DETECTION OF PULMONARY-EMBOLISM IN PATIENTS WITH UNRESOLVED CLINICAL AND SCINTIGRAPHIC DIAGNOSIS - HELICAL CT VERSUS ANGIOGRAPHY

OBJECTIVE. This study was designed to prospectively compare helical CT with pulmonary angiography in the detection of pulmonary embolism in patients with an unresolved clinical and scintigraphic diagnosis. SUBJ ECTS AND METHODS. Twenty patients with an unresolved suspicion of pulm onary embolism were evaluated with contrast-enhanced helical CT and wi th selective pulmonary angiography. An average of 11 hr separated the two studies. The CT scans were obtained during one 24-sec or two 12-se c breath-holds. CT scans were interpreted without knowledge of the res ults of scintigraphy or angiography. Selective pulmonary angiograms we re obtained with knowledge of the findings on the ventilation/perfusio n scan only. The sensitivity and specificity of CT were compared with those of angiography for central Vessels (segmental and larger) only a nd for all vessels. RESULTS. Eleven of the 20 patients had proved pulm onary embolism (seven in central vessels and four in subsegmental vess els only). When only central vessels were analyzed, CT sensitivity was 86%, specificity was 92%, and the likelihood ratio was 10.7. However, when subsegmental vessels were included, CT results were 63%, 89%, an d 5.7, respectively. CONCLUSION. In our subset of patients, helical CT was only 63% sensitive. Subsegmental emboli are difficult to diagnose . Pulmonary angiography remains the study of choice. CT has a limited role in the evaluation of acute pulmonary embolism.