Ronan Margey, Sammy Elmariah and Igor F. Palacios

9.1 Patient Selection

Selection of patients for PMV should be based on symptoms, physical examination, and two-dimensional (2D) and Doppler echocardiographic findings.4,17,27,28 PMV is usually performed electively. However, emergency PMV can be performed as a life-saving procedure in patients with mitral stenosis and severe pulmonary edema refractory to medical therapy and/or cardiogenic shock. Patients considered for PMV should be symptomatic (New York Heart Association [NYHA] ≥ II), should have no recent thromboembolic events, have less than two grades of mitral regurgitation (MR) by contrast ventriculography using the Sellers’ classification,²⁹ and have no evidence of left atrial thrombus on 2D and transesophageal echocardiography (Table 9–1). Transthoracic and transesophageal echocardiography should be performed routinely before PMV. Patients in atrial fibrillation and patients with previous embolic episodes should have treatment with warfarin to achieve anticoagulation with a therapeutic international normalized ratio (INR) for at least 3 months before PMV. Patients with left-atrium thrombus on 2D-echocardiography should be excluded. However, PMV could be performed in these patients if left-atrium thrombus has resolved after warfarin therapy.

A multifactorial score derived from clinical, anatomic/echocardiographic, and hemodynamic variables can predict procedural success and clinical outcome (Figure 9–1).²⁸ Demographic data, echocardiographic parameters (including echocardiographic score, Figure 9–2), and procedure-related variables recorded from 1085 consecutive patients who underwent PMV at the Massachusetts General Hospital (MGH) and their long-term clinical follow-up data (i.e., death, mitral valve replacement, redo PMV) were used to derive this clinical score. Multivariate regression analysis of the first 800 procedures was performed to identify independent predictors of procedural success. Significant variables were formulated into a risk score and validated prospectively. Six independent predictors of PMV success were identified: (1) age younger than 55 years, (2) NYHA classes I and II, (3) pre-PMV mitral area of 1 cm² or greater, (4) pre-PMV MR grade less than 2, (5) echocardiographic score of 8 or less, and (6) male gender.^4,27,28 A score was constructed from the arithmetic sum of variables present per patient. Procedural success rates increased incrementally with increasing score (0% for a score of 0/6, 39.7% for 1/6, 54.4% for 2/6, 77.3% for 3/6, 85.7% for 4/6, 95% for 5/6, and 100% for 6/6; p < 0.001). In a validation cohort (n = 285 consecutive procedures), the multifactorial score remained a significant predictor of PMV success (p < 0.001). Comparison between the new score and the echocardiographic score confirmed that the new index is more sensitive and specific (p < 0.001). This new score also predicts long-term outcomes (p < 0.001). Clinical, anatomic, and hemodynamic variables predict PMV success and clinical outcome and may be formulated in a scoring system that would help to identify the best candidates for PMV.

9.2 Technique of Percutaneous Mitral Balloon Commissurotomy

PMV is performed when the patient is in the fasting state and under mild sedation. Antibiotics (500 mg dicloxacillin per os [po] q/6 hours for four doses started before the procedure or 1 g cefazolin intravenously [IV] at the time of the procedure) are used. Patients allergic to penicillin should receive 1 g vancomycin IV at the time of the procedure. All patients carefully chosen as candidates for mitral balloon valvuloplasty should undergo diagnostic right and transseptal left heart catheterization. After transseptal left heart catheterization, systemic anticoagulation is achieved by the intravenous administration of 100 units/kg of heparin. In patients older than 40 years, coronary arteriography is recommended and should also be performed.

Hemodynamic measurements, cardiac output, and cine left ventriculography are performed before and after PMV. Cardiac output is measured by thermodilution and Fick method techniques. Mitral valve calcification and angiographic severity of MR (Sellers’ classification) are graded qualitatively from 0 to 4 as previously described.²⁹ An oxygen diagnostic run is performed before and after PMV to determine the presence of left-to-right shunt across the atrial septum after PMV.

