A diagnostic strategy using ventilation-perfusion studies in patients suspect for pulmonary embolism.

A diagnostic strategy for the assessment of pulmonary embolism was developed using results of scintigraphic examinations in over 100 patients, all of whom had angiographic assessment of their pulmonary vasculature and nearly 50% of whom had combined ventilation-perfusion studies. The highest-probability estimate of pulmonary embolism that could be made in the absence of a ventilation study was 80%. When a ventilation study was added, this probability increased to nearly 100% for patients with multiple large perfusion defects and normal ventilation. For smaller defects with normal ventilation, the probability of pulmonary embolism was only 50%. For perfusion defects corresponding to known radiographic abnormalities, the probability of pulmonary embolism was 25%.