Supravalvular Ring Mitral Stenosis Workup

Updated: Feb 11, 2014
  • Author: Michael D Pettersen, MD; Chief Editor: Howard S Weber, MD, FSCAI  more...
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Workup

Laboratory Studies

No specific laboratory blood tests are required for diagnosis of supravalvar mitral ring.

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Electrocardiography

In cases of isolated supravalvar mitral ring, the electrocardiogram demonstrates left atrial enlargement, right ventricular hypertrophy, and right atrial enlargement in proportion to the degree of obstruction.

Additional defects influence the electrocardiogram accordingly.

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Imaging Studies

Imaging studies are essential to define the anatomy of the ring and mitral valve, to assess the severity of obstruction, and to identify any associated defect before undertaking surgical treatment. Several examples of imaging studies are shown in the videos below.

Parasternal long axis echocardiographic image showing a supra mitral variant of supravalvular mitral stenosis. A discrete membrane is visualized superior to but distinct from the mitral valve. The mitral valve appears otherwise normal.
Parasternal long axis color flow image showing a supra mitral variant of supravalvular mitral stenosis. Turbulence is noted at the level of the supra mitral membrane. In this case, Doppler interrogation revealed only mild obstruction.
Apical 4-chamber echocardiographic image showing an intramitral variant of supravalvular mitral stenosis. A membrane is visualized that is closely adherent to the mitral valve leaflets, restricting leaflet mobility.
Apical 4-chamber color flow echocardiographic image showing an intramitral variant of supravalvular mitral stenosis. Color flow imaging demonstrates severe mitral valve stenosis.
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Chest Radiography

Left atrial enlargement, the most common abnormality on chest radiographs in patients with mitral obstruction, is diagnosed on the basis of straightening of the left cardiac border (mitralization), widening of the tracheal carina, and elevation of the left bronchus. In older children, the enlarged left atrium may be seen as a double opacity near the right cardiac border.

The left atrium tends to enlarge in a posterior direction.

Prominent upper-lobe pulmonary veins, increased interstitial markings, and Kerley lines indicate pulmonary venous hypertension. In severe cases, alveolar edema produces a hazy appearance in the hilar regions of both lung fields.

The pulmonary trunk and its branches become dilated with the rise in pulmonary arterial pressure. The cardiac contour reflects right ventricular hypertrophy.

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Echocardiography

Two-dimensional echocardiography with Doppler imaging is the most important tool for the diagnosis and detailed assessment of patients with supravalvar mitral ring. It depicts the lesion and helps in quantifying the severity of the obstruction. [2]

Detailed scanning of the mitral valve and left atrium should be performed using multiple transthoracic views and by paying particular attention to all components of the mitral valve apparatus. Use parasternal, apical, and subcostal views to visualize the mitral inflow region.

Using this technique allows visualization of the supravalvar mitral ring and definition of its exact position, size, and extent as well as assessment of the relationship of the ring to the mitral valve leaflets.

On occasion, a thin membrane may so closely adhere to the valve leaflets that it is difficult to visualize on 2-dimensional echocardiography. With an adherent membrane, the movements of mitral-valve leaflets may be impaired. The presence of supramitral flow acceleration identified with color Doppler imaging may help identify such a membrane. [3]

The mitral-valve chordae and papillary muscles should be carefully inspected for any associated abnormalities. Associated defects such as subaortic stenosis, ventricular septal defect (VSD), and coarctation of the aorta should be evaluated.

The pulmonary artery, right ventricle, and right atrium may be enlarged in patients with pulmonary arterial hypertension.

Use M-mode echocardiography of the pulmonary valve, which often shows such signs of pulmonary hypertension as an abbreviated A wave, midsystolic closure, and systolic flutter of pulmonary leaflets.

Real-time 3-dimensional echocardiography permits comprehensive assessment of the mitral valve and may compliment 2-dimensional transthoracic echocardiography. [4]

Doppler echocardiography

Doppler interrogation and color-flow mapping reveal the pattern of flow through the mitral valve, diagnose the presence and severity of obstruction, and demonstrate additional areas of abnormal flow in valvar or subvalvar mitral regions. The characteristic finding is turbulent flow with increased velocity across the supravalvar mitral ring into the mitral valve.

The severity of mitral obstruction may be assessed by measuring the mean velocity of diastolic flow through the mitral valve. The mean diastolic velocity and the pressure half-time (time for the peak diastolic velocity to decrease to half its initial value) are well correlated with the severity of obstruction.

The peak velocity of the tricuspid regurgitant jet in the right atrium can be measured to estimate the systolic right ventricular pressure.

Continuous wave Doppler interrogation is shown in the image below.

Continuous wave Doppler interrogation of the mitra Continuous wave Doppler interrogation of the mitral valve in a patient with supravalvular mitral stenosis demonstrates severe stenosis with a mean gradient of 25 mm Hg.

Transesophageal echocardiography

In children, transesophageal echocardiography is generally not necessary to assess a supravalvar mitral ring with obstruction because adequate information can be obtained from transthoracic windows.

In adults, transesophageal study can provide additional clear views to inspect all components of the supravalvar mitral ring and mitral valve.

Thrombi in the left atrium may be detected.

Intraoperative transesophageal echocardiography is useful for patients of all ages to assess adequacy of repair in the operating room.

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Cardiac Catheterization

Cardiac catheterization is not necessary if echocardiography provides all of the necessary anatomic and hemodynamic data in patients with supravalvar mitral ring. However, it can provide additional information about the severity of mitral obstruction, especially in the presence of other associated congenital heart disease (CHD).

Proximal left atrial pressure and pulmonary venous pressure are both elevated. A diastolic pressure difference can be demonstrated between the left atrium and the left ventricle (LV). Because entry into the left atrium may be difficult and because transseptal puncture may be required, the pressure recorded in the pulmonary artery wedge position is usually a reliable indicator of left atrial pressure. Simultaneous recording of pressures in the pulmonary artery wedge position and the LV is shown in the image below.

Simultaneous recording of pressures in the pulmona Simultaneous recording of pressures in the pulmonary artery wedge position (PAW) and the left ventricle (LV) shows a large gradient in diastole across the mitral valve. PAW pressure is markedly elevated.

Pulmonary artery pressure is elevated in chronic mitral obstruction. Associated shunts and other obstructive lesions are also identified and quantified during cardiac catheterization.

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Cardiac Angiography

With the availability of high-quality 2-dimensional and Doppler echocardiography, cardiac angiography has a limited role in the assessment of patients with supravalvar mitral ring. Echocardiography is superior to angiography in defining the anatomic and functional abnormality.

Left atrial angiography in the caudally angulated right anterior oblique view and the 4-chamber view may demonstrate the supravalvar mitral ring. However, a closely adherent ring may be difficult to visualize and differentiate from mitral valvar stenosis. The left atrium and appendage are enlarged, and clearance of contrast material from the left atrium into the LV is delayed.

An LV angiogram provides additional anatomic information about the mitral valve, ventricular septum, LV outflow tract, and aortic arch.

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