The future development of medical devices is limited by the designer's ability to accurately test and evaluate a product before it is used on human patients. The pre-clinical test methods currently available for product research and development and physician training are limited to animal testing and simple plastic models. Unfortunately, neither model is an accurate simulation of human in vivo operating conditions or cardiovascular disease. Additionally, animal testing is very expensive, unfeasible for high-volume physician training and raises ethical considerations.
As an alternative means of testing and training, the Vascular Intervention Group of Guidant Corporation has developed a Synthetic Arterial Model (SAM) of human anatomy. The Guidant SAM simulates the human vascular system from the knee to neck but currently lacks several significant features of true in vivo conditions. The addition of the following features would improve the clinical realism of the synthetic model and aid in physician acceptance:
During the winter quarter, the team focused on establishing design specifications and generating concepts to incorporate these desired features into the SAM. A Harvard apparatus pump was chosen to create pulsatile flow through the arterial model. After modeling the vasculature as a RCR circuit, we determined the dominant factors affecting the pressure and flow rate within the SAM and tested our theories on a simplified arterial model. The team used a system of connectors and valves located at the distal ends of the aortic branch arteries to impose resistance to flow through the model and produce physiologic conditions.
Alongside the flow modeling, the team developed design concepts for the actuation of heart wall motion. In the spring quarter, we built a critical function prototype to demonstrate the possibility of producing biphasic heart motion using fluid-filled chambers. We also used this prototype to experiment with different configurations of the heart, aorta and pump. The team chose to decouple the heart and the arterial models by the using two separate pumps to drive the models and synchronizing their motion by means of an electronic control circuit. We then designed and manufactured a silicone prototype heart featuring a separate atrium and ventricle chambers that are alternately filled to produce biphasic heart wall motion.
Our flow model and beating heart design will be used by engineers at Guidant in the early stages of device design. The addition of a beating heart and physiologic pulsatile flow will give designers an improved understanding of the actual operating conditions a device will encounter in use. Providing this kind of feedback early in the design process can save time, money, and lives. The SAM model is also used as a marketing tool for physician training. The more clinically realistic the model, the more confidant physicians will feel about purchasing and using Guidant products.