Ebstein's anomaly is a congenital heart defect in which the septal and posterior leaflets of the tricuspid valve are displaced towards the apex of the right ventricle of the heart. It is classified as a critical congenital heart defect accounting for less than 1% of all congenital heart defects presenting in around 1 per 200,000 live births. Ebstein anomaly is the congenital heart lesion most commonly associated with supraventricular tachycardia. Signs and symptoms The annulus of the valve is still in the normal position. The valve leaflets, however, are to a varying degree, attached to the walls and septum of the right ventricle. A subsequent "atrialization" of a portion of the morphologic right ventricle (which is then contiguous with the right atrium) is seen. This causes the right atrium to be large and the anatomic right ventricle to be small in size. S3 heart sound S4 heart sound Triple or quadruple gallop due to widely split S1 and S2 sounds plus a loud S3 and/or S4 Systolic murmur of tricuspid regurgitation = Holosystolic or early systolic murmur along the lower left sternal border depending on the severity of the regurgitation Right atrial hypertrophy Right ventricular conduction defects Wolff-Parkinson-White syndrome often accompanies Related abnormalities While Ebstein's anomaly is defined as the congenital displacement of the tricuspid valve towards the apex of the right ventricle, it is often associated with other abnormalities. Anatomic abnormalities Typically, anatomic abnormalities of the tricuspid valve exist, with enlargement of the anterior leaflet of the valve. The other leaflets are described as being plastered to the endocardium. Tethering the underlying ventricular wall is the most common for the posterior and septal leaflets, and sail-like anterior leaflets may be tethered to the RV free wall also. About 50% of individuals with Ebstein's anomaly have an associated shunt between the right and left atria, either an atrial septal defect or a patent foramen ovale. Electrophysiologic abnormalities About 50% of individuals with Ebstein's anomaly have an accessory pathway with evidence of Wolff-Parkinson-White syndrome, secondary to the atrialized right ventricular tissue. This can lead to abnormal heart rhythms including atrioventricular re-entrant tachycardia. Other abnormalities that can be seen on the ECG include: signs of right atrial enlargement or tall and broad 'Himalayan' P waves first degree atrioventricular block manifesting as a prolonged PR-interval low amplitude QRS complexes in the right precordial leads atypical right bundle branch block T wave inversion in