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(Circulation. 1995;91:671-676.)
© 1995 American Heart Association, Inc.

Articles

Clinical Follow-up of Patients Undergoing Percutaneous Mitral Balloon Valvotomy

Igor F. Palacios, MD; Murat E. Tuzcu, MD; Arthur E. Weyman, MD; John B. Newell, BA; Peter C. Block, MD

From the Department of Medicine (Cardiac Unit), Massachusetts General Hospital, Harvard Medical School, Boston, Mass.

Correspondence to Igor F. Palacios, MD, Director of Interventional Cardiology, Massachusetts General Hospital, Boston, MA 02114.

	Abstract

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Background This study is the clinical follow-up (20±12 months; range, 6 to 49 months) of 327 patients who had percutaneous mitral balloon valvotomy (PMV) at the Massachusetts General Hospital.

Methods and Results There were seven in-hospital deaths. Patients were divided into two groups according to their echocardiographic score; 211 patients had echocardiographic scores 8 and 116, echocardiographic scores >8. Patients with echocardiographic scores >8 were older (64±11 versus 48±14 years, P<.01), and more had atrial fibrillation (65% versus 40%, P<.01), calcium under fluoroscopy (81% versus 29%, P<.01), and previous surgical commissurotomy (30% versus 16%, P<.01) than patients with echocardiographic scores 8. With PMV, mitral valve area increased from 1.0±0.3 to 2.2±0.8 cm² in patients with echocardiographic scores 8 and from 0.8±1 to 1.7±0.7 cm² in those with echocardiographic scores >8. Rates of survival (98±2% versus 72±11%), survival with freedom from mitral valve replacement (91±4% versus 55±13%), and survival with freedom from combined events (79±10% versus 39±18%) at follow-up were greater in patients with echocardiographic scores 8 (P<.00005). Cox regression analysis identified the echocardiographic score as the most important unfavorable intermediate long-term follow-up prediction factor after PMV.

Conclusions The excellent intermediate long-term clinical follow-up of patients with echocardiographic score 8 and no calcified mitral valves suggests that PMV may be the treatment of choice in this group of patients.

Key Words: stenosis • mitral valve • follow-up studies

	Introduction

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Percutaneous mitral balloon valvotomy (PMV) has been accepted as an alternative to surgical mitral commissurotomy in the treatment of patients with symptomatic rheumatic mitral stenosis. PMV produces good immediate hemodynamic and clinical improvement in the majority of patients with mitral stenosis.^{1 2 3 4 5 6 7 8 9 10} Although PMV is a relatively new technique, follow-up studies after PMV are encouraging.^{11 12 13 14 15 16 17 18} In the present study, we report the intermediate long-term clinical follow-up (mean 20±12 months) of 327 patients who underwent PMV at the Massachusetts General Hospital.

	Methods

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Patient Population
Three hundred twenty-seven patients underwent PMV at the Massachusetts General Hospital between July 1986 and October 1989. Two patients died during PMV, and 5 patients died within 1 week of PMV. The remaining 320 patients were followed up for 20±12 (mean±SD; range, 6 to 49) months. There were 262 women and 58 men; mean age was 54±1 (range, 14 to 87) years.

Patients were divided into two groups by an echocardiographic score,^{19 20} which was obtained by a relatively simple, semiquantitative grading of leaflet thickening, mobility, calcification, and subvalvular involvement on a scale of 0 to 4 as described.^{19 20} Two hundred eleven patients had echocardiographic scores 8, and 116 had echocardiographic scores >8. Table 1 shows the baseline characteristics of these two groups. Patients with echocardiographic scores >8 were older, had a lower female/male ratio, and more frequently had atrial fibrillation, calcified mitral valves under fluoroscopy, and previous surgical mitral commissurotomy.

