Introduction

Mitral stenosis is quite uncommon in Western countries, yet it still is a frequent problem worldwide, particularly in developing countries. The low incidence in the United States, in particular, is largely because rheumatic fever resulting in rheumatic heart disease has been largely eradicated; nevertheless, occasional outbreaks do occur. The occurrence of rheumatic fever in Utah in the mid-1980s and early 1990s is notable.^1,2 That particular outbreak had two unusual aspects. First, as opposed to previous history of outbreaks typically appearing in lower socioeconomic groups, this outbreak seemed to affect the middle class. Second, there was a distressingly low incidence of a symptomatic streptococcal infection in the group developing rheumatic fever.

Rheumatic heart disease preferentially affects the mitral valve, with the order of involvement being (1) mitral, (2) aortic, (3) tricuspid, and (4) pulmonic. The mitral valve is involved in virtually all cases, whereas the aortic valve is affected in 20% to 25% of cases. Pulmonary valve involvement in rheumatic heart disease is exceedingly rare. Even though the tricuspid valve frequently is involved, tricuspid valvular disease often is clinically silent.³ From a functional standpoint, however, approximately 25% of patients with rheumatic heart disease have pure mitral stenosis and 40% have a combination of mitral stenosis and mitral regurgitation.⁴ Two thirds of all patients with rheumatic mitral stenosis are female⁵; however, in my experience, it is almost 90%. In the United States and other Western countries, mitral stenosis develops over a period of decades, with a mean age of onset of 45 years. However, for reasons that are not entirely understood, individuals in developing countries such as India, in Africa, and in Alaskan Inuits, the time from rheumatic fever to onset of clinically significant mitral stenosis can be as little as 10 years. The factors for this rapid onset, however, appear to be more socioeconomic than necessarily related to specific medical care.^6,7

Cardiac Imaging and Real-Time Three-Dimensional Echocardiography

From the standpoint of cardiac imaging, echocardiography is clearly the mainstay for evaluation of mitral stenosis. The extent of mitral valvular deformity traditionally has been evaluated by two-dimensional (2D) echocardiography and graded based on a score of 0 to 4 for each of four factors: (1) valvular thickening, (2) valvular mobility, (3) degree of leaflet calcification, and (4) extent of subvalvular thickening and calcification.⁸ The Wilkins scoring system does have several drawbacks, however. In particular, some patients with a high Wilkins score still respond well to percutaneous mitral valvuloplasty (PMV). Three-dimensional (3D) echocardiography provides incremental information regarding the status of rheumatic involvement of the mitral valve, particularly regarding the fusion of the commissures. Determination of the status of commissural fusion, particularly the symmetry and length of commissural fusion, is critical information to predict the success of treatment of mitral stenosis with PMV.⁹ That is, mitral valvuloplasty is most effective when extensive symmetric commissural fusion is present and when such fusion is alleviated at the time of the procedure. 3D echocardiography (3DE) has a particular strength for visualizing the mitral commissures and commissural fusion because of the added dimension of elevation (Figures 6-1 to 6-5; Videos 6-1 to 6-9). The elevation dimension allows clearer assessment of the degree and length of commissural fusion as well as the presence of structures that could inhibit the process, such as rheumatic nodules and subvalvular (typically chordal) thickening. Although in mitral stenosis symmetric commissural fusion is the optimal morphology for PMV success, evidence indicates that if the commissural fusion is accompanied by significant calcification, results are not as satisfactory, which is a predictable finding.^10–12

Figure 6-1 A and B, Two-dimensional (2D) and three-dimensional (3D) parasternal long-axis views of the mitral valve in a patient with mitral stenosis. Both show the characteristic “doming” or “hockey stick” appearance of the anterior mitral valve leaflet (arrow). The 3D details the subvalvular apparatus not appreciated on the 2D image (see Videos 6-1 and 6-2).

Figure 6-2 Two-dimensional (A) and three-dimensional (3D) (B) short-axis views of mitral stenosis. Both images show bilateral commissural fusion, with the lateral commissure more fused than the medial commissure. The 3D image allows superior visualization of the thickening of the mitral leaflets, particularly the commissures.

