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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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Flux in end-to-side anastomosis. Integrated volumetric flux (ml/sec) at indicated cross-sections (cuts) in the RCA and the end-to-side anastomosis.
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Figure 3: Flux in end-to-side anastomosis. Integrated volumetric flux (ml/sec) at indicated cross-sections (cuts) in the RCA and the end-to-side anastomosis.

Mentions: The mean volumetric flow through the right coronary artery was 3.07 ml/sec. The mean volumetric flow through the CABG was 1.81 ml/sec (Figure 3; cut 5). Quantifications of mass flow through the proximal and distal part of the right coronary artery and the bypass close to the end-to-side anastomosis are demonstrated in Figure 3. The distribution of pulsatile flow could be determined by using the flow curves at each time-step of the cardiac cycle. There was a significant backflow into the proximal segment of the RCA (Figure 3; cut 2), reaching a maximum of 0.48 ml/sec. Due to this high backflow, the next proximal branch of the RCA (Figure 3; cut 4) was filled by blood coming from the bypass for the largest part of the cardiac cycle. The amount of backflow depends on the coronary mass flow and the bypass mass flow, which are characterized by different mass flow curves at their inlets, the angle between the bypass and the RCA, and the degree of the stenosis in the bypassed artery. The retrograde flow into the RCA reached a distance of 2.8 cm from the end-to-side anastomosis (Figure 4), leading to an area of stagnation between the two more proximal branches (Figure 3; cut 1 and cut 2).


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)

Flux in end-to-side anastomosis. Integrated volumetric flux (ml/sec) at indicated cross-sections (cuts) in the RCA and the end-to-side anastomosis.
© Copyright Policy - open-access
Related In: Results  -  Collection

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

Figure 3: Flux in end-to-side anastomosis. Integrated volumetric flux (ml/sec) at indicated cross-sections (cuts) in the RCA and the end-to-side anastomosis.
Mentions: The mean volumetric flow through the right coronary artery was 3.07 ml/sec. The mean volumetric flow through the CABG was 1.81 ml/sec (Figure 3; cut 5). Quantifications of mass flow through the proximal and distal part of the right coronary artery and the bypass close to the end-to-side anastomosis are demonstrated in Figure 3. The distribution of pulsatile flow could be determined by using the flow curves at each time-step of the cardiac cycle. There was a significant backflow into the proximal segment of the RCA (Figure 3; cut 2), reaching a maximum of 0.48 ml/sec. Due to this high backflow, the next proximal branch of the RCA (Figure 3; cut 4) was filled by blood coming from the bypass for the largest part of the cardiac cycle. The amount of backflow depends on the coronary mass flow and the bypass mass flow, which are characterized by different mass flow curves at their inlets, the angle between the bypass and the RCA, and the degree of the stenosis in the bypassed artery. The retrograde flow into the RCA reached a distance of 2.8 cm from the end-to-side anastomosis (Figure 4), leading to an area of stagnation between the two more proximal branches (Figure 3; cut 1 and cut 2).

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