Lung ventilation-perfusion scintigraphy in pulmonary embolism. Diagnostic specificity compared to pulmonary angiography.

In 53 patients with possible pulmonary embolism, pulmonary abnormalities of 133Xe ventilation and 99Tcm albumin microsphere perfusion scintigraphy were compared with absence or presence of pulmonary emboli documented by concurrent pulmonary angiography. It was found that patients with combined scintigraphy considered as unlikely for pulmonary embolism (ventilation defect larger than perfusion defect) or indicative of pulmonary embolism (ventilation defect smaller than perfusion defect) provide high diagnostic specificity. Patients with equal ventilation-perfusion abnormalities (possible pulmonary embolism) require further evaluation by pulmonary angiography to ascertain diagnosis. Importantly, diagnostic accuracy, using ventilation-perfusion scintigraphy and the quantified method of evaluation delineated, is preserved in patients with severe congestive heart failure.