Ann Thorac Surg 2003;75:41-46
© 2003 The Society of Thoracic Surgeons
Original article: cardiovascular
Open mitral commissurotomy in the current era: indications, technique, and results
Shiv Kumar Choudhary, MCha,
Jayesh Dhareshwar, MSa,
Akhil Govil, MSa,
Balram Airan, MCha,
Arkalgud Sampath Kumar, MCha*
a Cardiothoracic Centre, All India Institute of Medical Sciences, New Delhi, India
Accepted for publication August 8, 2002.
* Address reprint requests to Dr Kumar, Department of Cardiothoracic and Vascular Surgery, All India Institute of Medical Sciences, Ansari Nagar, New Delhi 110 029, India.
e-mail: askumar{at}medinst.ernet.in
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Abstract
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BACKGROUND: The present retrospective study is focused on indications, techniques, and results of open mitral commisurotomy in the current era.
METHODS: Of the 1,280 patients undergoing open-heart surgical procedures for rheumatic mitral stenosis between January 1990 and July 2000, 276 (21.6%) patients underwent open mitral commissurotomy. Major indications included presence of left atrial thrombus/clot (n = 82, 29.7%), severe subvalvular disease (n = 110, 39.8%), mitral valve calcification (n = 42, 15.2%), mild mitral regurgitation (n = 28, 10.0%), associated aortic valve disease (n = 55, 19.9%), organic tricuspid valve disease (n = 20, 7.2%), and failure or restenosis after closed or balloon mitral valvuloplasty (n = 55, 19.9%). Age of patients ranged from 7 to 67 years (mean, 30.2 ± 12 years). The majority (76%) were in New York Heart Association class III or IV, and 6.9% were in congestive heart failure. Atrial fibrillation was present in 134 (48.6%) patients. Mitral valve area ranged from 0.3 to 0.7 cm2 (mean, 0.52 ± 0.12 cm2). Mid-diastolic gradients across the mitral valve ranged from 8 to 34 mm Hg (mean, 14.5 ± 6.2 mm Hg), and end-diastolic gradients ranged from 8 to 42 mm Hg (mean, 15.2 ± 5.7 mm Hg). Open mitral commissurotomy was performed using standard cardiopulmonary bypass. Associated aortic valve procedure was performed in 55 patients, and either tricuspid valvotomy or repair was performed in 28 patients.
RESULTS: There were four early deaths. All these patients had associated aortic valve procedure (Ross procedure in 2 and homograft aortic valve replacement in 2). Three patients developed severe mitral regurgitation in early postoperative period (
30 days) and required reoperation. Predischarge echocardiography showed mitral valve area from 1.4 to 3.5 cm2 (mean, 2.6 ± 0.6cm2) and moderate mitral regurgitation in 4 patients. Follow-up ranged from 1 to 130 months (mean, 64.5 ± 28.6 months). There was no late death. There were three reoperations for mitral valve failure, and an additional 2 patients developed severe mitral stenosis (mitral valve area < 1.0 cm2). In operative survivors, freedom from mitral valve failure at 10 years was 87.0% ± 3.5%. In patients with isolated open mitral commissurotomy, the incidence of thromboembolism was 0.5%/patient-year.
CONCLUSIONS: Open mitral commissurotomy provides excellent early and long-term results in a selected group of patients.
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Introduction
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In the current era, percutaneous balloon mitral valvuloplasty (BMV) has become the procedure of choice for isolated, uncomplicated mitral stenosis with favorable morphology [1]. Open-heart surgical procedures are mainly limited to the extensively damaged and calcified mitral valves, or to the patients who require left atrial thrombectomy. In the early decades, a significant proportion of patients underwent open mitral commissurotomy (OMC) [2, 3], but in the present decade, this proportion is decreasing, and in an increasing number of patients, the mitral valve is being replaced with a suitable prosthesis [4]. Besides proven durability of prosthetic valve, development of techniques to preserve the chordal apparatus at the time of mitral valve replacement (MVR) [5, 6] has further tilted the balance in favor of MVR [4, 7, 8]. In the present study, we analyze our experience and discuss the indications, techniques, and results of OMC in the current era.
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Patients and methods
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Between January 1990 and July 2001, 3,943 patients underwent BMV, and 1,004 patients underwent MVR for rheumatic mitral stenosis. During the same period, 276 patients underwent OMC and form the patient population of the present study. Preoperative profile of these patients is shown in the Table 1.
