the leaflet level while the opposite leaflet is kept taut. When the opposite leaflet is not prolapsed, the same procedures for BML prolapse can be accepted. In the case of diffuse mitral prolapse, however, we adjust the lengths of the PTFE chordae to align the edge of the leaflets with the level of the mitral annulus, and have to heavily rely on the findings of a preoperative echocardiographic examination. We determine the distance by measuring the diastolic distance between the apex and the mitral annulus by means of a preoperative echocardiographic examination. It is extremely important to maintain the predetermined distance between the apex and the mitral annulus to retain the natural geometry of the left ventricle during the operation.

In summary, we have reported 17 patients who underwent successful repair of BML prolapse including the diffuse type. Although there has yet to be adequate long-term follow-up for extended use of PTFE chordae, at present mid-term results are clearly demonstrating excellent ventricular function and preserving mitral valve function. We therefore conclude that the extensive use of PTFE artificial chordae appears to be a promising procedure for the repair of all types of mitral valve prolapse.


   References
Top
 Abstract
 1. Introduction
 2. Patients and methods
 3. Results
 4. Discussion
 References
 

  1. Ranganathan N., Silver M.D., Robinson T.I., Kostuk W.J., Felderhof C.H., Patt N.L., Wilson J.K., Wigle E.D. Angiographic-morphologic correlation in patients with severe mitral regurgitation due to prolapse of the posterior mitral leaflet. Circulation 1973;48:514-518.[Abstract/Free Full Text]
  2. Davis M.J., Moore B.P., Braimbridge M.V. The floppy mitral valve: study of incidence, pathology and complications in surgical, necropsy and forensic material. Br Heart J 1978;40:468-481.[Free Full Text]
  3. Carpentier A. Cardiac valve surgery – the "French correction". J Thoracic Cardiovasc Surg 1983;86:323-337.[Medline]
  4. David T.E. Replacement of chordae tendineae with expanded polytetrafluoroethylene sutures. J Card Surg 1989;4:286-290.[Medline]
  5. Zussa C., Frater R.W.M., Polesel E., Galloni M., Valfre C. Artificial mitral valve chordae: experimental and clinical experience. Ann Thorac Surg 1990;50:367-373.[Abstract]
  6. Frater R.W.M., Vetter H.O., Zussa C., Dahm M. Chordal replacement in mitral valve repair. Circulation 1990;82(Suppl IV):IV-125-IV-130.
  7. David T.E., Boss J., Rakowski H. Mitral valve repair by replacement of chordae tendineae with polytetrafluoroethylene sutures. J Thorac Cardiovasc Surg 1991;101:495-501.[Abstract]
  8. Zussa C., Polesel E., Da Col U., 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]
  9. Helmcke F., Nanda N.C., Hsiung M.C., Soto B., Adrey C.K., Goyal R.G., Gatewood R.P. Color Doppler assessment of mitral regurgitation with orthogonal planes. Circulation 1987;75:175-183.[Abstract/Free Full Text]
  10. Morita S., Yasui H., Harasawa Y., Tomita Y., Tominaga R. Extensive use of artificial chordae for repairing diffuse mitral valve prolapse. Ann Thorac Surg 1996;62:878-880.[Abstract/Free Full Text]
  11. Tomita Y., Yasui H., Tominaga R. Mitral valve repair for isolated double-orifice mitral valve with torn chordae. Ann Thorac Surg 1997;64:1831-1834.[Abstract/Free Full Text]
  12. Perier P., Deloche A., Chauvaud S., Fabiani J.N., Rossant P., Bessou J.P., Relland J., Bourezak H., Gomez F., Blondeau P. Comparative evaluation of mitral valve repair and replacement with Starr, Bjork, and porcine valve prostheses. Circulation 1984;70(Suppl I):I-187-I-192.
  13. Galloway A.C., Colvin S.B., Baumann F.G., Grossi E.A., Ribakove G.H., Harty S., Spencer F.C. A comparison of mitral valve reconstruction with mitral valve replacement: intermediate-term results. Ann Thorac Surg 1989;47:655-662.[Abstract]
  14. Duran C.G. Repair of anterior mitral leaflet chordal rupture or elongation (the flip-over technique). J Card Surg 1986;1:161-166.[Medline]
  15. Gregory F., Jr., Takeda R., Silva S., Faqanha L., Meier M.A. A new technique for repair of mitral insufficiency caused by ruptured chordae of the anterior leaflet. J Thorac Cardiovasc Surg 1988;96:765-768.[Abstract]
  16. Eishi A.E., Kawazoe K., Sasako Y., Kosakai Y., Kitoh Y., Kawashima Y. Comparison of repair techniques for mitral valve prolapse. J Heart Valve Dis 1994;3:432-438.[Medline]
  17. Cochran R.P., Kunzelman K.S. Comparison of viscoelastic properties of suture versus porcine mitral valve chordae tendinae. J Card Surg 1991;6:508-513.[Medline]
  18. Frater R.W.M. Editorial comment: 10th Gore-Tex chorda anniversary. J Heart Valve Dis 1996;5:348-351.[Medline]
  19. David T.E., Omran A., Armstrong S., Sun Z., Ivanov J. Long-term results of mitral valve repair for myxomatous disease with and without chordal replacement with expanded polytetrafluoroethylene sutures. J Thorac Cardiovasc Surg 1998;115:1279-1286.[Abstract/Free Full Text]
  20. Kobayashi Y., Nagata S., Ohmori F., Eishi K., Miyatake K. Mitral valve dysfunction resulting from thickening and stiffening of artificial mitral valve chordae. Circulation 1996;94(Suppl II):II-129-II-132.
  21. Cosgrove D.M., Stewart W.J. Mitral valvuloplasty. Curr Probl Cardiol 1989;14:355-415.
  22. Yacoub M., Halim M., Radley-Smith R., McKay R., Nijveld A., Towers M. Surgical treatment of mitral regurgitation caused by floppy valves: repair versus replacement. Circulation 1981;64(Suppl II):211-216.
  23. Deloche A., Jebara V.A., Relland J.Y.M., Chauvaud S., Fabiani J.N., Perier P., Dreyfus G., Mihaileanu S., Carpentier A. Valve repair with Carpentier techniques. The second decade. J Thorac Cardiovasc Surg 1990;99:990-1002.[Abstract]
  24. David T.E., Armstrong S., Sun Z., Daniel L. Late results of mitral valve repair for mitral regurgitation due to degenerative disease. Ann Thorac Surg 1993;56:7-14.[Abstract]
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