What is the result of abnormal vq scan if pulmonary embolus?

VQ scan...: There are 2 parts to a VQ scan: ventilation and perfusion. If there is a clot present, the scan will show that areas of the lung are being ventilated but not perfused. In other words, the clot is preventing blood flow in an area that is being ventilated. This is the classic finding for a pe in a VQ scan but not all scans are that clear-cut so additional testing is sometimes needed.

Particular pattern: If your chest radiograph is normal and VQ scan shows normal ventilation but perfusion defects usually means pulmonary embolism.If consolidation is on chest xray, then mismatches between areas of normal ventilation and areas of decreased perfusion are looked for to suspect pulmonary embolism.Scans are graded as to size of defects and multiplicity. Asthma and COPD can complicate interpretation.

Perfusion defect: Pulmonary emboli usually come from blood clots originating from the legs, pelvis or arms. These clots will be trapped into the pulmonary vascular bed, creating defects on the perfusion part of the scan. However, in acute emboli, ventilation is not affected so there is a mismatch between the ventilation and the perfusion defects. In chronic emboli however, ventilation may be affected as well.