There is not a unique technique of percutaneous mitral balloon valvuloplasty. Most of the techniques of PMV require transseptal left heart catheterization and use of the antegrade approach.15–24,26,30–32 Antegrade PMV can be accomplished using double balloon technique (Figure 9–3, A), or the more commonly used single balloon technique (Figure 9–3, B). In this latter approach the two balloons could be placed through a single femoral vein and single transseptal puncture or through two femoral veins and two separate atrial septal puncture. In the retrograde technique of PMV the balloon dilating catheters are advanced percutaneously through the right and left femoral arteries over guidewires that have been snared from the descending aorta. These guidewires have been advanced transseptally from the right femoral vein into the left atrium, the left ventricle, and the ascending aorta.³¹ A retrograde nontransseptal technique of PMV has also been described.¹⁵ A technique of PMV using a newly designed metallic valvulotome has also been introduced.¹⁶ The device consists of a detachable metallic cylinder with two articulated bars screwed onto the distal end of a disposable catheter, on which the proximal end is connected to activating pliers. Squeezing the pliers opens the bars up to a maximum of 40 mm (see Figure 9–3, C). The results with this device are at least comparable to those of the other balloon techniques of PMV.¹⁶ However, multiple uses after sterilization should markedly decrease procedural costs.

9.3 Predictors of Increase in Mitral Valve Area and Procedural Success

Univariate analysis demonstrated that the increase in MVA with PMV is directly related to the balloon size employed because it reflects in the EBDA, and inversely related to the echocardiographic score (see Figure 9–2), the presence of atrial fibrillation, the presence of fluoroscopic calcium, the presence of previous surgical commissurotomy, older age, NYHA classification pre-PMV, and presence of MR before PMV. Multiple stepwise regression analysis identified balloon size (p < 0.02), the echocardiographic score (p < 0.0001), and the presence of atrial fibrillation (p < 0.009) and MR before PMV (p < 0.03) as independent predictors of the increase in MVA with PMV.⁴

Univariate predictors of procedural success included age, pre-PMV MVA, mean pre-PMV pulmonary artery pressure, male gender, echocardiographic score, pre-PMV MR of 2+ or greater, history of previous surgical commissurotomy, presence of atrial fibrillation, and presence of mitral valve calcification under fluoroscopy.⁴

Multiple stepwise logistic regression analysis identified larger pre-PMV MVA (odds ratio [OR] 13.05; 95% confidence interval [CI] 7.74 to 22.51; p < 0.001), less degree of pre-PMV MR (OR 3.85; CI 2.27 to 6.66; p < 0.001), younger age (OR 3.33; CI 1.41 to 7.69; p = 0.006), absence of previous surgical commissurotomy (OR 1.85; CI 1.20 to 2.86; p = 0.004), male gender (OR 1.92; CI 1.19 to 3.13; p = 0.008), and echocardiographic score of 8 or lower (OR 1.69; CI 1.18 to 2.44; p = 0.004).⁴

9.4 Complications

Table 9–5 shows the complications reported by several investigators after PMV.^{4,12–18,22,34} Mortality and morbidity with PMV are low and similar to surgical commissurotomy. Overall, there is a less than 1% procedural mortality. Severe MR (4 grades by angiography) has been reported in 1% to 5.2% of patients, with some of these patients requiring in-hospital mitral valve replacement. Thromboembolic episodes and stroke have been reported in 0% to 3.1% and pericardial tamponade in 0.2% to 4.6% of cases in these series. Pericardial tamponade can occur from transseptal catheterization and more rarely from ventricular perforation. PMV is associated with a 3% to 16% incidence of left-to-right shunt documented by oxymetry immediately after the procedure. However, the pulmonary-to-systemic flow ratio is greater than or equal to 2:1 in only a minimum number of patients.

