Pulmonary Embolism

Gabriel Soudry, MD
J Stevan Nagel, MD

June 28, 1994

Presentation

Given the clinical picture of right heart strain in the presence of massive pulmonary embolism, the patient was treated with tissue plasminogen activator (TPA) at the regimen of 100 mg continuous infusion over 3 hours, then was switched to intravenous heparin and eventually begun on oral warfarin sodium (Coumadin). One week later, a second perfusion scan showed marked decrease in the perfusion defects, and on a repeat echocardiogram the systolic pulmonary pressure was in the range of 40 mm Hg.

Imaging Findings

On initial perfusion lung scan, a segmental perfusion defect involving the anterior segment of the right upper lobe is visible (arrows). In addition, a number of subsegmental perfusion defects are present in the right lower lobe, the left upper lobe, the lingula, and the left lower lobe.

These defects are mismatched in the ventilation study.

Findings are consistent with a high probability for pulmonary embolism.

A follow-up perfusion lung scan done one week after treatment with TPA shows major improvement in the perfusion of both lungs. Small residual perfusion defects (arrows) involving the left apex and the right lower lobe remain.

Diagnosis

Discussion

In 1993, Goldhaber et al [2] pursued these findings with a randomized protocol:

Hemodynamically stable patients were randomized to recombinant tissue plasminogen activator (alteplase, rt-PA) 100 mg over 2 hours followed by intravenous heparin (46 patients) or to heparin alone (55 patients). Right-ventricular wall motion was assessed qualitatively, and right-ventricular end-diastolic area was estimated by planimetry from echocardiograms at baseline and at 3 and 24 hours. Pulmonary perfusion scans were obtained at baseline and 24 hours. In 39% of rt-PA patients but in only 17% of heparin alone patients, right-ventricular wall motion at 24 hours had improved from baseline and in 2% and 17%, respectively, it worsened (p=.005). The rt-PA patients also had a significant decrease in right-ventricular end-diastolic area during the 24 hours after randomization and a significant absolute improvement in pulmonary perfusion (14.6% vs. 1.5%). No clinical episodes of recurrent pulmonary embolism were noted among rt-PA patients, but 2 fatal and 3 nonfatal clinically suspected recurrent embolic episodes occurred within 14 days in patients randomized to heparin alone.

The authors concluded that rt-PA rapidly improves right-ventricular function and pulmonary perfusion among patients with PE and may lead to a lower rate of adverse clinical outcomes.

References

2. Goldhaber SZ, Haire WD, Feldstein ML, Miller M, Toltzis R, Smith JL, et al. Alteplase versus heparin in acute pulmonary embolism: Randomized trial assessing right ventricular function and pulmonary perfusion. Lancet 1993; 341: 507-11.

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