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Flow and wall shear stress in end-to-side and side-to-side anastomosis of venous coronary artery bypass grafts.

Frauenfelder T, Boutsianis E, Schertler T, Husmann L, Leschka S, Poulikakos D, Marincek B, Alkadhi H - Biomed Eng Online (2007)

Bottom Line: CFD analysis based on in-vivo CT coronary angiography data was feasible in both patients.In contrast, the highest WSS values of the side-to-side anastomosis configuration were found in stenotic vessel segments and not in the close vicinity of the anastomosis.Flow stagnation zones were found in end-to-side but not in side-to-side anastomosis, the latter also demonstrating a smoother stream division throughout the cardiac cycle.

View Article: PubMed Central - HTML - PubMed

Affiliation: Institute of Diagnostic Radiology, University Hospital Zurich, Zurich, Switzerland. thomas.frauenfelder@usz.ch

ABSTRACT

Purpose: Coronary artery bypass graft (CABG) surgery represents the standard treatment of advanced coronary artery disease. Two major types of anastomosis exist to connect the graft to the coronary artery, i.e., by using an end-to-side or a side-to-side anastomosis. There is still controversy because of the differences in the patency rates of the two types of anastomosis. The purpose of this paper is to non-invasively quantify hemodynamic parameters, such as mass flow and wall shear stress (WSS), in end-to-side and side-to-side anastomoses of patients with CABG using computational fluid dynamics (CFD).

Methods: One patient with saphenous CABG and end-to-side anastomosis and one patient with saphenous CABG and side-to-side anastomosis underwent 16-detector row computed tomography (CT). Geometric models of coronary arteries and bypasses were reconstructed for CFD analysis. Blood flow was considered pulsatile, laminar, incompressible and Newtonian. Peri-anastomotic mass flow and WSS were quantified and flow patterns visualized.

Results: CFD analysis based on in-vivo CT coronary angiography data was feasible in both patients. For both types of CABG, flow patterns were characterized by a retrograde flow into the native coronary artery. WSS variations were found in both anastomoses types, with highest WSS values at the heel and lowest WSS values at the floor of the end-to-side anastomosis. In contrast, the highest WSS values of the side-to-side anastomosis configuration were found in stenotic vessel segments and not in the close vicinity of the anastomosis. Flow stagnation zones were found in end-to-side but not in side-to-side anastomosis, the latter also demonstrating a smoother stream division throughout the cardiac cycle.

Conclusion: CFD analysis of venous CABG based on in-vivo CT datasets in patients was feasible producing qualitative and quantitative information on mass flow and WSS. Differences were found between the two types of anastomosis warranting further systematic application of the presented methodology on multiple patient datasets.

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Shear stress distribution in end-to-side anastomosis. Color-coded wall shear stress (Pa) and corresponding values plotted against the distance (mm) from the green to the red point at timestep 20 on three different paths upon the walls of the end-to-side anastomosis.
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Figure 5: Shear stress distribution in end-to-side anastomosis. Color-coded wall shear stress (Pa) and corresponding values plotted against the distance (mm) from the green to the red point at timestep 20 on three different paths upon the walls of the end-to-side anastomosis.

Mentions: The WSS characterizes the tangential fluid forces that act on the vessel wall. The changes of WSS throughout the cardiac cycle showed a correlation with flow velocities, with WSS forces being high when blood flow was fast. Near the end-to-side anastomosis the maximum WSS spatial variation was approximately 1.5 Pa (Figures 4 and 5). The WSS ranged from 0.01 Pa at minimum inflow to approximately 2.0 Pa at maximum inflow. In the perianastomotic region, the time averaged WSS was 0.36 Pa. An area of high WSS was found during systole at the heel of the anastomosis. The lowest WSS was found in the RCA at the location where blood from the CABG hit the wall and was confronted by the flow coming from the native coronary artery. This formed a stagnation point at the impact site around which the bypass stream splits, as depicted by the flow streamlines in Figure 4. It is also shown here that backflow into the RCA persisted during most of the cardiac cycle. The highest WSS values were found during mid-systole (timestep 20) and were located at the heel of the anastomosis and at the side of a nearby clip that was placed during surgery (Figure 5). At the opposite side of the anastomosis the WSS values were lower, due to the presence of the stagnation zone.


