Deformationally dependent fluid transport properties of porcine coronary arteries based on location in the coronary vasculature

Abstract

Objective: Understanding coronary artery mass transport allows researchers to better comprehend how drugs or proteins move through, and deposit into, the arterial wall. Characterizing how the convective component of transport changes based on arterial location could be useful to better understand how molecules distribute in different locations in the coronary vasculature.

Methods and results: We measured the mechanical properties and wall fluid flux transport properties of de-endothelialized (similar to post-stenting or angioplasty) left anterior descending (LADC) and right (RC) porcine coronary arteries along their arterial lengths. Multiphoton microscopy was used to determine microstructural differences. Proximal LADC regions had a higher circumferential stiffness than all other regions. Permeability decreased by 198% in the LADC distal region compared to other LADC regions. The RC artery showed a decrease of 46.9% from the proximal to middle region, and 51.7% from the middle to distal regions. The porosity increased in the intima between pressure states, without differences through the remainder of the arterial thickness.

Conclusions: We showed that the permeabilities and mechanical properties do vary in the coronary vasculature. With variations in mechanical properties, overexpansion of stents can occur more easily while variations in permeability may lead to altered transport based on location.

Fig. 1

(A) Histological cross section (scale bar=0.25 mm). (B) Dimensions of the vessel segments. (C) Axial prestrain measured with sutures between marker points. (D) Opening angle between locations (p=NS). Bars p<0.05.

Fig. 2

Top: Axial maximum tangential modulus at 70 mmHg. Bottom: Circumferential maximum tangential modulus at in situ axial stretch. Bars indicate pair-wise significance to p<0.05.

Fig. 3

Top: Volume flow rate for each vessel section at each test pressure. Middle: Permeability from the optimization routine for each section. Bottom: Permeability (averaged for all samples and pressures) for each section. Bars p<0.05.

Fig. 4

Top row: Representative collagen orientation at 40% through the vessel wall (from the lumen) for a left proximal region. Note the uncrimping from 0 and 70 to 130 mmHg. Middle row: Representative elastin orientation for the same vessel at the intima. The white arrows are indicative of elastin bundles that exhibited the majority of the void ratio changes. Note how the image at 0 mmHg has elastin folding as indicated by the bright and dark bands in the elastin macrobundles. Bottom row: Thresholding of the elastin images showing the increase in void. Scale bar is 50 μm.

Fig. 5

Top: Void ratio variation through the vessel thickness of a representative proximal LAD. Middle: Void ratio of just the intima at each pressure for the different segments. Bottom: Average void ratio through the entire thickness for each of the segments.