View this table: [in this window] [in a new window]   Table 1. Baseline Characteristics of PMV Patients

Technique of PMV
PMV was performed in the fasting state under local anesthesia and mild sedation. Prophylactic antibiotics were given for 24 hours starting 12 hours before PMV, which was performed using the transseptal antegrade technique as described.^{2 3 21} The single-balloon technique was used in 27 patients and the double-balloon technique in 300 patients. After February 1988, balloon size was chosen with respect to body surface area.²² Left atrial pressure, left ventricular pressure, and cardiac output were measured simultaneously before and immediately after PMV. The corresponding pre- and post-PMV mitral valve areas were calculated. Complete right and left heart catheterization and oximetry studies were performed before and after PMV to evaluate the changes in hemodynamics produced by PMV and the presence and degree of left-to-right shunting through the created atrial communication. Cardiac output was measured by thermodilution technique. Blood samples were obtained from the superior vena cava, pulmonary artery, and aorta before and after the procedure in all patients. A diagnosis of left-to-right shunting through the created atrial communication was made when there was a 7% step up between superior vena cava and pulmonary artery samples in repeated samples. In the patients with severe tricuspid regurgitation and/or left-to-right shunt, cardiac output was measured by using the Fick principle. Oxygen consumption was measured using an MRM-2 oxygen consumption monitor (Waters Instrument Inc). Significant tricuspid regurgitation was diagnosed by clinical, Doppler echocardiographic, and hemodynamic findings. Finally, cine left ventriculography (45° right anterior oblique projection) was performed to assess the presence and severity of mitral regurgitation.

Follow-up Studies
Patients were followed up for 20±12 (6 to 49) months after PMV. End points of follow-up were death, mitral valve replacement (MVR), and clinical evaluation according to the New York Heart Association (NYHA) functional classification of congestive heart failure. Clinical evaluation was performed by direct or telephone interview of the patient. The interviewer was masked to the echocardiographic score and immediate outcome of PMV. All patients had their status checked within 2 months of the initial submission of this article. From the total population, 3.8% of the patients had follow-up at least up to 4 years, 11% at least up to 3 years, 33% at least up to 2 years, 68% at least up to 1 year, and 94% at least up to 6 months.

Estimated actuarial survivorship and rates of actuarial survival with freedom from MVR and survival with freedom from combined events (death, MVR, and NYHA class III or IV) were created. Curves were constructed for the whole group and for the subgroups of patients with echocardiographic scores 8 and >8. Predictors of each event and combined events were determined by using Cox regression analysis. Candidate predictor variables included in the analysis were sex, age, pre-PMV NYHA class, presence of fluoroscopic calcium, atrial fibrillation, history of previous surgical mitral commissurotomy, echocardiographic score, and pre- and post-PMV mitral valve areas.

Comparison between actuarial survival rates for patients with echocardiographic scores 8 and >8 was performed by using the Mantel-Cox test. A similar test was conducted for rate of survival with freedom from events.

Data on the valvotomy patients were prepared with RS/1 data management and analysis software²³ running on a Digital Equipment Corp micro VAX 3600. Actuarial survival analysis was performed with the BMDP survival analysis program²⁴ using the RS/1 interface to BMDP provided in RS/1. Survival functions by groups according to echocardiographic scores (8 and >8) were compared by using the grouping feature of BMDP1L and the Mantel-Cox statistic computed by that program. Cox proportional hazards models of the covariates of rates of survival and survival free of events were constructed with the BMDP2L program and were used to identify significant predictors of survival.²⁵ These covariates of survival were selected in a stepwise fashion, and only significant (P[x²]<.05) covariates were retained in each model. It should be noted, however, that after patients either died or were censored at the time of MVR or development of NYHA class III or IV, only 218 patients remained after 1 year for further observation. At the ends of 2, 3, and 4 years this number decreased to 106, 36, and 12 patients, respectively. All candidate independent variables were started outside the model, and only forward stepping was used to prevent the inclusion of too many independent variables for the limited number of events at any stage of the modeling. Thus, although nine candidate predictors were entered, only three were included in the final mortality model constructed from 25 deaths. This left an ample 21 df for estimation of confidence intervals about the three parameters of the Cox model associated with the three independent predictors. In addition, the three most significant independent predictors of mortality were forced into the two other models of rates of survival free of MVR and event-free survival. This was done to render the models mutually consistent and was justified by the fact that the three mortality predictors were also significant univariate predictors of the other classes of events. Estimates of errors cited in the text are mean±SD.

