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Ann Thorac Surg 2009;87:1715-1720. doi:10.1016/j.athoracsur.2009.03.003
© 2009 The Society of Thoracic Surgeons
Original Articles: Adult Cardiac
Chordae Replacement Versus Resection for Repair of Isolated Posterior Mitral Leaflet Prolapse: À Ègalité
Joerg Seeburger, MD*,
Volkmar Falk, MD, PhD,
Michael A. Borger, MD, PhD,
Jurgen Passage, MBBS, FRACS,
Thomas Walther, MD, PhD,
Nicolas Doll, MD, PhD,
Friedrich W. Mohr, MD, PhD
Heart Center, Leipzig University, Leipzig, Germany
Accepted for publication March 2, 2009.
* Address correspondence to Dr Seeburger, Heart Center, Leipzig University, Struempelstrasse 39, Leipzig, 04289, Germany (Email: j.seeburger{at}web.de).
| ADULT CARDIAC SURGERY:
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Abstract
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Background: Mitral valve (MV) repair for posterior mitral leaflet (PML) prolapse has proven excellent results. The loop technique, which involves insertion of polytetrafluoroethylene neochordae while preserving the native PML tissue, was developed to facilitate MV repair through a minimally invasive approach. The aim of this study was to assess the medium-term results of the loop technique in comparison with the widely adopted leaflet resection technique for repair of isolated PML prolapse.
Methods: Between March 1999 and January 2008, a total of 1,708 patients underwent minimally invasive MV repair. Six hundred and seventy patients (39.2%) had isolated PML prolapse and were treated with either the loop technique (n = 317) or the leaflet resection (n = 353) technique, according to surgeon preference. Mean follow-up time was 2.8 ± 2.2 years, and follow-up was 99% complete.
Results: Early postoperative echocardiography showed a significantly larger mitral orifice area (3.3 ± 0.3 cm2 versus 3.0 ± 0.8 cm2, p < 0.001) and lower mean pressure gradient (2.7 ± 1.7 mm Hg versus 3.1 ± 1.7 mm Hg, p = 0.03) after implantation of loops. Other perioperative outcomes were similar for the two groups of patients. Freedom from reoperation at 5 years was significantly higher after the loop technique (98.7%, 95% confidence interval [CI]: 96.7% to 99.5%) when compared with leaflet resection (93.9%, 95% CI: 90.7% to 96.1%, log-rank p = 0.005). Cox regression analysis revealed that implantation of a flexible, incomplete band was an independent predictor of reoperation (hazard ratio 6.2, 95% CI: 1.3 to 110.7), whereas use of leaflet resection had a nonsignificant trend toward an increased reoperation rate (hazard ratio 2.6, 95% CI: 0.9 to 9.1). Reoperation for excessive systolic anterior motion did not occur in any loop patient.
Conclusions: Both the loop technique and conventional leaflet resection yield excellent results for repair of isolated PML prolapse. The technical ease of performing the loop technique through a minimally invasive approach, however, makes this method a particularly valuable alternative for MV repair surgery.
Mitral valve (MV) repair has been proven to achieve excellent midterm and long-term results and is considered to be the gold standard therapy for patients with severe MV regurgitation [1–4]. Quadrangular or triangular leaflet resection, with or without a sliding annuloplasty, is the most common type of repair performed for isolated posterior mitral leaflet (PML) prolapse. Although effective, leaflet restriction may specifically be found after quadrangular resection of the PML and may impair, to some extent, its physiologic role [5, 6]. Newer methods of preserving the posterior leaflet by use of premeasured polytetrafluoroethylene (PTFE) neochordae (the loop technique) have been proposed [7–9]. These techniques were originally developed to facilitate MV repair during minimally invasive surgery, but can just as easily be applied to surgery performed through a sternotomy. To date, relatively little is known about the midterm durability of the loop technique and how it compares to the leaflet resection technique. We therefore sought to assess the results of the loop technique in comparison to leaflet resection, with a particular focus on reoperation during follow-up, for patients with isolated PML prolapse.
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Patients and Methods
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Patients
From March 1999 to January 2008, a total of 1,708 patients underwent minimally invasive MV repair at our center. Of this group, patients were included in the present study if (1) they had isolated PML prolapse and (2) they underwent MV repair with either the leaflet resection technique or the loop technique exclusively. Patients who underwent a combination of both techniques were excluded. A total of 670 patients (39.2% of the total population) were identified as meeting these criteria. Overall, 15 patients (2.2%) had previous cardiac surgery (coronary artery bypass graft surgery in 10 patients, mitral valve surgery in 2, mitral valve and coronary artery bypass graft surgery in 1, closure of an atrial septum defect in 1, and closure of a ductus arteriosus in 1). Details on preoperative patient demographics and MV characteristics of both patient groups are depicted in Tables 1 and 2.
