<p>Venoarterial extracorporeal membrane oxygenation (VA ECMO) is an advanced life-saving therapy for patients with severe cardiopulmonary failure. Understanding the performance of the drainage cannula is critical to minimizing complications such as thrombosis formation, platelet activation, and circuit failure. This study utilizes computational fluid dynamics (CFD) to analyze the flow characteristics within the drainage cannula under both normal vessel conditions and vessel collapse scenarios. The simulations focus on flow behavior, shear stress distribution, and regions prone to platelet accumulation and thrombus formation. In the collapsed vessel scenario, significant alterations in flow patterns were observed, including elevated shear stress, increased velocities near the cannula tip, and flow redistribution along the cannula holes. While the collapsed condition exhibited higher mechanical platelet activation due to increased shear forces, improved washout resulted in a lower accumulation of activated platelets compared to the normal condition. Additionally, thrombosis-prone regions were identified, particularly near the cannula tip for normal drainage condition. The findings of this study highlight the fluid flow mechanisms contributing to thrombosis risk in the drainage cannula during VA ECMO. These insights can inform cannula design improvements to minimize thrombosis and optimize ECMO performance.</p>