Radiographic parenchymal opacity, matching perfusion defect, and normal ventilation: a sign of pulmonary embolism? Work in progress

By conventional criteria, perfusion defects that correspond to radiographic parenchymal opacities of similar size have less diagnostic significance for pulmonary embolism (PE) than perfusion defects in areas that are radiographically clear, regardless of the findings on ventilation scan. It was proposed that the demonstration of normal ventilation in areas with matched radiographic opacity and perfusion defects does support the diagnosis of PE. To test this hypothesis, a retrospective review was done of selected cases from a consecutive series of 85 pulmonary angiography studies. Cases were reviewed if the following criteria were met: chest radiography, ventilation-perfusion scintigraphy, and angiography of the relevant regions had all been performed within 24 hours of one another, and there was a radiographic opacity corresponding to the perfusion defect. Sixteen cases fulfilled these criteria. Six patients had normal ventilation in the regions of the radiographic infiltrate and perfusion defect, and all had PE. No patient had an area of opacity and perfusion defect and normal ventilation without PE.