A 47-year-old male with a history of antithrombin III deficiency, recurrent pulmonary emboli, and chronic thromboembolic pulmonary hypertension presented for evaluation prior to pulmonary thromboendarterectomy. A routine pulmonary angiogram and selective coronary arteriogram were performed. The left lateral view of the pulmonary angiogram, shown in panel A, demonstrated complete occlusion of the left lower lobe pulmonary artery just after the takeoff of the branch to the lingual (large arrow). Coronary arteriography revealed separate ostia for the left anterior descending and left circumflex arteries and the unusual and unexpected finding of collateral flow between the left circumflex artery and the left lower lobe (small arrow). The collaterals are seen extending beyond the lower heart border. Anomalous pulmonary blood supply, including supply from the coronary circulation, has been described in other conditions including congenital (unilateral pulmonary artery agenesis) and acquired (Takaysu's arteritis, fibrosing mediastinitis) disease. Many patients may be asymptomatic, but cases of coronary steal inducing myocardial ischemia and chest pain have been reported.

Image provided by Christopher F. Barnett, MD, MPH, FACC,*† Kim M. Kerr, MD,‡ Ori Ben-Yehuda, MD,† from the *Critical Care Medicine Department, Clinical Center, National Institutes of Health, Bethesda, Maryland; and the Divisions of †Cardiology and ‡Pulmonary Critical Care, University of California at San Diego, San Diego, California