Pulmonary perfusion after rt-PA therapy for acute embolism: early improvement assessed with segmental perfusion scanning.

To determine if pulmonary perfusion was improved in acute pulmonary embolism after therapy with recombinant human tissue-type plasminogen activator (rt-PA), lung scans were obtained before and a mean of 22 hours after therapy in 19 patients. The posttherapy lung scans were compared with baseline, pretherapy scans with use of two semiquantitative methods--an anteroposterior view method, similar to that used in the Urokinase Pulmonary Embolism Trial, and a segmental method that emphasized pulmonary anatomy. There was an improvement in the defect score from 0.35 to 0.14 (P less than .01) when the anteroposterior view method was used and from 0.37 to 0.16 (P less than .01) when the segmental method was used. These encouraging results in the early posttherapy period suggest that rt-PA is especially effective in improving regional perfusion after pulmonary embolism and that a larger controlled trial of therapy with rt-PA for acute pulmonary embolism should be performed. Scoring lung scans with a segmental method is feasible and appropriate for present-day lung scan technique and should be considered in future studies.