Introduction

From the end of the 19th century, rheumatic fever and its cardiac complications have been a great public health issue in the western world. Since the use of penicillin, the prevalence of mitral valve pathology of rheumatic etiology has diminished in Mexico, however there are some regions where the disease has not yet been eradicated, therefore this disease still represents a health issue in the productive population.¹

Rheumatic fever is an autoimmune inflammatory process with multiorgan involvement. The valvular involvement due to the chronic inflammatory process leads to thickening of the valves, fibrosis, fusion and shortening of the valves and commissures, and finally deformation, reduction and calcification of the mitral annulus.²

Mitral stenosis is a late complication, usually after 10 to 20 years. It is more common in women. Valve regurgitation is more common in men.³

There are several options for treating symptomatic valvular stenosis: a) surgical closed mitral commissurotomy (CMC), b) surgical open mitral commissurotomy (OMC), c) percutaneous techniques and finally, d) valve replacement.⁴

Surgical options are associated with restenosis rates of less than 10% at ten years, however disadvantages are thoracotomy, extracorporeal circulation, and surgical morbidity with longer hospital stay and increased costs.⁴,⁵

In 1982 Kanji Inoue, Japanese cardiothoracic surgeon, designed the percutaneous mitral commissurotomy with a rubber balloon.⁶ Since then, the percutaneous mitral valvuloplasty (PMV) has become the treatment of choice of mitral stenosis with suitable anatomy.⁷,⁸

The success rate for the PMV depends on multiple factors:⁸-¹⁰

Therefore, echocardiography is important for adequate evaluation and selection of patients.

When immediate post-procedure results are successful, adequate long-term results are predicted. When initial results are suboptimal, it is expected that patient’s symptoms will not improve or only improve transiently and is associated with the need for surgical treatment in short term.¹¹,¹²

Our hospital, a tertiary referral center, has eighteen years of experience in PMV. Therefore, the aim of this study is to determine the clinical and echocardiographic related factors associated with success of PMV.

Material and methods

This is a comparative, retrospective, cross-sectional and observational study. We evaluated clinical records of patients with diagnosis of rheumatic severe mitral stenosis who were treated with PMV from 2000 to 2016 in the High Speciality Medical Unit Num. 34 of Mexican Institute of Social Security, in Monterrey, Nuevo León, México. They should have complete medical records for analysis and fulfill the inclusion criteria: age over eighteen-years old, mitral valve area (MVA) ≤ 1.5 cm², symptoms (NYHA class > 2), echocardiographic Wilkins’ score < 10 pts, mild to moderate subvalvular calcification, no severe mitral regurgitation. We excluded patients with severe mitral regurgitation, another pathology that warrants cardiac surgery and Wilkins’ score > 10 p.

We defined success of PMV: achieved MVA > 1.5cm², post-procedure non-severe mitral regurgitation and a decrease in mean trans-mitral gradient to less than 10 mmHg.¹⁰,¹³

For the purpose of analysis, patients were divided in two groups according to achieved or not immediate success of PMV and then we analyzed the following variables to find the more prevalent in each group:

Also, we determined the incidence of complications and reported acute complications: death, severe mitral regurgitation, cardiac tamponade, arrhythmias, vascular access complications, contrast related complications and thrombosis.

Patients were followed for 30 days, using digital clinical records of the institution and we evaluated adverse cardiovascular events: death, cardiac tamponade, urgent mitral valve surgery, arrhythmias and stroke.

We compared the characteristics of both groups and its association with the complications to determine also risk factors of procedure.

Results

From November 2000 until June 2016, 363 patients were included

Discussion

In this analysis that included 363 patients in which mitral balloon valvuloplasty was performed, we evaluated the main factors associated to success or failure of the procedure.

