Abstract
Ischemia is a main cause for many cardiovascular diseases, and can be caused by increases in the vascular resistance at the artery (Ra), as a result of a decreased artery diameter. Although Ra is useful for cardiovascular diagnoses, its evaluation was difficult in the past because Ra cannot be measured directly. The purpose of this study is to construct and verify a method for the quantitative evaluation of Ra for the future application of cardiovascular diagnosis. Ra cannot be measured directly; therefore, we developed a method for identifying Ra using the Aortic blood-pressure (AoP) and the blood-flow volume (Flow), which are measurable. In this method, we use a mathematical model that represents the characteristics of the vascular dynamics. Here, Ra is a parameter in the model, and is identified using the least square method applied to the measured AoP and Flow volume. Thus, Ra can be evaluated quantitatively as a reflection of the actual vascular resistance at the artery. Through animal experiments on seven pigs, we verified that Ra reflects the actual vascular resistance at the artery. First, the femoral arteries were exposed in order to install a flow-meter probe and a catheter for AoP measurement. Next, the femoral artery near the flow-meter probe was intentionally stenosed. As a result, the identified value of Ra significantly increased (P<0.05) by a factor of 3.58 (from 0.233±0.151 to 0.836±0.654 [mmHg min/ml] ). This result indicates that the identified resistance, Ra, reflected the vascular resistance at the artery. In conclusion, we showed it is possible to realize an evaluation method for vascular resistance at artery that can improve cardiovascular diagnoses.
