Mitral stenosis (MS) is characterized by a decrease in mitral valve (MV) orifice area leading to compromised left ventricular filling. The consequence is blood stagnation proximal to MV leading to elevated left atrial, pulmonary venous, and pulmonary artery pressures .
Mitral stenosis usually occurs decades after the occurrence of rheumatic fever . However, in developed countries, calcific changes of the mitral annulus can induce degenerative MS in a sizeable proportion of patients, especially in the elderly .
Before the appearance of percutaneous therapy, the treatment of MS included open or closed commissurotomy and replacement with biological or mechanical prostheses. Later, the development of percutaneous devices allowed percutaneous mitral valvuloplasty (PMV) to emerge; beginning in the 1980s, not only as a valid alternative to surgery but also the procedure of choice for all MS patients with favorable valve anatomy. Percutaneous mitral valvuloplasty is a safe and cheap procedure that does not require general anesthesia. It is not a contraindication for subsequent surgical valvuloplasty or valve replacement, and it does not require permanent anticoagulant therapy .
Despite the considerably high success rates and low complication rates in both short- and long-term follow-ups, mitral regurgitation (MR) remains the commonest procedure-related complication . This complication is usually mild and well tolerated. Even in a few patients, the severity of MR has been reported to be decreased . However, severe MR requiring valve replacement may be seen  .
Although the development of MR after valvuloplasty is frequently seen, the determinant factors of severe MR have not been adequately studied. Given that, this study was designed to investigate the predictors of severe MR as a complication following percutaneous multitrack balloon mitral valvuloplasty.
2. Patients and Methods
This cohort study was conducted at both Menoufia University Hospital and Mabaret Misr Elkadima Hospital.
We enrolled a convenient sample of 121 patients with MS who were subjected to PMV using multitrack balloon technique during the period from October 2017 to October 2019. We included patients (males and females) with severe MS who had suitable mitral valve morphology and symmetric commissural morphology. Patients with left atrial thrombi, moderate to severe MR, severe calcification of commissures, and high echocardiographic scores were excluded from the study.
The included patients were divided into 2 groups according to the resultant MR. Group A included patients with no or mild mitral regurgitation, while Group B enrolled patients with severe mitral regurgitation. All patients were subjected to full history taking, through clinical examination, and transthoracic echocardiography before and after balloon commissurotomy.
We reported several variables including demographic (such as age, weight, height, BMI, and BSA), clinical, echocardiographic and catheterization data (such as right and left heart pressures, end-diastolic and end-systolic volumes, cardiac ejection fraction, valve morphology and calcifications, Wilkins score, MR severity, Balloon sizing, and the development of atrial fibrillation).
The severity of MR was based on the following criteria: regurgitation volume > 60 ml and vena contracta > 7 mm.
Before starting the research, we got ethical approval from Menoufia University Ethics Committee. An informed written consent was obtained from each patient before enrollment into the study.
Data were collected and analyzed using the Statistical Package for Social Sciences program, version 18 (Chicago, Inc, Illinois. Quantitative data were presented as means and standard deviation (SD). Qualitative data were expressed as frequency and percent (%). Independent sample t-test was done to measure association between 2 quantitative variables. P value < 0.05 was considered statistically significant.
This study enrolled 121 patients; 71 females (58.7%) and 50 males (41.3%), and their mean age was 35.2 ± 9.7 years-old. We divided our patients into 2 groups according to the resultant MR post-commissurotomy; patients with no or mild MR (group A, N = 109) and those with severe MR (group B, N = 12). Their basic data are demonstrated in Table 1. Left ventricular ejection fraction (EF) was 69.9 ± 4.6%. Mitral valve annulus area was measured through planimetry (35.6 ± 2.3 mm2) with Wilkins score 8.0 ± 1.2.
Transthoracic echocardiographic evaluation showed significant reductions of gradient pressure; right ventricular systolic pressure (RVSP) and left atrium (LA) pressure means (P < 0.001 for each) after MV commissurotomy (Table 2).
Regarding post-commissurotomy MR, 12 (9.9%) patients developed severe MR. They were compared with other patients to identify important distinction points. Sever MR group showed significantly higher weight, height, body mass
Table 1. Demographic and clinical data of the studied patients.
BMI: Body mass index, BSA: Body surface area, LVES: Left Ventricular End Systolic, LVED: Left Ventricular End diastolic, LA: left atrium, LV: left ventricle, RVSP: right ventricular systolic pressure, EF: ejection fraction, Ao: aortic Dicemeter.
Table 2. Cardiac chamber pressures before and after mitral commissurotomy.
LA: left atrium, LV: left ventricle, RVSP: right ventricular systolic pressure.
index (BMI), and body surface area (BSA) (P < 0.001 for each) without significant differences regarding age and sex (P = 0.383 and 0.394, respectively). Also, there was significant differences between both groups regarding pre-operative Wilkins score (8.7 ± 1.3 for severe MR versus 7.9 ± 1.2 for No/Mild MR, P = 0.046), RVSP (37.3 ± 2.0 for severe MR versus 35.0 ± 3.2, P = 0.002), and MV balloon size (17.3 ± 1.0 for severe MR versus 16.5 ± 0.8 for No/Mild MR, P = 0.001). Pre-operative transthoracic echocardiography also showed that patients who developed severe MR had higher incidence of other valvular lesions, such as mild aortic regurgitation (91.7% versus 36.7%, P < 0.001), higher MV commissural calcification (50.0% versus 14.7%, P = 0.008), pre-operative MR (100.0% versus 35.8%, P < 0.001), higher prevalence of atrial fibrillation (AF) (100.0% versus 38.5%, P < 0.001) (Table 3).