All patients underwent transthoracic echocardiography. Mitral valve area ranged from 0.3 to 0.7 cm2 (mean, 0.52 ± 0.12 cm2). Mid-diastolic gradients across the mitral valve ranged from 8 to 34 mm Hg (mean, 14.5 ± 6.2 mm Hg) and end-diastolic gradients ranged from 8 to 42 mm Hg (mean, 15.2 ± 5.7 mm Hg). Transesophageal echocardiography was performed to evaluate the left atrial thrombus/clot. In 124 patients, cardiac catheterization was performed. Mean left atrial pressure ranged from 12 to 46 mm Hg (mean, 26.0 ± 8.4 mm Hg), and in 52 patients (42%), it was more than 25 mm Hg. Similarly, mean systolic pulmonary artery pressure ranged from 18 to 64 mm Hg (mean, 42.0 ± 12.6 mm Hg), and in 46 patients (37.2%), it was more than 45 mm Hg.
Indications for OMC are shown in the Table 2.
After induction of anesthesia, intraoperative transesophageal echocardiography was performed in all the patients after January 1994. Standard cardiopulmonary bypass techniques and cold, hyperkalemic antegrade blood cardioplegia were used.
Technique of open mitral commissurotomy
After cardioplegic arrest, the left atrium is opened and search is made for any clot/thrombus. The left atrial appendage is invaginated into the atrium and inspected. Any thrombus or clot, if present, is removed and the left atrial cavity is generously washed with ice-cold saline. The mitral valve is inspected. Usually, both the commissures are fused and it is not difficult to identify the correct position of commissural lines. The process of commissurotomy is started at anterolateral commissure. A blunt-ended, long-handled hook is placed beneath each leaflet on either side of the anterolateral commissure and gentle traction is applied. Anterior hook is pulled antero-inferiorly, and the posterior hook is pulled postero-inferiorly (Fig 1a).
This displays and spreads out the region of anterolateral commissure. With a knife (no. 11 blade), a stab incision is made midway between valve orifice and the valve annulus (Fig 1b). Care is taken to maintain a distance of about 3 to 4 mm from the annulus. Otherwise, if the commissure is incised too close to the annulus, there is risk of flail anterior leaflet and subsequent postoperative eccentric mitral regurgitation. A right-angled clamp is passed from the stab incision towards the valve orifice and is gently opened (Fig 1c). This spreads the commissural chordae and the line of cuspal fusion becomes well defined. The fused commissure between the initial stab incision and the valve orifice is incised open with a no. 11 blade or angled scissors. Subsequently, the fused chordae are separated with knife or scissors and, when appropriate, the incision is carried down into the center of the papillary muscle (Fig 1d). A similar procedure is repeated on the posteromedial commissure. After release of fused commissural and subvalvular components, the pliability of mitral leaflets is restored by cuspal thinning [9]. Calcification is shaved off from the leaflets and the annulus-leaflet junction. The thick fibrous layer covering the atrial surface of the leaflets is peeled off. At the completion of the procedure, at present, we routinely perform bilateral commissural plication (Fig 2).
This shortens the posterior annulus and increases the coaptational area of leaflets, and thus effectively prevents any eccentric mitral regurgitation.
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Fig 2. Commissural annuloplasty. (a) Both the needles of a double-armed 4-0 polypropylene suture are passed from the ventricular side to the atrial side of mitral annulus at the anterolateral commissure. The anterior needle is passed just anterior to the commissure, whereas the posterior needle is passed about 1 cm posterior to the commissure. (b) With the posterior needle, a bite is taken from the free edge of posterior mitral leaflet, about 5 mm from the commissure. (c) The posterior needle is again passed from the ventricular to the atrial surface of mitral annulus. This time, the needle comes out close to the anterior needle. (d) The sutures are pulled and tied together. A similar procedure is repeated on the posteromedial commissure. Shown is the completed procedure.
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Movement of the anterior mitral leaflet is checked and the mitral valve area is assessed. The competence of the mitral valve is assessed by injecting saline with a bulb syringe into the left ventricle directly through the mitral valve. If central mitral regurgitation persists, a modified Cooley’s annuloplasty is performed [10]. In the present experience, 20 patients required modified Cooley’s annuloplasty. These were the patients who had some degree of mitral regurgitation preoperatively.
After satisfactory mitral valve reconstruction, the other associated procedures were performed (Table 3).
Since January 1994, after termination of the cardiopulmonary bypass, the mitral valve performance was again assessed by intraoperative transesophageal echocardiography.
Transthoracic echocardiography was performed in all the patients before discharge from the hospital. Only those patients who had a prosthetic aortic valve received anticoagulation. Antiplatelet agents were prescribed to patients who had a left atrial thrombus/clot. Patients were followed up in the outpatient department, and electrocardiographic and echocardiographic evaluation was performed at 1 month, 6 months, and every year thereafter.
