Study objective: To assess the frequency of a normal perfusion lung scan in a consecutive series of patients with clinically suspected pulmonary embolism, to determine the complication risk of heparin therapy in those patients treated while awaiting lung scanning, and to evaluate the clinical validity of withholding anticoagulant therapy in patients with a normal lung scan result.
Design: Prospective cohort.
Setting: Two teaching hospitals in Amsterdam, the Netherlands.
Patients: Consecutive inpatients and outpatients referred for clinically suspected pulmonary embolism who underwent lung scintigraphy.
Interventions: Initiation of intravenous heparin therapy before lung scanning was left to the discretion of the attending physician. Anticoagulant therapy was withheld or withdrawn in patients with a normal lung scan. Patients were followed-up for 6 months.
Measurements and results: A normal perfusion scan was obtained in 114 of 412 consecutive patients (28%; 95% confidence interval [CI] 23 to 32%). Major bleeding complications occurred in 2 of 30 patients (6.7%; 95% CI 0.8 to 22.1%) in whom heparin was administered while awaiting lung scintigraphy. One patient was lost to follow-up, and venous thromboembolism (0%; 95% CI 0 to 3.2%) did not develop in the remaining 113 patients.
Conclusions: In a substantial proportion of patients with clinically suspected pulmonary embolism (28%) the diagnosis is excluded by lung scintigraphy. The test should be performed as soon as feasible to prevent unnecessary hospitalization and bleeding complications. Long-term anticoagulant therapy can be safely withheld in symptomatic patients with a normal perfusion lung scan.