Congenital Cardiovascular Diseases: Left-to-Right Shunts

Imaging Manifestations: The chronic increase in pulmonary flow causes the radiographic changes associated with the pulmonary hypertension of L-to-R shunts: increased size of the pulmonary trunk and central pulmonary arteries, diminished peripheral vessel caliber, and right ventricular chamber dilation (figure 1). It is important to note, however, that normal chamber size may represent increasing pulmonary pressures with progression towards Eisenmenger's physiology.

Figure 1. Chest Radiography in Pulmonary Hypertension in a Patient with Congenital Cardiovascular Disease (Atrial Septal Defect)

Note the extreme enlargement of the central pulmonary arteries.

For the assessment of patients with pulmonary hypertention, MR provides anatomic information equivalent to CT, but also offers the advantage of a noniodinated contrast medium (gadolinium), as well as the ability to provide physiologic information, such as shunt quantification.

vsd

 

 

Figure 2A. Pulmonary Hypertension due to Congenital Cardiovascular Shunt

Axial T1-weighted MR image through the heart shows an abnormal connection between the right ventricular outflow tract and the base of the aorta, consistent with a supracristal ventricular septal defect.

Find the defect.

Click here to see a labeled image.

 

 

 

jet

Figure 2B. Axial Cine MR Image

In the same patient shown in 2A, a linear, low-signal focus within the right ventricular cavity represents a jet of blood coursing through the supracristal ventricular septal defect.

Find the jet through the defect.

Click here to see a labeled image.

CT may display calcification, as already noted, and thrombus, secondary to high pressures and turbulent flow. CT, particularly helical CT pulmonary angiography, may also directly show abnormal vascular connections, such as ventricular septal defects (figure 3) and atrial septal defects (figure 4).

vsd

Figure 3. Axial Helical CT

Helical CT pulmonary angiography image shows a ventricular septal defect.

RVH = Right ventricular hypertrophy

RA = Right atrium

RV = Right ventricle

IV septum = Interventricular septum

LA = Left atrium

LV = Left ventricle

Outline the ventricular septal defect.

asd

Figure 4. Helical CT Pulmonary Angiography Image in a Patient with Pulmonary Hypertension Due to an Atrial Septal Defect

Thoracic CT obtained for suspected pulmonary embolism shows the defect in the atrial septum.

RA = Right atrium

RV = Right ventricle

IA septum = Interatrial septum

LA = Left atrium

LV = Left ventricle

Outline the defect.

 

 

 

In the case of a patent ductus arteriosus, CT or MR imaging may reveal dilation of the patent ductus, possibly with aneurysm formation or mural calcification.

Figure 5A. Axial MR Image

A connection between the lumen of the proximal descending thoracic aorta and left pulmonary artery is consistent with a patent ductus arteriosus.

Locate the ductus arteriosus.

Answer

Figure 5B. Coronal MR Angiography

The presence of the patent ductus arteriosus (above) is confirmed on the coronal magnetic resonance angiography image.

Find the ductus arteriosus.

Answer

Reference: To return to reference section after viewing abstract, click here before clicking on "abstract".

Frazier AA, Galvin JR, Franks TJ, Rosado-De-Christenson ML. From the archives of the AFIP: pulmonary vasculature: hypertension and infarction. Radiographics 2000; 20:491-524. Abstract

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Ventricular septal defect

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LPA = Left pulmonary artery

Desc Ao = Descending aorta

Arrows mark the site of the ductus arteriosus.

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Atrial septal defect

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