Ann Thorac Surg 2004;78:815-819
© 2004 The Society of Thoracic Surgeons
Original article: cardiovascular
Extensive use of polytetrafluoroethylene artificial grafts for prolapse of posterior mitral leaflet
Yukihiro Tomita, MDa,*,
Hisataka Yasui, MDa,
Toshiro Iwai, MDa,
Takahiro Nishida, MDa,
Shigeki Morita, MDa,
Munetaka Masuda, MDa,
Tetsuro Sano, MDa,
Yosuke Nishimura, MDa,
Hideki Tatewaki, MDa
a Department of Cardiovascular Surgery, Faculty of Medicine, Kyushu University, Fukuoka, Japan
Accepted for publication March 15, 2004.
* Address reprint requests to Dr Tomita, Department of Cardiovascular Surgery, Faculty of Medicine, Kyushu University, 3-1-1 Maidashi, Higashi-ku, Fukuoka 812-8582, Japan
tomita{at}heart.med.kyushu-u.ac.jp
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Abstract
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BACKGROUND: There are an increasing number of reports concerning mitral valve repair by means of reconstruction of the chordae tendinae with expanded polytetrafluoroethylene (e-PTFE) sutures. However little information is available about extended application or results of this technique for extended prolapse of posterior mitral leaflets.
METHODS: Between March 1994 and December 2000, 22 patients with moderate-to-severe mitral regurgitation (MR) as the result of a prolapse of posterior leaflets (age range, 39–73 years) underwent mitral valve repair by means of reconstruction of artificial chordae with 4-CV e-PTFE sutures without leaflet resection. Either Kay's suture or ring 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 indicated less than moderate MR in 20 out of 22 patients. The follow-up was complete in all cases by clinical examination and serial echocardiograms and the median follow-up period was 87 months (range 24–108). There were two failures that required reoperation because of unsuccessful repair and worsening MR (elongation of the anchored side of the papillary muscle). When the reoperated patients were excluded from the follow-up data, the degree of MR, estimated by echocardiography that was performed at a recent follow-up period, was nonexistent in 6 patients, trivial in 10 patients, and mild in 4 patients. The systolic and diastolic dimensions of the left ventricle decreased significantly (p < 0.01).
CONCLUSIONS: Replacement of the artificial chordae was not complicated and seemed to preserve favorable relationships among leaflet tissues, chordae, and papillary muscles. We therefore suggest that the extensive use of PTFE artificial chordae seems to be a promising procedure regarding the repair of many kinds of mitral lesions causing MR.
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Introduction
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Al though 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) or bilateral mitral leaflets (BML). Mitral valve incompetence in these patients can be treated by resection of the prolapsing segment of PML followed by mitral annuloplasty (MAP) [3]. Furthermore surgical outcomes regarding PML prolapse are widely accepted [1–3]. When the incompetence is due to the extended lesion of PML, repair of the mitral valve is more complicated and sometimes not feasible because of the impossibility of resecting the large segment of PML. Similarly patients with advanced rheumatic mitral valve disease may exhibit excessively thickened and calcified chordae tendinae preventing a satisfactory repair.
In 1989 David and associates [4] demonstrated the possibility of the extended operative application for mitral valve prolapse by the chordal replacement with expanded polytetrafluoroethylene (e-PTFE) sutures. Since then the effectiveness and reliability of this technique for AML and BML has been presented both experimentally and clinically [5–10]. Similarly we have also reported our experiences with regard to repairing BML prolapse of mitral valve repair [11]. However the efficacy of chordal replacement with e-PTFE sutures for prolapse of the posterior has not been documented. For the repair of PML prolapse, we herein report our experience in performing artificial chordal reconstruction without leaflet resection.
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Patients and methods
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Patients
From March 1994 through December 2000, mitral valve repair was performed in 22 patients with PML prolapse. There were 15 men and 7 women whose mean age was 58.8 years ranging from 39–73 (Table 1). During this period our policy of operative technique was chordal replacement with PTFE grafts. Leaflet resection and annuloplasty for PML prolapse was performed in only 1 patient with deformed leaflet caused by infective endocarditis in 1999. The preoperative electrocardiogram revealed sinus rhythm in 21 patients and atrial fibrillation in 1 patient. Preoperative echocardiographic studies indicated degenerative disease and rheumatic heart disease of the mitral valve in 19 and 1 out of 22 patients, respectively (Table 2). Two patients exhibited infective endocarditis. No patient had previously undergone cardiovascular procedures.
Mitral regurgitation (MR) was assessed using transthoracic echocardiography [12]. MR was graded according to the percentage of regurgitant jet area to the left atrial area (mild = < 20%, moderate = 20–40%, severe = > 40%). Preoperative MR indicated a moderate degree in 3 patients and a severe degree in the other 19 patients. Preoperative cardiac catheterization was performed in all patients. Preoperative left ventriculography indicated a grade 3/4 MR in 4 patients and a grade 4/4 in 18 patients. Fifteen patients were designated as New York Heart Association (NYHA) functional class II, 5 patients were designated as class III, and 2 patients were designated as class IV.