The operative approach was minimally invasive in all patients using a right lateral minithoracotomy and femoral cannulation for cardiopulmonary bypass, as described in detail elsewhere [4, 10]. Ethics approval without individual patient consent was granted from the local Ethics Committee.
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Table 1 Preoperative Characteristics of 670 Patients With Isolated Posterior Leaflet Prolapse Undergoing Mitral Valve Repair Using Either Leaflet Resection or Loop Technique
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Mitral Valve Repair Technique
All patients underwent MV repair with insertion of an annuloplasty ring. Details regarding the surgical approach [4, 10] and the type of repair techniques have been described extensively elsewhere [7, 8, 11, 12]. The classic Carpentier type technique with resection of valvular tissue, plus or minus a sliding annuloplasty, was performed in all patients in the leaflet resection group. All patients in the loop group underwent implantation of premeasured PTFE loops without resection of any leaflet tissue. The length of the loops was determined by measuring the distance from the tip of the corresponding papillary muscle to the free margin of a nonprolapsing segment of the posterior leaflet. The type of MV repair performed was according to surgeon preference, but the loop technique has become increasingly common over the last few years.
Follow-Up and Statistical Analysis
Follow-up was performed by personal contact, mailed questionnaire, or by phone contact with patients and family members, with supplemental information supplied from family physicians and referring cardiologists. Follow-up was 99% complete.
Categorical variables are expressed as proportions and continuous variables as mean ± SD throughout the manuscript. Categorical data were compared by the 
2 test and continuous data by Student's unpaired t test. Analysis of medium-term reoperation and survival rates were evaluated using the Kaplan-Meier estimated model and tested for significance by the log-rank and Wilcoxon tests. Cox regression analysis was performed to determine the independent predictors of valve-related reoperation. Statistical significance was considered at the p less than 0.05 level. All analyses were performed with SAS JMP 7.0 software (SAS Institute, Cary, NC). Guidelines for reporting morbidity and mortality after cardiac valvular operations were obeyed [13].
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Results
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All 670 patients in the current study underwent minimally invasive MV repair. In 353 patients (52.7%), repair consisted of leaflet resection; in 317 patients (47.3%), the loop technique was performed (Table 3).
Implantation of a mitral annuloplasty ring was performed in all patients (Table 3). The implanted ring size was significantly larger in the loop group than in the resection group (mean ring size 32.6 ± 2.7 mm versus 31.1 ± 3.2 mm, p < 0.001). Concomitant MV repair techniques such as edge-to-edge (Alfieri), commissural plication, and others were performed in a small percentage of patients (Table 3).
There were no differences between groups regarding concomitant surgical procedures such as atrial fibrillation ablation or tricuspid valve surgery, but significantly more patients in the loop group received closure of an atrial septum defect/patent foramen ovale (Table 3). Mean total operating time, duration of cardiopulmonary bypass, and aortic cross-clamp times were significantly longer in the loop group than in the leaflet resection group (increased length of time 9, 11, and 13 minutes, respectively).
In-hospital echocardiographic examination 1 week after surgery revealed excellent valve function with a mean grade of mitral regurgitation of 0.3 ± 0.6 in the overall group. Mean grade of MR was significantly lower in the loop group (0.2 ± 0.5 versus 0.4 ± 0.6, p = 0.007). The mitral orifice area (MOA) was also significantly larger after repair with loops (3.3 ± 0.8 cm2 versus 3.0 ± 0.8 cm2, p < 0.001; Table 4). The mean MV pressure gradient after loop implantation was also significantly lower when compared with leaflet resection (Table 4).
The mean number of loops used on the P2 segment (3.4 ± 1.4) was nearly double the number of loops used on the P1 or P3 segment (Table 5). Loops used on the P2 segment were shorter than those on the remaining segments (Table 5).
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Table 5 Details on Loop Technique for Mitral Valve Repair in 317 Patients With Isolated Posterior Leaflet Prolapse
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Postoperative course included reoperation for bleeding in 38 patients overall (5.7%), with 17 occurring in the loop and 21 in the resection group (p = 0.7). Overall stroke rate was 0.9%, with 3 strokes occurring in each group (p = 0.9). Hospital stay was 11.8 ± 7.5 days in the resection group and 10.9 ± 6.3 days after the loop technique (p = 0.12). Overall 30-day mortality was 1.8% (12 of 670): 2.3% (8 of 353) after posterior leaflet resection and 1.3% (4 of 317) after the loop technique (p = 0.4).
