Radiology, Vol 187, 51-54, Copyright © 1993 by Radiological Society of North America
Pulmonary embolism: increased ventilation in areas of decreased perfusion
RT Go, WJ MacIntyre, MA Meziane, GK Lammert, SA Cook and DR Neumann
Department of Nuclear Medicine, Cleveland Clinic Foundation, OH 44195- 5074.
An abnormal finding that is considered characteristic of large or extensive
pulmonary embolism has been observed on ventilation-perfusion (V-P) lung
scans. This observation is a regional area of increased ventilation
radioactivity in the embolized region of the lung that is more than the
normal ventilation radioactivity in the adjacent or contralateral normally
perfused lung. It has been designated the "enhanced V-P mismatch sign."
This sign was noted in 15 cases among approximately 700 routine V-P lung
scans interpreted by a nuclear radiologist. Of these, large or extensive
emboli were confirmed in only 10 cases, nine by means of angiography and
one by means of autopsy studies. The remaining five cases demonstrated
clinical correlation only and are not included in this report. Of the 10
confirmed cases with enhanced V-P mismatch sign, increased ventilation
radioactivity involved unilateral lung distribution in five and zonal or
lobar distribution in five. The Westermark sign was seen in only seven of
the 10 cases. It is hoped that this observation will prove useful in the
diagnosis of large or extensive pulmonary emboli.
