Percutaneous Mitral Valve Procedures
Jayendrakumar S. Patel
Amar Krishnaswamy
Percutaneous strategies for the treatment of mitral valve (MV) stenosis and MV regurgitation are important therapeutic options for selected patients. In the growing field of structural cardiac interventions, the MV presents a new frontier for technologic innovation and less-invasive patient care. In this chapter, we discuss patient selection, technical aspects, and data supporting percutaneous mitral valvotomy, repair, and valve replacement.
I. PERCUTANEOUS MITRAL BALLOON VALVOTOMY
A. Introduction. First performed in the mid-1980s, percutaneous mitral balloon valvotomy (PMBV) has now become the preferred method of treating symptomatic patients with severe mitral stenosis (MS) of rheumatic etiology and favorable valve morphology. The procedure entails controlled fracture and separation of fused commissures. Hence, there is no role for PMBV in cases of MS without commissural fusion (e.g., congenital MS or MS secondary to mitral annular calcification) or in cases where the valves are not pliable. Several randomized trials have shown that PMBV offers outcomes that are equivalent to or better than surgical closed or open commissurotomy, with added benefits of lower cost and a minimally invasive approach. Optimal outcomes depend upon accurate assessment of valve anatomy, valve hemodynamics, and patient symptoms.
B. Indications
1. The indications for intervention for patients with rheumatic MS are shown in Figure 11.1 and are derived from the 2014 American Heart Association/American College of Cardiology (AHA/ACC) Guidelines for the Management of Patients with Valvular Heart Disease. In general, there is strong evidence supporting PMBV in patients with reduced exercise capacity and exertional dyspnea in the setting of moderate-to-severe MS and with favorable valve characteristics in the absence of contraindications as detailed later. Weak evidence suggests that the procedure is reasonable for asymptomatic patients with very severe MS (mitral valve area [MVA] ≤1.0 cm2) and may be considered in those with severe MS with MVA ≤1.5 cm2 and systolic pulmonary pressure >50 mm Hg, need for major noncardiac surgery, or new-onset atrial fibrillation, as this represents a high risk of thromboembolism.
2. Although the European Society of Cardiology does not recommend intervention in patients with MVA >1.5 cm2 regardless of the presence of symptoms, the AHA/ACC guidelines state that PMBV may be considered in symptomatic patients with increased transmitral flow velocities, mild-to-moderate left atrial enlargement, and pulmonary capillary wedge pressure >25 mm Hg or mean gradient >15 mm Hg during exercise. Pregnancy also presents unique hemodynamic considerations, and there is a weak level of evidence in support of preconception PMBV for women with asymptomatic MS with MVA ≤1.5 cm2, especially if there is pulmonary hypertension at rest or with exercise. Patients with recurrence of symptomatic MS post-PMBV and with evidence of commissural fusion can also be considered for a repeat intervention if anatomy is favorable.
 FIGURE 11.1 Indications for intervention in patients with rheumatic mitral stenosis. LA, left atrium; MR, mitral regurgitation; MVA, mitral valve area; MVR, mitral valve replacement; PCWP, pulmonary capillary wedge pressure; PMBC, percutaneous mitral balloon commissurotomy. (Adapted from Figure 3 in Nishimura RA, Otto CM, Bonow RO, et al. 2014 AHA/ACC guideline for the management of patients with valvular heart disease: executive summary: a report of the American College of Cardiology/American Heart Association Task Force on Practice Guidelines. J Am Coll Cardiol. 2014;63[22]:2438-2488.) |
C. Contraindications to PMBV
1. Transesophageal echocardiography (TEE) must be performed before PMBV to accurately assess valve anatomy and most importantly to ensure the absence of left atrial clot and/or moderate-to-severe mitral regurgitation (MR). If thrombus is present and the need for intervention is not urgent, the patient may undergo a trial of therapeutic anticoagulation for 2 to 6 months followed by reassessment with TEE. If thrombus persists or the need for intervention is urgent, a surgical approach is indicated.
2. Several scoring systems have been developed to assess anatomic suitability for PMBV and are discussed later. In order for PMBV to be successful with sustained durability, the valve leaflets and commissures should be relatively noncalcified and pliable with minimal valvular and subvalvular thickening. Heavy calcification of the commissures (especially both commissures) predicts development of postprocedural severe MR; thus, percutaneous valvotomy should be avoided in such patients. Similarly, asymmetric fusion of only one commissure may provide a greater risk for tearing the valve and creating significant MR. Nevertheless, patients with less-than-ideal valve anatomy may still be considered for PMBV if surgery is contraindicated or considered too high risk. Finally, the concomitant presence of MS and severe aortic valve disease, severe tricuspid stenosis or regurgitation, or severe coronary artery disease requiring bypass should prompt consideration of surgical intervention.
D. Evaluation
1. Evaluation of the patient begins with careful assessment of symptoms and the degree of functional disability (New York Heart Association [NYHA] class). These include dyspnea with exertion or at rest, cough, hoarseness, hemoptysis, atrial fibrillation, thromboembolism, and right-sided heart failure from elevated pulmonary pressures. For asymptomatic patients or patients with symptoms that seem out of proportion to valve severity, exercise or dobutamine echocardiography can help identify patients with hemodynamically significant disease.
