Introduction
Mitral stenosis (MS) is the most common sequelae of rheumatic heart disease and is characterized by diffuse fibrous thickening of the margins of the mitral valve (MV) leaflets and fusion of the commissures. Untreated, severe MS can lead to significant derangement of the functional status of patients and reduced long-term survival. Since its introduction in the 1980s, percutaneous balloon mitral valvuloplasty (PBMV) has proven to be an effective and durable treatment option for selected patients with rheumatic MS. Although it is more challenging, PBMV has also been utilized in patients with nonrheumatic MS (e.g., calcific MS). This chapter focuses on the contemporary indications, patient selection, and techniques of PBMV.
Indications and patient selection
PBMV is recommended for symptomatic patients with severe MS (mitral valve area [MVA] <1.5 cm 2 , stage D) and favorable valve morphology in the absence of contraindications ( Fig. 14.1 ). The goal of PBMV for patients with rheumatic MS is to directly affect the main valvular pathology by inducing an effective commissural split without a significant increase in mitral regurgitation (MR). Hence, in symptomatic patients, the main determinants of patient selection for PBMV are the anatomic features of the mitral apparatus. Other considerations include the patient’s age, functional status, and the presence or absence of atrial fibrillation or pulmonary hypertension.
Patients who are being considered for PBMV should undergo a comprehensive assessment with transthoracic ± transesophageal echocardiography (TEE). The MV and subvalvular apparatus need to be systematically evaluated for favorable and unfavorable features for PBMV. Attempts have been made to incorporate certain individual characteristics into a holistic scoring system to predict optimal PBMV results. The Wilkins echocardiography score is the most commonly used scoring system for PBMV. This score incorporates four echocardiographic characteristics of the mitral apparatus, including leaflet mobility, leaflet thickness, leaflet calcification, and subvalvular thickening ( Table 14.1 ). Each component is given a 1- to 4-point score. Patients with Wilkins scores ≤8 are, in general, suitable for PBMV. When the Wilkins score is >10, the risk of complications, including severe MR requiring urgent or emergent MV replacement, is significantly higher. Patients with a Wilkins score between 8 and 10 may be considered for PBMV on an individual basis. A simpler scoring system is the Lung and Cormier score, which divides the valvular anatomy into three groups, with patients in group 1, 2, and 3 considered optimal, intermediate, and borderline candidates for PBMV, respectively ( Table 14.2 ). Newer scoring systems to predict PBMV outcomes have been proposed. , These scores incorporate novel predictors of PBMV outcomes, such as commissural morphology, leaflet displacement, commissural calcium, and commissural fusion. These scoring systems have weaknesses and strengths. One fundamental criticism applying to all scoring systems is that they are mainly derived from single-center experience and with a limited number of operators. Furthermore, assessment of the subvalvular apparatus is difficult in most patients, despite TEE. Most of the echocardiographic assessments are qualitative, which makes the reproducibility of a specific scoring system more challenging. Nevertheless, using any of these scoring systems might help the operator in predicting the outcome and potential complications that should be discussed with the patient as part of the informed consent and shared decision-making.
| Grade | Leaflet Mobility |
|---|---|
| 1 | Highly mobile with only leaflet tips restricted |
| 2 | Leaflet midportions and base portions have normal mobility |
| 3 | Valve continues to move forward in diastole, mainly from the base |
| 4 | No or minimal forward movement of the leaflets in diastole |
| Leaflet Thickening | |
| 1 | Leaflets near normal in thickness (4-5 mm) |
| 2 | Middle of the leaflets normal, considerable thickening of margins (5-8 mm) |
| 3 | Thickening extending through the entire leaflets (5-8 mm) |
| 4 | Considerable thickening of all leaflet tissue (>8-10 mm) |
| Leaflet Calcifications | |
| 1 | A single area of increased brightness on echocardiogram |
| 2 | Scattered areas of brightness confined to leaflet margins |
| 3 | Brightness extending into the midportions of the leaflets |
| 4 | Extensive brightness throughout much of the leaflet tissue |
| Subvalvular Thickening | |
| 1 | Minimal thickening just below the mitral leaflets |
| 2 | Thickening of chordal structures extending to one of the chordal lengths |
| 3 | Thickening extended to distal third of the chords |
| 4 | Extensive thickening and shortening of all chordal structures extending to the papillary muscles |
| Echocardiographic Group | Mitral Valve Anatomy | Suitability for PBMV |
|---|---|---|
| Group 1 | Pliable, noncalcified anterior mitral leaflet and mild subvalvular disease (thin chordae ≥10 mm long) | + |
| Group 2 | Pliable, noncalcified anterior mitral leaflet and severe subvalvular disease (thickened chordae <10 mm long) | ± |
| Group 3 | Calcification of mitral valve of any extent, as assessed by fluoroscopy, whatever the state of the subvalvular apparatus | − |
Contraindications to PBMV
The presence of greater-than-moderate MR is considered an absolute contraindication to PBMV. Relative contraindications include a Wilkins score >10, left atrial or left atrial appendage thrombus, severe or bicommissural calcification, absence of bicommissural fusion, severe mitral annular calcification, international normalized ratio (INR) >1.5 or bleeding diathesis, and other significant coronary or valvular pathology requiring surgery.
