The goal of our project is to deliver to Guidant an improved version of their Synthetic Arterial Model. The original project description included the introduction of physiologically accurate pulsatile flow, heart wall motion and respiratory motion. However, due to the complexity of each desired feature, the team consulted with the project sponsors and decided to focus on the first two deliverables:
· Pulsatile flow at physiologic flow rate and pressure
· Heart wall motion producing coronary artery displacement
During the winter quarter, the team developed an analytical model of flow through the arterial model to gain insight into the regulation of pressure and flow rate through the SAM. Then we began to experimentally develop a flow regulation system using equipment available in Dr. Charles Taylor's lab. This required developing a system of distal valves at the vessel outlets to regulate flow through the vasculature as well as connecting the model to a data acquisition system to measure pressure and flow velocity. The preliminary experimental data was very encouraging; we were able create physiologic pressures inside the aortic model. In addition to flow modeling, the team began to brainstorming mechanisms to produce heart wall motion. We then refined and evaluated alternative heart designs and presented the most promising ideas to our Guidant sponsors.
Based on the positive sponsor response to the beating heart designs, the team built a critical function prototype in the spring to demonstrate the ability to produce biphasic motion using expandable, fluid-filled chambers. We also explored alternative system configurations of the pump, heart prototype and arterial model. Ultimately, we decided to decouple the beating heart and the arterial model by using two pumps. This required developing an electronic control circuit to synchronize the two independent systems.
Finally, we refined the aortic model by building converging networks on the branch vessels, placing distal resistors at the network outlets and repairing leaks in the model from the manufacturing process in order to determine the final valve setting recommendations. At the same time, we created a SolidWorks model of the beating heart prototype and then had the model parts 3D-printed. These parts were then used to create flexible molds and cast the final heart prototype at the Guidant facility in Santa Clara. While the heart models were being fabricated, the team constructed and tested the control circuit to synchronize the heart and the aortic model. The final step was to integrate the three project components; the arterial model, the beating heart and the control circuit.