Pulmonary infarction: spectrum of findings on multidetector helical CT.

OBJECTIVE: Despite the dual blood supply to the lung, acute pulmonary embolism (PE) can lead to a spectrum of ischemic injury to the lung resulting in infarction and hemorrhage. In this series we systematically describe the spectrum of CT findings and clinical correlates of pulmonary infarction in patients with PE.
METHODS: We retrospectively identified 24 consecutive adults with pulmonary infarction on multidetector CT between July 2002 and March 2004. There were 13 women and 11 men, with a mean age of 59 years. The cases were identified by review of 74 consecutive CTs demonstrating PE. Each CT was evaluated by 2 of 3 reviewers in consensus for presence and characteristics of peripheral parenchymal opacities and extent of PE. Peripheral opacities were evaluated for degree of enhancement, internal air lucencies, and contour. The presence of adjacent vessels and linear strands were noted. At the end of interpreting each case, the reviewers determined whether or not an infarct was present based on the constellation of previously described imaging features. The extent of pulmonary vascular obstruction was graded using the CT clot burden scoring system. Each chart was reviewed for predisposing factors for PE and infarction, presenting clinical symptoms/signs, and co-existing pulmonary or cardiac conditions.
RESULTS: Thirty-two percent (24/74) of patients with PE had pulmonary infarction. Thirty-three percent (8/24) of patients had more than 1 infarct. Seventy-three percent (27/37) of infarcts were in the lower lobes. The CT findings of pulmonary infarction included: focal decrease in parenchymal enhancement in 95% (35/37), broad pleural base in 65% (24/37), truncated apex in 57% (21/37), convex border in 46% (17/37), internal air lucencies in 32% (12/37), linear stranding from the apex toward the hilum in 24% (9/37), and a thickened vessel leading to the apex of the infarct in 14% (5/37). There was a trend toward a higher mean clot burden (12.3 vs. 10.5) between the patients with PE with and without infarction. Ninety-six percent (23/24) of patients with pulmonary infarction had predisposing factors for infarction, including PE involving more than 1 lobe (n = 21), malignancy (n = 5), and heart failure (n = 3). Pleuritic chest pain was significantly more frequent in patients with infarction (P = 0.0064).
CONCLUSION: Pulmonary infarction occurred in nearly 1/3 of patients with PE in this series. The infarcts were peripheral parenchymal opacities characterized by a distinctive complex of findings on CT reflecting ischemic injury in the setting of a dual blood supply to the lung. Pleuritic chest pain was significantly associated with infarction.