Figure 6-3 A, QLAB (Phillips Healthcare, Andover, MA) evaluation of the mitral valve area. This is the first step in using a transthoracic three-dimensional (3D) full-volume acquisition of the mitral valve to quantify the degree of mitral stenosis by measuring the mitral valve area. This is the starting point, with the full volume acquired and initial autocropping performed automatically by the software. The autocropping shows the mitral valve in the parasternal long-axis view. Here, the parasternal long-axis view has been acquired in full-volume mode and has been stored to an Xcelera (Phillips Healthcare) page. From here, the operator activates the QLAB icon (pyramid) to move into the cropping function and the 3DQ quantification package. B, Quantification step 2. The operator is now within the QLAB software. This particular view shows the full volume within QLAB, with the crop box turned off. From here, the operator enters the 3DQ quantification package. C, Quantification step 3 is the multiplanar reconstruction mode of QLAB. Here, the mitral valve is shown in parasternal long axis (upper left), parasternal short axis (upper right), a composite (lower left), and the entire volume of the heart (lower right). Placing the red plane cursor so the mitral valve is cut in cross-section (upper right) at the very tip of the mitral valve leaflets allows the mitral valve area to be measured at the most optimal angle. D, Quantification step 4. Here, the red plane is positioned at the tips of the mitral leaflets (upper left) so that the operator can be certain that the orifice is in the true en face view in the upper right plane. The lower right image is a view of the entire volume that can be manipulated to see how the red plane is being moved relative to the entire mitral valve apparatus. E, Quantification final step. The mitral valve area is traced, resulting in a mitral valve area of 1.86 cm in this case.

Figure 6-4 A, Two-dimensional (2D) transthoracic image of mitral stenosis. Note the marked thickening of the anterior mitral leaflet. B, The same patient as viewed by parasternal three-dimensional (3D) transthoracic echocardiography from the left ventricular side of the valve. Note the rheumatic nodules that are noted by 3D echocardiography that were not appreciated in 2D. Also note the details of commissural fusion shown in this swivel display and the asymmetric fusion of the commissures. The same patient viewed from the left atrial side (C) and ventricular side (D) with a slight tilt toward the anterior leaflet so that the extensive rheumatic disease, accentuated by the nodules (arrow), is seen (see Videos 6-6 to 6-9).

Figure 6-5 A patient 3 years after percutaneous mitral valvuloplasty. The splitting of the commissures is seen on both sides (arrows). In this case, the lateral commissure is more open; the three-dimensional view shows this in more detail (see Video 6-5).

Mitral Valve Area Determination

The severity of mitral stenosis can be determined by several echocardiographic measures: peak and mean pressure gradient by Doppler and mitral valve area by (1) Doppler pressure half-time, (2) Doppler-based continuity equation, and (3) direct planimetry of the mitral valve area by 2DE or 3DE. Direct planimetry of the mitral valve orifice by real-time 3DE (RT3DE) has now emerged as the gold standard, thanks to several investigations and publications.^13–20 RT3DE quantification of the mitral valve orifice begins with a full-volume RT3D transthoracic echocardiography (RT3DTTE) acquisition obtained in the parasternal long-axis orientation. From this full-volume dataset, the mitral valve can be cropped to obtain an en face view of the mitral orifice. A precise en face image of the stenotic mitral valve is crucial for accurate measurement of the mitral valve area. In addition to being lined up with the tips of the mitral valve leaflets using the orthogonal plane, the en face view can be panned above and below the valve and viewed from the atrial and ventricular sides. The cropping function markedly enhances the confidence in the accuracy of valve area quantification because multiple plane cropping ensures that the orifice area is traced in a plane that is (1) at the tips of the mitral valve and (2) perpendicular to the inflow through the valve. The progression shown in Figure 6-3 demonstrates the sequential plan for procurement of an accurate mitral valve area using planimetry of an RT3DE dataset. Note that such a dataset could be obtained using either RT3DTTE or RT3D transesophageal echocardiography (RT3DTEE).