Operative technique
The approach to the heart was through a midline sternotomy and the mitral valve repair was performed using cardiopulmonary bypass and moderate hypothermia (28°–30°C) [11, 13, 14]. Myocardial protection was provided by topical cooling and intermittent cold crystalloid cardioplegic solution (Kyushu University Solution; Kyushu University, Fukuoka, Japan)[15].
Approach to the mitral valve was through a superior transseptal method. The entire mitral valve apparatus was carefully inspected and prolapsed legions were identified. The main cause of prolapse was degenerative (chordal elongation or torn chordae) (Table 1). Flail segment was described as the proportion of PML. Subsequently we performed mitral valve repair by chordal replacement followed by MAP. The prolapsed PML was not resected. We reconstructed the chordae tendinae with CV-4 e-PTFE sutures [4, 8]. Briefly the double-armed sutures are passed twice through the fibrous portion of the papillary muscle head that anchors the elongated or ruptured chordae and are tied down (7 or 8 knots are required 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 chordae 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 e-PTFE chordae is adjusted by approving the coating area of the opposite leaflet [13, 14]. 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. Kay's suture annuloplasty (n = 20) or ring annuloplasty (Cosgrove ring n = 2; Edwards Lifesciences, Irvine, CA) was added according to the dilation of the mitral annulus.
To evaluate residual MR, cold cardioplegic solution was then injected into the left ventricular cavity. The repair was considered acceptable when the regurgitation was less than trivial during testing. After the removal of cardiopulmonary bypass, residual MR was reevaluated by the intraoperative transesophageal echocardiography in all cases. When the regurgitant area was less than 3 cm2, the repair was considered acceptable (when the area was greater than 3 cm2, the repair was considered unacceptable and mitral valve replacement was chosen).
Follow-up
All patients underwent 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 to keep the international normalized ration (INR) between 2.0–2.5. Anticoagulation was discontinued after 3 months except in a patient who was in atrial fibrillation.
Statistical analysis
Computerized statistical analysis was performed with StatView 5.0 for Macintosh statistical program (Abacus Concepts Inc., Berkeley, CA). All values are expressed as the mean ± standard deviation (SD). A Student's t test and a paired t test were also used to analyze the data when it seemed parametric. When the data seemed nonparametric (preoperative and postoperative MR and NYHA), however, the Wilcoxon signed-rank test was used.
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Results
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No operative death or morbidity was observed. Before being discharging from the hospital, echocardiography was performed in all patients. The results revealed no MR in 6 patients, trivial regurgitation in 10 patients, mild regurgitation in 4 patients, moderate regurgitation in 1 patient, and severe regurgitation in 1 patient. (Table 2).
The follow-up on these patients extended from 24–108 months with a median of 87 months. In 2 patients the operation seemed to be unsuccessful (patients 9 and 15, Table 1). Patient 9 exhibited 1/3 PML prolapse at posteromedial side caused by rheumatic change. Elongated chordae were replaced with two strands (pairs) of 4-CV PTFE grafts. This patient experienced an acceptable hemodynamic result from the mitral valve repair with only mild residual MR (evaluated by intraoperative transesophageal echocardiography). Unfortunately, however, the regurgitation worsened to severe MR by 2 weeks postoperative. This patient was discharged because of refusal for reoperation once, but underwent successful mitral valve replacement 8 months after mitral valve repair because of the progression toward congestive heart failure. At operation the anchored sites of papillary muscles were elongated, suggesting that the anchored portions did not seem enough to suspend PTFE chordae. The other patient exhibited 1/2 PML prolapse at anterolateral side. Prolapse was caused by degenerative change (chordal elongation + torn chordae). Elongated chordae were replaced with three strands (pairs) of 4-CV PTFE grafts. This patient also experienced an acceptable hemodynamic result from the mitral valve repair with only mild residual MR. Unfortunately, however, the regurgitation worsened to moderate MR by 1 week postoperatively and advanced to severe after 12 months. This patient underwent successful mitral valve replacement. At operation the anchored sites of papillary muscles were elongated, suggesting that the anchored portions did not seem enough to suspend PTFE chordae either.
There were no late deaths, no episodes of hemorrhage, and no thromboembolism reported. The postoperative MR was significantly reduced compared with the preoperative MR (p < 0.01). When the reoperative patients were excluded from the data, no progressive MR was observed that was more than mild. The NYHA functional class, cardiothoracic ratio, left ventricular end-systolic dimension (LVDs), and left ventricular end-diastolic dimension (LVDd) in all patients based on echocardiographic findings obtained during the follow-up period are presented in Table 3.