	Results

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Immediate Outcome
The hemodynamic changes produced by PMV in both groups of patients (echocardiographic scores 8 and >8) are shown in Table 2. PMV resulted in a significant decrease in mitral gradient and increases in both cardiac output and mitral valve area in both groups of patients; the increase in mitral valve area produced by PMV was greater in patients with echocardiographic scores 8 than in those with echocardiographic scores >8 (2.2±0.8 versus 1.7±0.7 cm², P<.001). The incidence of left-to-right shunt through the atrial communication was greater in patients with echocardiographic scores >8 (P<.05). The cohort of 116 patients with echocardiographic scores >8 was further divided into those with echocardiographic scores >8 but <12 (n=100) and those with echocardiographic scores >12 (n=16). Post-PMV mitral valve areas in these two groups were 1.7±0.7 and 1.4±0.8 cm², respectively. The corresponding percentages of patients having a good outcome (defined as a post-PMV mitral valve area 1.5 cm²) from the procedure were 57 of 100 (57%) and 5 of 16 (31%) (P=.05), respectively.

View this table: [in this window] [in a new window]   Table 2. Hemodynamic Characteristics of PMV Patients

The 27 single-balloon PMV patients did not differ from the 300 double-balloon PMV patients with regard to sex, occurrence of atrial fibrillation, fluoroscopic calcification, or prior surgical commissurotomy. However, the single-balloon patients were older (62±15 versus 53±15 years, P=.007) and had a higher NYHA functional class (3.2±0.6 versus 2.8±0.7, P=.005), higher echocardiographic score (9.4±2.8 versus 7.6±2.1, P=.0001), smaller mitral valve area before PMV (0.74±0.25 versus 0.9±0.3 cm², P=.008), and smaller valve area after PMV (1.4±0.5 versus 2.0±0.8 cm², P=.0001).

Of the 25 total deaths, 7 occurred in hospital or immediately after discharge. The causes varied: electromechanical dissociation after percutaneous aortic balloon valvuloplasty, which had been undertaken 24 hours after PMV; sudden death 1 day after PMV, with the autopsy showing an acute myocardial infarction and a tear of the posterior leaflet of the mitral valve with hematoma of the annulus; massive right-to-left shunt due to pulmonary hypertension and hypoxemia leading to cardiac arrest; death in the operating room after emergency MVR (which itself was uneventful); left ventricular perforation and tamponade 12 hours after PMV; sepsis unrelated to PMV followed by renal failure and respiratory acidosis; and a death at home 3 weeks after PMV from a large pulmonary embolus. These seven patients were significantly older than the other patients in the study (76±6 versus 54±15 years, P=.0002) and had a higher NYHA class (3.7±0.5 versus 2.9±0.7, P=.001) and a higher echocardiographic score (10.8±2.5 versus 7.7±2.2, P=.0009). The individual echocardiographic scores of these seven early-death patients were 7 (one), 9 (one), 11 (three), 12 (one), and 15 (one); in all other respects they were similar to the other patients in the study.

Follow-up
The mean follow-up period was 20±12 (range, 6 to 49) months. It should be noted, however, that after patients either died or were censored at the time of MVR or development of NYHA class III or IV, only 218 patients remained after 1 year for further observation. At the ends of 2, 3, and 4 years this number decreased to 106, 36, and 12 patients, respectively. During this follow-up period there was a significant difference in mortality and mitral valve surgery between the subgroup of patients with echocardiographic scores 8 and those with echocardiographic scores >8. The former group, comprising 211 patients, had 2 deaths, 13 MVRs, and 11 cases with NYHA class III or IV. The second group, with 116 patients, had 23 deaths, 18 MVRs, and 6 cases of NYHA class III or IV. These correspond to 0.9% versus 19.8% mortality, 6.2% versus 15.5% MVR, and an equal incidence of NYHA class III or IV at 5.2%. Death and MVR rates differed significantly (P<.006) and by wide margins of 19% and 9%, respectively, all favoring the low echocardiographic score group.

