Organised chronic clot looks different from acute clot: eccentric wall-adherent thrombus, webs and bands, abrupt narrowing and post-stenotic dilatation, mosaic perfusion and bronchial artery collaterals — findings that mean referral for endarterectomy or angioplasty.
Orient first
- Acute emboli are central in the lumen with an acute angle; chronic thrombus is eccentric with an obtuse angle and may calcify.
- V/Q scintigraphy is the screening test of choice — more sensitive than CTPA for CTEPH (verify guideline).
- Enlarged bronchial arteries and mosaic attenuation support chronicity.
Acquire the study
- CT pulmonary angiography with thin sections, MIP and multiplanar reformats; lung window; V/Q scan as screening.
The manoeuvre
- Pulmonary arteries on the arterial phase: eccentric thrombus, webs, bands, abrupt cut-offs, post-stenotic dilatation.
- Main pulmonary artery diameter in mm; right ventricle size and septal flattening.
- Lung window: mosaic attenuation with small vessels in the lucent areas.
- Bronchial artery collaterals (> 2 mm) on the arterial phase.
- Peripheral scars and infarct sequelae.
What confirms it
- Chronic thromboembolic changes with pulmonary hypertension on right heart catheterisation after ≥ 3 months of anticoagulation.
What licenses you to exclude it
- A normal V/Q scan essentially excludes CTEPH.
The classic misread
- Reporting chronic webs as "no acute PE" without mentioning them.