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Comment
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Surgical repair for mitral valve insufficiency permits total preservation of the mitral valve apparatus and ventricular function with only few valve-related complications [16, 17]. Classically Carpentier reported excellent results using various repair techniques [3]. Limited prolapse of PML can be repaired in a straightforward manner by leaflet resection and suture followed by MAP [3, 18]. The technique of leaflet resection and MAP demonstrated excellent clinical results and world-wide approval. Within the past 15 years we have performed 27 cases that were successfully repaired using this technique (n = 24, October 1985 to February, 1994; n = 1, 1999; n = 2, 2000) with the significant MR-free ratio being approximately 90% (unpublished data). Actually, however, we have also encountered a few cases that required reoperation because of tearing at the site of leaflet resection and suture. Furthermore extended PML prolapse is impossible to repair and requires the application of the other complex techniques. Although the sliding valvuloplasty technique can be applied in extended PML [18], more than 1/2 prolapse of PML is impossible. Other complex techniques such as chordae shortening, chordal transposition, or a flip-over technique [3, 19, 20] are not acceptable for PML prolapse. Thus we applied the technique of chordal replacement without leaflet resection for all kinds of PML prolapse from March 1994 through December 2000 (n = 25) and 22 operations were successful. Three patients were operated with leaflet resection and MAP because prolapse lesions were deformed by infective endocarditis. Our results indicated that both limited and extended lesion of PML prolapse could be repaired by the same technique of chordal replacement and MAP.
The experimental evidence that e-PTFE is a reliable material to replace mitral valve chordae has been confirmed by Cochran and Kunzelman [21] who compared the viscoelastic properties of natural mitral chordae with those of different sutures. Clinically David and associates reported excellent midterm results in 44 cases with chordal replacement including leaflet resection followed by ring annuloplasty [8]. The chordal replacement technique with PTFE is very attractive and conceives the possibility of repairing all types of MR. Thus we reconfirmed that PTFE sutures are suitable for artificial chordae repair as well as for extended operative application for BML prolapse and initially began to accept the potential regarding this technique for AML prolapse in 1991. Our results indicate that chordal replacement technique is applicable for repair of all types of both BML prolapse [11] and PML prolapse.
The major concern regarding artificial chordae, however, is the long-term durability, as well as flexibility, of the material. Several authors summarized their recent findings regarding the use of PTFE sutures as artificial chordae [5, 22, 23]. First PTFE chordae became covered by a host fibrosa and an endothelium layer within 1 year. Second after being covered by the host the PTFE sutures exhibited flexibility similar to that of natural chordae. However, Kobayashi and associates [24] describe mitral valve dysfunction resulting from the thickening and stiffening of the PTFE chordae. Third no report has determined PTFE chordae breakage, either early or late. Fourth calcification had been indicated in an isolated PTFE chordae used experimentally, but has not been otherwise been reported. Finally anchored papillary muscle rarely revealed mechanical problems although PTFE grafts themselves are not of concern. In the present series we performed two reoperations. In both cases the anchored sites of papillary muscles were elongated, suggesting that the anchored portions did not seem enough to suspend PTFE chordae either. We now use pledgeted PTFE sutures to reinforce anchored sites.
Mitral valve repair is associated with a low operative mortality and the long-term survival is highly favorable [25–28]. Deloche and associates [28] reported an actuarial survival (excluding operative mortality) of 71% ± 3% at 15 years in a group of 113 patients operated on from 1972–1979. The survival rate at 8 years in that series was very similar to a more recent report [29]. Many studies indicate that the actuarial survival at 5 years is around 90% [25–29]. More recently 10-year surgical outcome using the chordal replacement technique clarified a late mortality similar to the one indicated by others [30]. Within the past 15 years we performed mitral valvuloplasty in 125 patients (this includes the present cases). No operative deaths or late mortality were encountered (unpublished data). The survival is higher than that observed after mitral valve replacement [31] and valve-related deaths are less common among patients who underwent mitral valve repair than in patients who underwent mitral valve replacement [26].
For success regarding the use of this technique, the most important factor seems to be that of accurately determining the proper length of the reconstructed chordae. During this procedure many surgeons tie the suture at the leaflet level whereas the opposite leaflet is kept taut. When the opposite leaflet is not prolapsed in the PML, the same procedures can be used. In the case of diffuse mitral prolapse (board PML prolapse and bileaflet mitral prolapse), however, we have to rely heavily on the findings of a preoperative echocardiographic examination. It seemed 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 (Tomita, personal communication).
In summary, we have observed and reported on 22 patients who underwent successful repair of PML prolapse including the diffuse type. Although there has yet to be adequate long-term follow-up regarding the extended use of PTFE chordae, present midterm results clearly demonstrate highly favorable ventricular function and preserved mitral valve function. We therefore conclude that the extensive use of PTFE artificial chordae seems to be a promising procedure for the repair of all types of mitral valve prolapse.
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Acknowledgments
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The authors thank Dr Tarek EL-Sawy and Dr Qi-Wei Zhang (Lerner Research Institute, Cleveland Clinic Foundation, Cleveland, OH) for English editing and critical comments. The authors also thank Dr Naoko Kinugawa (Department of Medical Information, Kyushu University Hospital, Fukuoka, Japan) for consultation regarding statistical analyses.
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Abstract
Introduction
