Approach Considerations
In patients with suspected double orifice mitral valve, the anatomy of the valve and also the hemodynamic abnormalities should be investigated by imaging studies and cardiac catheterization, as indicated.
No specific laboratory blood tests are required for diagnosis.
Imaging Studies
Chest radiography
A left atrial enlargement is suspected (the most common abnormality in double orifice mitral valve [DOMV]) if straightening of the left upper cardiac border (mitralization) and widening of the tracheal carinal angle secondary to the elevation of the left bronchus are present. In older children, the enlarged left atrium may be observed as a double opacity near the right atrial border that tends to enlarge in a posterior direction. Mitral incompetence, if severe, causes left ventricular (LV) enlargement.
Barium-swallow study in lateral projection shows a rounded indentation from the enlarged left atrium on the anterior wall of the esophagus.
Prominent upper-lobe 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.
Echocardiography
Two-dimensional echocardiography (2DE) with Doppler interrogation is the most important tool for the diagnosis and detailed assessment of double orifice mitral valve. [25] Transthoracic echocardiography (TTE), whether 2D or 3D, is the mainstay for evaluation of this condition. [2, 25]
Systematic examination of the mitral valve by using multiple views for imaging and Doppler interrogation is important. Particular attention should be given to evaluate all components of the mitral valve apparatus. Refer to the image below.
Double Orifice Mitral Valve. Two-dimensional echocardiogram (apical view) in a patient with duplicate mitral valve. Two mitral valves can be seen opening into the left ventricle. Each valve has a separate annulus, and a separate set of mitral valve leaflets and subvalvar apparatus.
The two orifices in double orifice mitral valve are best demonstrated in a cross-sectional short-axis view of the left ventricle(LV) by scanning the ventricle from the apex to the base. Apical and subcostal four-chamber views are also useful to visualize the subvalvular apparatus. [2] See the images depicted below.
Double Orifice Mitral Valve. Two-dimensional echocardiogram (parasternal short-axis view) shows a double-orifice mitral valve, the orifice divided by a bridge of tissue.
Double Orifice Mitral Valve. Two-dimensional echocardiogram (parasternal short-axis view) in a patient with duplicate mitral valve. This diastolic frame shows two typical mitral valve orifices opening into the left ventricle. The two orifices are placed apart, unlike the more common type of double orifice mitral valve (see image above) where the orifice is divided by a bridge of tissue.
The relative positions of the two openings should be identified and the area should be measured. The nature and size of the bridging tissue and leaflets, as well as the movements of the valve cusps should be studied. Any associated congenital heart defect may also be identified and quantified.
Measuring the enlargement of the left atrium, LV, right ventricle (RV), and pulmonary artery on 2DE is important.
M-mode echocardiography of the pulmonary valve often shows signs of pulmonary hypertension such as an abbreviated a wave, midsystolic closure, and systolic flutter of the pulmonary leaflets.
Real-time 3DE allows comprehensive noninvasive assessment of the anatomical details in patients with double orifice mitral valve and provides incremental information to that obtained by 2DE as depicted in the images below. [26]
Double Orifice Mitral Valve. Two-dimensional echocardiogram (parasternal short-axis view) shows a double-orifice mitral valve, the orifice divided by a bridge of tissue.
Doppler echocardiography
2DE with Doppler study and color flow mapping (as shown below) are useful to show the pattern of flow through the mitral valve and to identify the exact site of regurgitation or stenosis. [2]
Double Orifice Mitral Valve. Two-dimensional echocardiogram of a double-orifice mitral valve (apical view) with color flow mapping, which shows diastolic flow through two separate orifices.
The severity of mitral regurgitation should be assessed in a semiquantitative manner by evaluation of the area of the regurgitant jet in the left atrium as well as jet width at its origin.
The severity of mitral obstruction can be quantified 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 mitral stenosis.
Estimating the systolic pressure in the pulmonary artery by measuring the peak velocity of the tricuspid regurgitant jet in the right atrium (only in the case of no right ventricular outflow obstruction) is crucial. The real-time 3DE can allow detailed and comprehensive assessment incremental to that obtained by 2DE. [3, 27]
Transesophageal echocardiography
In children, transesophageal echocardiography is generally not necessary to assess double orifice mitral valve because adequate information can be obtained by using the transthoracic and subcostal windows.
