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Comparison of Inoue Balloon, Metallic Commissurotome and Multi-Track Double-Balloon Valvuloplasty
In the Treatment of Rheumatic Mitral Stenosis
ABSTRACT: Background. Percutaneous mitral valvuloplasty (PMV) is a well known non-surgical technique for treating patients with rheumatic mitral stenosis (MS). There are very few studies that have compared the 3 techniques together for their safety and efficacy. Methods. To compare the three different techniques for percutaneous mitral valvuloplasty (PMV) using Inoue balloon (IB), metallic commissurotome (PMMC), or multi-track double balloon (MTDB) in patients with MS. Results. A total of 486 patients were subjected to PMV using any of the 3 techniques, IB, PMMC or MTDB. The overall success rate was 97.3% (n = 473); 95.7% for IB, 97.6% for PMMC, and 98.3% for MTDB. Overall, the transmitral gradient decreased from 20.7 ± 7.2 mmHg to 6.5 ± 3.7 mmHg (p < 0.001) and mitral valve area (MVA) increased from 0.87 ± 0.2 cm2 to 1.9 ± 0.4 cm2 (p < 0.001). Left atrial pressure decreased from 29.3 ± 8.4 mmHg to 16.1 ± 11.5 mmHg (p < 0.001) and pulmonary arterial pressure decreased from 76.9 ± 41.8 mmHg to 45.2 ± 17.6 mmHg (p < 0.001). Thirteen patients (2.7%) required mitral valve replacement (MVR) for severe mitral regurgitation (MR) while one patient (0.2%) developed cardiac tamponade requiring urgent pericardiocentesis followed by surgical repair of the tear and open mitral valvotomy. There was no statistical difference among the 3 techniques used. Conclusion. In conclusion, percutaneous mitral valvuloplasty is an effective procedure for MS with any of the three above techniques.
J INVASIVE CARDIOL 2008;20:521–525
Although the incidence and severity rates of rheumatic mitral stenosis (MS) have declined in developed countries, the disease is still highly prevalent in many countries.1,2 The introduction of percutaneous mitral valvuloplasty (PMV) has brought up a revolution in the management of mitral stenosis especially in the last 30 years with results comparable to closed and open surgical procedures.1,3,4
In 1984, through percutaneous introduction of balloon, Inoue et al5 successfully dilated a stenotic mitral valve by separating fused commissures of the mitral valve in a young symptomatic patient, opening an era of PMV. In 1986, McKay et al6 and Palacios et al7 simultaneously reported the first PMVs performed in adult patients with calcified mitral valves.
Soon after, Al-Zaibag et al8 introduced the double-balloon (DB) technique, and in the same year Meier et al9 used the Trefoil balloon. Bonhoeffer et al10 in 1995 further simplified the double-balloon technique by introducing the Multi-Track system. With this system, one of the balloons is a rapid exchange balloon, while the other has a conventional design, enabling both to be aligned in the mitral valve orifice over a single guidewire. The other advantage of this technique is it did not require predilatation of the septum in contrast to all other techniques except for the Inoue technique.
Cribier et al in 199511,12 introduced a metallic commissurotome for percutaneous dilation of the mitral valve (PMMC). The principle is basically the same as the Tubbs dilator used for closed mitral commissurotomy,1,3,4 and its main advantage is that its performance is not affected after being reused several times.11
Studies have compared PMMC with Inoue balloon technique13,14 and Inoue balloon with double-balloon techniques,15,16 but very few compared the three techniques.1,17 Therefore, we report our experience with the above three techniques in a single tertiary care center.
Methods
Study Population. We carried out a retrospective chart review of 486 patients who underwent percutaneous mitral valvuloplasty (PMV) for moderate to severe mitral stenosis at the National Institute of Cardiovascular Diseases Karachi, Pakistan, between March 2001 and June 2006, using either: 1) Inoue Balloon (IB), 2) metallic commissurotome (PMMC), or 3) Multi-track double balloon (MTDB).
Eligibility criteria were:
1) Symptomatic patients with moderate or severe mitral stenosis (mitral valve area [MVA] < 1.5 cm2); and
2) New York Heart Association (NYHA) functional class II–IV. Patients with bilateral commissural calcification, mitral regurgitation (Sellers’ classification18) > 2, recent embolic event, severe aortic or tricuspid valve disease who require surgery and echocardiographic evidence of left atrial thrombus were excluded from the study. Echocardiographic scoring was done according to Wilkins’ classification.19
Outcomes. Successful dilatation was defined as improvement in the transmitral pressure gradient and by echocardiographic assessment of the mitral valve area (MVA) after dilatation12,13 with MVA > 1.5 cm2 in the absence of greater than grade 2 (Seller’s classification18) mitral regurgitation.
