Evaluation of Bypass Graft Flow Using Computational Flow Dynamics Model
Kazuki Morimoto, Keiichi Itatani, Satoshi Numata, Sachiko Yamazaki, Suguru Ohira, Haruka Fu, Hitoshi Yaku.
Kyoto Prefectural University of Medicine, Kyoto, Japan.
OBJECTIVE: To create systematic coronary arterial model after coronary artery bypass grafting (CABG) using computational fluid dynamics and to validate the accuracy of the simulation with actual intraoperative flow measurement of internal thoracic artery (ITA) to left anterior descending artery (LAD) graft.
METHODS: Using three-dimensional computational models based on postoperative coronary computed tomography (CT) which was performed one week after CABG, we simulated coronary arterial flow in 3 cases with left main disease or triple vessel disease. We compared the simulated graft flow to intraoperatively measured graft flow using transit-time flow meter (TTFM). Two types of conditions with different coronary vascular resistance were simulated; hyperemia as intra-operation and rest as after discharge. Peripheral coronary resistance was estimated from ventricular muscular volume perfused from each branch.
RESULTS: The streamline and flow measurements are listed in Figure. The median difference in graft flow between simulated graft flow in hyperemia and actual one from TTFM was -4.3 ml/min (range; -12.3 to +9.2 ml/min). In one case, ITA-LAD occluded one year after surgery regardless of confirmed patency without graft stenosis on postoperative CT. In this case, the simulated graft flow in hyperemia was 20.2 ml/min (intraoperative flow; 11ml/min). However, in rest condition, the simulated graft flow was 6.4 ml/min with reverse flow from native coronary artery, which had not been seen in the other cases.
CONCLUSIONS: We performed systematic flow simulation of CABG and validated the system with actual graft flow measurement. This system enabled evaluation of flow competition. We might be able to predict graft flow before surgery to avoid graft occlusion risk in future.
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