Comparison of Hemodynamic Energy between Expanded Polytetrafluoroethylene and Dacron Artificial Vessels

Abstract

Background: Artificial grafts such as polyethylene terephthalate (Dacron) and expanded polytetrafluoroethylene (ePTFE) are used for various cardiovascular surgical procedures. The compliance properties of prosthetic grafts could affect hemodynamic energy, which can be measured using the energy-equivalent pressure (EEP) and surplus hemodynamic energy (SHE). We investigated changes in the hemodynamic energy of prosthetic grafts.

Methods: In a simulation test, the changes in EEP for these grafts were estimated using COMSOL MULTIPHYSICS. The Young modulus, Poisson ratio, and density were used to analyze the grafts' material properties, and pre- and post-graft EEP values were obtained by computing the product of the pressure and velocity. In an in vivo study, Dacron and ePTFE grafts were anastomosed in an end-to-side fashion on the descending thoracic aorta of swine. The pulsatile pump flow was fixed at 2 L/min. Real-time flow and pressure were measured at the distal part of each graft, while clamping the other graft and the descending thoracic aorta. EEP and SHE were calculated and compared.

Results: In the simulation test, the mean arterial pressure decreased by 39% for all simulations. EEP decreased by 42% for both grafts, and by around 55% for the native blood vessels after grafting. The in vivo test showed no significant difference between both grafts in terms of EEP and SHE.

Conclusion: The post-graft hemodynamic energy was not different between the Dacron and ePTFE grafts. Artificial grafts are less compliant than native blood vessels; however, they can deliver pulsatile blood flow and hemodynamic energy without any significant energy loss.

Keywords: Artificial blood vessles; Energy; Hemodynamics; Pulse.

Fig. 1

Geometry for simulation and EEP distribution for graft and blood vessels. The inlet and the outlet were set at y=0 and y=300. (A, B) The blood vessel is closed by the clip and the graft is open. The blood flows through the graft. (C, D) The graft is closed and the blood vessel is open. The blood flows through the blood vessel. (E) Square function (SQ) and (F) pressure setting for 30 seconds at the inlet and outlet. Inlet pressure (red graph) varies from 80 to 120 mm Hg and outlet pressure (black graph) varies from 80 to 100 mm Hg.

Fig. 2

Deformation of the blood vessel by stress from blood pressure as time passes. Deformations of the blood vessel at 0.5, 3, 5, 10, 20, and 30 seconds are displayed for when (A–F) the blood vessel is closed and (G–L) the graft is closed.

Fig. 3

Flow meter probe and arterial pressure line were placed on the descending aorta at the juxta-distal anastomosis site to measure mean arterial flow and mean arterial pressure. * indicates flow meter and ★ indicates pressure line.

Fig. 4

(A) The hemodynamic energy of the ePTFE graft was measured with the Dacron graft and descending thoracic aorta blocked with a clamp. (B) The hemodynamic energy of the Dacron graft was measured with the ePTFE graft and descending thoracic aorta blocked with a clamp. ePTFE, expended polytetrafluoroethylene; Dacron, polyethylene terephthalate.