Univariate regression was performed in this study to identify possible factors that could predict outcome of MV commissurotomy. It revealed that BMI, EF, MV commissural calcification, MV commissural asymmetry, and MV balloon size were significantly able to predict the development of severe MR (P = 0.045, 0.029, 0.006, <0.001, 0.004, respectively) (Table 4).
Multivariate regression analysis identified MV balloon sizing (OR 3.877, CI 95% 1.131 - 13.289, P = 0.031) and MV commissural asymmetry (OR 67.48, CI 95% 5.759 - 790.72, P = 0.001) as significant predictors of outcomes of MV commissurotomy (Table 5).
Table 3. Comparison of demographic and echocardiographic data of both groups of MR.
BMI: Body mass index, BSA: Body surface area, LVES: Left Ventricular End Systolic, LVED: Left Ventricular End diastolic, LA: left atrium, LV: left ventricle, RVSP: right ventricular systolic pressure, EF: ejection fraction. AR: aortic regurgitation, MR: mitral regurgitation, AF: atrial fibrillation, MV: mitral valve.
Table 4. Univariate regression for predicting severe MR post commissurotomy.
BMI: Body mass index, EF: ejection fraction, MV: mitral valve, MR: Mitral regurgitation.
Table 5. Multivariate regression for predicting severe MR post commissurotomy.
BMI: Body mass index, EF: ejection fraction, MV: mitral valve.
Receiver operating characteristic analysis was also done to determine possible MV balloon size that can be associated with possibility of severe MR post-commissurotomy. It showed that size of ≥17 had sensitivity of 66.7% and specificity of 77.1% with area under the curve (AUC) of 0.719.
The results of the current study showed that multitrack balloon technique can significantly improve MS as proved by significant reduction of the means of gradient pressure, RVSP, and LA pressure. Actually, PMV is an effective procedure for MS with any of its technique either by Inoue balloon, metallic commissurotome, or multitrack double balloon as reported by Sharieff et al. , Sherif et al. , Sowdagar and Subba , Alkhouly et al. .
The second outcome of this study is that the twelve patients who developed severe MR had significantly higher weight, height, BMI, and BSA. Higher incidence (13.3%) of severe MR was observed by Elsawy et al. . However, in the study of Sadaka et al. , no one developed severe MR even after follow up for 3 months. Actually, Sherif et al.  noticed that Multi-Track technique of PMV can result in immediate increase in the grade of MR more than other techniques of PMV. Farman et al.  reported that 8.1% of 258 patients who performed PMV developed MR (more than mild degree). However, these patients had less weight, height, and BSA compared with other patients, in contrast to the current results. In fact, the annular dimensions of the mitral valve have been reported to increase linearly with body surface area.  This is probably the reason for the tendency of using a more aggressive approach as the use of a bigger balloon that was significantly correlated with the outcome of severe MR as will be demonstrated later in this study.
Also, in this study, there was a significant difference between the both groups regarding pre-operative Wilkins score. Similarly, Elasfar and Elsokkary  noticed a significant higher Wilkins score among patients with severe MR compared to patients without severe MR. Zhang et al.  reported patients with lower echocardiographic scores as Wilkins score benefit more from percutaneous balloon mitral valvuloplasty than patients with higher scores. In contrast, Paiva et al.  noticed none significant differences between patients with score 9 - 11 and patients with score < 8 regarding major complication or success rate.
Pre-operative transthoracic echocardiography also showed that patients who developed severe MR had higher incidence of other valvular lesions, MV commissural calcification, pre-operative MR, and higher prevalence of AF. The study of Sharma et al.  delineated that AF, higher functional class, and worse valve morphology were independent predictors of a poor balloon MV outcome. Regarding pre-operative MR, Palacios et al.  identified MR that is ≥2+ to be associated with worse outcome of PMV.
Regarding balloon sizing, it was significantly higher among patients who developed severe MR compared with patients with mild or no MR. Tastan et al.  studied 2 groups of patients undergoing percutaneous balloon mitral valvuloplasty. One group was subjected to conventional height-based balloon reference sizing (the HBRS group) and the other was assigned to balloon sized by echocardiographic measurement of the diastolic inter-commissural diameter (the EBRS group). They noticed that the mean of the calculated balloon reference sizes was significantly higher in the HBRS than in the EBRS group and MR > 2+ was less in the EBRS group.
Univariate regression analysis revealed that BMI, EF, MV commissural calcification, MV commissural asymmetry, and MV balloon size were significant predictors of the development of severe MR. In the study of Aslanabadi et al. , patients with increased MR post procedure had a significantly higher calcification score before the procedure compared to other patients. In contrast, Dreyfus et al.  reported that the rate of post-PMC mitral regurgitation of grade ≥ 3 was not different among different groups of mitral calcification.
In the current study, multivariate regression analysis identified MV balloon sizing and MV commissural asymmetry as significant predictors of outcome of MV commissurotomy. Receiver operating characteristic analysis also showed that the size of ≥17 had a sensitivity of 66.7% and specificity of 77.1% with AUC of 0.719. Farman et al.  reported that there was significant difference between patients with successful and unsuccessful (more than mild MR) PMV regarding balloon size, and the size of 14 × 16-mm was the most successful.
To the best of our knowledge, this study is the first to shed light on predictors of severe MR after multitrack PMV.
5. Study Limitations
The most important limitations of the current study were the relatively small sample size and the absence of long-term follow-up data for those patients.
In this study, we identified several factors that can predict the development of severe MR after multitrack PMV including MV calcification, balloon sizing, and MV asymmetry.
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