Pulmonary embolism: segmental appearance of perfusion lung scan defects correlates with successful response to thrombolytic therapy.

Lung scan data from a series of 45 patients receiving thrombolytic therapy were reviewed to determine if any pattern on the pretherapy perfusion lung scans could be identified that predicted response to therapy. A segmental appearance on the pretherapy scans (complete or nearly complete absence of perfusion in a whole segment or a very large subsegment) was correlated with the amount of improvement in perfusion on lung scans obtained 24 hours after the start of thrombolytic therapy. As a group, patients with a segmental appearance on the pretherapy lung scans had more improvement in the perfusion reduction score than patients with a nonsegmental appearance (P less than .005). However, the correlation between segmental appearance and a favorable response to thrombolytic therapy was not strong enough to allow use of this appearance in the selection of patients for therapy.