Mean clinical follow-up time was 2.8 ± 2.2 years: 3.9 ± 2.3 years in the resection group and 1.6 ± 1.1 years in the loop group. Follow-up was 99% complete.
Kaplan-Meier estimates for cumulative survival at 5 years was 96.6% (95% confidence interval [CI]: 93.5% to 98.3%) after the loop technique and 86.9% (95% CI: 81.9% to 90.6%) after leaflet resection (log-rank p = 0.2; Fig 1).
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Fig 1. Kaplan-Meier curve for survival after mitral valve repair of isolated posterior leaflet prolapse in 670 patients using either the leaflet resection technique or the loop technique. (CI = confidence interval; Pts = patients.)
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Mitral valve reoperation occurred in 21 patients in the leaflet resection group versus 4 patients in the loop technique group (p = 0.002). The reasons for reoperation are depicted in Table 6, with leaflet associated dysfunction (n = 9) being the most common cause.
Freedom from valve-related reoperation at 5 years was significantly higher after loop implantation (98.7%, 95% CI: 96.7% to 99.5%) when compared with leaflet resection (93.9%, 95% CI: 90.7% to 96.1%, log-rank p = 0.005; Fig 2). Cox regression analysis revealed that the only independent predictor of reoperation was use of a flexible incomplete ring (hazard ratio 6.2, 95% CI: 1.3 to 110.7, p = 0.02). The use of leaflet resection for MV repair was associated with a nonsignificant trend toward increased valve-related reoperations (hazard ratio 2.6, 95% CI: 0.9 to 9.1, p = 0.08).
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Fig 2. Kaplan-Meier curve for freedom from valve-related reoperation after mitral valve repair of isolated posterior leaflet prolapse in 670 patients according to type of repair technique used. (CI = confidence interval.)
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Comment
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Reconstructive MV surgery aims to preserve native valve anatomy and function to the greatest possible extent, resulting in several well-documented advantages when compared with MV replacement. The goal of MV repair is to restore physiologic leaflet motion and to preserve a large mitral orifice and a sufficient line of coaptation, as well as to remodel the mitral annulus [12].
The most popular technique for correction of PML prolapse is quadrangular resection, with or without a sliding annuloplasty, as introduced by Carpentier [11, 12]. This technique comprises resection of excessive prolapsing leaflet tissue with subsequent reapproximation of the leaflet remnants. The advantage of this procedure lies in its proven excellent rate of long-term freedom from valve-related reoperation [11]. However, quadrangular PML resection leads to the loss of native valve tissue, altered native valve anatomy, and impairment of physiologic function of the PML. As a result, the PML is usually stiff, with limited mobility and limited surface area for coaptation with the anterior leaflet [5, 6]. Often, concomitant repair techniques such as plication of the mitral annulus or sliding annuloplasty are applied to compensate for the loss of tissue and support the reapproximated leaflet remnants. That may lead to a reduction in annular size that subsequently requires implantation of a smaller size ring.
The implantation of neochordae using PTFE sutures as a way to preserve native valve anatomy was first introduced by David and coworkers [7] in 1991, predominantly as a method to treat anterior leaflet prolapse. A modification of this approach, the so-called loop technique using premeasured PTFE sutures, was first described by our group in 1999 [8]. This technique follows several principles of reconstructive MV surgery by restoring physiologic leaflet function, creating the largest possible mitral orifice area, preserving ventriculoannular continuity, and minimizing leaflet tension. Although the loop technique was originally developed as a way to facilitate repair of anterior prolapse during a minimally invasive approach, we have increasingly applied this technique to posterior and bileaflet prolapse over time as we have become increasingly confident with the results. We have found that the loop technique results in a high rate of successful MV repair in patients with a wide spectrum of pathologies causing mitral regurgitation [14]. Despite our positive results, little is known about the medium- and long-term durability of this repair technique, since it was relatively recently developed. The goal of the current study was, therefore, to assess our medium-term results for the loop technique, when compared with conventional leaflet resection, in patients with isolated PML prolapse.
