Ventilation-perfusion-chest radiography match is less likely to represent pulmonary embolism if perfusion is decreased rather than absent.

PURPOSE

The authors' goal was to determine whether the prevalence of pulmonary embolism in patients with matching ventilation-perfusion (V-Q) defects and chest radiographic opacities differs depending on the degree of perfusion deficit (absent versus decreased).

METHODS

The authors performed a retrospective analysis of the data obtained from the Prospective Investigation of Pulmonary Embolism Diagnosis (PIOPED) study. In 233 patients, angiograms were of diagnostic quality for 275 lung zones that showed matching V-Q defects and chest radiographic opacities (triple matches). Of these, V-Q scans and chest radiographs from 217 patients with triple matches in 255 lung zones were retrieved and reviewed. Areas corresponding to chest radiographic opacities were scored as having either decreased perfusion or absent perfusion by consensus. Information regarding the presence or absence of pulmonary embolism in corresponding lung zones was obtained from the PIOPED database.

RESULTS

The overall prevalence of pulmonary embolism in all lung zones with triple matches was 27% (69 of 255). Of the 255 areas of triple matches, the perfusion was decreased in 153 (60%) and absent in 102 (40%). The prevalence of pulmonary embolism in areas of triple matches with decreased perfusion and triple matches with absent perfusion was 13% (20 of 153) and 48% (49 of 102), respectively (P = 0.0001 by the chi-square test). When these were divided further by lung zones, triple matches with decreased perfusion and triple matches with absent perfusion in the upper-middle lung zone were associated with a prevalence of 0% (O of 44), and 25% (9 of 36), respectively. The prevalence of pulmonary embolism in areas of triple matches with decreased perfusion and triple matches with absent perfusion in the lower lung zone was 18% (20 of 109), and 61% (40 of 66), respectively.

CONCLUSIONS

A V-Q/chest radiographic match is less likely to represent pulmonary embolism if perfusion is decreased rather than absent. The overall prevalence of pulmonary embolism associated with all triple matches in all lung zones varied from very low (0% in this series) to upper intermediate (61 %), depending on whether perfusion was decreased or absent and also on the location of the triple match.