The lack of blood flow filling at the plaque is an indication that the plaque is an unstable plaque and prone to dislodgement. The structure of the plaque is surface fiber cap, internal thrombus fibers, etc. Normally the surface fiber cap of the plaque is intact, covering the whole plaque, and the blood flow passes through the hard fiber cap surface. When the surface fibrous cap of the plaque is not intact, the blood flow is fast, there is a gap on the surface of the plaque, and the blood flow injects into this gap and enters into the interior of the plaque, resulting in the phenomenon seen on ultrasound as the plaque out of the blood flow filling defect. This is because blood flow through an unstable plaque will wash over the inside of the plaque, carrying away emboli, and will also tend to form blood clots due to eddy currents. When the blood flow filling defect at the plaque is found, it must be diagnosed in time and treated with oral anticoagulant and antiplatelet drugs under the guidance of professional doctors to avoid adverse consequences.