Severe MR (4 grades by angiography) occurs in about 3% of patients undergoing PMV.28,42 An undesirable increase in MR (≥2 grades by angiography) occurred in 10.1% of patients. This undesirable increase in MR is well tolerated in most patients. Furthermore, more than half of them have less MR at follow-up cardiac catheterization. The ratio of the EBDA to body surface area is a predictor of increased MR after PMV.^28,42,43 The EBDA is calculated using standard geometric formulas (see Table 9–2). The incidence of MR is lower if balloon sizes are chosen so that EBDA/body surface area is less than or equal to 4.0 cm²/m². The single balloon technique results in a lower incidence of MR but provides less relief of mitral stenosis than the double balloon technique. Thus there is an optimal EBDA between 3.1 and 4.0 cm²/m² that achieves a maximal MVA with a minimal increase in MR. An echocardiographic score for the mitral valve that can predict the development of severe MR after PMV has also been described.³⁵ This score takes into account the distribution (even or uneven) of leaflet thickening and calcification, the degree and symmetry of commissural disease, and the severity of subvalvular disease (Table 9–6).

Left-to-right shunt through the created atrial communication determined by oximetry occurred in 3% to 16% of patients undergoing PMV. The size of the defect is small as reflected in the pulmonary-to-systemic flow ratio of less than 2:1 in the majority of patients. Older age, fluoroscopic evidence of mitral valve calcification, higher echocardiographic score, pre-PMV lower cardiac output, and higher pre-PMV NYHA functional class are the factors that predispose patients to develop left-to-right shunt post-PMV.⁴⁴ Clinical, echocardiographic, surgical, and hemodynamic follow-up study of patients with post-PMV left-to-right shunt demonstrated that the defect closed in approximately 60% of patients. Persistent left-to-right shunt at follow-up study is small () and clinically well tolerated. In the series from MGH there is one patient in whom the atrial shunt remained hemodynamically significant at follow-up study. This patient underwent percutaneous transcatheter closure of her iatrogenic residual atrial defect with a clamshell device. Desideri et al.⁴⁵ reported atrial shunting determined by color flow transthoracic echocardiography in 61% of 57 patients immediately after PMV. The shunt persisted in 30% of patients at 19 ± 6 (range 9 to 33) months’ follow-up examination. They identified the magnitude of the post-PMV atrial shunt (), use of bifoil balloon (2 balloons on 1 shaft), and smaller post-PMV MVA as independent predictors of the persistence of atrial shunt at long-term follow-up study. Together with the authors’ results, these findings suggest that those patients with persistently elevated left atrial pressures resulting from either suboptimal PMV or poor diastolic compliance after PMV are more likely to experience persistent left-to-right shunting.

9.5 Clinical Follow-Up Studies

Long-term follow-up studies after PMV are encouraging.4,22–26,30,46–60 After PMV, the majority of patients have marked clinical improvement and are scored at NYHA Class I or II. The symptomatic, echocardiographic, and hemodynamic improvement produced by PMV persists in intermediate and long-term follow-up study. The best long-term results are seen in patients with echocardiographic scores of 8 or less. When PMV produces a good immediate outcome in this group of patients, restenosis is unlikely to occur at follow-up study. Although PMV can result in a good outcome in patients with echocardiographic scores higher than 8, hemodynamic and echocardiographic restenosis is often demonstrated at follow-up study despite ongoing clinical improvement. Table 9–7 shows long-term follow-up results of patients undergoing PMV at different institutes. An estimated 12-year survival rate of 74% in a cohort of 879 patients undergoing PMV at the MGH was reported (Figure 9–5).⁴ Death at follow-up study was directly related to age, post-PMV pulmonary artery pressure, and pre-PMV NYHA functional class IV. In the same group of patients, the 12-year event-free survival rate (alive and free of mitral valve replacement or repair and redo PMV) was 33% (Figure 9–6). Cox regression analysis identified age (risk ratio [RR] 1.02; CI 1.01 to 1.03; p < 0.0001), pre-PMV NYHA functional class IV (RR 1.35; CI 1.00 to 1.81; p = 0.05), prior commissurotomy (RR 1.50; CI 1.16 to 1.92; p = 0.002), the echocardiographic score (RR 1.31; CI 1.02 to 1.67; p = 0.003), pre-PMV MR greater than or equal to 2+ (RR 1.56; CI 1.09 to 2.22; p = 0.02), post-PMV MR greater than or equal to 3+ (RR 3.54; CI 2.61 to 4.72; p < 0.0001), and post-PMV mean pulmonary artery pressure (RR 1.02; CI 1.01 to 1.03; p < 0.0001) as independent predictors of combined events at long-term follow-up study.

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