Endocardial Cushion Defects (Atrioventricular Canal Defects, Atrioventricular Septal Defects) Workup

Updated: Dec 28, 2020
  • Author: Mary C Mancini, MD, PhD, MMM; Chief Editor: Yasmine S Ali, MD, MSCI, FACC, FACP  more...
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Laboratory Studies

Laboratory testing for patients with suspected endocardial cushion defect (atrioventricular [AV] canal or septal defects) include the following

  • Complete blood cell (CBC) count: Blood tests determine the presence of polycythemia in a potentially cyanotic condition.

  • Prothrombin time/activated partial thromboplastin time (PT/aPTT): In children with cyanotic heart disease, the coagulation profile may be abnormal because of associated polycythemia.

  • Electrolytes: This test detects any abnormalities incurred with treatment of congestive heart failure (CHF).


Imaging Studies

Electrocardiography (ECG)

The typical ECG in patients with partial atrioventricular (AV) septal defects (AVSDs) shows first-degree AV block and left-axis deviation (because of late left anterior fascicular depolarization). Patients with right ventricular (RV) dilatation usually have partial or complete right bundle-branch block. Complete AV block and atrial fibrillation commonly occur in older patients.

A prolonged PR interval accompanied by biventricular or left ventricular (LV) hypertrophy also may be seen. 

Chest radiography

Chest radiography is a good general screening study that shows cardiac enlargement, particularly of the right atrium and ventricle.

The main pulmonary artery usually is prominent with increased pulmonary vascular markings. After pulmonary hypertension develops, a reduction in pulmonary vascular markings is observed.


M-mode echocardiography shows diastolic movement of the mitral valve with enlarged RV and paradoxical motion of the interventricular septum.

Two-dimensional echocardiography is highly reliable in identification of septal defects. Echocardiography identifies the absence of the interventricular septum. Findings may include RV dilatation and paradoxical motion of the interventricular septum. The extent of septal defects as well as the left-to-right shunting and degree of valvular insufficiency can be determined as well as an estimate of pulmonary artery pressure. Lack of displacement of the left and right AV valves is a characteristic finding in this condition. Prolonged diastolic contact between the anterior mitral leaflet and the interventricular septum also may be noted. Associated defects that may require attention also can be detected.

Abnormalities in the AV valves can be identified reliably. Transesophageal echocardiography (TEE) clearly identifies AV valve morphology. [5, 6, 7]

Magnetic resonance imaging (MRI)

MRI readily visualizes the deficiency in the ventricular septum as well as AV valve morphology. [8, 9]



Cardiac catheterization

Cardiac catherization is indicated when clinically significant questions remain unanswered after a comprehensive noninvasive evaluation. If other lesions are suspected or if operative planning cannot be performed adequately after noninvasive testing, then catheterization should be undertaken. Left ventricular angiography in the frontal plane shows an elongated left ventricular outflow tract, called a "gooseneck deformity," which is characteristic of this condition. Catheterization should involve quantitation of the shunts and valvular insufficiency and calculation of pulmonary vascular resistance. Aortography may be performed to determine whether a patent ductus arteriosus is present.