Statistical analysis
Continuous or interval-related variables were expressed as means ± standard deviation. Categorical variables were expressed as percentages. Univariate analysis was performed with the 
2 test, Fisher’s exact test, and Student’s t test. Actuarial estimates were calculated and compared using the Kaplan-Meier technique [11] and Mantel-Cox (log-rank) test [12]. For the purpose of analysis, mitral valve failure was considered as the end point. Mitral valve failure included mitral valve–related death, mitral valve related reoperation, development of severe mitral regurgitation, and development of severe mitral stenosis (mitral valve area < 1.0 cm2). A number of variables were analyzed as predictors of early death, mitral valve failure, and development of recurrent mitral stenosis (Appendix). A step-wise multiple logistic regression analysis was used to find independent predictors of early death. Prognostic factors for mitral valve failure were identified using Cox’s proportional hazard model. All statistical analysis was performed with the SPSS for Windows 7.5 software package (SPSS Inc., Chicago, IL).
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Results
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Early results
There were four early deaths in the whole group. All of these patients had associated aortic procedure (Ross procedure in 2 and homograft aortic valve replacement in 2). Thus, there was no operative mortality in patients who had undergone OMC without any aortic procedure (n = 221). Three patients developed severe mitral regurgitation in the early postoperative period (< 30 days) and required reoperation. All these 3 patients had eccentricmitral regurgitation due to flail anterior mitral leaflet. Commissural annuloplasty was not performed in any of these patients. In 2 patients, the mitral valve was replaced with a prosthetic valve, whereas commissural annuloplasty restored competence in the third one. In predischarge echocardiography, mitral valve area ranged from 1.4 to 3.5 cm2 (mean, 2.6 ± 0.6 cm2), and 27 patients had mild mitral regurgitation. Four patients had moderate mitral regurgitation at the time of discharge.
Late results
Follow-up ranged from 1 to 130 months (mean, 64.5 ± 28.6 months) and was 94.6% complete. There was no late death in this series.
During the follow-up, 2 patients who had moderate mitral regurgitation at the time of discharge developed severe mitral regurgitation and required reoperation after 36 and 43 months. One patient developed severe mitral stenosis and was reoperated on after 108 months. Besides the above-mentioned patients, 2 more patients developed severe mitral stenosis (mitral valve area, < 1.0 cm2) after a follow-up of 96 and 120 months. Thus, there were eight instances of mitral valve failure (three early and five late), and the actuarial freedom from mitral valve failure at 10 years was 87.0% ± 3.5% (Fig 3).
None of the variables listed in the Appendix proved to be a significant predictor of early or late mitral valve failure.
Postoperatively, there were nine episodes of thromboembolism (4 of these patients had prosthetic aortic valve replacement),and two episodes of anticoagulant-related hemorrhage (both the patients had prosthetic aortic valve replacement).
Echocardiography performed after a mean interval of 60 months (range, 1 to 126 months) showed the mitral valve area from 0.4 to 3.2 cm2 (mean, 2.2 ± 0.5 cm2). To predict the development of recurrent mitral stenosis, it was graded according to the mitral valve area (> 2.0 cm2 = 0, 1.5 to 2.0 cm2 = 1, 1.0 to 1.5 cm2 = 2, 0.5 to 1.0 cm2 = 3, and < 0.5 cm2=4), and the outcome was correlated with factors in the Appendix. Preoperative presence of severe subvalvular disease was the single most important predictor (hazards radio, 1.3; 95% CI, 1.0 to 1.8; p = 0.03) for development of recurrent mitral stenosis postoperatively. Mild mitral regurgitation was present in 46 patients, moderate mitral regurgitation in 8, and severe mitral regurgitation in 2 (both reoperated). Eighteen patients had severe tricuspid regurgitation. Significant aortic regurgitation was present in 3 patients who had associated Ross procedure at the time of initial operation. Six patients had evidence of left ventricular dysfunction (ejection fraction, 50%).
At the time of their last follow-up visit (n = 262), 240 patients (91.6%) were in New York Heart Association (NYHA) class I or II, and 16 patients (6.1%) were in class III. Six patients were in NYHA class IV, primarily due to severe tricuspid regurgitation. Fifty-one patients continued to remain in atrial fibrillation.
Results in patients with isolated OMC
A total of 193 patients underwent isolated OMC (without an aortic or tricuspid procedure). There was no early or late death. There were eight instances of mitral valve failure (three early and five late). There were five episodes of thromboembolism over a mean follow-up of 62.5 ± 26.6 months (0.5%/patient-year). At the time of last follow-up (n = 187), 182 patients (97.3%) were in NYHA class I or II.
