Postatelectatic ventilation-perfusion mismatch simulating a pulmonary embolus.

Ventilation-perfusion imaging was performed on a patient with chronic intermittent atelectasis of the right lung and revealed a mismatch simulating a pulmonary embolus in the right lung. A pulmonary arteriogram revealed no evidence of embolic disease; however, there was reduced capillary phase opacification of the right lung and increased pulmonary artery pressure. The findings are consistent with an isolated right pulmonary artery hypertension secondary to prolonged atelectasis causing an apparent mismatch on the ventilation-perfusion scan.