Summary

Pulmonary embolism (PE) may encompass a wide spectrum of severity.To determine whether clinical findings, D-dimer (DD) concentration,and deep vein thrombosis (DVT) shown by lower-limb venouscompression ultrasonography (US) might predict the scintigraphic extentof PE, we studied 104 hemodynamically stable consecutive outpatientswith acute PE diagnosed by a high-probability ventilation-perfusionlung scan. Scintigraphic extent of PE was classified into three categories:perfusion defects corresponding to <30%, 30-50%, or >50%of the total lung area. Median respiratory and heart rates were found tobe significantly related to the extent of PE. Higher median alveolararterialoxygen difference values were observed as the proportion oflung perfusion defects increased (>50% vs. <30%, 6.3 vs. 3.6 kPa,P <.0001). Median plasma DD concentration was 7950 Mµg/L in patientswith >50% perfusion defects compared to 2731 µg/L in those with<30% defects (P = .0001). DD levels above 4000 µg/L were associatedto more extensive perfusion defects (>50% vs. <30% defects, OR 30;95% CI 5.8-155). Finally, a proximal DVT was more likely among patientswith larger perfusion defects (>50% vs. <30% defects, OR 4.5;95% CI 1.5-13.6). In conclusion, clinical signs such as tachypnea andtachycardia, alveolar-arterial oxygen difference, plasma DD concentration,and presence of DVT on US are predictors of a larger PE, as assessedby the extent of perfusion defects on high probability lung scans.