Which Patients Benefit From Percutaneous Mitral Balloon Valvuloplasty?
Prevalvuloplasty and Postvalvuloplasty Variables That Predict Long-Term Outcome
Background— Percutaneous mitral balloon valvuloplasty (PMV) results in good immediate results, particularly in patients with echocardiographic scores (Echo-Sc) ≤8. However, which variables relate to long-term outcome is unclear.
Methods and Results— We report the immediate and long-term clinical follow-up (mean, 4.2±3.7 years; range, 0.5 to 15) of 879 patients who underwent 939 PMV procedures. Patients were divided into 2 groups, Echo-Sc ≤8 (n=601) and Echo-Sc >8 (n=278). PMV resulted in an increase in mitral valve area from 1.0±0.3 to 2.0±0.6 cm2 in patients with Echo-Sc ≤8 and from 0.8±0.3 to 1.6±0.6 cm2 in patients with Echo-Sc >8 (P<0.0001). Although adverse events (death, mitral valve surgery, and redo PMV) were low within the first 5 years of follow-up, a progressive number of events occurred beyond this period. Nevertheless, survival (82% versus 57%) and event-free survival (38% versus 22%) at 12-year follow-up was greater in patients with Echo-Sc ≤8 (P<0.0001). Cox regression analysis identified post-PMV mitral regurgitation ≥3+, Echo-Sc >8, age, prior surgical commissurotomy, NYHA functional class IV, pre-PMV mitral regurgitation ≥2+, and higher post-PMV pulmonary artery pressure as independent predictors of combined events at long-term follow-up.
Conclusions— The immediate and long-term outcome of patients undergoing PMV is multifactorial. The use of the Echo-Sc in conjunction with other clinical and morphological predictors of PMV outcome allows identification of patients who will obtain the best outcome from PMV.
Received December 6, 2001; revision received January 16, 2002; accepted January 17, 2002.
The role of percutaneous mitral balloon valvuloplasty (PMV) in the management of patients with rheumatic mitral stenosis has continued to evolve during the last 19 years. Patient selection is fundamental in predicting the immediate results of PMV. The evaluation and selection of candidates for PMV requires a precise assessment of mitral valve morphology.1–5⇓⇓⇓⇓ The echocardiographic score (Echo-Sc) is presently the most widely used technique for the evaluation of the morphological characteristics of the mitral valve associated with a higher likelihood of good immediate and follow-up outcome from PMV.6–12⇓⇓⇓⇓⇓⇓ Immediate, short, and intermediate follow-up studies have shown that patients with Echo-Sc ≤8 have superior immediate results and significantly greater survival and freedom from combined events than patients with Echo-Sc >8.6,9,10⇓⇓ However, long-term follow-up studies of PMV are scarce.12–14⇓⇓ In the present study, we report the immediate and long-term clinical follow-up (up to 15 years) of 879 consecutive patients who underwent PMV at the Massachusetts General Hospital. Analysis of this data allows the identification of those patients more likely to benefit from PMV.
The patient population includes 879 consecutive patients who underwent 939 PMVs between July 1986 and July 2000. For the purpose of analysis, patients were divided in 2 groups according to the Echo-Sc.15 The first group included 601 patients with Echo-Sc ≤8 and the second group included 278 patients with Echo-Sc >8.
Technique of PMV
PMV was performed using the double-balloon or the Inoue techniques, as previously described.1,16–18⇓⇓⇓ Right and left heart pressure measurements, cardiac output, and diagnostic oxygen saturation run were performed before and after PMV. The mitral valve area (MVA) was calculated with the Gorlin formula.19 Left ventriculography was performed before and after PMV to assess the severity of mitral regurgitation (MR) using the Sellers’ classification.20 The effective balloon-dilating area (EBDA) of the balloons used was calculated with standard geometric formulas and normalized by body surface area (EBDA/BSA) as previously described.16,21⇓ Severity of mitral valve calcification under fluoroscopy was graded from 0+ (none) to 4+ (severe), as previously described.16,22⇓
Demographic, clinical and procedural variables, and in-hospital adverse events were prospectively collected. In-hospital procedure-related adverse events included procedural and total in-hospital deaths, emergency and total in-hospital mitral valve surgeries (MVR), pericardial tamponades, thromboembolic events, and complete heart blocks. Procedure-related deaths were defined as those occurring during the PMV procedure and those occurring from complications directly related to the PMV index procedure. In-hospital death was defined as any death occurring during the hospitalization independent of its cause. Emergency MVR was defined as a MVR procedure performed within 24 hours of PMV. A successful PMV was defined as a post-PMV MVA ≥1.5 cm2 and post-PMV MR <3 Sellers’ grade.
