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Matched ventilation, perfusion and chest radiographic abnormalities in acute pulmonary embolism
A Gottschalk1, P D Stein, J W Henry
1Michigan State University, East Lansing 48224, USA.
Unlabelled:
This investigation assessed the positive predictive value of matched ventilation/perfusion (V/Q) and chest radiographic defects (triple-matched defects) for the detection of acute pulmonary embolism (PE).
Methods:
Data are from the Prospective investigation of Pulmonary Embolism Diagnosis (PIOPED). Only patients randomized for obligatory pulmonary angiography were included. Lungs were excluded if they showed any mismatched V/Q defect or any pleural effusion.
Results:
Positive predictive values of triple-matched defects in the upper plus middle zones, 1 of 27 (4%), were less frequent than in the lower zones, 13 of 57 (23%) (p < 0.05). Triple-matched defects that involved 25-50% of a zone showed PE in 12 of 38 (32%) which was a higher positive predictive value than with smaller or larger triple-matched defects, 2 of 46 (4%) (p < 0.001).
Conclusion:
Refinement of the PIOPED data by elimination of nonrandomized patients, elimination of lungs with mismatched perfusion defects and elimination of lungs with a pleural effusion indicate that triple matches with PE (radiographic pulmonary infarcts) are infrequent in the upper and middle lung zones. When a triple match with PE occurs, it is most likely to be 25-50% of a zone.