Survival
The actuarial survival curve for the whole group of patients is shown in Fig 1A. The 1-, 2-, 3-, and 4-year estimated actuarial survival rates were 94±2%, 91±4%, 90±4%, and 90±4%, respectively.

View larger version (15K): [in this window] [in a new window]   Figure 1. Line graphs of actuarial survival estimated from life-table analysis. Numbers in parentheses represent patients alive and uncensored at the end of each of the 4 years. A, All patients with 95% confidence intervals (CIs) for 1-, 2-, 3-, and 4-year survival at (92%, 96%), (87%, 95%), (86%, 94%), and (86%, 94%), respectively. B, Comparative survival for the two echocardiographic (echo) score groups. For the group with echocardiographic scores 8 (211 patients at the outset of the study), the 95% CIs for percent survival at the end of years 1 through 4 were (98%, 100%), (97%, 100%), (96%, 100%), and (96%, 100%), respectively. For the group with echocardiographic score >8, the corresponding 95% CIs were (76%, 90%), (66%, 86%), (61%, 83%), and (61%, 83%). One hundred sixteen patients in this group were entered at the outset. F/U indicates follow-up.

Fig 1B shows the estimated actuarial survival curves for patients with echocardiographic scores 8 and >8. Actuarial survival rates throughout the follow-up period were significantly better in patients with echocardiographic scores 8 than in those with echocardiographic scores >8.

Among patients with echocardiographic scores >8, actuarial survival rates throughout the follow-up period were significantly better in patients with echocardiographic scores of 9 to 11 than in those with echocardiographic scores 12. At 3 years of follow-up, actuarial survival rates were 83±9% and 18.9±30% (P<.00005) for patients with echocardiographic scores 9 to 11 and 12, respectively.

Cox regression analysis demonstrated that death during follow-up was directly and independently related to echocardiographic score (P=.0004), age (P=.004), and pre-PMV NYHA class (P=.01).

Survival With Freedom From MVR
Fig 2A shows the estimated actuarial survival with freedom from MVR curve for the overall group.

View larger version (16K): [in this window] [in a new window]   Figure 2. Line graphs of actuarial survival with freedom from mitral valve replacement (MVR) estimated from life-table analysis. Numbers in parentheses are the same as for Fig 1 because MVR events were counted as censored observations for those analyses. A, All patients with 95% confidence intervals (CIs) for 1-, 2-, 3-, and 4-year survival at (82%, 90%), (76%, 86%), (73%, 85%), and (73%, 85%), respectively. Numbers in parentheses represent patient counts as a function of time. B, Comparative survival with freedom from MVR for the two echocardiographic (echo) score groups. For the group with scores 8, the 95% CIs for percent survival with no MVR at the end of years 1 through 4 were (92%, 98%), (87%, 95%), (87%, 95%), and (87%, 95%), respectively. Numbers in parentheses represent patients alive and free of MVR uncensored at the end of each of the 4 years out of a total of 211 entering at the outset of the study. For the group with echocardiographic scores >8, the corresponding 95% CIs were (62%, 80%), (52%, 72%), (42%, 68%), and (42%, 68%). F/U indicates follow-up.

Fig 2B shows the estimated actuarial survival with freedom from MVR curves for both groups of patients (echocardiographic scores 8 and >8). Actuarial survival with freedom from MVR rates throughout the follow-up period were significantly better in patients with echocardiographic scores 8 than in those with echocardiographic scores >8.

Cox regression analysis demonstrated that the presence of MVR at follow-up was directly and independently related to echocardiographic score (P=.0008), age (P=.03), pre-PMV NYHA class (P=.026), and the presence of atrial fibrillation (P=.033) and fluoroscopic mitral valve calcification (P=.009).

Event-Free Survival
Fig 3A shows the estimated actuarial event-free survival curve (death, MVR, and NYHA class III or IV) for the overall group.