Treatment: Percutaneous Mitral Valvuloplasty

PMV is the current state-of-the-art treatment when valve morphology is favorable and mitral regurgitation is no worse than mild. Previously, Applebaum²¹ had suggested the use of 3DE during PMV, although this was prior to the development of RT3DE. RT3DTTE and RT3DTEE have drastically changed the approach to PMV at some centers. PMV is a unique procedure that, along with a few others, has advanced the term “interventional echocardiography” to a new level. Echocardiography guidance of PMV can be performed with either RT3DTTE or RT3DTEE. RT3DTEE, however, provides benefits to the interventional cardiologist from the transseptal puncture, to positioning the Inoue balloon, to avoiding the left atrial appendage, and finally to assessing the splitting of the commissures on both the atrial and ventricular sides of the valve. The transseptal puncture is theoretically safer using RT3DTEE guidance because of the use of biplane or “X-plane” to view two orthogonal 2D views of the septum simultaneously. Classically, the two orthogonal planes that are used are (a) the bicaval view at 110 degrees and (b) the four-chamber view at the aortic valve area, roughly 30 degrees (Figure 6-6; Video 6-12). The bicaval view guides the interventionalists to the superior portion versus the inferior portion of the septum, and the four-chamber view is useful to avoid damaging the aortic valve and root during the transseptal puncture (see Figure 6-6; Videos 6-10 to 6-12). Visualization of the fossa ovalis is also safer by RT3DTEE by both X-plane orthogonal views as well as 3D zoom mode (to visualize the entire fossa ovalis en face in real time and the catheter relationship to the superior vena cava [SVC] and the inferior vena cava [IVC] as it traverses the interatrial septum) (see Figure 6-6; Video 6-13). RT3DTEE has the advantage of providing particularly vivid images of the interatrial septum, the left atrium, the left atrial appendage, and the mitral orifice. All four of these structures are important anatomic landmarks used during the procedure, so optimal visualization also is crucial to the success or failure of the procedure.^9,22,23

Figure 6-6 A, Transesophageal echocardiography (TEE) performed during percutaneous mitral valvuloplasty using biplane (X-plane) technology. Although the images are two-dimensional (2D), there are two simultaneously acquired 2D images. This is made possible by the three-dimensional (3D) TEE probe. That is, the matrix array transducer allows simultaneous display of two orthogonal planes. In this case, two orthogonal planes are displayed during the transseptal needle puncture portion of the procedure. The arrows point out “tenting” of the interatrial septum. The two orthogonal planes allow two perspectives on the septum. In particular, on the right image, the operator can tell how superior or inferior they are on the septum, given the relationship to the superior vena cava (SVC), and also, most importantly, avoid the aortic root. B, SVC and fossa ovalis shown by real-time 3DTEE. In the transseptal puncture procedure, the Brockenbrough needle is positioned to puncture the center of the fossa ovalis and then enter the left atrium (see Videos 6-12 and 6-13). IVC, inferior vena cava.

Although severe mitral regurgitation can be a complication of PMV, the development of some minor mitral regurgitation actually can be viewed as a sign of success. That is because the mechanism of mitral regurgitation is typically related to the splitting of the mitral commissures during the procedure.²⁴ Further examples of RT3DTEE and RT3DTTE use during the course of PMV are shown in Figures 6-7 to 6-15 (Videos 6-14 to 6-24).

Figure 6-7 Three-dimensional transesophageal echocardiography of the mitral valve in two different patients with mitral stenosis are shown viewing the mitral orifice (arrow) from the left atrial side. The aortic valve is shown for orientation. This image display is shown in the surgeon’s view. Mitral stenosis (A) is more severe with fusion of both the lateral (arrow) and medial commissures; in this case, the medial commissure is more fused. Note the more restricted orifice compared with that in B with a larger mitral orifice grossly and a much smoother orifice that is relatively early in the disease process (see Videos 6-14 and 6-15).