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Comment
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In our practice, BMV is the procedure of choice for isolated uncomplicated mitral stenosis. Though, as compared with BMV, better hemodynamic and long-term results are obtained with OMC [13–15], it is procedure of second choice because of higher cost and surgery-related morbidity. All patients with symptomatic rheumatic mitral stenosis with a favorable morphology are subjected to BMV. If the valve is calcified or is having severe subvalvular disease, an open-heart surgical procedure is performed. Similarly, if the associated left atrial/appendicular clot/thrombus does not dissolve after adequate anticoagulant therapy, an open-heart surgical procedure is performed. Presence of mild to moderate mitral regurgitation, organic tricuspid valve disease, or significant aortic valve disease also necessitates open-heart procedure. However, OMC is not always possible in patients with mitral stenosis undergoing open-heart surgical procedure. In our experience, we could save the mitral valve in only about 25% patients. Though extensive calcification and gross destruction of valve necessitated mitral valve replacement in a majority of the patients, it was not always a contraindication. Similar to experience of Eguaras and colleagues [16], we also found that with some effort and commitment, a good number of valves could be salvaged.
MVR is definitely a much simple and more durable option for this subset of patients, but patient survival is much better with OMC [8, 16]. Similarly, thromboembolism, anticoagulant-related hemorrhage, and other valve-related complications outweigh the durability of valve replacement [16]. In addition to this, the cost benefit and freedom from expensive anticoagulation and its monitoring are some important advantages of OMC, especially for rural people in developing countries.
We did not find any single factor responsible for failure of OMC. This was because of the fact that our patients represented a group of well-selected patients. Final decision for OMC was made only after direct inspection of the mitral valve. Thus, a judicious surgical understanding is necessary to assess the fibrosed and calcified valves. In our experience, three early and two late failures were because of development of severe mitral regurgitation. All these patients had significant (moderate or severe) mitral regurgitation in the early postoperative period, and hence, could be considered as technical failures. With routine use of commissural plication and, if required, posterior annuloplasty, the problem of postoperative mitral regurgitation could be avoided. Postcommissurotomy intraoperative transesophageal echocardiography is also an important adjunct to assess any valve malfunction and its subsequent correction.
With commissural plication, the posterior annulus is shortened by about 1 cm, and the posterior mitral leaflet is pulled anteriorly. Though it reduced the mitral valve opening to a minor degree, it increased the coaptation of the anterior and posterior mitral leaflet significantly, and thus effectively eliminated the mitral regurgitation that could have resulted from commissurotomy. Commissural plication also eliminated a mild degree of central mitral regurgitation. However, if commissural plication is not sufficient to eliminate the mitral regurgitation, a posterior collar annuloplasty (modified Cooley’s annuloplasty) is a useful adjunct. Similarly, if post-BMV tear of any leaflet is repaired, a posterior collar annuloplasty is always added to reduce the stress on the leaflet sutures.
In the present series, only those patients who had a prosthetic aortic valve received anticoagulation therapy. Patients who had left atrial thrombus or clot preoperatively received only antiplatelet therapy. Despite this fact, the incidence of thromboembolism was strikingly low. A majority of the patients with preoperative atrial fibrillation returned to sinus rhythm. Only about 40% (51/134) of our patients who had atrial fibrillation preoperatively continued to remain in atrial fibrillation. A majority of these patients also had atrial thrombus/clot, and thus received antiplatelet therapy postoperativly. Considering the risks of anticoagulation and the problems of its monitoring, as most of the patients belonged to remote areas, anticoagulation was not prescribed for persistent atrial fibrillation. However, with the encouraging results of the Maze procedure in patients with mitral valve disease [17–20], it can be considered as a useful adjunct to open mitral commissurotomy.
More than one-third (37.2%) of our patients had severe pulmonary arterial hypertension, and some of these had severe tricuspid regurgitation. In a majority of the patients, tricuspid regurgitation regressed, but it persisted or progressed in 18 patients. This tricuspid regurgitation was the major cause of poor functional class in a number of patients. This shows the need of operating on patients with mitral stenosis before the development of severe, and sometimes irreversible, pulmonary arterial hypertension and right ventricular dysfunction.
In conclusion, OMC provides excellent early and long-term results in a selected group of patients. Although OMC is a palliative procedure and reoperation is a distinct possibility, patients who underwent OMC do benefit in terms of low valve-related complications and better survival.
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Acknowledgments
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We thank Rajvir Singh, MS (Stat) for the statistical analysis.
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Appendix
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Preoperative variables
- Age
- Gender (male/female)
- Rhythm (sinus or atrial fibrillation)
- New York Heart Association class (II, III, IV)
- Congestive heart failure
- Cerebrovascular accident
- Peripheral thromboembolism
- Previous closed mitral commissurotomy
- Previous balloon mitral valvuloplasty
- Failed balloon mitral valvuloplasty
- Emergency surgery
- Associated aortic valve disease
- Associated tricuspid valve disease
- Severe pulmonary venous hypertension (mean left atrial pressure
15 mm Hg)
- Severe pulmonary arterial hypertension (mean systolic pulmonary artery pressure > 45 mm Hg)
Peroperative variables
- Mitral valve calcification
- Presence of left atrial clot/thrombus
- Severe subvalvular fusion
- Need for posterior annuloplasty
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References
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Abstract
Introduction
