Computational fluid dynamics of internal mammary artery–left anterior descending artery anastomoses

Abstract

OBJECTIVES The aim of this study was to elucidate the remodelling of the internal mammary artery (IMA)–left anterior descending artery anastomosis and compare 2 different anastomosis techniques (end-to-side versus side-to-side) using computational fluid dynamics. METHODS This study included 9 patients. Computed tomography (CT) angiography was performed immediately after coronary artery bypass grafting (CABG) and at 3–6 months later. The computational fluid dynamics models were made using the CT data. The pulsatile 3-dimensional blood flow was achieved with the finite volume method to evaluate the postoperative morphological and haemodynamic changes at the anastomosis in each patient. Flow velocity distribution, wall shear stress (WSS) and its fluctuation oscillatory shear index were measured. RESULTS No early or mid-term graft occlusion was observed in the study series. In the side-to-side anastomosis, pouch formation at the distal end of IMA caused a vortex flow with low WSS immediately after CABG. However, at 3–6 months after surgery, this pouch disappeared. As a result, the laminar straight flow with uniform WSS distribution was achieved inside the anastomosis. In the end-to-side anastomosis, the anastomosis shape was remodelled, resulting in a laminar flow pattern with uniform WSS distribution. A patchy high oscillatory shear index was detected at the IMA wall on the top of anastomosis in either anastomosis techniques immediately after the surgery, but it disappeared at 3–6 months after surgery. CONCLUSIONS Regardless of the anastomosis technique used, a successful remodelling of the IMA–left anterior descending artery anastomosis shape was achieved a few months after surgery, resulting in a straightforward flow streamline, with uniform WSS distribution and minimal oscillatory shear index.

Changes in Internal Thoracic Artery Blood Flow According to the Degree of Stenosis of the Anterior Descending Branch of the Left Coronary Artery

“…Kanzaki et al reported that there was no significant difference in bypass blood flow between end-to-side anastomosis and side-to-side anastomosis using CFD. 17) In this study, all anastomoses were performed by sideto-side anastomosis, and Case 2 was selected because of its favorable OSI and TTFM values. By selecting the case with the most stable anastomotic conditions, it was possible to remove the bias due to anastomotic factors.…”

“…Kanzaki et al reported that there was no significant difference in bypass blood flow between end-to-side anastomosis and side-to-side anastomosis using CFD. 17) …”

“…First, as mentioned by Kanzaki et al, 17) the simulation geometry is based on coronary artery CT, so the patient’s condition and CT scan data may affect the shape of the simulation geometry. In CFD blood flow analysis, geometry and boundary conditions have a very large influence on the results.…”