Pediatric Mitral Valve Insufficiency Workup
- Author: Monesha Gupta, MD, MBBS, FAAP, FACC, FASE; Chief Editor: Stuart Berger, MD more...
Imaging Studies
Chest radiography
With mild mitral regurgitation (MR), the heart size is normal.
With increasing mitral regurgitation, cardiomegaly may develop, and left atrial enlargement becomes apparent. Left atrial dilation caused by chronic rheumatic heart disease often includes radiographically apparent dilation of the left atrial appendage. Left ventricle (LV) enlargement and pulmonary congestion may also be present.
In cases of acute mitral regurgitation, pulmonary venous vasculature markings and pulmonary edema without signs of left atrial enlargement may be increased.
Left lung atelectasis and hyperinflation may be visible due to compression of left main bronchus by enlarged left atrium.
Transthoracic echocardiography
Echocardiography is the most valuable technique used to evaluate mitral regurgitation. Echocardiography is usually readily available and portable. Knowledge of mitral valve apparatus, including the labeling of the scallops of each of the 2 valve leaflets is essential. An understanding of the anatomy from surgeon's perspective is needed to explain the findings.
The 2-dimensional (2D) echocardiography allows depiction of the size of the chambers and assessment of ventricular systolic function, as well as determination of the morphology of the mitral valve leaflets, the annulus, chordal tissue, and papillary muscles. The parasternal long axis view may provide the best images of mitral valve prolapse, whereas the parasternal short axis view is better for depicting papillary muscle anatomy and leaflet cleft.
M-Mode assessment of cardiac function is extremely important. Cardiac function should be carefully evaluated in mitral regurgitation and one can use different techniques, including 2D, 3-dimensional (3D), tissue Doppler, and strain imaging to assess the LV function. The LV function should be hypernormal, indicating a preserved myocardial function with mitral regurgitation. In the presence of normal or mildly depressed function, one should expect myocardial failure postoperatively. In case of acute rheumatic fever, mitral valve replacement traditionally reverts the function back to normal. However, in other lesions, this is not the usual case. Scalloping of mitral leaflets can occur in mitral valve prolapse and can be seen using M-Mode. In addition, ventricular dimensions should be measured and followed for LV enlargement. LV hypertrophy can also be determined and may be present in hypertrophic cardiomyopathy with mitral regurgitation.
Color-flow Doppler echocardiography demonstrates duration and direction of the regurgitant flow.[6] The degree of regurgitation may be underestimated if the jet hugs the walls of the atrium. Furthermore, the structures are 3D, and multiple views and scans must be performed with optimal transducer frequency to determine the entire regurgitant jet.
Spectral Doppler imaging demonstrates a high-velocity signal across the mitral valve in systole entering retrograde into the left atrium. Mitral regurgitation can be seen and evaluated best in the apical 4-chamber and parasternal-long views. Concomitant mitral stenosis should also be determined. The peak velocity of mitral regurgitation can be used to calculate several other parameters, including LV dP/dT.
Visualizing mitral regurgitation is not as difficult as classifying the severity. In adults, many echocardiographic methods are used with varying results. The grading of mitral regurgitation in the pediatric population as mild, moderate, and severe is based on the size and extent of the color-flow Doppler signal (jet area) into the left atrium (left atrial area).
Other factors to consider include left atrium and ventricular size and function. In mild mitral regurgitation, the signal is located in the proximal third of the left atrium near the mitral valve. The left atrium is usually not enlarged, and the ventricular function is normal. In moderate mitral regurgitation, the signal is mid cavity, with left atrial dilation and increased ventricular function. With severe mitral regurgitation, the signal reaches the posterior third of the left atrium and the pulmonary veins, and the left atrium and ventricle are usually enlarged, with increased ventricular function. Other techniques useful in quantification include measurement of vena contracta, proximal isovelocity surface area (PISA), pulmonary vein flow reversal, and regurgitant fraction.
Transesophageal echocardiography (TEE)
This may be required if further detailed anatomic information is needed. TEE views correlate better with angiographic grading than transthoracic views. In addition, intraoperative TEE is absolutely essential in guiding mitral valve surgery.
3D echocardiography
This provides a an excellent anatomical evaluation of mitral valve and help with decisions regarding therapy and possible surgical intervention
Cardiac MRI
Cardiac MRI is a newer modality for imaging the heart. Cardiac MRI provides 3D imaging of the heart and great vessels and does not depend on acoustic windows, as echocardiography does.
Cardiac MRI provides more accurate evaluation of both left and right ventricular size and function.
The degree of mitral regurgitation determined by cardiac MRI has not been adequately evaluated. However, velocity flow imaging may potentially provide additional information.
Other Tests
Electrocardiogram
The 12-lead ECG is likely to show normal results in children with mild mitral regurgitation.
In more chronic mitral regurgitation, ECG findings demonstrate left atrial and LV enlargement.
When pulmonary hypertension is present, ECG may also demonstrate right ventricular hypertrophy.
Rhythm changes, such as atrial fibrillation, are often observed in adults but are rare in children.
Procedures
Evaluation of mitral regurgitation in children usually does not require cardiac catheterization. Some pediatric patients undergo catheterization to evaluate other cardiac defects that may be present.
Mitral regurgitation is best evaluated using angiography obtained in the right anterior oblique view. Retrograde flow of injected dye demonstrates the degree of mitral regurgitation, which is quantitatively graded (grades I-IV) depending on the level of left atrial opacification (see below). LV injections obtained via the retrograde approach are preferred to an anterograde approach to prevent the catheter from holding the mitral valve open and creating artifactual mitral regurgitation.
To quantitate mitral regurgitation, a combination of angiography and cardiac output measurements must be used. Either thermodilution or the Fick principle helps measure forward cardiac output, while angiography allows determination of total LV output. Keep in mind that tricuspid regurgitation can invalidate the thermodilution method.[7]
Subtracting the forward output from total LV output yields the regurgitant fraction. A regurgitant fraction of 0.5 or greater is generally considered clinically significant.
The LV ejection fraction may be increased initially; however, as the LV decompensates, the ejection fraction decreases to normal or subnormal values, signifying LV failure. As LV failure develops, LV end-diastolic pressure increases, resulting in an increase in left atrial and pulmonary venous pressure. Increased pulmonary venous pressure is manifested as an increase in pulmonary capillary wedge pressure. At catheterization, the wedge pressure a wave amplitude is increased along with a rapid rise of the v wave. The latter occurs when LV compliance decreases.
A study evaluating mitral regurgitation compared cardiac catheterization to echocardiography (transesophageal, transthoracic) and found no advantage to catheterization in clinical decision making. Cardiac catheterization should be used when noninvasive data are discordant, limited, or differ from the clinical status of the patient. Ventriculography may add new information if more complex congenital cardiac problems are present.
Estimation of mitral regurgitation using angiography is as follows:
- Regurgitation grade of 1+: Trace amounts of contrast are seen in the left atrium, but the amount is insufficient to outline the left atrium.
- Regurgitation grade of 2+: The contrast opacifies the entire left atrium but less than that of the LV. The contrast clears quickly (within 2-3 beats).
- Regurgitation grade of 3+: The contrast opacifies the left atrium and LV equally.
- Regurgitation grade of 4+: The contrast opacifies the left atrium more than the LV and progresses to the pulmonary veins.
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