A prospective,comparative study of ventilation-perfusion scintigraphy and clinical evaluation versus digital subtraction angiography in acute pulmonary thromboembolism

Patients with symptoms of acute pulmonary thromboembolism (APE) of short duration were investigated with digital subtraction angiography (DSA) and ventilation/perfusion lung scintigraphy (V/Q scan), and a standardised clinical evaluation was performed. Forty-six angiograms (96%) were diagnostic at the segmental level and were used as reference. In all V/Q scans classified as normal or of high probability for APE, a complete agreement with DSA was found. In scan categories with low or intermediate probability, where the incidence of APE was 32%, there was considerable inter-observer disagreement. Clinical assessment alone was of limited value, but in patients with low clinical suspicion no APE was found. The results indicate that normal and high probability V/Q scans are very reliable for excluding and identifying APE, respectively, but also that fairly large APE cannot be diagnosed with lung scanning. Subdivision of V/Q scans into more than three categories (normal, high probability and inconclusive) seems to be of no practical value. Using a pulsed sequence technique, high frame rate and central injection, DSA is a valuable clinical tool for diagnosing APE down to the segmental level.Correspondence to: B. Hedlund