Patients and Methods

Echocardiography Assessment

Perioperative transthoracic echocardiography (TTE) on a Siemens Acuson SC2000 ultrasound machine was performed in all patients, and intraoperative transesophageal echocardiography was carried out to analyze the valve before and after the repair process. The morphology and structure of mitral valves were carefully assessed according to the Wilkins score. Based on 2014 and 2017 American Heart Association/American College of Cardiology guidelines for the management of patients with valvular heart disease,¹² mitral stenosis (MS) was graded as follows: very severe (mitral orifice area [MVOA] ≤1.0 cm²), severe (MVOA, ≤1.5 cm²), and progressive (MVOA, ≤2.0 cm²). Mitral regurgitation was graded as mild (effective regurgitant orifice [ERO] <0.2 cm²), moderate (ERO, <0.4 cm²), or severe (ERO, ≥0.4 cm²). The length of anterior mitral leaflet (L-AML), length of posterior mitral leaflet (L-PML), and coaptation length (CL) were measured from the parasternal long axis view. Leaflet mobility was reflected by the angle between the leaflet and mitral annulus line. A line was drawn at the level of the mitral annulus. Then, 2 lines were drawn connecting the tips of the leaflets and the annulus, and α and β referred to anterior and posterior leaflet angles, respectively. During diastole, α₁ and β₁ were defined as anterior and posterior leaflet angles in diastole, respectively, and α₂ and β₂ were anterior and posterior leaflet angles in systole, respectively (Fig. 1).

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Surgical Techniques

The median sternotomy approach and conventional ascending aorta and bicaval cannulation were performed in all patients. The interatrial approach was carried out for mitral valve exposure. The repair techniques were performed in 4 steps in general and mainly based on commissuroplasty (Fig. 2).

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• Step 1: Shaving. Sutures were made within the annulus for good exposure of the mitral valve. A 4-0 traction suture was made on each commissural leaflet and used to pull the 2 sides of the commissure into the same plane. Then, commissure and leaflet shaving and decalcification were performed to recover the mobility of the commissure.

• Step 2: Checking. Two nerve hooks were used for traction, which allows visualization of the distribution of the subvalvular apparatus as well as the natural delineation between the anterior and posterior commissural leaflets.

• Step 3: Commissurotomy. An incision was made along the natural commissural line toward about 2 to 3 mm from the annulus. The surgeon monitored the distribution of the chordae tendineae during this process.

• Step 4: Releasing. The corresponding adherent chordae or papillary muscle was split in case the leaflets remained retracted or of insufficient MVOA after commissurotomy.

Following the steps above, to complete the operation in the anterior and posterior commissure continuously, the saline test was performed to assess mitral valve competence. An annuloplasty ring was implanted in all patients. Individuals with atrial fibrillation (AF) underwent the Cox-maze IV procedure, and the left atrial (LA) appendage was closed from the inside of the LA simultaneously.

Results

Baseline Patient Characteristics

A total of 60 patients were analyzed, including 42 (70%) women. The mean (SD) age at surgery was 56.9 (9.9) years, with a range from 28 to 75 years. Exertional dyspnea was the predominant symptom in most patients. A total of 25 (41.7%) patients had NYHA class III or higher. Fifty-six (93.3%) patients had an MVOA below 1.5 cm². The mean (SD) Wilkins score was 9.23 (2.56) preoperatively. Atrial fibrillation was present in 46 (76.7%) patients, 4 of whom had LA thrombus. Detailed baseline characteristics are summarized in Table I.

TABLE I Baseline Patient Characteristics

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Surgical Outcomes

All patients survived the repair operation. There was no mitral replacement and re-cross-clamp during the operation. The mean (SD) cardiopulmonary bypass time was 110.38 (28.46) minutes, and the mean (SD) aorta cross-clamp time was 82.36 (23.10) minutes. A total of 93.3% of all patients underwent tricuspid valve repair. Commissurotomy was the main technique used in rMVR and was performed in 58 patients (96.7%) on both commissures and in only 2 patients on single anterior commissure. Leaflet shaving on the commissure area was used in 57 individuals (97%), with extra shaving on leaflet body of A2 and P2 in 5 patients. An annuloplasty ring was implanted in all patients. A total of 26 (43.3%) patients had 30-mm rings implanted. Table II summarizes the details of MVR techniques.

