What is the characteristic feature of an arterial thrombus?

An arterial thrombus is characterized by the formation of Lines of Zahn, which are alternating layers of platelets and red blood cells that develop as blood flows through the artery. This layered appearance occurs because arterial blood flow is typically fast and laminar, allowing the components of blood—primarily platelets and fibrin— to be deposited in distinct layers. The presence of these lines indicates that the thrombus has formed in an environment of relatively high shear stress, typical of arterial circulation.

In contrast, the presence of only red blood cells would not accurately represent the composition of thrombi in arteries, where a significant number of platelets and fibrin are also involved. Similarly, a complete clot without layering suggests a more disorganized structure, which is more characteristic of venous thrombi, where stasis allows for less organized clot formation. The presence of fibrin only does not adequately describe arterial thrombi, as they contain a mixture of components, not just fibrin. Therefore, the formation of Lines of Zahn is the definitive feature that distinguishes arterial thrombus from other types of clots.