IS Case 378: Ebstein's anomaly
2009 URMC Imaging Sciences
Publication Date: 2010-03-02
Patient is a 17-year-old male with chest pain.
Frontal view of the chest demonstrate cardiomegaly, particularly of the right heart border, with normal pulmonary vasculature. In some cases, decreased pulmonary vasculature would be seen. Although not present with this patient, lateral views of the chest sometimes demonstrate posterior bulging of the heart, representing the enlarged right atrium or displacement of the left heart by the enlarged right heart.
Differential diagnosis for enlarged right heart with normal or decreased pulmonary vascularity includes tricuspid atresia, tricuspid stenosis, tricuspid regurgitation, pulmonic valve stenosis, pulmonic valve regurgitation, Tetralogy of Fallot, Ebstein's anomaly, and Uhl's anomaly.
Ebstein anomaly is a congenital heart defect caused by apical displacement of the septal and posterior tricuspid valve leaflets with associated variable displacement of the anterior tricuspid leaflet and dysplasia of one or more leaflet. This downward displacement of the tricuspid valve results in incorporation of a portion of the right ventricle into the right atrium--that is, atrialization of the right ventricle. The abnormally formed tricuspid valve leads to varying degree of regurgitation depending on the severity of the displacement. The atrialized right ventricle contracts discordantly with the right atrium, leading to inefficient propulsion of blood through the right side of the heart. As a result of tricuspid regurgitation and discordant contraction, the right atrium or both the right atrium and ventricle becomes enlarged.
Ebstein anomaly is associated with other congenital heart defects and/or arrhythmias. The prevalence is unknown but is estimated to account for 0.5% of congenital heart diseases. Patients may present with symptoms of cyanosis, right heart failure, fatigue and dyspnea. Treatment depends on severity of the defect and includes surgical repair, medical therapy (prophylactic antibiotics, heart failure regimen, anti-arrhythmic drugs), and/or radiofrequency ablation of accessory conduction pathways for patients with associated arrhythmias.
Chest radiographs may be normal or may show the following: cardiomegaly which may have a square or box-like contour, normal or decreased pulmonary vasculature, small aortic root and small main pulmonary artery shadow. On lateral radiograph projection, a cardiac posterior bulge may be present secondary to the markedly enlarged right atrium or posterior displacement of the left heart. Echocardiography is currently the modality of choice for diagnosing Ebstein anomaly, where apical displacement of septal tricuspid valve leaflet is the most specific sign. Dilated right atrium (with or without dilated right ventricle), paradoxical right atrial motion, delayed closure of tricuspid valve with respect to mitral valve and tricuspid regurgitation among other findings are also seen on echocardiogram. MRI with and without cine may be a promising imaging modality in the future.
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