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Original Article
Volume 331:961-967 October 13, 1994 Number 15
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Percutaneous Balloon Valvuloplasty Compared with Open Surgical Commissurotomy for Mitral Stenosis
Vincent P. Reyes, B. Soma Raju, Joshua Wynne, Larry W. Stephenson, Raghava Raju, Barbara S. Fromm, P. Rajagopal, Prabodh Mehta, Shailender Singh, D. Prasada Rao, P.V. Satyanarayana, and Zoltan G. Turi

 

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ABSTRACT

Background Percutaneous balloon mitral valvuloplasty has been proposed as an alternative to open surgical commissurotomy for the treatment of rheumatic mitral-valve stenosis.

Methods We enrolled 60 patients with severe mitral stenosis and favorable valvular anatomy in a prospective, randomized trial comparing the two procedures. All patients underwent cardiac catheterization before the procedure and one week, six months, and three years thereafter. Hemodynamic data were analyzed by investigators who were blinded to the patients' treatment assignments.

Results Mitral-valve areas improved initially in both groups, from a mean (±SD) of 0.9 ±0.3 cm2 to 2.1 ±0.6 cm2 in the balloon-valvuloplasty group (30 patients; P<0.01) and from 0.9 ±0.3 cm2 to 2.0 ±0.6 cm2 in the surgical group (30 patients; P<0.001). Although improvement was maintained in both groups, mitral-valve areas were greater in the patients in the balloon-valvuloplasty group at three years (2.4 ±0.6 cm2, vs. 1.8 ±0.4 cm2 in the surgery group; P<0.001). Restenosis occurred in three patients in the balloon-valvuloplasty group and four in the surgery group. One patient in the balloon-valvuloplasty group died of an apparent stroke after 2.5 years; four patients in the balloon-valvuloplasty group had residual atrial septal defects, and three patients (two in the balloon-valvuloplasty group and one in the surgery group) were judged to have severe mitral regurgitation. Seventy-two percent of the patients who underwent balloon valvuloplasty and 57 percent of the surgically treated patients were in New York Heart Association functional class I (i.e., they had no cardiovascular symptoms) at three years. No patient was lost to follow-up.

Conclusions In the treatment of mitral stenosis, balloon valvuloplasty and open surgical commissurotomy have comparable initial results and low rates of restenosis, and both produce good functional capacity for at least three years. The potential complications associated with balloon valvuloplasty should be noted. The better hemodynamic results at three years, lower cost, and elimination of the need for thoracotomy suggest that balloon valvuloplasty should be considered for all patients with favorable mitral-valve anatomy.

Percutaneous balloon mitral commissurotomy (valvuloplasty), first described in 1984,1 has had good short- and intermediate-term results2,3,4,5,6. In a randomized trial in patients with favorable anatomical features,7 we reported that the outcome of balloon valvuloplasty was similar to that of closed surgical commissurotomy. Although the superiority of open over closed commissurotomy in patients with ideal valvular anatomy remains controversial,8 open commissurotomy (which allows the inspection of the valve and the separation of fused chordae under direct vision) is the preferred treatment for severe mitral stenosis in most industrialized nations9. We therefore compared the results of percutaneous balloon mitral valvuloplasty with those of open mitral commissurotomy in a randomized, prospective trial, with serial invasive and noninvasive testing of all patients through three years of follow-up.