With regard to perioperative outcomes, our study reveals that the leaflet resection technique was associated with significantly shorter operation times, duration of cardiopulmonary bypass, and aortic cross-clamp times when compared with the loop technique, although the increased length of time was modest (9 to 13 minutes). We attribute this finding to the distinct simplicity of the resection technique and to the multiple number of loops that were used to repair the prolapsing segment (Table 5). Although the loop technique was associated with longer operative times, we do not believe that this technique is significantly more complex.
Regarding the size of implanted mitral annuloplasty rings, we found that the loop technique allowed for implantation of significantly larger rings (32.6 m versus 31.1 mm, p < 0.001) with a subsequent greater MOA (3.3 cm2 versus 3.0 cm2, p < 0.001), one of the major goals of reconstructive MV surgery [11]. Furthermore, lower mean pressure gradients were observed after PTFE loop implantation, even though all native leaflet tissue was retained. The latter observation confirms that the preservation of native prolapsing leaflet does not result in excessive tissue in the subvalvular region. The clinical relevance of these hemodynamic observations, however, is currently unknown. Further follow-up will be required to determine if a larger MOA and lower pressure gradient will lead to improved long-term clinical outcomes.
We found by univariate analysis that the loop technique was associated with a significantly better 5-year freedom from valve-related reoperation than leaflet resection for patients with isolated PML prolapse (98.7% versus 93.9%, respectively; p = 0.005). Although the reoperation rate for our leaflet resection group was somewhat elevated, it is within the range of those rates commonly found in the literature (93% to 96%) [1–6]. It should be noted, however, that several differences existed between our two groups with regard to operative techniques. Specifically, loop patients were more likely to receive a rigid complete ring and were less likely to undergo chordal transfer or an Alfieri stitch. We therefore performed a multivariable Cox regression analysis to account for these differences. The only independent predictor of valve-related reoperation was use of a flexible incomplete band (p = 0.02), although leaflet resection also had a statistical trend toward increased reoperations (p = 0.08). We feel confident in concluding that the loop technique results in clinical outcomes and durability that are at least as good as those of the leaflet resection technique, which is the current gold standard for repair of posterior leaflet prolapse. Further follow-up will be required to determine if the long-term results remain just as encouraging for the loop technique.
We recently compared the loop technique to conventional leaflet resection in a prospective, randomized trial [15]. A total of 129 patients were randomly assigned to receive MV repair using one of the two techniques. We found a significantly longer line of leaflet coaptation in the loop technique group, but failed to demonstrate any significant differences in terms of MOA or transvalvular gradients [15]. A longer line of coaptation has been shown to be associated with better long-term durability after MV repair for functional mitral regurgitation [16], and may explain to some extent the improved freedom from reoperation rate that we observed in the current study. The discrepancy between our randomized trial and the current study with regard to MOA and transvalvular gradient may be related to the much larger sample size in the current retrospective study.
Study Limitations
This study is retrospective in nature and is therefore subject to the inherent weaknesses of a retrospective analysis. However, our conclusions are compatible with a recent randomized, prospective study performed by our group [15]. Another weakness of the current study is the relatively small number of patients available for analysis at 5 years of follow-up in the loop implantation group. This finding is a result of the leaflet resection technique being our procedure of choice for PML prolapse in the early years of the study, but has been slowly replaced by the loop technique as we have become increasingly confident with this technique. Although the number of patients available for analysis at 5 years was suboptimal in the loop study group, Figure 2 and Table 6 show that the majority of reoperations occurred within the first year of surgery and longer follow-up is unlikely to alter our conclusions. Our finding that most reoperations occur early after MV repair has also been demonstrated by other groups with a large MV repair experience [17, 18]. Therefore, we believe that our conclusions are valid when stating that the loop technique results in durability that is at least as good as the conventional leaflet resection technique for isolated PML prolapse, at least in the medium term.
In conclusion, both leaflet resection and the loop technique are effective methods of treating patients with severe mitral regurgitation due to isolated PML prolapse. However, the loop technique results in a larger effective orifice area and a lower transvalvular mean gradient than does leaflet resection. In addition, the loop technique may be associated with better freedom from reoperation in the medium term. The loop technique should be considered a valuable alternative when performing MV repair in patients with MV prolapse, particularly when a minimally invasive approach is used.
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References
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- Falk V, Seeburger J, Borger MA, et al. How does the use of PTFE neochordae for posterior mitral valve prolapse (loop technique) compare with leaflet resection?. A prospective randomized trial. J Thorac Cardiovasc Surg 2008;136:1200-1206.[Abstract/Free Full Text]
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Abstract
Introduction