View larger version (17K): [in this window] [in a new window]   Figure 3. Line graphs of actuarial survival with freedom from either New York Heart Association functional classifications III or IV or from mitral valve replacement (MVR) (combined events). A, All patients with 95% confidence intervals (CIs) for 1-, 2-, 3-, and 4-year survival with freedom from combined events at (80%, 88%), (72%, 82%), (63%, 77%), and (57%, 75%), respectively. Patient counts as a function of time (numbers in parentheses) are the same as for Fig 1A because all combined events except mortality were counted as censored observations for that analysis. B, Comparative survival free of combined events for the two echocardiographic (echo) score groups. For the group with scores 8, the 95% CIs for percent survival free of combined events at the end of years 1 through 4 were (88%, 96%), (82%, 92%), (75%, 91%), and (69%, 89%), respectively. For the group with echocardiographic scores >8, the corresponding 95% CIs were (60%, 78%), (48%, 68%), (31%, 61%), and (21%, 57%). Patient counts (numbers in parentheses) are identical to those in Fig 1B. F/U indicates follow-up.

Fig 3B shows the estimated actuarial event-free survival curves for both groups of patients. Actuarial event-free survival rates throughout the follow-up period were significantly greater in patients with echocardiographic scores 8 than in those with echocardiographic scores >8.

Among patients with echocardiographic scores >8, actuarial survival with freedom from combined events rates throughout the follow-up period were significantly better in patients with echocardiographic scores of 9 to 11 than in those with echocardiographic scores 12. At 3 years of follow-up, actuarial survival free of combined events rates were 43.9±21% and 16.2±26% (P<.005) for patients with echocardiographic scores 9 to 11 and 12, respectively.

Cox regression analysis demonstrated that the incidence of events at follow-up (death, MVR, and NYHA class III or IV) was directly and independently related to age (P=.005), NYHA functional class before PMV (P=.03), echocardiographic score (P<.05), and history of prior surgical mitral valve commissurotomy (P=.02).

	Discussion

Top Abstract Introduction Methods Results Discussion References

 
This study demonstrates that PMV results in a good immediate hemodynamic and clinical improvement in the majority of patients with mitral stenosis and produces good intermediate long-term follow-up in a selected group of patients with mitral stenosis. Throughout the follow-up period, patients with echocardiographic scores 8 had significantly greater actuarial survival, actuarial survival with freedom from MVR, and event-free survival rates than those patients with echocardiographic scores >8. The patients with the lower echocardiographic scores also experienced a significantly greater increase in mitral valve area. The results of the present study substantiate our previous reports^{3 8 9 10 11} that the best immediate outcome with PMV occurs in those patients with echocardiographic scores 8.

In addition to its well-known negative effect on the immediate outcome of PMV, the echocardiographic score is also the strongest independent predictor factor for intermediate long-term survival. Consequently, echocardiographic evaluation of the mitral valve is essential in both patient selection and in predicting immediate outcome and intermediate long-term follow-up of candidates for PMV.^{12 19 20 26}

The present study also ratifies previous studies that have shown that patients with higher echocardiographic scores are more likely to be older, to have mitral valve calcification under fluoroscopy, to be on atrial fibrillation, and to have a history of previous surgical mitral commissurotomy.^{9 10 11} Our study shows that all these factors are significant univariate predictors of survival and event-free survival after PMV. Our findings agree with several follow-up studies^{27 28} of surgical commissurotomy that show that patients with advanced age, calcified mitral valves, and atrial fibrillation had a poorer rate of survival.