2. A thorough assessment of the valve apparatus using either transthoracic echocardiography (TTE) or TEE is imperative to determine suitability and likelihood of success (and complications) of PMBV. This can be accomplished through several scoring systems, the most common of which is shown in Table 11.1 (Wilkins score). Of note, none of the scoring systems are perfectly reproducible and the Wilkins score omits commissural calcification. Thus, even patients deemed to have an ideal Wilkins score may experience suboptimal outcomes, including the development of severe MR. The commissural calcification scoring system shown in Table 11.2 can be used adjunctively to further predict the development of severe MR. In patients with an echo score that is favorable (i.e., ≤8 by Wilkins score),
a commissural calcification score ≥2 predicts a smaller increase in valve area and reduced success rate of achieving a final valve area >1.5 cm2 without MR. Cardiac catheterization with direct measurement of valve gradients has largely been supplanted by echocardiography and is only necessary when there is conflicting information derived from noninvasive studies.
a commissural calcification score ≥2 predicts a smaller increase in valve area and reduced success rate of achieving a final valve area >1.5 cm2 without MR. Cardiac catheterization with direct measurement of valve gradients has largely been supplanted by echocardiography and is only necessary when there is conflicting information derived from noninvasive studies.
TABLE 11.1 Wilkins Echocardiographic Scoring System of the Mitral Valve | ||||||||||||||||||||||||||||||||||||||||
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TABLE 11.2 Commissural Calcification Scoring System | ||||||||||||||||
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E. Technique
1. A transvenous approach (femoral or jugular) is most commonly employed to perform PMBV. Arterial access may be helpful to perform left ventriculography before the start of the PMBV procedure in order to establish the MV plane and also the degree of MR. Transseptal catheterization to gain access to the left atrium and MV is routinely performed using a Brockenbrough needle via a Mullins sheath (Medtronic Inc, Minneapolis, MN). In some labs, this step is performed with intracardiac echocardiography guidance as an adjunct to routine fluoroscopic imaging. Once this step is complete, the operator may choose a single (more common) or double balloon technique to perform commissurotomy (Fig. 11.2).
2. With the single balloon technique, an Inoue balloon (Toray Industries, Tokyo, Japan) is selected according to the patient’s height (maximum diameter [mm]: [patient height in cm]/10 + 10). The device is then passed through the atrial septum into the left atrium and the distal portion of the balloon is inflated with a few milliliters of diluted contrast. This action serves to reduce the risk of ventricular perforation. After crossing the valve and entering the left ventricle (LV), the distal portion of the balloon is further inflated and then pulled back into the mitral orifice. The proximal and central portions are then inflated up to 4 mm below the maximum balloon size for the initial balloon procedure.
3. TTE or TEE is then utilized to assess the response to balloon inflation (MV orifice is assessed by planimetry), and if the valve area is inadequate without an increase in MR by more than one grade (based on color Doppler), repeat valvotomy is performed with a 1-mm increase in balloon diameter. Such stepwise dilation ensures that the risk of creating severe MR is minimized. Further balloon dilations are ceased if the MVA is >1 cm2/m2 of the body surface area, if there is complete opening of at least one commissure, or if there is worsening of MR by more than one grade. Greater caution is taken in patients older than age 65 or
pregnant patients. Good immediate results are defined as final valve area >1.5 cm2 and an increase of at least 25% of valve area, or final valve area >1.5 cm2 with less than moderate MR.
pregnant patients. Good immediate results are defined as final valve area >1.5 cm2 and an increase of at least 25% of valve area, or final valve area >1.5 cm2 with less than moderate MR.
 FIGURE 11.2 Key steps in percutaneous mitral balloon valvotomy. A: Left ventriculography is performed to establish the plane of the mitral valve and assess the degree of mitral regurgitation. B: Transseptal puncture is then performed (arrowheads). C: The deflated Inoue balloon is then passed through the atrial septum into the left atrium (arrows). D: The distal portion of the balloon is inflated with a few milliliters of diluted contrast. E: The mitral valve is crossed. The distal portion of the balloon is further inflated and then pulled back into the mitral orifice. F: The proximal and central portions are finally inflated. |
F. Periprocedural management. All patients who have undergone PMBV should be admitted to the hospital and monitored for complications. Approximately 24 to 48 hours after the procedure, repeat TTE is indicated to assess valve area and the degree of MR. If MR appears to be significantly worsened, TEE can be performed to determine the mechanism and further assess severity and need for valve surgery.
G. Complications. Rates of various complications from PMBV are fairly low and are dependent upon a variety of factors including operator experience, technique employed, patient clinical profile, and valve characteristics. In-hospital death is rare (<1%), and embolic events can be seen in up to 1.8% of cases. The most catastrophic complication is left ventricular perforation, with the development of hemopericardium necessitating emergent pericardiocentesis (observed in 1% of cases). Severe MR post-PMBV is not common but is difficult to predict owing to imprecise anatomic prediction scores. The frequency of severe MR ranges from 2% to 19% and can be due to tearing of the leaflets, excessive commissural splitting, or papillary muscle rupture. The most frequent mechanism is MR at the site of successful commissurotomy. Valve replacement is usually necessary in cases of leaflet laceration as valvular and subvalvular anatomy is not ideal for repair. Overall survival rate for those who develop severe MR is not significantly different when compared with those who do not develop severe MR.
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