On angiography, how can you differentiate thrombotic occlusion from embolic occlusion?

• A. Thrombotic occlusion is abrupt with no underlying disease; embolic occlusion occurs at diseased segments.
• B. Thrombotic occlusion often occurs at a diseased segment with underlying atherosclerosis; embolic occlusion is abrupt with minimal underlying disease and potential cardiac source.
• C. Embolic occlusion always occurs due to atrial fibrillation.
• D. Both occur with equal underlying disease.

Answer: (B)

On angiography the clue is how the blockage relates to existing vessel disease and how abruptly it appears. Thrombotic occlusion typically occurs at a segment with known atherosclerotic changes—the vessel shows underlying plaque, irregularity, or prior narrowing at or near the site. The thrombosis forms in situ on that diseased plaque, so you’re often seeing evidence of chronic disease in or around the occluded region.

Embolic occlusion, by contrast, is usually abrupt and occurs in a relatively normal-looking segment or with minimal underlying atherosclerosis. The blockage tends to originate from a cardiac or proximal arterial source and lodge suddenly, so the vessel beyond the occlusion can appear suddenly cut off without long-standing plaque changes at the site.

So the best differentiator is the pattern of disease at the occlusion: thrombotic events align with diseased, plaque-bearing segments, whereas embolic events present as sudden, pristine-appearing occlusions with a probable cardiac source.