Although it seems reasonable to recommend PMV as the treatment of choice in patients with an echocardiographic score <8 and no calcified mitral valves, the question remains as to which procedure, surgical or PMV, is more suitable for patients with echocardiographic scores >8. Our results show that 69±9%, 58±10%, 46±15%, and 39±18% of the patients with echocardiographic scores >8 were free of combined events at 1, 2, 3, and 4 years of follow-up, respectively. Since a good outcome is obtained in only 31% of patients with echocardiographic scores 12, and only 16% of them were free of combined events at intermediate-term follow-up, it has been our practice to recommend surgery for these patients as a first choice and to use PMV only if they are considered noncandidates or very-high-risk candidates for surgery. A good immediate outcome can be achieved in 57% of patients with echocardiographic scores between 9 and 11, with 43.9% of them free of combined events at intermediate long-term follow-up. Therefore, we recommend PMV as the first choice in these patients, particularly if the contributions of mitral valve thickening and subvalvular disease to the overall echocardiographic score are less than the other two components.⁸

Although our results agree with other follow-up studies showing a low incidence of clinical restenosis in patients with uncalcified mitral stenosis undergoing PMV,^{11 12 13 14 15 16 17 18} they appear to disagree with those of Cohen et al,¹⁸ who report lower (88% 2-year and 76% 5-year) survival and lower (74% 2-year and 51% 5-year) combined event-free survival rates in a group of 146 patients undergoing PMV. Their lower combined event-free survival can be explained by a larger number of patients with higher echocardiographic scores and mitral valve calcification. In their study, patients were not excluded on the basis of mitral valve calcification or morphological features of the mitral valve. Furthermore, in that study 39% of the patients were considered to be high-risk candidates for surgery due to the presence of important coexisting conditions or advanced age. As we have shown, advanced age has a significant negative effect on the immediate outcome and follow-up of patients undergoing PMV; a successful outcome with PMV was achieved in only 46 (46%) of 99 elderly (65 years) patients.¹⁴ Event-free survival rates at 1, 2, and 3 years of follow-up were 72±5%, 53±6%, and 46±7%, respectively.

Other follow-up studies^{11 13 16} have shown that the incidence of hemodynamic and echocardiographic restenosis is low 2 years after PMV. In a prospective study¹³ of a group of patients undergoing simultaneous clinical evaluation, two-dimensional (2D) Doppler echocardiography, and transseptal catheterization 2 years after double-balloon PMV, we showed no significant decrease in mitral valve area. Chen et al,¹⁶ using the Inoue balloon technique, showed no significant differences in mitral valve area determined by 2D echocardiography in 71 patients at a mean follow-up of 27±11 months.

Studies show that restenosis occurs after both closed and open surgical commissurotomy.^{29 30 31 32 33 34 35 36} John et al²⁹ report a restenosis rate of 4.2 to 11.4 per 1000 patients per year in 3724 patients who underwent surgical closed mitral commissurotomy. Although rates of actuarial survival with freedom from MVR and actuarial survival with freedom from combined events after PMV in the present study are lower than reported after surgical commissurotomy, actuarial survival rate with freedom from both MVR and combined events in the subgroup of patients with echocardiographic scores 8 is similar to that reported after surgical mitral commissurotomy.^{29 30 31 32 33}

Turi et al³⁷ have recently reported a prospective study of 40 patients with severe mitral stenosis who were blindly randomized to either PMV or closed surgical mitral commissurotomy. They demonstrated no significant differences in immediate outcome, complications, or 3.5-year clinical follow-up between these groups of patients.

The stepwise Cox regression algorithm used in this data analysis produces a model of the hazard of a poor outcome after PMV that is composed of a small number of predictor variables that contain independent information. This does not mean that a predictive model that is not significantly worse than ours could not be constructed from other combinations of variables from our candidate set of nine variables (or, indeed, of other variables that we did not include as candidates). This is a limitation of all multiple regression analyses, but a more exhaustive comparison of alternative models is not warranted by the limited number of events (at most 72 combined, when MVR and poor NYHA class are included) in our sample of 327 patients and by the risk of spurious results due to multiple comparisons.

We conclude that PMV produces a good clinical outcome in a high percentage of patients at intermediate-term follow-up. Patients who have the best results are <65 years of age, have echocardiographic scores 8, are in sinus rhythm, and have no evidence of valve calcification under fluoroscopy. Thus, it seems reasonable to recommend PMV for the treatment of symptomatic patients with rheumatic mitral stenosis and suitable mitral valve anatomy (low echocardiographic scores and absence of fluoroscopic calcium).

Received March 2, 1994; accepted July 31, 1994.

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