Congenital anomalous venous drainage of the right
pulmonary veins into the inferior vena cava, associated with hypoplasia or
aplasia of one or more lobes of the right lung.
Mild to moderate hypoplasia of the right lung results in displacement of
the heart to the right side in a 6-year-old girl with scimitar syndrome.
Right ventricular enlargement is seen. There is an anomalous pulmonary vein
on the right side (because of its shape called scimitar vein (see text,
white arrows) draining into the inferior vena cava. This vein has been
surgically clipped (black arrow). Furthermore, the persistent ductus
arteriosus had to be coiled (triangle).
In this posterior view of the three dimensional reconstruction of the
chest CT scan of the same patient, the scimitar vein can easily be
identified (white arrows) draining into the inferior vena cava. The
triangles indicate the aorta.
The name scimitar syndrome originates from the anomalous pulmonary vein on
the right side, which drains into the inferior vena cava. This vein is
sometimes visible on the radiograph of the chest resulting in a curvilinear
shadow just above the right diaphragm. The shape of this shadow resembles a
scimitar, a saber typically used by Arabs and Turks.
Anomalous venous drainage of the right lung into
the inferior vena cava represents a large left-to-right shunt. If an atrial
septal defect is present and is not restrictive, right-to-left shunting
occurs at the atrial level and compensates for the shunt caused by the
anomalous pulmonary venous drainage. The left side of the heart is volume
underloaded while the right side has an increased load. The scimitar
syndrome is associated with pulmonary artery hypoplasia or atresia,
predisposing to right ventricular failure. Obstruction of the anomalous
venous drainage may occur at the level of the diaphragm or at insertion into
the inferior vena cava, resulting in pulmonary venous congestion and
Cyanotic heart disease in presence of 'scimitar sign'
on chest radiograph. Echocardiography is nonspecific. Anomalous venous
drainage confirmed by cardiac catheterization.
Failure to thrive, cyanosis, tachycardia, signs
and symptoms of right ventricular failure. Auscultation may reveal fixed,
wide splitting of the second heart sound, a diastolic murmur of tricuspid
origin, and a pulmonary ejection murmur in the presence of pulmonary
hypoplasia. Presentation may be delayed in the presence of a nonrestrictive
atrial septal defect until growth results in the atrial septal defect
becoming restrictive causing a fall in arterial oxygen pressure (PaO2).
The ECG shows right axis deviation and signs of right ventricular strain.
The anomalous vein(s) cause a vertical scimitar shape on chest radiograph.