In spite of non-thrombogenic coating, the patency of smalldiameter vascular prosthesises not determined the kinetic property of natural or synthetic vascular grafts is considered one of the most important factors for patency, but accurate measurement of this property is an elusive goal. In order to measure the vascular kinetic property
in vivo, we developed a novel contact-type vascular shape sensor. The displacement of vascular shape is transmitted to slender probes and is sensed by eddy current sensors outside the body. Another feature of this sensor is the precise measurement in two dimensions using two pairs of probes and sensors. We simultaneously measured blood pressure and a cross section area of the porcine carotid artery
in vivo using this device. In addition to the native artery, an interposed femoral vein graft and expanded polytetrafuluoroethylene (ePTFE) graft were assessed. When the pressure / sectional area ratio for the vessels was plotted, hysteresis loops reflecting viscoelasticity were observed. Elasticity was assessed by compliance, so distensibility was calculated from systolic / diastolic pressure and the sectional area gradient. Viscosity was estimated as the area within the hysteresis loop. Results showed distensibility to be 19.6×10
-4 mmHg
-1 in the artery, 8.9×10
-4 mmHg
-1 in the venous graft, and 2.2×10
-4 mmHg
-1 in the ePTFE graft. Areas within the loop were 0.114 mmHg for the artery, 0.037 mmHg for the venou graft, 0.062 mmHg for the ePTFE graft. Thus, the native artery showed not only higher compliance but also higher viscosity than the natural or synthetic vascular grafts. We succeeded in assessing vascular viscoelasiticity quantitatively using the sensor.
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