Zones of increased perfusion (hot spots) on perfusion lung scans: correlation with pulmonary arteriograms

Perfusion lung scans are occasionally characterized by focal zones of apparent hyperperfusion ("hot spots"). To investigate the frequency and significance of this phenomenon, ventilation-perfusion lung scans and pulmonary arteriograms were reviewed in 72 patients who underwent both procedures for the evaluation of suspected pulmonary embolism. Hot spots were present in the scans of 13 patients and usually occupied less than one pulmonary segment. Most hot spots were detected within a region of atelectasis identified on chest radiographs (38%). A substantial number of the remaining hot spots were located in the lung adjacent to regions of embolus. In patients with massive embolus, hot spots actually represented normally preserved perfusion in the presence of globally reduced perfusion elsewhere.