What is a characteristic finding of the Chiari network?

The correct answer highlights the characteristic finding of a Chiari network, which is indeed a web-like structure located in the right atrium. The Chiari network is a remnant of embryonic development, representing an incomplete resorption of the right sinus venosus. It appears as fine, filamentous structures that can be visualized during echocardiographic imaging.

This web-like appearance can sometimes mimic other cardiac structures or pathologies, but its location in the right atrium is key to identifying it correctly. Understanding this characteristic is important for differentiating it from other possible findings during an echocardiogram.

The other options present structures or findings that do not correctly describe the Chiari network. A fixed position in the left atrium refers to a different anatomical structure, while a mobile structure in the left ventricle does not pertain to the Chiari network at all. Lastly, describing a large mass in the aorta inaccurately reflects the nature and location of the Chiari network's findings.