Methods

Study Design

All the patients were enrolled during a three-week period in August and September 1989. Patients with severe rheumatic mitral-valve stenosis were screened in the clinics of the Nizam's Institute of Medical Sciences, Hyderabad, India, and referred for enrollment if they were 15 through 75 years of age and had no history of other cardiac disease or stroke, were in sinus rhythm, and had no severe subvalvular disease, calcification, or more than mild mitral regurgitation. A history was obtained from all patients, who also underwent physical examination, two-dimensional echocardiography and color Doppler study, exercise testing, chest radiography, and quality-of-life evaluation. A mitral-valve echocardiographic score was derived according to the criteria of Wilkins and colleagues,10 in which a maximum of 4 points was assigned according to the severity of each of four characteristics: mitral-valve-leaflet calcification, impaired mobility, thickening of the valve, and subvalvular disease (0 indicates normal and 4 the most severe abnormality); the four separate scores were totaled to give the overall echocardiographic score. A committee of cardiologists and a committee of cardiac surgeons screened each patient; both groups had to agree that the patient was a suitable candidate for their procedures. The protocol was approved by the institutional review board of the Wayne State University School of Medicine and the Human Investigation Committee of the Nizam's Institute of Medical Sciences. Informed consent was obtained from all patients, and the study was conducted in accordance with the guidelines of the 1975 Helsinki Declaration on the Rights of Human Subjects Enrolled in Medical Research.

Cardiac catheterization was performed at base line and one week, six months, and three years after the procedure. Cardiac output was determined by the Fick technique; the Flamm correction was applied if the oxygen saturation in the pulmony artery was more than 6 percent higher than that in the superior vena cava11. All cardiac-catheterization data were photocopied, coded with use of random numbers to mask the patient's identity, the group assignment, and the time at which data were obtained and were analyzed by an investigator remote from the study site.

We assessed functional capacity by treadmill exercise testing according to a modified Naughton protocol and by the interview-based Duke Activity Status Index,12 generating a score based on the percentage of activities (related to personal care, ambulation, household tasks, sexual function, and recreation) that individual patients could perform without substantial limitation.

The patients were randomly assigned to treatment groups after all base-line data were obtained. Those assigned to balloon valvuloplasty underwent the procedure after initial catheterization; for this procedure we used a modified version13 of the technique of Al Zaibag and colleagues14. After a single atrial transseptal puncture, an 8-French Mullins sheath (USCI, Billerica, Mass.) was advanced to the left atrium. A balloon flotation catheter was used to cross the mitral valve, after which two 0.035-in. (0.9-mm) Extra Stiff guidewires (Cook, Bloomington, Ind.) were placed in the apex of the left ventricle. An 8-mm septostomy balloon was used to dilate the septum (PE Plus II, USCI), after which two valvuloplasty balloons, 5.5 cm long (Boston Scientific, Watertown, Mass.), were inflated simultaneously across the mitral valve (20 mm and 15 mm in 26 patients; 18 mm and 15 mm in 4 patients). The therapeutic end point was nearly complete elimination of the mitral-valve gradient without a substantial increase in mitral regurgitation.

The patients randomly assigned to open surgical commissurotomy underwent a midline sternotomy, cannulation of the inferior and superior vena cava through the right atrium, and cardiopulmonary bypass (with use of a bubble oxygenator) and moderate systemic hypothermia15. After the aorta was cross-clamped, approximately 1 liter of a cold crystalloid-potassium cardioplegia solution was used to arrest the heart. The mitral valve was approached through a left atriotomy; if fused chordae were noted under the leaflets during commissurotomy, an attempt was made to separate the area of abnormal fusion.

Patients were discharged from the hospital after echocardiography and cardiac catheterization were performed one week after the procedure. The investigators made extensive efforts to maintain communication with patients, whose homes were scattered over a wide geographic area. Patients received laminated identification cards noting their participation in the study and were photographed for identification purposes. Six-month and three-year follow-up examinations were performed during two-week periods in February 1990 and September 1992, with the majority of the investigators present, including cardiologists from both the U.S. and Indian teams and the study statistician.

