Adult Echocardiography Practice Exam

The correct answer identifies arterial thrombus as the least likely source of right atrial thrombus. This is because arterial thrombi typically originate from the left side of the heart, particularly in the presence of conditions such as atrial fibrillation, myocardial infarction, or other forms of cardiac dysfunction where blood flow may stagnate. These thrombi usually travel to the systemic circulation rather than the venous return pathway that leads to the right atrium.

On the other hand, venous thrombus formations, commonly found in conditions like deep vein thrombosis (DVT), can lead to thrombus migration through the right heart, particularly if they enter the pulmonary circulation. Catheters can cause turbulence and damage to the endothelium, which increases the risk of thrombus formation in the right atrium, making them a likely source. Similarly, pacer wires can induce localized trauma and facilitate thrombus formation in the right atrial area.