Ventilation–perfusion mismatch: scintigraphy

Mismatch means reduced perfusion in a region with relatively preserved ventilation; its distribution matters for interpretation.

Check orientation, technique and quality; compare the same regions on ventilation and perfusion using all available projections.

A shows relatively uniform ventilation; B contains several regional defects. This pair represents only part of the complete examination.

Segmental vascular mismatch suggests embolic obstruction. The source reports a patient with already documented pulmonary embolism.

Artefacts, lung disease and vascular abnormalities may complicate interpretation. Matched ventilation–perfusion defects have a different meaning.

Integrate clinical probability, symptoms, risk factors and chest imaging; abnormalities on an isolated view do not establish the diagnosis alone.

Shock, hypotension or respiratory distress requires an urgent pathway adapted to stability; do not await routine scintigraphy.

Do not automatically apply validated SPECT thresholds to these planar views. Scintigraphy does not directly show the thrombus.

Compare ventilation and perfusion, verify vascular distribution and review the complete study; distinguish learning the sign from treatment decisions.

• Bajc et al. EANM guideline for ventilation/perfusion SPECT for diagnosis of pulmonary embolism and beyond (2019) ↗
• Westgate and FitzGerald. Pulmonary Embolism in a Woman Taking Oral Contraceptives and Valdecoxib (2005), Figure 1 ↗

Documentary review: 2026-10-15