Statistical Analysis

The prospectively determined primary end point was the mitral-valve area one week, six months, and three years after the procedures. Power calculations were based on data from our previous study7; we estimated that the enrollment of 28 patients in each treatment group would give the study 80 percent power to detect a difference of at least 25 percent in mitral-valve area between the groups. Intraobserver variability was tested and found to be reproducible within a mean (±SD) of 1.2 ±1.8 mm Hg for the pulmonary wedge pressure or the left atrial pressure, 0.02 ±0.03 second for the diastolic filling period, 2.3 ±3.1 beats per minute for the heart rate, and 0.5 ±0.6 mm Hg for the mitral-valve gradient. Because the original formula of Gorlin and Gorlin for calculating the areas of the stenotic mitral valve and other cardiac valves was derived from a group of patients with small valve areas16 and therefore tends to overestimate valve area in high-flow states,17 valve areas greater than 3.0 cm2 were considered to be 3.0 cm2 (all valve areas derived from the formula of Gorlin and Gorlin without truncation are shown in Figure 2). Repeated-measures analysis of variance was performed for continuous variables to assess change over time and the effect of treatment18; between-group and within-group pairwise comparisons were made with the use of the least-squares means. Categorical variables were compared by chi-square analysis. No adjustment was made for multiple comparisons, and all tests of the hypothesis were two-tailed. The results are reported as means ±SD.


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  		Figure 2. Cumulative Frequency Distribution of Mitral-Valve Areas in Patients Who Underwent Balloon Valvuloplasty (Open Symbols) or Open Surgical Commissurotomy (Solid Symbols).

The vertical axis shows the percentage of patients whose mitral-valve area was less than the area on the horizontal axis.

 
Results

Study Population

Of the initial 82 patients who underwent cardiac catheterization, 22 were excluded from randomization because of the presence of coexisting myocardial or other valvular disease (7 patients), noncritical mitral stenosis (6), severe pulmonary hypertension (3), low body weight (2), severe subvalvular disease (1), Lutembacher's syndrome (1), the patient's decision not to undergo randomization (1), or left atrial thrombus demonstrated by echocardiography (1). By means of sealed envelopes, the remaining 60 patients were randomly assigned to percutaneous balloon mitral valvuloplasty (n = 30) or open surgical commissurotomy (n = 30) and underwent the assigned procedures within the next several days.

Base-line demographic, hemodynamic, and echocardiographic characteristics and functional-activity ratings are shown in Table 1. The patients in the two groups were similar in age, New York Heart Association (NYHA) functional class, hemodynamic variables, and echocardiographic scores at study entry. There were more men (P = 0.01) and exercise times were longer (P = 0.03) in the surgery group than in the balloon-valvuloplasty group.

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  		Table 1. Base-Line Characteristics of Patients Who Underwent Balloon Valvuloplasty or Open Surgical Commissurotomy.

 
Outcome of the Procedures

All 60 patients underwent their assigned procedures. Cardiac catheterization, echocardiography, exercise testing, and quality-of-life evaluation were performed as scheduled for every patient, except for the 3-year study in the patient who died at 2.5 years; no patient was lost to follow-up. Hemodynamic measurements in the two groups are presented in Figure 1. The initial improvement in pulmonary-artery wedge pressure, mitral-valve gradient, and mitral-valve area was sustained throughout the three years of follow-up (P<0.001 for the comparison with the base-line values). In both groups, pulmonary-artery wedge pressures were further improved at three years as compared with the values at the one-week or six-month evaluation (P<0.001). Both the mitral-valve gradient and the pulmonary-wedge pressure were lower in the balloon-valvuloplasty group than in the surgery group throughout follow-up, but these differences were not statistically significant. The difference in mitral-valve area between the balloon-valvuloplasty group and the surgery group became significant at three years (P<0.001). The exclusion of patients with evidence of left-to-right shunting on oxymetry or color Doppler echocardiography did not change the above findings. Pulmonary hypertension resolved more slowly in the surgery group; a continuing decrease in pulmonary-artery pressures was noted at six months and at three years.


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  		Figure 1. Hemodynamic Variables at Base Line and One Week, Six Months, and Three Years after Balloon Mitral Valvuloplasty or Open Surgical Commissurotomy.

The asterisk indicates P<0.001 for the comparison with the base-line value in all panels. The dagger (in Panel A) indicates P<0.001 for the comparison with the values at base line, at one week, and at six months. The double dagger (in Panel B) indicates P = 0.002 for the comparison with the balloon-valvuloplasty group and P = 0.16 (not significant) for the comparison with the base-line value. The section mark in Panel D indicates P<0.001 for the comparison with the surgery group. The bars indicate the standard errors.

