Discussion

The bronchopulmonary vascular system comprises of bronchial, pulmonary arterial and pulmonary venous systems. Bronchopulmonary vascular malformations include any disruption in the normal communication and/or formation of abnormal communications between one or more of these three components. The spectrum of malformations ranges from simple bronchogenic cyst to the scimitar syndrome. The term “malinosculation” is used to describe the presence of an abnormal communication between the various components of the bronchopulmonary vascular system. ^{Reference Clements and Warner2} Lee and colleagues, based on the extent of involvement of various components, classified these malformations into seven types. (Table 1). ^{Reference Lee, Lue and Chiu3}

Table 1.

Schematic representation of bronchopulmonary vascular malformations with examples

IVC=inferior caval vein; LUPV=left upper pulmonary vein; PA=pulmonary artery; PV=pulmonary veins; RIPV=right inferior pulmonary vein; SVC=superior caval vein.

Isolated systemic arterial supply to normal lung is a congenital malformation wherein an anomalous artery from the systemic circulation supplies an otherwise normal lung segment (type B bronchopulmonary vascular malformation) and represents an isolated arterial malinosculation (Table 1). ^{Reference Lee, Lue and Chiu3} The anomalous artery mostly originates from the descending aorta, usually between the eighth and eleventh thoracic vertebra, and supplies the lower lobe of left lung. Rarely, the anomalous artery may originate from the celiac trunk, subclavian or internal mammary arteries. ^{Reference Miyake, Hori and Takeoka4} In the complete variant, there is no alternative blood supply whereas in the incomplete type, the affected lung segment has intact vascular supply from the native pulmonary arteries. ^{Reference Yamanaka, Hirai and Fujimoto5} Most often, the patients are asymptomatic while others present with recurrent hemoptysis. In some patients as in this case, a relatively lower resistance in the lung vasculature permits intrapulmonary left-to-right shunt resulting in left ventricular volume overload.

In the absence of any other abnormality, the shunt can be easily abolished by occlusion of the anomalous arterial supply. Intuitively, occlusion of the artery is safer in the incomplete type although, despite concerns, safe occlusion or ligation has been reported in the complete type as well. ^{Reference Izzillo, El Hajjam and Qanadli6–Reference Jiang, Shi and Zhu9} Nevertheless, occlusion of the sole supply to the affected lung segment in the complete type converts the lung segment non-functional with subsequent risk of infection and bronchiectasis. Besides, recanalisation of the arterial channel as well as recruitment of newer bronchial collaterals is known, thus mandating careful follow-up after occlusion of the anomalous artery. ^{Reference Jiang, Shi and Zhu9,Reference Abe, Mori and Shiigai10} Incomplete type of systemic supply to normal lung in our patient made it safer for interventional closure.