Supracristal Ventricular Septal Defect Workup

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, the electrocardiogram (ECG) may show left atrial enlargement, as well as both left and right ventricular hypertrophy.

With progressive aortic 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.

Chest radiography

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

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.

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 with turbulent flow directed into the pulmonary outflow tract and often across the pulmonary valve. This turbulence 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.)

The best way to detect aortic 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 insufficiency. Numerous methods are available to provide semiquantitative information on the severity of aortic insufficiency (eg, color jet–to–outflow width ratio, pressure half time).

The best way to identify progression of aortic 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

Supracristal VSD is best defined 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.

Cardiac catheterization can quantify shunt volume and pulmonary arterial resistance.^[17] Step-up in oxygen saturation may be detected in the pulmonary artery 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.

Postcatheterization concerns include hemorrhage, vascular disruption after balloon dilation, pain, nausea and vomiting, and arterial or venous obstruction from thrombosis or spasm. Possible complications also include blood vessel rupture, tachyarrhythmias, bradyarrhythmias, and vascular occlusion.