Figure 6-8 Real-time three-dimensional transesophageal echocardiography of a patient with mitral stenosis, showing an oval-shaped, restricted orifice with commissural fusion bilaterally. The orifice is viewed from the ventricular side. The commissural fusion is more severe with the medial commissure (arrow). The left ventricular outflow tract (LVOT) is shown for orientation (see Video 6-16).

Figure 6-9 A three-dimensional transesophageal echocardiography image showing the Inoue balloon initially expanded across the mitral valve and then deflated (see Video 6-17).

Figure 6-10 Three-dimensional transesophageal echocardiography image of a patient with mitral stenosis acquired during percutaneous mitral valvuloplasty. The site of the transseptal puncture is clearly seen (arrow). The balloon is being inflated across the mitral orifice (see Video 6-18).

Figure 6-11 Unsuccessful attempt at crossing the mitral orifice by the balloon valvuloplasty catheter. In this three-dimensional transesophageal echocardiography view of a stenotic mitral valve, the interventional cardiologist is attempting to cross the orifice with the Inoue balloon. This particular attempt illustrates the importance of ruling out the left atrial appendage prior to percutaneous mitral valvuloplasty; in this case, the catheter lodged in the left atrial appendage (see Video 6-19).

Figure 6-12 An example of successful crossing of the mitral orifice using three-dimensional transesophageal echocardiography guidance in percutaneous mitral valvuloplasty (see Video 6-20).

Figure 6-13 Transesophageal echocardiography (TEE) view of the Inoue balloon expanded across the mitral orifice. Once again, the matrix TEE probe is used to show two orthogonal two-dimensional views simultaneously; in this case, the Inoue balloon expanded across the mitral orifice (see Video 6-21).

Figure 6-14 A successful percutaneous mitral valvuloplasty after the procedure. The commissures have been successfully split. A, The splitting by two-dimensional (2D) and three-dimensional (3D) echocardiography. The considerable commissural splitting is shown in the 3D view (B) to have considerable depth in a way that cannot be appreciated by the 2D image (arrows) (see Videos 6-22 and 6-23).

Figure 6-15 Evaluation of mitral regurgitation after mitral valvuloplasty. A two-dimensional color view of the mitral orifice and mitral regurgitation. A very small jet of mitral regurgitation is present along the medial commissure. This jet has developed as a result of the percutaneous mitral valvuloplasty and the commissural splitting. There clearly is a tradeoff between going too far with the valvuloplasty and causing significant regurgitation versus not going far enough and not relieving the mitral stenosis (see Video 6-24).

Cases

Case 2

A 48-year-old woman presented to the cardiology clinic reporting the presence of a heart murmur but also having symptoms of palpitations and dyspnea. The symptoms necessitated obtaining an echocardiogram that showed moderate mitral stenosis. The patient was gravida 3 para 3 and had not had any significant problems during her pregnancy with dyspnea, palpitations, or known arrhythmia. However, her most recent pregnancy was 7 years ago. The mitral valve area was 1.2 cm² by 3D planimetry and 1.3 cm² by Doppler pressure half-time. Pulmonary artery pressure was 45 mm Hg but increased to 60 mm Hg with bicycle exercise. Hence, the patient was deemed a candidate for PMV. A few challenges with the procedure were clearly aided by RT3DTEE. The first was a potential thrombus in the left atrial appendage, identified using standard 2DTEE (Figure 6-16, A). However, with the use of the biplane or X-plane feature, when viewing this structure in the orthogonal plane, the structure was clearly a trabeculation of the left atrial appendage wall rather than a thrombus (see Figure 6-16, B). This also was demonstrated using the RT3DTEE mode of 3D zoom. The second was the positioning of the catheter. It was difficult to cross the valve, and use of the RT3DTEE to steer the Ionue balloon dramatically hastened the procedure (see Figures 6-10 and 6-11; see also Videos 6-17 to 6-19). After successfully navigating these potential hurdles, the procedure had a successful result, increasing the mitral valve area to 1.7 cm² and decreasing the transmitral gradient to 5 mm Hg.

Figure 6-16 Possible thrombus in the left atrial appendage. The biplane, or X-plane, view shows that the possible thrombus in A is clearly a trabeculation seen in the orthogonal plane in B.