Images in Clinical Medicine

Right-to-Left Shunt on a Lung Scan

Catherine A. Moses, M.D., and Fred S. Mishkin, M.D.

N Engl J Med 1999; 340:857March 18, 1999

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Figure 1 A 45-year-old woman with pulmonary hypertension and polycythemia presented with increasing cyanosis, edema of the legs, and dyspnea on exertion. She had a partial pressure of arterial oxygen of 35 mm Hg (pH, 7.35). The chest radiograph (lower left panel) showed an enlarged pulmonary artery, small peripheral vessels, and global cardiomegaly. Right posterior oblique (RPO) and left posterior oblique (LPO) perfusion scans showed medium-sized segmental defects in the posterior segment of the right upper lobe and the superior segments of both the right and left lower lobes (arrows in upper left and middle panels). These defects were normally ventilated, indicating a high likelihood of pulmonary embolism. There was also abnormal uptake of tracer in the brain (upper right panel, posterior projection) and kidneys (arrowheads in upper left panel), indicating a substantial right-to-left shunt. The former finding is pathognomonic of a right-to-left shunt. Another unusual finding was myocardial uptake (arrowheads in upper middle panel) due to the large shunt. Subsequent computed tomography of the chest (lower right panel) showed a large saddle embolism in the main pulmonary artery (PA), extending into the right pulmonary artery (arrowheads). The diameter of the pulmonary artery was greater than that of the ascending aorta (Ao), a finding consistent with the diagnosis of pulmonary hypertension. Follow-up studies revealed a large atrial septal defect and Eisenmenger's complex. After treatment with heparin, the patient was sent home with instructions for warfarin and oxygen therapy.

Catherine A. Moses, M.D.
Ventura Radiology Medical Group, Ventura, CA 93003

Fred S. Mishkin, M.D.
Harbor–UCLA Medical Center, Torrance, CA 90509

Citing Articles (2)

Citing Articles

1. 1

   EMMANUEL ITTI, ZOULIKHA MALEK, OVIDIU VANDICI, RAFIK KHETIB, MICHEL MEIGNAN. (2000) Shunt Imaging in a Complex Congenital Cardiomyopathy. Clinical Nuclear Medicine 25:10, 827-828
   CrossRef

2. 2

   George Panoutsopoulos, Ioannis Ilias, Ioulia Christakopoulou. (2000) Transient right-to-left shunt in massive pulmonary embolism. Annals of Nuclear Medicine 14:3, 217-221
   CrossRef