TABLE II Details of Rheumatic Mitral Valve Repair Techniques

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Echocardiographic Data After the Operation

No moderate or severe MR was detected by TTE in any patient before discharge. Rheumatic MVR caused substantial changes in the morphologic and hemodynamic characteristics of the mitral valve. There were significant changes in MVOA and LA diameter postoperatively. The mean (SD) MVOA increased from 1.20 (0.34) cm² to 2.24 (0.38) cm² postoperatively (P < .001). Meanwhile, the mean (SD) LA diameter decreased significantly from 49.41 (10.89) mm to 45.89 (7.83) mm (P < .001). However, no statistically significant differences were found in left ventricular ejection fraction, left ventricular end-diastolic dimension, or left ventricular end-systolic dimension postoperatively vs preoperative values.

Regarding leaflet parameters, both α₁ and α₂ changed substantially after surgery. In fact, the mean (SD) α₁ increased from 44.53° (9.68°) to 59.87° (7.27°) (P < .001), and the mean (SD) α₂ decreased from 25.07° (4.10°) to 16.80° (6.16°) (P < .001) after surgery. However, β₁ and β₂ did not have such changes. There were no substantial changes in L-AML or L-PML postoperatively. The mean (SD) CL improved significantly, from 6.69 (1.32) mm to 7.92 (1.24) mm (P < .001) after surgery (Table III).

TABLE III Echocardiographic Data

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Follow-Up Findings

All patients completed the 1-year follow-up visits through January 2020. Of these, 58 patients were evaluated by TTE at 3 months postoperatively. Further, 51 patients completed echocardiography evaluation in the study center throughout the follow-up period, while 9 were examined at their local hospitals.

No deaths, reoperations, or severe complications occurred during follow-up. Three patients were readmitted for transthoracic synchronized defibrillation therapy because of AF after discharge. Only 1 patient showed moderate or severe MR (ERO, 0.3 cm² near the posterior commissure) at 6 months after surgery. Because of the absence of obvious clinical symptoms, the patients were followed up by medical therapy. Echocardiography follow-up data are summarized in Table IV.

TABLE IV Echocardiographic Data During Follow-Up ^a

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Discussion

This prospective study demonstrated that the SCORe procedure is effective in improving the mobility of mitral leaflets and MVOA in rMVR, with minimal complications and promising results. Although rMVR remains controversial, many studies have confirmed its feasibility and effectiveness as well as advantages in survival, complications, and other aspects, compared with mitral valve replacement.^5,8,14 However, in most reports about rMVR, mitral insufficiency is considered the predominant lesion.^15–18 In contrast, this study focused on patients with MS.

Thickening, fibrosis, and calcification are factors affecting the activity of the leaflet; therefore, leaflet thinning is an important technique in rMVR.¹⁹ Commissural fusion in a rheumatic mitral valve is the most important reason for decreased MVOA and valve insufficiency.¹⁰ Therefore, commissurotomy is a widely used technique for alleviating valve stenosis in rMVR.^17,20,21 In the past, for the correction of MS, simple commissurotomy was performed to improve the mitral orifice and to recover the mobility and coaptation by correcting the length and thickness of leaflets. However, correction of commissural leaflet areas has been neglected. Although simple commissurotomy indeed increases the orifice area, it does not improve the activity of commissural leaflets that may cause regurgitation in the commissure area because of poor coaptation. Moreover, the thickened and fused leaflets affect the identification of natural commissure by the surgeon, which may affect the result of commissurotomy. If an incision is too small, the mitral valve cannot fully open, whereas too large an incision may destroy the commissural leaflets and cause regurgitation at the commissural area in systole. Commissural leaflet shaving and decalcification not only help improve the softness of the commissure; they also reveal the boundary of fused anterior, posterior, and commissural leaflets, which is a good indicator for commissurotomy. After this commissure shaving, commissurotomy effectively improves the opening of the mitral valve and the mobility of leaflets. Therefore, leaflet shaving and decalcification were performed as the first procedural step in the study center.