PBMV with the inoue balloon
The patient preparation is similar to all other procedures in the catheterization laboratory. We do not recommend general anesthesia unless in rare conditions in which the patient is not cooperative or for airway protection. Anecdotally, in pregnant patients in whom the operator aims to use minimal fluoroscopy, general anesthesia may be considered for transseptal puncture and navigating the balloon across the MV under the guidance of TEE. Intracoronary cardiac imaging (ICE) is an alternative that does not require general anesthesia.
We use intravenous short-acting beta-blockers to treat patients with AF and rapid ventricular rate, aiming to reduce the heart rate to <100 and ideally <80 beats per minute. Patients with a history of AF should also have a TEE within a week before the procedure to demonstrate the presence or absence of left atrial or left atrial appendage thrombus. If the patient is taking anticoagulation, it should be held per standard protocol. In the case of warfarin, the INR should be less than 2 before the procedure.
The retrograde (transarterial) approach to the MV through the aortic valve has fallen out of favor due to the significant challenges. The transseptal approach is currently the standard method for PBMV. Historically, PBMV was first performed with the double-balloon technique through a transseptal approach. In 1984, Dr. Inoue introduced the single modified balloon technique, which is currently utilized in the majority of PBMV procedures.
Transseptal Puncture for PBMV: We obtain percutaneous access in the right femoral vein with a 12F sheath. We also insert a 5F sheath in the radial and femoral artery and advance a pigtail catheter into the aortic root via this sheath. We use an 8.5F Mullins transseptal introducer sheath and Brockenbrough-1 needle (Medtronic, Minneapolis, MN) to perform the transseptal puncture. In patients with MS, atrial enlargement and inferior displacement of the fossa ovalis are common. Imaging-guided transseptal puncture (with TEE or ICE), albeit not mandatory, increases the safety of the procedure and affords the ability to puncture the fossa ovalis in the specific desired location. Ideally a mid-mid or mid-posterior location on the superior/inferior and anterior/posterior axes of the fossa ovalis is preferable for PBMV. If cost of TEE or ICE is a concern, transseptal puncture can be performed under fluoroscopy and the rest of the procedure can be carried out using transthoracic echocardiography (TTE) guidance alone.
Also, in challenging anatomies, levo-phase right atrial angiography can delineate the landmarks necessary to perform the transseptal puncture. Patients with severe MS almost always have an enlarged left atrium (LA) that is visible on the posterior-anterior (PA) view on the chest x-ray—the so-called “double-shadow” sign. This double shadow can also be observed on the PA projection with fluoroscopy. By placing a pigtail in the noncoronary cusp of the aortic root (the most posterior cusp of the aortic valve), the operator can identify this point as a surrogate for the anterior tricuspid leaflet. This point is at the proximity of the nadir of the pigtail in the PA view.
The Inoue Balloon Components: Because the Inoue balloon is the most utilized balloon system for PBMV, we will elaborate on its components and operating mechanisms. We will subsequently address other systems that can be used for PBMV.
The Inoue balloon kit has seven components ( Fig. 14.2 ): (1) the balloon-stretching tube, which is a silver-colored, long, metal hypo-tube that is used to elongate and slenderize the balloon system by passing it through the inner tube; (2) a calibrated syringe used for inflation of the balloon; (3) a 14F dilator used to dilate the subcutaneous tissue at the femoral venous puncture site and the fossa ovalis; (4) a 0.025-inch stainless steel spring guidewire; (5) a steering stylet that is introduced through the inner tube after the balloon is in the LA to help guide it across the MV; (6) the balloon catheter itself, which has a W connector from which arise a vent tube, an inner tube (gold color), and a main stopcock for balloon inflation; and (7) a caliper, which is used to confirm that the graduations on the syringe used to inflate the balloon result in the desired inflation diameters. The main balloon is connected to an inner tube that can be stretched by the hypo-tube. The stretcher (silver color) hypo-tube and the inner tube (gold color) can be locked together. The silver stretcher only moves in or out simultaneous with the gold hypo-tube. If one inadvertently pushes the gold inner tube to stretch the balloon, it may kink the balloon and it may not be stretched again. Therefore stretching of the balloon should always be via the silver hypo-tube, and ideally it should always be over the wire.
