"High probability" perfusion lung scans in pulmonary venoocclusive disease

"High-probability" ventilation/perfusion (((V) over dot/(Q) over dot)) lung scans generally indicate proximal pulmonary arterial occlusion by thromboe mboli or, rarely, other processes such as tumors, fibrosing mediastinitis, or vasculitis. In this report we describe three patients with high probabil ity (V) over dot/(Q) over dot scans in whom pulmonary angiography failed to demonstrate arterial occlusion. All three patients were determined to have pulmonary venoocclusive disease (PVOD). In two patients, a tissue diagnosi s of PVOD was made, in one case with explanted tissue taken after a success ful heart-lung transplant and in the other case with tissue taken at autops y. PVOD in the third patient was diagnosed with pulmonary venography. A pot ential explanation for the discrepancy between perfusion lung scan and pulm onary angiographic findings in PVOD is discussed.