Answer of April 2008

Clinical History:

A 34-years-old lady enjoyed good past health.  Routine chest radiograph showed reduced left lung volume and right-sided aortic arch.  Pulmonary angiogram, aortogram and innominate arteriogram were performed.

Diagnosis:

Interruption of left pulmonary artery with right-sided aortic arch.

Discussion:

Pulmonary arteriography reveals single trunk outflow tract with supply to right lung while the left pulmonary artery is absent.  Right-sided aortic arch is evident.
Left lung is being supplied via hypertrophied collaterals arising from the left internal mammary artery as well as from the thoracic branches of left subclavian artery.  It is better shown on angiogram performed via selective catheterization of the left innominate artery.  Features are suggestive of interruption of left pulmonary artery with right-sided aortic arch.

Congenital absence of one pulmonary artery is a rare entity, with an estimated prevalence of 1 in 200,000. In proximal interruption, the pulmonary artery ends blindly at the hilum, and blood is supplied to the lung through collateral systemic vessels, mainly bronchial arteries but also transpleural branches of the intercostal, internal mammary, subclavian, and innominate arteries.

Interruption of the left pulmonary artery is usually associated with right aortic arch and other congenital cardiovascular anomalies, most commonly tetralogy of Fallot. Right pulmonary artery interruption is more common than left, and it is an isolated finding in most instances.