Supracristal Ventricular Septal Defect Workup

Updated: Aug 31, 2015
  • Author: Ira H Gessner, MD; Chief Editor: Howard S Weber, MD, FSCAI  more...
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Workup

Approach Considerations

The recurrence risk for the offspring of mothers with supracristal ventricular septal defect (VSD) is estimated at 4-5%; the recurrence risk for the offspring of fathers with the condition is approximately 2-3%. Detailed prenatal fetal echocardiography (ECHO) may be indicated. Supracristal VSD cannot be identified from a routine prenatal 4-chamber view.

Electrocardiographic findings may be normal in infancy, because the defect may not be large enough to cause a significant left-to-right shunt and ventricular hypertrophy. With larger defects and beyond the first few months of life, the electrocardiogram (ECG) may show left atrial enlargement, as well as both left and right ventricular hypertrophy.

With progressive aortic valve insufficiency in the older child or adult, electrocardiography usually reveals evidence of left heart enlargement from volume overload (ie, left atrial enlargement and left ventricular hypertrophy [tall R waves in the left precordium with or without ST-T changes]).

A diagnostic pitfall associated with supracristal VSD is the failure to diagnose the condition adequately and, therefore, failure to recognize the potential for aortic valve involvement.

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Imaging Studies

Chest radiography

Chest radiography is normal in infancy if the left-to-right shunt is small. If a large shunt is present, eventual cardiomegaly (left heart enlargement, both the left atrium and the left ventricle) with increased pulmonary vascularity from increased pulmonary blood flow will occur.

Radiography in the older child or adult with progressive aortic insufficiency may reveal left heart enlargement (particularly left ventricular enlargement) and prominence of the ascending aorta. Shunt volume is generally smaller, thus pulmonary arterial vascularity is generally normal. Advanced left heart failure produces pulmonary edema.

Two-dimensional transthoracic echocardiography

Echocardiography (ECHO) provides the most efficient means to diagnose supracristal ventricular septal defect (VSD) accurately (see the image below) and the most effective means to monitor progressive aortic insufficiency. [7] An accurate diagnosis can generally be made in infants and children with standard transthoracic ECHO examination findings. In the older child and adult, transthoracic ECHO findings may be inconclusive; in such cases, transesophageal ECHO may be extremely helpful.

Parasternal long-axis echocardiogram view showing Parasternal long-axis echocardiogram view showing supracristal ventricular septal defect (arrow) with buckling and prolapse (***) of the right coronary cusp of the aortic valve.

Two-dimensional (2D) imaging reveals the supracristal VSD in the parasternal short-axis view or the modified apical 3-chamber view (ie, left atrium, left ventricle, aortic root, and pulmonary root, equivalent to the transesophageal view with transducer at 90°). The defect can also be observed well in the subcostal parasagittal view (ie, visualizing the pulmonary and aortic outflow tracts).

A supracristal VSD cannot be imaged from the apical 4-chamber view because of the orientation of the outlet septum. Distortion of the right aortic leaflet may be the only clue to the presence of a significant supracristal VSD, because the aortic leaflet may obstruct the defect.

Color Doppler echocardiography

Color Doppler examination using the parasternal short-axis view reveals left-to-right shunting immediately below the pulmonary valve and directed into the pulmonary outflow tract. If the flow is turbulent, it may be confused with pulmonary stenosis; however, careful, slow-motion review of color flow results (with electrocardiographic timing) may reveal the early appearance of turbulent flow below the pulmonary valve. (See the images below.)

Parasternal short-axis echocardiogram view with co Parasternal short-axis echocardiogram view with color Doppler showing proximity of ventricular septal defect jet to the pulmonic valves. The patient is an infant with neither aortic valve prolapse nor aortic insufficiency.
Subcostal "right ventricular inflow/outflow" view Subcostal "right ventricular inflow/outflow" view showing the close relationship between the aortic and pulmonic valves in the presence of supracristal ventricular septal defect. Turbulent shunt flow is shown directed into the main pulmonary artery. The patient is an infant with neither aortic valve prolapse nor insufficiency.
Transesophageal horizontal view of aortic root and Transesophageal horizontal view of aortic root and right ventricle, showing sinus of Valsalva aneurysm leaking through a supracristal ventricular septal defect (VSD)(>

The best way to detect aortic valve insufficiency is by color Doppler in the parasternal long-axis and apical 5-chamber views. The modified apical 3-chamber view can also be used to detect left-to-right shunting and aortic valve insufficiency. Numerous methods are available to provide semiquantitative information on the severity of aortic valve insufficiency (eg, color jet–to–outflow width ratio, pressure half time).

The best way to identify progression of aortic valve insufficiency by echocardiography is by serial comparison of left ventricular systolic and diastolic dimensions and ventricular function (shortening fraction or ejection fraction). Progressive left atrial enlargement can be a sign of ventricular diastolic dysfunction.

Three-dimensional echocardiography

Three-dimensional (3D) echocardiographic imaging of VSDs closely correlates with surgical findings, although specific findings with supracristal defects have not been reported. [15] Three-dimensional echocardiography may prove useful in differentiating supracristal VSD from unruptured sinus of Valsalva aneurysm. [16]

Angiography

Although rarely performed in the modern era, a supracristal VSD is best delineated in the right anterior oblique projection or in the cranially tilted left anterior oblique projection. Small supracristal defects may not be identified in the standard long-axial oblique projection because of rotation of the septum. [17]

Distortion of an aortic valve cusp may be the only clue to a supracristal VSD of significant size, even though the apparent volume of the left-to-right shunt may be small.

Magnetic resonance imaging

Magnetic resonance imaging (MRI) may be used with appropriate projections and alignment to show the pulmonary outflow tract. [18] Serial MRI studies can be helpful in that they do not expose the patient to ionizing radiation. Blood flow studies can be used to provide quantitative information on regurgitant volume in the assessment of aortic insufficiency.

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Catheterization

Although rarely performed in the modern era, cardiac catheterization can quantify shunt volume and pulmonary arterial resistance. [17] Step-up in oxygen saturation may be detected in the distal branch pulmonary arteries rather than in the right ventricular cavity because of streaming of the shunted blood into the pulmonic trunk.

If aortic valve prolapse is significant, left-to-right shunting by oximetry may be fairly unremarkable, because the ventricular septal defect (VSD) in such cases is partially obstructed.

Rare catheterization complications include hemorrhage, pain, nausea and vomiting, arterial or venous obstruction from thrombosis or spasm, tachyarrhythmias, and bradyarrhythmias.

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