Flow and wall shear stress in end-to-side and side-to-side anastomosis of venous coronary artery bypass grafts.

Frauenfelder T, Boutsianis E, Schertler T, Husmann L, Leschka S, Poulikakos D, Marincek B, Alkadhi H - Biomed Eng Online (2007)

Shear stress distribution in end-to-side anastomosis. Color-coded wall shear stress (Pa) and corresponding values plotted against the distance (mm) from the green to the red point at timestep 20 on three different paths upon the walls of the end-to-side anastomosis.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC2089073&req=5

Figure 5: Shear stress distribution in end-to-side anastomosis. Color-coded wall shear stress (Pa) and corresponding values plotted against the distance (mm) from the green to the red point at timestep 20 on three different paths upon the walls of the end-to-side anastomosis.
Mentions: The WSS characterizes the tangential fluid forces that act on the vessel wall. The changes of WSS throughout the cardiac cycle showed a correlation with flow velocities, with WSS forces being high when blood flow was fast. Near the end-to-side anastomosis the maximum WSS spatial variation was approximately 1.5 Pa (Figures 4 and 5). The WSS ranged from 0.01 Pa at minimum inflow to approximately 2.0 Pa at maximum inflow. In the perianastomotic region, the time averaged WSS was 0.36 Pa. An area of high WSS was found during systole at the heel of the anastomosis. The lowest WSS was found in the RCA at the location where blood from the CABG hit the wall and was confronted by the flow coming from the native coronary artery. This formed a stagnation point at the impact site around which the bypass stream splits, as depicted by the flow streamlines in Figure 4. It is also shown here that backflow into the RCA persisted during most of the cardiac cycle. The highest WSS values were found during mid-systole (timestep 20) and were located at the heel of the anastomosis and at the side of a nearby clip that was placed during surgery (Figure 5). At the opposite side of the anastomosis the WSS values were lower, due to the presence of the stagnation zone.

Bottom Line: CFD analysis based on in-vivo CT coronary angiography data was feasible in both patients.In contrast, the highest WSS values of the side-to-side anastomosis configuration were found in stenotic vessel segments and not in the close vicinity of the anastomosis.Flow stagnation zones were found in end-to-side but not in side-to-side anastomosis, the latter also demonstrating a smoother stream division throughout the cardiac cycle.

View Article: PubMed Central - HTML - PubMed

Affiliation: Institute of Diagnostic Radiology, University Hospital Zurich, Zurich, Switzerland. thomas.frauenfelder@usz.ch

ABSTRACT

Purpose: Coronary artery bypass graft (CABG) surgery represents the standard treatment of advanced coronary artery disease. Two major types of anastomosis exist to connect the graft to the coronary artery, i.e., by using an end-to-side or a side-to-side anastomosis. There is still controversy because of the differences in the patency rates of the two types of anastomosis. The purpose of this paper is to non-invasively quantify hemodynamic parameters, such as mass flow and wall shear stress (WSS), in end-to-side and side-to-side anastomoses of patients with CABG using computational fluid dynamics (CFD).

Methods: One patient with saphenous CABG and end-to-side anastomosis and one patient with saphenous CABG and side-to-side anastomosis underwent 16-detector row computed tomography (CT). Geometric models of coronary arteries and bypasses were reconstructed for CFD analysis. Blood flow was considered pulsatile, laminar, incompressible and Newtonian. Peri-anastomotic mass flow and WSS were quantified and flow patterns visualized.

Results: CFD analysis based on in-vivo CT coronary angiography data was feasible in both patients. For both types of CABG, flow patterns were characterized by a retrograde flow into the native coronary artery. WSS variations were found in both anastomoses types, with highest WSS values at the heel and lowest WSS values at the floor of the end-to-side anastomosis. In contrast, the highest WSS values of the side-to-side anastomosis configuration were found in stenotic vessel segments and not in the close vicinity of the anastomosis. Flow stagnation zones were found in end-to-side but not in side-to-side anastomosis, the latter also demonstrating a smoother stream division throughout the cardiac cycle.

Conclusion: CFD analysis of venous CABG based on in-vivo CT datasets in patients was feasible producing qualitative and quantitative information on mass flow and WSS. Differences were found between the two types of anastomosis warranting further systematic application of the presented methodology on multiple patient datasets.

Show MeSH
Related in: MedlinePlus