In this study, 57 patients (95%) underwent commissure leaflet shaving, and extra peeling of leaflet body was performed in only 5 individuals. The rate of decalcification was approximately 46.7%, and no obvious calcified annulus was found. To reduce the limitation of leaflet mobility, calcification in any position on the leaflet should be removed to the extent possible. The results showed that valve opening and movement were improved after repair, mean (SD) α₁ increased from 44.53° (9.68°) preoperatively to 59.87° (7.27°) (P < .001), whereas the mean (SD) β₁ increased from 74.00° (17.12°) preoperatively to 76.93° (11.55°) postoperatively (P = .591). In addition, as in rheumatic mitral valve disease, thickening, fibrosis, and calcification are often more serious on the posterior leaflet body.¹⁰ Here, the improvement in the mobility of the anterior leaflet was more substantial than that of the posterior leaflet postoperatively (Fig. 3). However, the increased MVOA was unaffected by the posterior leaflet. These findings suggest that it is very important to recover the mobility of the anterior mitral leaflet in rMVR.

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A shortened leaflet affects its mobility. Gupta et al²² suggested L-AML as a predictor of rMVR, with a value of 26 mm or more predicting reparability. In that study, a pericardial patch was used to increase the area of the anterior leaflet to increase its mobility and CL. Although many studies have confirmed good outcomes for autologous pericardial patch in rMVR,^20,23,24 the procedure is relatively complex, as the patch size is often difficult to determine and the subvalvular structure is usually destroyed. In addition, Dion et al²⁵ used a pericardial patch on posterior mitral leaflet for MS repair and achieved good clinical results. However, this method requires more precision in patch creation to avoid systolic anterior motion. In contrast, the repair method in this study did not affect the length of mitral leaflets. The mean (SD) L-AML value was 26.50 (3.68) mm (range, 20–33 mm), and 48% of the assessed patients had a length less than 26 mm. This did not affect repair outcome. Further, the anterior leaflet area can be obtained indirectly by measuring the size of the artificial ring. In the present study, 83.3% of patients had rings implanted with a diameter of 30 mm or 32 mm. Although the ring size was smaller than that commonly used in degenerative MVR, the results of this study indicated that most patients with rheumatic MS had sufficient leaflet body area to meet the need for coaptation.

Chordal thickening and fusion are the most common subvalvular pathology in rMVR, which restricts the mitral valve in the cardiac cycle and decreases coaptation. According to previous studies, the rate of subvalvular release might be lower in cases of rheumatic MR.^18,26 Unlike MR, in which valve prolapse or enlarged annulus results in a loss of coaptation, patients with pure MS do not have coaptation problems preoperatively. However, with mitral orifice opening and increased volume of the left ventricle after surgery, leaflet movement will be restricted and cause regurgitation. Therefore, subvalvular apparatus release is beneficial to render the valve more mobile and freer to move. Chotivatanapong et al²⁷ assessed 221 rMVR procedures; of these, secondary chordal resection and papillary muscle splitting accounted for 54.7% and 49.8%, respectively.

In this study, 35% of patients underwent chordae splitting only, and 56% required splitting of both the chordae tendineae and papillary muscles. The mean (SD) CL was significantly improved postoperatively (7.92 [1.24] mm vs 6.69 [1.32] mm; P < .001) and was maintained at 8.02 (1.22) mm 1 year after surgery. However, whether this increase was affected by the use of annuloplasty rings is unknown. In addition, α₂ and β₂ decreased postoperatively, which indicated that with the relief of subvalvular restriction, the movement of leaflets was improved in systole. Although chordae transfer and artificial chordae are also available and effective in rMVR, these options are not commonly applied in the center in the present study.

The use of an annuloplasty ring has become a standard technique in MVR, especially for degenerative MR, which is often accompanied by annular dilatation. Annuloplasty using a prosthetic ring in degenerative MR can effectively improve short-term and long-term repair efficacy. However, there is still some controversy about the need for prosthetic rings in patients with rheumatic mitral valve disease. Li et al²⁸ compared the annular structure between rheumatic and degenerative mitral valve diseases and found that the annulus structure in rheumatic mitral valve also changes, losing its saddle shape. Bernal et al²⁹ reported that an artificial ring could also substantially reduce the reoperation rate in patients with rheumatic mitral dysfunction. Therefore, a 3-dimensional complete annuloplasty ring is routinely implanted in all patients, even those with rheumatic MS. Previous findings²¹ suggested implanting an oversized ring in rMVR to prevent stenosis and systolic anterior motion. However, selection of annuloplasty ring size based on anterior leaflet length could be just enough and achieve good results.

