Coronary artery pseudothrombus: angiographic filling defects caused by competitive collateral flow.

Two cases are described of intraluminal coronary artery filling defects resembling thrombus caused by nonopacified collateral blood flow mixing with injected contrast just distal to a severe coronary artery stenosis. The term pseudothrombus is ascribed to this appearance to emphasize this differential diagnosis of intraluminal filling defects.