 
Figure 2 shows the mitral-valve area for each patient plotted against the cumulative percentile distribution of valve areas in each group at base line and at each follow-up evaluation. The balloon-valvuloplasty and surgery groups overlap closely at base line; the curve for the balloon-valvuloplasty group shifts to the right of that for the surgery group at all three follow-ups, demonstrating that the valve areas were consistently larger after balloon valvuloplasty than after surgical commissurotomy.

Functional Capacity

The majority of patients enrolled in this study engaged in at least moderate physical activity despite having severe mitral stenosis at base line. By six months after the procedure, approximately 80 percent were in NYHA functional class I (23 patients in the alloon-valvuloplasty group and 24 in the surgery group), indicating that they had no symptoms; at three years, 21 patients in the balloon-valvuloplasty group and 17 in the surgery group remained in class I. We also compared hemodynamic variables during exercise at three years in the two groups: although the duration of exercise and the exercise gradient were essentially the same, the mean wedge pressure during exercise was significantly greater (P = 0.03) in the patients who underwent surgery (Figure 3).


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  		Figure 3. Pulmonary-Artery Wedge Pressure and Mitral-Valve Gradient during Exercise and Duration of Exercise at the Three-Year Follow-up Examination.

The bars indicate the standard errors.

 
The scores on the Duke Activity Status Index were similar at base line (Table 1), and improvement persisted through three years (at six months and three years, P<0.001 for the comparison with the base-line values in both groups). The six-month score was higher in the balloon-valvuloplasty group (activities performed easily, 82 percent vs. 72 percent; P = 0.01), but the scores were similar by three years (96 percent vs. 90 percent, P = 0.09).

Complications

No patient had a serious complication during the initial hospitalization. Complications during three years of follow-up are listed in Table 2. One patient in the balloon-valvuloplasty group died approximately 2.5 years after valvuloplasty; this patient, a 52-year-old woman, had a valve area of 2.6 cm2 immediately after the procedure; at the 6-month follow-up examination, she had a residual atrial septal defect with a ratio of pulmonary to systemic flow of 2.6. The information provided by her son after her death was consistent with a diagnosis of left hemispheric stroke, dehydration, and subsequent death. One week after the procedure, 13 patients in the balloon-valvuloplasty group and 5 in the surgery group had moderate or severe mitral regurgitation (P = 0.03); mitral insufficiency was classified as severe in 2 who underwent balloon valvuloplasty and none who underwent surgical commissurotomy. At three years, mitral regurgitation was mild or absent in 25 patients in the balloon-valvuloplasty group and 27 in the surgery group; 3 patients had severe mitral regurgitation (2 in the balloon-valvuloplasty group and 1 in the surgery group). No patient had left ventricular dilatation or dysfunction. There were four patients with a pulmonary-to-systemic flow ratio of more than 1.5 at three years, all of whom had undergone atrial septostomy for balloon valvuloplasty. All patients remained in sinus rhythm at the three-year follow-up.

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  		Table 2. Complications of Percutaneous Balloon Valvuloplasty and Open Mitral Commissurotomy through Three Years of Follow-up.

 
By definition, restenosis was indicated by a mitral-valve area of less than 1.5 cm2 and a loss of more than 50 percent of the initial gain after the procedure19,20; three patients in the balloon-valvuloplasty group and four in the surgery group fit these criteria and were scheduled for balloon valvuloplasty.

Cost

We calculated the charges for hospitalization and physicians' fees for the two groups of patients. With accounting for the reuse of disposable balloons in India, the cost of surgery was at least twice that of balloon valvuloplasty; in the United States, on the basis of Medicare reimbursement at Harper Hospital in Detroit, this ratio was nearly three to one.

