Pediatric Partial and Intermediate Atrioventricular Septal Defects Workup
- Author: M Silvana Horenstein, MD; Chief Editor: P Syamasundar Rao, MD more...
In patients with atrioventricular septal defects (AVSDs), chest roentgenography usually reveals the following:
- Prominent pulmonary artery segment and abnormally dense pulmonary vascular markings
- Cardiac enlargement, especially enlargement of the right atrium (RA) and right ventricle (RV)
Echocardiography and Doppler Studies
Echocardiography is the diagnostic method of choice. Note the following:
- Ostium primum defect is seen as an echo dropout in the lower portion of the septum at the crux of the heart, as shown below.
- Abnormal morphology of the atrioventricular valves can be studied in detail, including small inferior and mural leaflets, lack of coaptation of leaflets, and a cleft in the anterior mitral valve leaflet.
- The attachments of the atrioventricular valves may extend into the left ventricular outflow tract (LVOT) and may create obstruction. Atrioventricular valve tissue may extend to the crest of the ventricular septum.
- Apical 4-chamber view (see the image below) reveals the tricuspid and mitral valve components at the same level without the normal apical displacement of the tricuspid valve.
- Anterior and superior displacement of the aorta, with elongation and narrowing of the LVOT, is seen in the long parasternal axis.
Doppler and color Doppler studies are used for the following:
- Demonstration of left-to-right shunting through the atrial septal defect (ASD) and detection of presence and severity of mitral regurgitation (MR); shunting from the left ventricle (LV) to the RA may also be identified. See the images shown below.Color Doppler demonstrates left-to-right shunting through the partial atrioventricular septal defect (AVSD) shown in the following images.Partial atrioventricular septal defect (AVSD): The mitral and tricuspid annuli are separate. The cleft in the mitral leaflet is in the anterior position. This type of anatomy is usually associated with a primum atrial septal defect (ASD). Partial AVSD is more common than intermediate AVSD.Intermediate atrioventricular septal defect (AVSD): A single valve annulus is present. The anterior and posterior bridging leaflets are fused (whereas in complete AVSD the anterior and posterior bridging leaflets are not fused). Therefore, the atrioventricular valve has a tricuspid and a mitral component. Intermediate AVSD is the least common type of AVSD.
- If tricuspid regurgitation is present, RV pressure may be estimated. Care is needed to interrogate tricuspid regurgitation rather than the LV-to-RA jet; otherwise, a falsely high ventricular pressure estimate results.
- LVOT obstruction may be identified and quantitated.
- Three dimensional (3-D) echocardiography has been shown to provide excellent quality images of the atrioventricular valve morphology and relationships with the rest of the cardiac structures. (Singh A, 2006)
- It is also being used in centers to assess the dynamic morphology of the left-sided AV valve and LVOT anatomy after AVSD repair.
- Intraoperative assessment with transesophageal echocardiography is an invaluable tool for the surgeons to assess adequacy of AV valve repair.
Magnetic Resonance Imaging
MRI is being more frequently used because more precise delineation of anatomy and evaluation of function may be obtained with this noninvasive method than with either echocardiography or angiography alone.
MRI can be used to help define morphologic abnormalities in AVSD as well as important anatomic variations.
MRI is particularly useful for evaluating shunt severity, expressed quantitatively as the ratio of pulmonary flow to systemic flow (Qp/Qs).
Classic anatomic studies of the conduction tissue have shown that the atrioventricular node is usually displaced posteriorly, originating in the posterior wall of the RA.
The bundle of His is posteriorly displaced and skirts the lower margin of the ventricular septal defect (VSD); the right bundle may give off several branches instead of continuing as a single trunk through the RV.
This unusually long course and peculiar orientation of the conduction tissue creates a different advancing front of depolarization, resulting in the following characteristic electrocardiographic (ECG) features:
- The superior-oriented, counterclockwise vector loop in the frontal plane occurs commonly in AVSD.
- The mean QRS axis ranges from -30 º to -120 º (mostly between -30 º and -90 º).
- On the standard 12-lead ECG, the small R wave is followed by a prominent S wave in lead aVF; in aVL, a small Q wave is followed by a prominent R wave. This pattern is caused by abnormal septal depolarization in AVSD, including PR-interval prolongation and RV hypertrophy, particularly an rSR' or RSR' pattern.
- P-wave enlargement concordant with RA, left atrium (LA), or biatrial enlargement is seen in approximately half of patients with AVSDs.
Cardiac catheterization and angiography is no longer needed to confirm the diagnosis of partial AVSD.
This procedure may be performed if echocardiography is not sufficient to delineate anatomy and if pulmonary hypertension is suspected. The shunt can be measured, and the response of the pulmonary arterial pressure and resistance to pulmonary vasodilators can be assessed.
If present, LVOT obstruction can be quantified or other associated lesions can be evaluated.
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