Hemodynamically motivated choice of patch angioplasty for the performance of carotid endarterectomy

Abstract

Patch angioplasty is the most common technique used for the performance of carotid endarterectomy. A large number of materials are available, but little is known to aid the surgeon in choosing a patch while caring for a patient with carotid disease. The objective of this study was to investigate biomechanics of the carotid artery (CA) repaired with patch angioplasty, study the influence of patch width and location of closure on hemodynamics, and to select the optimal patch material from those commonly used. For this purpose, a mathematical model was built that accounts for fluid-structure interaction, three-dimensional arterial geometry, non-linear anisotropic mechanical properties, non-Newtonian flow and in vivo boundary conditions. This model was used to study disease-related mechanical factors in the arterial wall and blood flow for different types of patch angioplasty. Analysis indicated that patch closures performed with autologous vein and bovine pericardium were hemodynamically superior to carotid endarterectomy with synthetic patch angioplasty (polytetrafluoroethylene, Dacron) in terms of restenosis potential. Width of the patch and location of arteriotomy were found to be of paramount importance, with narrow patches being superior to wide patches, and anterior arteriotomy being superior to the lateral arteriotomy. These data can aid vascular surgeons in their selection of patch angioplasty technique and material for the care of patients undergoing open CA repair.

FIGURE 1.

Scheme of the carotid artery bifurcation showing carotid bulb, apex and conventions on orientations (anterior–posterior, lateral-medial) for common (CCA), internal (ICA) and external (ECA) carotid arteries.

FIGURE 2.

Variation of axial velocity along the anterior–posterior and lateral-medial directions of the lumen (top) and 3D axial velocity profiles assigned to the outlets of the ICA and ECA (bottom). Figures are plotted for peak systole (time of maximum flow, red graph) and late diastole (end of cardiac cycle, blue graph).

FIGURE 3.

Surgical suture incorporated into the model of CEA with anterior patch angioplasty.

FIGURE 4.

Temporal mean WSS (in Pa) contours for anterior and lateral views of the carotid artery repaired with different patch angioplasties. Logarithmic scale is in use. Low WSS (<0.4 Pa) is outlined and represented by shades of dark blue. Stars indicate the locations of WSS measurements used to produce graphs on Fig. 5. Wall of the artery is removed for better visualization.

FIGURE 5.

Temporal variations of WSS (in Pa) in the center of the carotid bulb (left, location is marked with the hollow star on Fig. 4) and in the distal ICA 3 cm off the carotid apex (right, location is marked with the solid black star on Fig. 4). Values of WSS lower than 0.4 Pa are thought to stimulate the atherogenic phenotype while values higher than 1.5 Pa are reported to induce endothelial quiescence.

FIGURE 6.

Contours of OSI (left) and endothelial platelet residence time $T_{\text{r}}$ (right) for carotid artery repaired with different types of patch angioplasty. The wall of the artery is removed for better visualization of the flow.

FIGURE 7.

VS at peak systole (left) and late diastole (right) for carotid artery repaired with different types of patch angioplasty. VSs are colored with scalar shear rate (s⁻¹) and were educed with ${\lambda }_2$-method of Jeong and Hussain using threshold value of ${\lambda }_2=-20{\text{s}}^{-2}$. Wall of the artery is removed for better visualization.

FIGURE 8.

CS for anterior and lateral views of carotid artery repaired with different types of patch angioplasty.

FIGURE 9.

ES at peak systole for anterior and lateral views of carotid artery repaired with different types of patch angioplasty. Common logarithm of ES is plotted to emphasize the differences between high and low values.

FIGURE 10.

Abnormality factor (%) calculated for carotid artery repaired with different types of patch angioplasty. Smaller values represent hemodynamically better results.