Pendulum Movement of Contrast Agent Indicating to-and-fro Blood Flow Stasis in a Patient with Carotid Near-Occlusion.

In the present case, we directly visualized the pendulum movement of the contrast agent downstream of a carotid near-occlusion during digital subtraction angiography, suggesting the existence of "to-and-fro" stagnant flow created by the significant flow reduction and high back pressure from visible ophthalmic collaterals with blood stagnation distal to the stenosis. The pendular movement phenomenon represents a stagnation of blood that could be associated with an increased risk of thrombus formation and subsequent embolization to more distal arterial territories. This case may partially explain not only the embolic mechanism for stroke in carotid near-occlusion but the recent observation that collateral circulation through the ipsilateral ophthalmic artery is associated independently with an increased risk of the progression of carotid near-occlusion to complete occlusion.