Discussion

In our patients with severe mitral stenosis, both balloon valvuloplasty and open surgical commissurotomy resulted in sustained improvement through three years of follow-up. Our initial prediction, that the advantages of surgery under direct vision, including controlled separation of fused commissures, would result in a larger mitral-valve area21 and less mitral regurgitation, was not borne out. In addition to the larger mitral-valve areas in the balloon-valvuloplasty group, the preponderance of evidence based on other measurements (mitral-valve gradient, pulmonary-artery wedge pressure, pulmonary-artery pressure, and hemodynamic measurements during exercise) showed trends indicating the superiority of balloon valvuloplasty over surgery.

The occurrence of atrial septal defect in over 10 percent of patients who underwent balloon valvuloplasty is in keeping with published data22 and may reflect two aspects of the technique used in India at that time: the reuse of balloons, a practice that tends to result in a higher profile during withdrawal across the septum, and the use of relatively large, 8-mm septostomy balloons, which were standard at that time. Since the reuse of disposable equipment to limit costs is a standard practice in most parts of the world where mitral stenosis is prevalent, we believe that our results are typical for the double-balloon technique.

Although some increase in mitral regurgitation has been reported to be common during follow-up, severe mitral regurgitation is less common23,24,25; two patients in the balloon-valvuloplasty group and one in the surgery group were judged to have severe mitral incompetence at three years. Although improvement in the degree of postprocedural mitral regurgitation over time has been reported,26 in our study regurgitation was predominantly mild one week after the procedure. All three patients who had severe mitral regurgitation at three years had at least moderate mitral regurgitation at one week.

It has been postulated that what is labeled restenosis may merely reflect poor initial results. In the seven patients who met the criteria for restenosis, the mean valve area one week after balloon valvuloplasty or surgical commissurotomy was 2.4 ±0.9 cm2, narrowing to 1.4 ±0.1 cm2 at three years, thus representing true restenosis. Although this 12 percent rate of restenosis is in the middle of the 4-to-27-percent range reported in previous studies,20,27,28,29 earlier reports relied at least in part on clinical criteria, did not include routine follow-up catheterization, and did not approach our 100 percent follow-up. Furthermore, three of our seven patients who had restenosis were in NYHA class I (i.e., they had no cardiac symptoms) despite hemodynamic evidence of severe recurrent mitral stenosis; thus, they would not have been described as having restenosis according to the criteria used by most previous investigators30,31.

In order to minimize the effect of the experience and skills of individual physicians on the results of this study, balloon valvuloplasty was performed by a team of interventional cardiologists from the United States and India who had two years of experience working together, had previously conducted a comparative study of balloon valvuloplasty and surgery (closed commissurotomy),7 and had performed several hundred balloon-valvuloplasty procedures before this study. Similarly, open commissurotomy was performed by an experienced team of cardiac surgeons from India, the United States, and the United Kingdom, with extensive experience in open mitral commissurotomy. As was the case for the balloon-valvuloplasty procedures, the 30 open commissurotomies were performed during a two-week period; the members of the surgical team who participated in the various operations overlapped, and attempts were made to maintain uniform operative technique.

Limitations of the Study

The patients in this study had characteristics that made them ideal candidates for balloon valvuloplasty and surgical commissurotomy, including an absence of factors known to increase the risk and limit the success of both procedures. However, a substantial number of our patients had characteristics associated with high risk during and after commissurotomy,32 including critical mitral stenosis with mitral-valve areas of <= 0.7 cm2 (23 percent) and moderately severe or severe pulmonary hypertension (42 percent had a mean pulmonary-artery pressure >40 mm Hg). Despite our favorable results, caution should be exercised in extrapolating our findings to older patients with high echocardiographic scores, severe subvalvular disease, or thickened, poorly mobile, calcified leaflets or to patients in atrial fibrillation. Studies in less-than-ideal patient groups, especially studies including procedures performed while physicians gained experience,33 have reported higher morbidity and mortality31.