In adults, transesophageal study may enable clear visualization of all valve components. A deep transgastric view with Doppler interrogation is often useful to show the 2 orifices and the precise origin of the regurgitant jet.
Thrombi in the left atrium can be detected.
In patients of all ages, intraoperative transesophageal echocardiography is extremely useful to assess the adequacy of mitral valve repair in the operating room.
Other Tests
Electrocardiography
The EKG findings may be normal, if no mitral stenosis, mitral regurgitation, or other associated cardiac pathology is found.
The mean frontal-plane QRS axis may be normal or shifted to the right.
Left atrial enlargement occurs in most patients with double orifice mitral valve and is diagnosed on the basis of wide bifid P waves (P mitrale pattern) in the limb leads and/or an increased P terminal force in lead V1.
Mitral incompetence is associated with LV hypertrophy. RV hypertrophy is common in stenotic double orifice mitral valve. Tall, peaked P waves in the inferior leads indicate right atrial hypertrophy because of pulmonary hypertension and tricuspid incompetence.
A sinus rhythm is commonly present. On occasion, atrial flutter or atrial fibrillation may develop in patients with double orifice mitral valve and chronic left atrial dilatation.
Associated congenital heart defects may modify electrocardiographic findings.
Procedures
Cardiac catheterization
Cardiac catheterization is often used to quantify the hemodynamic effects of abnormal mitral valve function.
Double orifice mitral valve with obstruction is characterized by elevation of left atrial pressure. Pressure tracings obtained from the pulmonary-artery wedge position reflect left atrial pressure and avoid the need to enter the left atrium by puncturing the interatrial septum. Simultaneous pressure recording from the pulmonary-artery wedge position and the LV shows that pulmonary-artery wedge pressure is substantially higher than LV pressure throughout diastole.
In patients with mitral regurgitation, the left atrial and pulmonary-artery wedge pressures are elevated, but no gradient can be demonstrated across the mitral valve at the end of diastole; LV diastolic pressure is often increased.
Cardiac output and pulmonary vascular resistance may be calculated. Associated shunts and other lesions, if any, may also be identified and quantified during cardiac catheterization.
Cardiac cineangiography
With the availability of high-quality echocardiography, cardiac angiography has a limited role in the assessment of double orifice mitral valve. Echocardiography is superior to angiography in defining anatomic and functional abnormalities of the valve.
LV angiography may be performed to confirm the severity of mitral regurgitation and to assess LV function.
Cardiac angiography is also helpful to assess other associated defects.
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Double Orifice Mitral Valve. Two-dimensional echocardiogram (apical view) in a patient with duplicate mitral valve. Two mitral valves can be seen opening into the left ventricle. Each valve has a separate annulus, and a separate set of mitral valve leaflets and subvalvar apparatus.
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Double Orifice Mitral Valve. Two-dimensional echocardiogram (parasternal short-axis view) shows a double-orifice mitral valve, the orifice divided by a bridge of tissue.
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Double Orifice Mitral Valve. Two-dimensional echocardiogram of a double-orifice mitral valve (apical view) with color flow mapping, which shows diastolic flow through two separate orifices.
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Double Orifice Mitral Valve. Two-dimensional echocardiogram (parasternal short-axis view) in a patient with duplicate mitral valve. This diastolic frame shows two typical mitral valve orifices opening into the left ventricle. The two orifices are placed apart, unlike the more common type of double orifice mitral valve (see image above) where the orifice is divided by a bridge of tissue.
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Double Orifice Mitral Valve. Real-time two-dimensional echocardiogram (apical view) in a patient with duplicate mitral valve. Two mitral valves can be seen opening into the left ventricle. Each valve has a separate annulus, and a separate set of mitral valve leaflets and subvalvar apparatus.
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Double Orifice Mitral Valve. Real-time two-dimensional echocardiogram (subcostal short-axis view) in a patient with duplicate mitral valve showing two typical mitral valves opening into the left ventricle. The two orifices are placed apart, unlike the more common type of double orifice mitral valve (see the previous image) where the orifice is divided by a bridge of tissue.
