Normal lung perfusion scan with extensive thromboembolic disease.

A 50-year-old woman with unexplained pulmonary hypertension had normal findings on six-view lung perfusion scan prior to open lung biopsy. The biopsy demonstrated old organized thrombi. The patient expired and autopsy disclosed extensive thromboembolic disease, both old and new. A six-view lung scan may not distinguish primary pulmonary hypertension from thromboembolic hypertension when diffuse symmetrical thrombi are present. Under such conditions, when invasive diagnostic procedures have an unacceptable morbidity, empiric anticoagulation should be considered.