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Design Evaluation

Our team feels that we have met the overall goal of the project; to improve the clinical realism of the SAM for Guidant designers.  We developed a simple system of distal valves to regulate pulsatile flow from a Harvard Apparatus pump to produce physiologic pressure and flow rates in target areas of the model.  We also designed and manufactured a prototype beating heart that displays dramatic biphasic motion.  We were able to use a manufacturing process similar to that currently used by Guidant technicians to manufacture the solid hearts used in the SAM.  Therefore, the interface between the heart and the coronary arteries (the critical point of focus in the SAM) remains largely the same.  We created a set of flexible molds to cast our prototype that can be used at Guidant to make additional heart prototypes in the future and continue the design process.  The wall thickness and inlet diameter of the ventricle chamber could be altered in the next heart iteration to produce more realistic expansion.

The original problem statement we received from Guidant (see Appendix) listed the following desired deliverables:

With the exception of the diaphragm motion, the team has developed solutions to incorporate all of the desired features into the synthetic model.  The diaphragm motion was designated a lower priority by our project sponsors because of their focus on the treatment of coronary artery disease.  Therefore, the team decided early in the winter quarter to focus our attention on the flow model and heart prototyping.  The flow regulation system and beating heart mechanism fulfill all of the physical requirements outlined in the project description.  The team used fluid-filled cavities to generate heart wall motion and moved the flow restriction valves outside of the field of view of a fluoroscope to ensure that all visible model components are transparent under fluoroscopy.  This allows medical devices operating inside model to be visualized.   At our sponsor's request, the heart prototype is slightly larger than the solid SAM heart to create more surface area for the coronary arteries.  The prototype heart will still fit inside the chest cavity of the phantom body. 

The introduction of a beating heart and physiologic pulsatile flow is extremely useful to device designers.  By incorporating these features into the SAM, designers can test the performance of devices under operating conditions in the early stages of product development without the expense of animal studies.  This early feedback can save time and money and produce safer, more effective medical devices.  Operating on a beating heart is one of the major challenges of minimally invasive cardiac surgery.  By providing device engineers and physicians with a clinically realistic training ground, this challenge can be met and new treatments for cardiovascular disease can be made possible.


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