Patients were followed-up for mean period of 4.2±3.7 years (range, 0.5 to 15) after PMV. Incidence of death, MVR (replacement or repair), redo PMV, stroke, and clinical evaluation to determine NYHA functional class were recorded. Clinical evaluation was accomplished by direct or telephone interview of the patient. The interviewer was blinded to the procedural variables and immediate outcome after PMV. When necessary, local physicians were contacted for additional information and medical records were reviewed. All patients had their status checked within 3 months of the initial submission of this manuscript.
Continuous variables are expressed as mean±SD, and categorical variables are expressed as percent. Student’s t test and χ2 analysis were used to compare continuous and categorical variables, respectively. P≤0.05 was considered significant. Demographic, clinical, echocardiographic, procedural, and angiographic variables were tested to determine significant (P≤0.05) univariate correlates of immediate success. Multiple stepwise logistic regression analyses of these significant variables were performed to identify independent predictors of immediate success. Kaplan-Meier estimates were used to determine total survival and event-free survival (survival with freedom from MVR and redo PMV) for the overall group and for patients with Echo-Sc ≤8 and >8. Comparison between groups was performed using the log-rank test. Cox proportional hazards regression analyses were used to identify independent correlates of long-term mortality and event-free survival. The variables included in the Cox analyses were age, sex, pre-PMV NYHA functional class, history of previous surgical commissurotomy, fluoroscopic presence of calcium ≥2+, Echo-Sc, technique of PMV, pre- and post-PMV MVA, MR, and pulmonary artery pressure. All analyses were performed using SAS software version 6.10 (SAS Institute).
Patient Population and Preprocedural Clinical and Morphological Variables
The patient population included 879 consecutive patients who underwent 939 PMV procedures. There were 160 male and 719 female patients with a mean age of 55±15 years. There were 601 patients with Echo-Sc ≤8 who underwent 634 PMV procedures and 278 patients with Echo-Sc >8 who underwent 305 PMV procedures. Patients with echocardiographic scores >8 were older and presented more frequently in atrial fibrillation. They had more calcified valves under fluoroscopy, and more were NYHA class IV. In addition, the incidence of pre-PMV MR and a history of previous surgical commissurotomy were also higher in this cohort of patients (Table 1).
Six hundred ninety-five PMV procedures were performed using the double-balloon technique, 237 with the Inoue technique, and 7 with a combination of both techniques. The hemodynamic findings before and after PMV of the overall patient population and of patients with Echo-Sc ≤8 and >8 are shown in Table 2. PMV resulted in an increase in MVA from 0.9±0.3 to 1.9±0.7 cm2 (P<0.0001). As shown in Figure 1, there is an inverse relationship between Echo-Sc and both post-PMV MVA and PMV success. Patients with Echo-Sc ≤8 had larger increase in post-PMV MVA (2.0±0.6 versus 1.6±0.6; P<0.0001). Procedural success was 71.7% for the overall group, with patients with Echo-Sc ≤8 having a higher procedural success (79.0% versus 56.4%; P<0.0001). Two hundred sixty-six patients had unsuccessful procedures because of a post-PMV MVA <1.5 cm2 (178 patients) and post-PMV MR ≥3 Sellers’ grade (88 patients). Procedure success for the overall group was 83.4% when a post-PMV MVA ≥1.5 cm2 or a ≥50% increase in post-PMV MVA and a post-PMV MR ≤2+ was used as a definition of success. Similarly, with this later definition of success, patients with Echo-Sc ≤8 had a higher procedural success (86.5% versus 76.6%, P=0.0002).
Univariate predictors of success included age (P<0.0001), pre-PMV MVA (P<0.0001), mean pre-PMV pulmonary artery pressure (P<0.0001), male sex (P=0.0002), echocardiographic score (P<0.0001), pre-PMV mitral regurgitation ≥2+ (P=0.009), history of previous surgical commissurotomy (P=0.009), presence of atrial fibrillation (P<0.0001), and presence of mitral valve calcification under fluoroscopy (P<0.0001). Multiple stepwise logistic regression analysis identified larger pre-PMVMVA, less degree of pre-PMV MR, younger age, absence of previous surgical commissurotomy, male sex, and Echo-Sc ≤8 as independent predictors of procedural success (Table 3).