Major complications included death, pericardial tamponade, greater than grade 2 mitral regurgitation, systemic embolization and cardiac perforation. Minor complications included arrhythmia, significant atrial septal defect (ASD), vascular injury at the access site, and bleeding requiring blood transfusion.
Percutaneous mitral valvuloplasty (PMV): PMV was performed with either Inoue Balloon {IB},5 (Toray Industries, Inc. Tokyo, Japan; Figures 1A and B), percutaneous mitral metallic commissurotomy {PMMC} (Commissurotomy Kit, Bolton Medical, SA, France; Figures 2A and 2B),11,12 and Multi-track double balloon (MTDB) valvuloplasty10 (Multi-track balloon for Mitral valvuloplasty, Numed, Inc. New York, New York; Figures 3A and B) using techniques as described in earlier studies.5,10–12
There was only one interventionist who performed/ supervised all the procedures. The choice of technique at our center was based on the availability of the device rather than patient’s baseline characteristics or personal preference for the device. Thus, patients in all groups had similar sociodemographic and clinical characteristics.
With resterilization the average Inoue balloon was used seven times, metallic commissurotome 45 times and double balloon 6 times. The average cost for each of the technique in U.S. dollars at our center was $485 for Inoue balloon technique, $81 for PMMC and $323 for MTDB technique. This includes the cost of device, re-sterilization cost, operator’s fees and catheterization laboratory time. On average IB and PMMC techniques take 20–25 minutes while MTDB takes 30–35 minutes. The average length of stay in hospital was 1.5 days and patients were discharged on the next day if there were no complications.
Statistical analysis. Data were summarized using descriptive statistics (mean, standard deviations (SD), percentages), and box and whisker plots. Continuous variables were reported as mean ± SD. Binary variables were reported as percentages. Groups were compared using two-way analysis of variance (ANOVA) models. These models had post-procedure pressures as dependent variables, and group allocation and pre-procedure pressures as independent variables. Tukey’s adjustment was used for multiple comparisons. A p-value < 0.05 was considered significant. All statistical and graphical analyses were performed using SAS version 9.1 (Carey, North Carolina).
Results
The demographic data are shown in Table 1. The overall success rate of PMV was 97.3% (n = 473 patients); 95.7% for IB, 97.6% for PMMC and 98.3% for MTDB. Following PMV, the transmitral pressure gradient (PG) decreased from 20.7 ± 7.2 mmHg to 6.5 ± 3.7 mmHg (p < 0.001); a 70.5% drop of trans-valvular gradient. MVA doubled in successful cases; MVA increased from 0.87 ± 0.2 cm2 to 1.9 ± 0.4 cm2 (p < 0.001). Left atrial pressure (LAP) decreased from 29.3 ± 8.4 mmHg to 16.1 ± 11.5 mmHg (p < 0.001). Pulmonary arterial pressure (PAP) decreased from 76.9 ± 41.8 mmHg to 45.2 ± 17.6 mmHg (p < 0.001) (Table 2). Figure 4 shows PG before and after each procedure.
There were a total of thirteen (2.7%) unsuccessful cases. Mean mitral valve area (MVA) for unsuccessful cases was 0.68 ± 0.12 cm2 as compared to 0.87 ± 0.14 cm2 for successful cases (p < 0.001), mean echocardiographic score was 8.0 ± 0.8 as compared to 6.8 ± 1.5 for successful cases (p < 0.001) and mean age was 32.5 ± 8.1 years as compared to 25.9 ± 8.2 years for successful cases (p < 0.001).
As shown in Table 3, thirteen patients (2.7%) developed severe mitral regurgitation (MR) due to valve leaflet tears requiring mitral valve replacement (MVR). Six patients (1.2%) developed left-to-right shunting across the iatrogenic atrial septal defect as assessed by oxymetry run immediately after the procedure. One patient (0.2%) developed cardiac tamponade due to tear of the LV while the device (PMMC) was advanced across the mitral valve; the patient survived after urgent pericardiocentesis followed by repair of the tear and open mitral valvotomy. The majority of these complications occurred during the early phase of the learning curve. Six patients had restenosis during the follow-up period and underwent a repeat procedure, which was successful (the device used for repeat valvuloplasty was also based on availability). Mean follow-up period was 17.3 ± 6.7 months, during which the MVA was maintained at 1.9 ± 0.3 cm2.
Discussion
This study compared the immediate and short-term results of the 3 techniques, IB, PMMC and MTDB. There was no significant difference in the demographics of the patients subjected to any of the three techniques used in this study, including age, NYHA functional class, echocardiographic score and mitral valve areas.
