Diagnosis of pulmonary embolism. A correlative study of the clinical, scan, and angiographic findings.

Seventy-one patients with suspected pulmonary embolism had both pulmonary scans and angiograms. Clinically it was impossible to predict the absence or presence of subsequent angiographic evidence of pulmonary embolism in the individual patient. In 24 patients the scans showed defects that were believed to indicate a high probability of pulmonary embolism-namely, perfusion defects that corresponded to specific anatomical segments of the lung together with normal chest radiographs or radiographs suggestive of pulmonary embolism. Specific angiographic evidence of pulmonary embolism was found in 18 (75%) of these patients. Diffuse, patchy, and non-segmental perfusion defects were seen in 28 patients. Only seven (25%) of this group had angiographic abnormalities specific for embolism. In 12 patients with normal lung scans none showed subsequent evidence of embolism by angiography. It is concluded firstly that lung scanning is a sensitive screening procedure for pulmonary embolism and, secondly, that segmental perfusion defects are highly suggestive of pulmonary embolism.