In-Hospital Adverse Events
The incidence of major adverse in-hospital events is shown in Table 4. There were 18 (1.9%) in-hospital deaths, and 6 (0.6%) of these were procedure-related deaths. Severe post-PMV MR (≥3 grade Sellers’ grade) occurred in 88 (9.4%) patients, with Sellers’ grade III in 56 (6%) and Sellers’ grade IV in 32 (3.4%). Thirty-one patients (3.3%) underwent MVR during their hospitalization, with a higher incidence in patients with Echo-Sc >8. Emergent MVR was required in 13 of 939 (1.4%) patients. Pericardial tamponade occurred in 9 (1%) patients. A left to right shunt with a pulmonary to systemic flow ratio >1.5:1 was detected in 50 (5.3%) patients. Thromboembolic events occurred in 17 (1.8%) patients in the overall population. Finally, 5 (0.5%) patients developed complete atrioventricular block, with only 1 requiring permanent pacemaker implantation.
Clinical follow-up information was available in 844 (96%) of the overall patient population at a mean follow-up time of 4.2±3.7 years. The follow-up was completed in 575 (96%) of patients with Echo-Sc ≤8 and in 269 (97%) of patients with Echo-Sc >8. The frequency of follow-up events is shown in Table 6. For the entire population, there were 110 deaths (25 noncardiac), 234 MVRs, and 54 redo PMVs, accounting for a total of 398 patients with combined events (death, MVR, or redo PMV). Of the remaining 446 patients that were free of combined events, 418 (94%) were in NYHA class I or II. Follow-up events occurred less frequently in patients with Echo-Sc ≤8 and included 51 deaths, 155 MVRs, and 39 redo PMVs, accounting for a total of 245 patients with combined events at follow-up. Of the remaining 330 patients who were free of combined events, 312 (95%) were in NYHA class I or II. Follow-up events in patients with Echo-Sc >8 included 59 deaths, 79 MVRs, and 15 redo PMVs, accounting for a total of 153 patients with combined events at follow-up. Of the remaining 116 patients who were free of any event, 105 (91%) were in NYHA class I or II.
Figure 2 shows estimated actuarial total survival curves for the overall population and for patients with Echo-Sc ≤8 and >8. Actuarial survival rates throughout the follow-up period were significantly better in patients with Echo-Sc ≤8. Survival rates were 82% for patients with Echo-Sc ≤8 and 57% for patients with Echo-Sc >8 at a follow-up time of 12 years (P<0.001). Survival rates were 82% and 56%, respectively, when only patients with successful PMV were included in the analysis. Figure 3 shows estimated actuarial total event-free survival curves for the overall population and for patients with Echo-Sc ≤8 and >8. Event-free survival (38% versus 22%; P<0.0001) at12-year follow-up were also significantly higher for patients with Echo-Sc ≤8. Event-free survival rates were 41% and 23%, respectively, when only patients with successful PMV were included in the analysis.
Independent predictors of long-term mortality and combined events are shown in Tables 5 and 6⇑. Cox regression analysis identified post-PMV MR ≥3+, Echo-Sc >8, age, prior commissurotomy, NYHA class IV, pre-PMV MR ≥2+, and post-PMV pulmonary artery pressure as independent predictors of combined events at long-term follow-up (Table 6).
This study confirms earlier reports that PMV results in good immediate hemodynamic and clinical improvement in most patients with mitral rheumatic stenosis.6–14⇓⇓⇓⇓⇓⇓⇓⇓ Superior long-term follow-up is seen in a selected group of these patients, particularly those with Echo-Sc ≤8. This study identifies other clinical and morphological factors that help predict long-term results after PMV. They include pre-PMV variables (MVA, history of previous surgical commissurotomy, age, and MR) and post-PMV variables (MR ≥3+ and pulmonary artery pressure). The use of these factors in conjunction with the Echo-Sc allows optimal selection of patients for PMV. In this score, leaflet mobility, leaflet thickening, valvular calcification, and subvalvular disease are each scored from 1 to 4, yielding a maximum total Echo-Sc of 16.15 There is an inverse relationship between the Echo-Sc and the percentage of patients obtaining a good immediate result from PMV. Furthermore, the present study demonstrates that in addition to its impact on the immediate outcome, the Echo-Sc is also an independent predictor of long-term survival and event-free survival.