Analyzing the demographic characteristics of the patients, we found female gender to be the most prevalent, with almost 80% of the cases being women, and with a mean age around 50 years. In our study, 52% of the patients were older than 50 years, as found by Elisabete et al.¹⁴

The rest of the baseline characteristics in our population were similar to the information reported by previous studies,⁷,¹⁴-¹⁶ except for the cardiac rhythm, in which atrial fibrillation was found to predominate in our center.⁷,¹⁶

The procedure was performed in three pregnant women, in which all were successful, except one patient developed a left appendage thrombus and was treated with thrombolysis without any further complication. The procedure in the other two patients was safe and effective as reported previously by other centers.¹⁷

Regarding procedural characteristics, the most common balloon used was the Inoue balloon. Finding success rates of 85.1%, which are similar to those reported in other centers where success rates are between 85 and 90%.¹⁰,¹⁸ We found an increase of almost 100% in mitral valve orifice.

According to the previous reports where certain characteristics, like history of previous procedure and very severe mitral stenosis (area less than 1 cm²) represent technical difficulties and could alter success rates, however we found no significant association between those variables and failure.³,⁹,¹⁹

As previously reported and in our center, the PMV is safe and with high success rates, but we found only two factors associated to failure with statistical significance. Wilkins score between 8-10 points with odds ratio 2.6 (IC 95%; 1.3-5.2), and previous moderate mitral insufficiency with odds ratio 3.3 (IC 95%; 1.28-8.93). This is similar to the data reported in other centers. Moreover, in our center the number of patients with Wilkins score 8-10 points (63%) was greater than other series.¹⁶,²⁰ For example, the number of patients with these characteristics reported by Elisabete et al,¹⁴ was only 8%. Selection of the patients with scores > 8 was made on the basis of low score on the subvalvular apparatus and the experience of the center. However, Wilkins score > 8 is associated to bad outcomes, in spite of acceptable success rate in our center, avoiding this condition could improve success rate. Echocardiographic evaluation of patients is essential, and consideration of clinical characteristics allows optimal selection of patients.¹³

Complications

Our complication rate was 7.16%, which is similar to those reported by other centers.³,⁹,¹⁰ However, this percentage was due to minor complications, which do not have an impact on the patient’s long-term outcomes (pericardial effusion, site access hematoma, arrhythmias, allergic reaction to contrast). In our registry, two patients developed intracardiac thrombus during the procedure (0.55%), a complication that is rarely reported in other series. Post-procedural severe mitral insufficiency was observed less than those reported by other centers.²¹ We had an overall 30-day mortality of 0.82%, similar to other studies.⁹,¹⁰,²²

In the follow-up the composite of death, mitral surgery, arrhythmia, tamponade and stroke was only 3.30%, which demonstrates the safety of the procedure.

We found characteristics associated with complications (pulmonary systolic arterial pressure > 60 mmHg, transmitral gradient > 10 mmHg, pre-procedural moderate mitral regurgitation, and the use of double-balloon technique), that forced us to be cautious in certain patients and techniques. Double-balloon techniques had already been associated with more complications.⁶

We assessed event-free survival at 30 days according to Kaplan-Meyer method, and elaborated survival curves (Figure 1). Also, factors associated with adverse events were analyzed with survival curves (Figure 2).

Figure 1: Adverse cardiovascular events post-Percutaneous mitral valvuloplasty. 

Figure 2: Kaplan-Meyer event free survival stimates at 30 days adverse cardiac events and association with. A. Previous moderate mitral regurgitation (p = 0.001); B. Pulmonary hypertension (> 60 mmHg) (p = 0.01); C. Trans-valvular gradient (mean > 10 mmHg) (p = 0.0049). 

Conclusions

In our study, we had a successful procedure in 85.1% of the cases. The mortality and complications rates were similar to previous worldwide series.

We found that only Wilkins score ≥ 8 points and previous moderate mitral insufficiency are strong predictors of an unsuccessful valvuloplasty. We also found that a high number of patients in our study had a Wilkins score over 8 points, which could have diminished the number of successful procedures. Nevertheless, our success rate was within normal range.

In conclusion, all these variables should be taken into consideration in the selection process of the patients in order to choose the most accurate technique and improve the success rates while reducing complications.