Abstract
The Coronary Artery Bypass Grafting (CABG) has been established as one of the most effective treatments for the ischemic heart disease. Graft flow (blood flow in graft) measurement is used for the intraoperative assessment. However, graft flow is influenced by various factors that are unrelated to graft. Therefore, a method that only depends on the graft failure factors is required to improve the reliability of the intraoperative assessment. That method can be designed by using a mathematical model based on the dynamics characteristics of the vascular system underwent CABG. The purpose of this study is to develop a mathematical model of the vascular system underwent CABG and a method of the parameter identification for the intraoperative assessment. By regarding a bypassed vascular system as single circulatory loop, the mathematical model can be simplified. Parameters in the model represent the dynamics characteristics of the vascular system underwent CABG that can be used to the intraoperative assessment. Furthermore, the model can represent the influence of the contraction of the cardiac muscle by changing its parameters. In order to avoid the influence of the cardiac muscle during the identification process, we developed a method that limits identification to the diastolic phase. We verified developed model and method by simulating graft flow and identifying parameters in the model from simulated data with computer. As a result of the computer simulation, graft flow increased during the diastolic phase and backflow was observed. Parameters were identified with small error (maximum 3%), but only if the developed method was applied. The results showed the model could represent features of the vascular system underwent CABG and the identification method could avoid the influence of the cardiac muscle. We confirmed that the developed model was feasible for representing the dynamics characteristics of the vascular system underwent CABG and the developed method was appropriate to identify parameters in the model avoiding the influence of the cardiac muscle.