Enlarged LA affects left ventricular function and sinus rhythm maintenance after radiofrequency ablation.³⁰ After correction of valve orifice stenosis in LA dilatation caused by MS, LA volume can be effectively reduced to improve ventricular function, decrease the risk of thrombosis, and improve the outcome of radiofrequency ablation on AF, which may substantially increase the odds of mitral dysfunction and adverse outcomes. Left atrial plication was suggested for an LA diameter exceeding 50 mm on preoperative echocardiography.⁸ In the current patients, LA plication was not applied. Although the patients had LA dilatation (mean [SD], 49.41 [10.89] mm) at baseline, the mean (SD) LA size was substantially reduced to 45.08 (8.32) mm at 12 months after surgery. Internal obliteration of LA appendage was performed in patients with AF to decrease the risk of thrombosis.

Percutaneous mitral balloon commissurotomy is considered the first choice for selected suitable rheumatic MS by guidelines for the management of valvular heart disease in Europe and the United States.^12,31 Because of regional and pathologic differences, as well as the development of valvular surgery, PMBC is used less frequently in China. Although PMBC and surgical repair have not been fully compared, commissuroplasty has certain advantages over PMBC, as follows.

• Release of subvalvular apparatus, which may enhance the effect of commissurotomy, cannot be performed in PMBC.

• Commissuroplasty can accurately separate the fused commissure along the normal anatomic position, whereas PMBC splits the weakest area of the leaflets with high risk of MR.

• Applying an annuloplasty ring can increase CL and stabilize the annular structure, which cannot be achieved by PMBC.

The present study examined the short-term results of all patients. Clinical outcomes were promising during the follow-up visits. MVOA was stable in patients 12 months postoperatively (Fig. 4). Only 1 patient showed moderate MR (1.67%) but without clinical symptoms during follow-up. In a study by Kim,³² 61 patients showed severe valve dysfunction postoperatively, within a mean (SD) follow-up of 71.9 (41.0) months, with 51 (83.6%) MR cases, suggesting MR as the main cause of long-term mitral dysfunction. According to a study by Kim et al,³³ most reoperations because of recurrent MR occur within the first 6 months after surgery, with the reoperation rate decreasing afterward. The above-described findings indicate that the current patients may also experience satisfactory long-term results.

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Although rMVR provides multiple advantages, not all patients with rheumatic mitral disease are eligible for repair in current clinical practice. In addition, success in this procedure depends on the severity of valvular calcification as well as the surgeon's technical skills. The primary limitation of the study is that it was a pre/post study with no control group of patients with rheumatic MS who underwent other surgeries. Furthermore, this was a single-center study focusing on a patient population predominantly with MS, instead of all types of rheumatic mitral lesions. Follow-up was also relatively short in this study. Although the early outcomes can reflect changes in mitral leaflet mobility and subsequent efficacy after rMVR to some degree, long-term follow-up is still needed for a comprehensive evaluation, particularly valve leaflet activity assessment. Finally, the sample size was relatively small, and larger studies are required to improve the generalizability of these findings.

In all, repair surgery for rheumatic MS is rarely carried out because the related surgical methods are diverse and inconsistent, making it difficult to master. The SCORe surgery provides a new idea for repairing rheumatic MS. Previous studies have also confirmed the effectiveness of this method. However, studies examining the improvement of valve leaflet activity are lacking. Therefore, this study aimed to assess the activity of the valve leaflet. Long-term follow-up of valve leaflet activity still deserves further investigation.

Conclusion

In select patients with rheumatism in China, commissuroplasty effectively improves leaflet mobility, thereby increasing MVOA and CL while preserving the original mitral leaflet length and the subvalvular apparatus. These short-term results need to be further validated with large sample sizes and prospective studies.