The sex imbalance between the groups does not account for the superior results in the balloon-valvuloplasty group. The mitral-valve areas in the 47 women were identical at base line (0.9 ±0.3 cm2 in both groups), but at the three-year follow-up the valve area was 2.4 ±0.6 cm2 in the women in the balloon-valvuloplasty group and 1.9 ±0.5 cm2 in those who underwent surgery (P = 0.005).

Our study did not compare the double-balloon with the Inoue single-balloon technique, since the latter was not available to the investigators at the beginning of the study. Comparisons of the two techniques have thus far failed to demonstrate a compelling difference in hemodynamic results34,35,36,37 or left-to-right shunting38,39. The ability of either technique to open valves in these nearly ideal candidates for the procedure makes it unlikely that our overall findings would have been affected by the choice of valvuloplasty technique40.

Our results suggest that balloon valvuloplasty should be considered for patients with uncomplicated mitral-valve stenosis. Open surgical commissurotomy will continue to be useful for patients with severe subvalvular disease, calcification, or thrombus who are judged to be candidates for plastic procedures rather than mitral-valve replacement. Because mitral commissurotomy is a palliative procedure, the likelihood that thoracotomy will be needed at some point later in the course of the disease is substantial. By avoiding a heart operation early, these patients will avoid the higher rate of complications associated with a second thoracotomy.

The prevalence of rheumatic mitral stenosis in developing countries, where health care funds are limited, will dictate the routine use of balloon valvuloplasty, as long as disposable equipment can be reused safely. In industrialized nations, cost factors also favor balloon valvuloplasty, even without such reuse. The improvement in mitral-valve area after balloon valvuloplasty needs to be considered in the light of the one late death from cardiovascular causes in our study, the four patients with persistent atrial septal defects, and the one additional case of severe mitral regurgitation. A longer follow-up period will be important (follow-up of seven years is planned). Nevertheless, the shorter hospital stays, avoidance of the discomfort and other problems associated with thoracotomy, and superior hemodynamic results of balloon valvuloplasty dictate that this procedure be considered for all patients with severe mitral stenosis in whom the anatomical features of the valve are favorable.

Supported in part by a grant from the General Electric Company.

We are indebted to the directors of the Nizam's Institute of Medical Sciences for their generosity in making available their facilities and personnel; to Dr. Peter Farkas for analyzing hemodynamic data; to Dr. David Anderson (Guy's Hospital, London) for participating in the open-heart-surgery team; to Drs. D.N. Kumar, N. Krishna Reddy, P. Kishore, Padma Kumar, N.V. Rayadu, Prasad Reddy, M.S. Rao, Sunil Kapoor, B.K.S. Sastry, S. Srinivas, Syamasundera Zampani, Susan Farkas, and Shukri David and Sister Mercy Augustine for assistance in patient care and the collection of clinical data; to Mr. Michael Andersen (deceased), Mr. P. Appaya, Ms. Debbie Boldea, Ms. Priscilla Peters, and the technicians and nurses of the cardiac catheterization laboratory of the Nizam's Institute of Medical Sciences; to the C.R. Bard, Boston Scientific, Namic, Cordis, and Winthrop-Sanofi corporations for generously providing supplies; and to the health ministers of the state of Andhra Pradesh for their continuing support of this work.


Source Information

From the Divisions of Cardiology (V.P.R., J.W., B.S.F., P.M., Z.G.T.) and Cardiothoracic Surgery (L.W.S.), Departments of Internal Medicine and Surgery, Harper Hospital, Wayne State University School of Medicine, Detroit; and the Departments of Cardiology (B.S.R., R.R., S.S.) and Cardiac Surgery (P.R., D.P.R., P.V.S.), the Nizam's Institute of Medical Sciences and MediCiti, Hyderabad, India. Presented in part in abstract form at the 63rd and 66th Scientific Sessions of the American Heart Association, Dallas, November 14, 1990, and Atlanta, November 9, 1993.

Address reprint requests to Dr. Turi at Wayne State University School of Medicine, Harper Hospital, 3990 John R., Detroit, MI 48201.

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