Our overall success rate was 97.3% and the failure rate was 2.7% which is comparable to previous studies that have shown success rates ranging from 80% to 95%, and failure rates ranging from 0.8% to 2.3%.19 Similarly, the observed doubling of MVA and a drop of 70.5% of transvalvular gradient from baseline value after dilation is also consistent with previous observations.20 In this study, the overall final MVA was 1.9 ± 0.4 cm2 and as shown in numerous studies21–24 MVA > 1.5 cm2 is an independent predictor of long-term event free survival. The final gain of MVA was not statistically different among the 3 techniques.25–28
There were no significant differences among the 3 techniques in pressure gradients across mitral valve, pulmonary arterial pressures, and MVAs after adjusting for baseline values among the three techniques. The only difference noted was in the left atrial pressure. Although the IB technique resulted in more significant reduction in LAP as compared to other two techniques but the baseline LAP was also lower in IB technique as compared to other techniques which might be the reason for showing comparatively less post-procedure LAP with the IB.
An improvement was noted in the NYHA class and function after successful procedure presumably due to improvement of valve function and subsequent drop of pressure and pulmonary vascular resistance. These changes tend to improve the function of the right ventricle with the increase of its systolic volume index. All these led to improvement of left ventricular ejection fraction, and exercise capacity over next several weeks.29 On the other hand, when the immediate results of the procedure are not satisfactory, the patient’s functional improvement is either transient or nonexistent.
Unsuccessful cases had higher echocardiographic scores and smaller mitral valve area as compared to successful cases. The previous studies have also shown valve anatomy defined by the echo score,19,30,31 calcification at fluoroscopy,30,32 initial MVA,33 previous MR,34 and symmetry of commissural fusion35 as independent predictors of procedural success, and post-PMV MVA and restenosis as independent predictors of the long-term success of PMV;15,30,36 age, functional class IV, previous surgical commissurotomy, initial MR ≥ 2, echo score > 8, severe MR postdilatation and higher pulmonary artery pressure postdilatation37 are predictors of late cardiac events.
Overall, the complication rate in this study was 4.1%; severe MR in 2.7%, ASD in 1.2%, and cardiac tamponade in one patient (0.2%). Previous studies have reported different mechanism for the development of mild and severe mitral regurgitation; mild MR is due to complete commissurotomy, and severe MR is due to leaflet tears or choral rupture.38 Complete commissurotomy and commissural mitral regurgitation (CMR) might prevent immediate recoil and late fusion of split commissures by preventing apposition of the split commissures, which ultimately might lead to decrease in MVA after PMV. This suggests complete commissurotomy with larger MVA or CMR may prevent fibrous fusion of split commissures and restenosis.
The development of ASD after PMV is usually small, undetectable by oxymetry and in most cases, it closes spontaneously; except if the shunt is significant or if dilatation fails. With valve restenosis, defects may reappear, and creates a variation of the Lutembacher Syndrome.39 Those of our patients who developed severe MR were referred for surgery.
In most of the series, mortality ranges between 0–3%. The major causes of death are cardiac tamponade, severe MR, and deterioration of the patient's general condition.40 The occurrence of hemopericardium, at average rates of 1–3%, is related to transeptal puncture or perforation of the LV’s apex by the guidewire or by the balloon itself.41 One of our patients did developed tamponade but survived after emergent corrective surgery.
In conclusion, this study demonstrates that the 3 techniques, IB, PMMC and MTDB, were equally effective in achieving MVA > 1.5 cm2, which is an independent predictor of long-term event free survival. The only difference noted in this study was a greater reduction of LA pressure in IB technique and as the reduction of LAP generally improves the left atrial mechanical function, IB technique might be considered to have a slight edge over the other two techniques, and that it should be considered as a technique of choice if affordable.
Study limitations. Our results should be interpreted in the context of study limitations. This was not a randomized study so selection bias cannot be ruled out. However, this is unlikely to have affected the results. The other limitation was unavailability of long-term follow-up data. Majority of patients seen at our center are referred from remote rural areas. They go back to their homes after treatment, and hence are not available for long-term follow up. Thus, our data do not directly assess long-term effectiveness of these devices.
The most common reason for not finding a significant difference among groups is lack of statistical power. However, this was not the case in our study. For the primary outcome (successful dilatation) sample size ranged from 141–180 per group, thus we have 90–95% power to detect a relative risk reduction of at least 15% among groups with the conventional Type 1 error rate of 5%. Similarly, in the cohort of successful dilatation, we have more than 90% power to detect a difference of at least 0.5 cm in MVA; 5 mmHg in LAP, and 10 mmHg in PAP, among groups. Hence our study was adequately powered. It is one of the largest series presented on the subject to date.