Echocardiographic evaluation of the mitral valve is essential to predict immediate and long-term follow-up results of candidates for PMV. However, other factors even in patients with Echo-Sc ≤8 play a role, because they are not a homogeneous population. Our patients with Echo-Sc ≤8 had a 10.5% incidence of ≥2+ calcified valves under fluoroscopy, 41.6% were >55 years old, 44.1% were in atrial fibrillation, 14.3% had a history of previous surgical commissurotomy, and 5.5% had pre-PMV MR ≥2 Sellers’ grade.
Our results are in agreement with other follow-up studies showing that the incidence of adverse clinical events is low in the early years after PMV in patients with optimal mitral valve morphology.2,5–7,9,12,13,23,24⇓⇓⇓⇓⇓⇓⇓⇓ In the present study, events are low in the first 5 years after PMV. However, there is a progressive number of events, mostly MVRs, beyond this period of follow-up. Importantly, at 8 years of follow-up, 50% of patients with Echo-Sc ≤8 are free of combined events, whereas only 38% of them are free of events at 12 years of follow-up.
Patients with Echo-Sc >8 are more likely to be older, have mitral valve calcification under fluoroscopy, be in atrial fibrillation, and have a history of previous surgical mitral commissurotomy.22–29⇓⇓⇓⇓⇓⇓⇓ Differences in age, clinical characteristics, and valve morphology may account for the lower long-term event-free survival in this and other PMV studies from the United States and Europe compared with younger patients in series from Asia and South America.5,9,12–14,22–29⇓⇓⇓⇓⇓⇓⇓⇓⇓⇓⇓⇓ This relationship is evident in the present study, where 601 patients with Echo-Sc ≤8 and a mean age of 51±14 years have an actuarial 82% survival and 38% event-free survival rate at 12-year follow-up. In contrast, 278 patients with Echo-Sc >8 and a mean age of 63±14 years had an actuarial 57% survival and 22% event-free survival rate at the same period of follow-up. Moreover, in the present study, an actuarial 95% survival and 61% event-free survival rate at 12-year follow-up after successful PMV was present in 136 patients with Echo-Sc ≤8, age ≤45 years, pre-PMV MR <2 Sellers’ grade, and no history of previous surgical commissurotomy. These are the patients with the most favorable characteristics.
Comparison between PMV and surgical commissurotomy techniques is difficult in view of differences in patient clinical and mitral valve morphology characteristics among different series. Most surgical series have involved a younger population with optimal mitral valve morphology and pliable valves with no calcification and no evidence of subvalvular disease. In these patients with optimal mitral valve morphology, surgical mitral commissurotomy has favorable long-term hemodynamic and symptomatic improvement. Similarly to PMV, patients with advanced age, calcified mitral valves, and atrial fibrillation had a poorer survival and event-free survival rate. Several studies have compared the immediate and early follow-up results of PMV versus open or closed surgical commissurotomy. These initial trials results of PMV versus surgical commissurotomy are encouraging and favor PMV for the treatment of patients with rheumatic mitral stenosis with suitable mitral valve morphology.30–35⇓⇓⇓⇓⇓
Thus it seems reasonable to recommend PMV for patients with Echo-Sc ≤8, especially if they have other favorable characteristics (age <45 years, <2+ MR, and no previous mitral surgery). The question remains as to which procedure, MVR or PMV, is more suitable for patients with Echo-Sc >8. A successful PMV result is obtained in 54% of these patients, and only 33% of them were free of combined events at 5-year follow-up. Because a good immediate outcome was achieved in 61% of patients with Echo-Sc between 9 and 11 and 39% were free of combined events at 5-year follow-up (Figure 4), PMV might be considered the first choice in these patients if they are free of other risk variables. Conversely, patients with Echo-Sc ≥12 should be referred for MVR, because only 36% had successful PMV and 10% were free of events at 4 years (Figure 4). Nevertheless, PMV could be considered as a palliative procedure if the patients are nonsurgical candidates.
In conclusion, our study shows that PMV should be the procedure of choice for the treatment of patients with rheumatic mitral stenosis who are, from the clinical and morphological points of view, optimal candidates for PMV. Pre-PMV variables identify the patients who will benefit early. Immediate post-PMV variables (degree of MR and post-PMV pulmonary artery pressure) in conjunction with pre-PMV clinical and mitral morphology variables identify the patients most likely to benefit long-term.
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