Pediatric Complete Atrioventricular Septal Defects Workup

Updated: Sep 13, 2019
  • Author: Michael D Pettersen, MD; Chief Editor: Syamasundar Rao Patnana, MD  more...
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Workup

Laboratory Studies

Although basic chemistry panels and the CBC count may aid in overall care, complete atrioventricular septal defect (AVSD) requires no specific laboratory tests.

If Down syndrome or another chromosomal abnormality is suspected, chromosome studies are indicated.

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Electrocardiography

Electrocardiography reveals many typical findings and may provide clues to the presence of complete atrioventricular septal defect. The underlying rhythm most is often sinus. The PR interval may be prolonged secondary to atrial enlargement and increased atrial conduction time. The p-wave may be indicative of right atrial, left atrial, or biatrial enlargement.

The QRS complex reveals the most characteristic findings of atrioventricular septal defect. Posterior displacement of the atrioventricular node and His bundle results in left axis deviation with a superiorly oriented QRS frontal plane axis and counterclockwise depolarization pattern. The QRS frontal axis is usually between -30º and -90º. Right ventricular volume and pressure overload leads to evidence of right ventricular hypertrophy and the presence of an rsR’ or RSR’ pattern in the right precordial chest leads. Left ventricular hypertrophy may be present in the setting of significant mitral or common atrioventricular valve regurgitation.

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Imaging Studies

Chest radiography shows enlargement of the cardiac silhouette. Enlargement of the right atrium and right ventricle is most apparent. Evaluation of the left ventricle may be difficult because it is often displaced by the enlarged right ventricle. The main pulmonary artery segments are prominent, as well as the overall pulmonary vascular markings. In the setting of pulmonary vascular disease, the distal pulmonary vessels may have a lucent, pruned appearance.

Echocardiography reveals defects of the atrial and ventricular septae [30, 31, 32] and is the most useful study in the identification, diagnosis, and evaluation of most important aspects anatomy and physiology.

The subcostal 4-chamber and long axial oblique (modified left oblique) views reveal many important aspects of complete atrioventricular septal defect, including the size of the atrial and ventricular defects, the nature of the atrioventricular valve attachments, the distribution of atrioventricular valve tissue, and the left ventricular (LV) outflow tract (LVOT).

The videos below demonstrate echocardiographic findings:

Apical 4-chamber echocardiographic image demonstrating a complete atrioventricular septal defect. A large primum atrial septal defect, a large inlet ventricular septal defect, and a single common orifice atrioventricular valve are noted.
Apical 4-chamber echocardiographic image with color Doppler demonstrating moderately-severe insufficiency of the common atrioventricular valve.
Parasternal long axis echocardiographic image of a complete atrioventricular septal defect. A large inlet ventricular septal defect is seen. Accessory atrioventricular valve tissue is visualized within the left ventricular outflow tract.
Subcostal sagittal echocardiographic image demonstrating the common atrioventricular valve. The anterior bridging leaflet inserts onto the interventricular septum consistent with a Rastelli type A valve.

Other anatomic features, such as ventricular size, atrioventricular valve insufficiency, aortic arch anatomy, and a patent ductus arteriosus (PDA), may be accurately assessed with echocardiography, especially in the infant.

Echocardiography also can reveal a single LV papillary muscle, which may influence the success of mitral reconstruction.

In some centers, 3-dimensional (3D) reconstructions of echocardiographic images are used to evaluate atrioventricular valve morphology, and proponents claim increased diagnostic accuracy with this technique compared with transthoracic echocardiography. [33, 34, 35]

Abnormal atrioventricular valve leaflets may be classified into the following three types:

  • Rastelli type A involves minimal bridging of the superior cushion-derived leaflet and attachment of the leftward component of the anterior bridging leaflet to the crest of the interventricular septum.

  • Rastelli type B is rare and involves chordal support of the anterior bridging leaflet attaching to the body of the right ventricle (RV).

  • Rastelli type C valve has a free-floating anterior bridging leaflet that is attached at its rightmost extent to the anterior papillary muscle of the RV.

Doppler echocardiography can reveal common atrioventricular valve regurgitation as well as the flow through the atrial and ventricular septal defects (VSDs).

Hemodynamic information, such estimated RV and pulmonary artery pressure, may be obtained.

Many clinicians believe that a preoperative echocardiogram with Doppler and color flow mapping provides sufficient anatomic and functional information for young infants undergoing repair and that cardiac catheterization may yield little additional information. Other diagnostic tools are occasionally used to diagnose atrioventricular canal defects.

The complete form of atrioventricular canal can be prenatally diagnosed by performing fetal echocardiography. Because two thirds of neonates with complete atrioventricular septal defect also have trisomy 21, this finding by fetal echocardiography should prompt a search for associated chromosomal abnormalities, especially Down syndrome. Fetuses with complete atrioventricular septal defect may develop hydrops fetalis if insufficiency of the common atrioventricular valve is severe.

Transesophageal echocardiography (TEE) is extremely valuable in the large child or adult patient in whom transthoracic echocardiographic windows are limited. It is also ideal for intraoperative evaluation at the time of repair in infancy. TEE provides detailed anatomic information regarding the atrioventricular valves, ventricular function, residual shunts, LVOT obstruction, and atrioventricular valve insufficiency or stenosis.

MRI has been used to identify complete atrioventricular septal defect, but is not routinely required.

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Procedures

Cardiac catheterization is no longer routine for anatomic delineation in many centers. However, when used, it is performed to verify whether the VSD component is nonrestrictive, to determine if additional VSDs are present, to calculate the pulmonary vascular resistance (PVR), and to determine if the pulmonary vascular bed is responsive to pulmonary vasodilators.

The most frequent use of catheterization in common atrioventricular canal is to accurately measure the PVR and, if it is elevated, to evaluate its response to vasodilators, such as oxygen, sodium nitroprusside, calcium-channel blockers, or inhaled nitric oxide.

PVR is calculated as the mean pulmonary artery pressure minus the mean left atrial pressure, divided by the pulmonary blood flow.

Response in the PVR (with oxygen, nitric oxide, or other pulmonary vasodilators) may suggest that a child with high PVR may still benefit from surgery to close atrial and ventricular communications, as outlined above.

Patients with a calculated PVR of 10 Wood units/m2 or greater that does not fall below 5-7 Wood units/m2 in response to vasodilators are at increased risk for death after surgical repair.

In patients younger than 1 year, irreversible pulmonary vascular obstructive disease (PVOD) is rare; hence, PVR data are often ignored.

The second most frequent use for cardiac catheterization is LV angiography to rule out coexisting muscular VSDs.

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Histologic Findings

Complete atrioventricular septal defect is associated with high flow at systemic pressure, which leads to severe hypertrophy of the media of the small arteries of the lung. Intimal fibrosis may also be seen.

Acute fibrous proliferation and atrophy of the peripheral pulmonary arterial media are associated with aging and Down syndrome, which, in addition, reduces the total cross sectional area of the pulmonary vascular bed.

Chronic hypoxemia, upper airway obstruction, and Down syndrome may hasten these vascular changes.

Except in rare cases, surgery within 6 months prevents irreversible PVOD. In Down syndrome babies, most centers perform surgical correction around the age of 3 months.

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