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Objectives: End-to-side anastomosis is common in coronary artery bypass grafting, although restrictive suturing can narrow the anastomosis. We evaluated ex vivo end-to-side models by numerically simulating fluid dynamics to compare various degrees of stenotic anastomoses to predict haemodynamic effects., Methods: A carotid artery was grafted via an end-to-side anastomosis onto the left anterior descending artery of a porcine heart, with liquid silicone injected into the vessels. The end-to-side image was acquired via multidetector computed tomography for reference, and models of longitudinal shortening and bilateral narrowing were created with 25%, 50%, 75%, along with 90%, and 100% stenosis in the native coronary artery. Haemodynamics were analysed using computational fluid dynamics simulations to calculate streamlines, wall shear stress and oscillatory shear index., Results: In the reference model, the graft inflow impinged on the floor of the native artery, creating a recirculating vortex and a high oscillatory shear index region near the heel. As the graft flow angle increased with longitudinal stenosis, bilateral stenosis generated helical flow near the lateral wall of the native artery, worsening with increased stenosis. At 75% stenosis, both longitudinal shortening and bilateral narrowing caused abnormal flow separation, with low wall shear stress and high oscillatory regions forming distal to the toe of the anastomosis., Conclusions: Computational fluid dynamics modelling predicts that end-to-side anastomoses with 75% longitudinal or bilateral stenosis are at a risk of intimal hyperplasia causing graft failure, while anastomotic stenosis <50% indicates acceptable haemodynamics. Future studies should explore long-term clinical outcomes with suboptimal surgical anastomotic construction., Clinical Registration Number: Not applicable., (© The Author(s) 2025. Published by Oxford University Press on behalf of the European Association for Cardio-Thoracic Surgery.)

Objectives: It is difficult to estimate the improvement in left ventricular (LV) function after aortic valve replacement (AVR). The present study aimed to evaluate whether energy loss (EL) can predict the postoperative LV function after AVR., Methods: Nine patients who underwent AVR with a bioprosthetic valve were enrolled in the present study. Porcine prostheses were used in 5 patients and bovine pericardial prostheses were used in 4 patients. The aortic flow pattern was visualized and EL and cardiac output (CO) were measured using 4-dimensional flow magnetic resonance imaging from the LV to the descending aorta; the EL/CO ratio in the extracted area was calculated as total EL/CO ratio., Results: With a porcine valve, a severe helical flow was observed in the ascending aorta during the holosystolic phase. In contrast, with a bovine pericardial valve, straight transvalvular aortic flow was observed in the early systolic phase and 2 large vortical flows occurred on both sides of the greater and lesser curvature of the ascending aorta after the mid-systolic period. The total EL/CO ratio was strongly correlated with LV ejection fraction improvement after AVR (r = 0.74, P = 0.02)., Conclusions: The aortic flow pattern is different between the porcine valve and bovine pericardial valve. The total EL/CO ratio is a valuable tool for evaluating the postoperative LV ejection fraction improvement after AVR. Optimization of total EL/CO ratio would have potential to improve haemodynamic performances after AVR., (© The Author(s) 2021. Published by Oxford University Press on behalf of the European Association for Cardio-Thoracic Surgery. All rights reserved.)

Objectives: A novel surgical strategy using haemodynamic analyses based on virtual operations with computational simulations has been introduced for complicated pulmonary stenosis. We evaluated the efficacy of this strategy., Methods: Six patients were enrolled. Before surgery, the optimal pulmonary arteries were constructed based on computational fluid dynamics using 3-dimensional computed tomography. Energy loss (EL, mW) and wall shear stress (WSS, Pa) were calculated. We compared the shapes of preoperative and optimal pulmonary arteries to determine the surgical strategy, including the incision line and the shape of the patch (virtual surgery). EL and WSS were compared between virtual and actual surgeries using flow analysis., Results: In both the virtual and actual surgeries, postoperative EL tended to be lower than the preoperative EL, although there were no significant differences (P = 0.12 and P = 0.17, respectively). The mean WSS in the virtual surgery was significantly reduced from 112 ± 130 Pa to 25 ± 24 Pa (P = 0.028). After the actual surgery, the mean WSS was also significantly reduced to 30 ± 23 Pa (P = 0.047). There were no significant differences in the values for EL and WSS before and after surgery or between virtual and actual surgery (P = 0.94 and P = 0.85, respectively)., Conclusions: Pulmonary artery plasty, using computational fluid dynamics based on virtual surgery, is an efficient surgical strategy. This novel strategy can easily and successfully provide an optimal pulmonary artery plasty equivalent to that using the conventional approach, which is based on the surgeon's personal experience and judgement., (© The Author(s) 2018. Published by Oxford University Press on behalf of the European Association for Cardio-Thoracic Surgery. All rights reserved.)

Objectives: The purpose of this study was to calculate the changes in the blood flow direction and volume in the aortic lumen and at the entry and re-entry sites using 4-dimensional (4D) phase-contrast magnetic resonance imaging (MRI) after performing entry closure with thoracic endovascular aortic repair for chronic DeBakey IIIb aortic dissection., Methods: Aortic blood flow was analysed at 3 phases with 4D phase-contrast MRI in a single therapeutic DeBakey IIIb aortic dissection case., Results: Primary entry was in the distal arch, and there were 4 re-entry sites downstream in the diaphragm. Preoperatively, the entry site formed a large antegrade flow (1082 ml/min) to the 4 re-entry sites, but soon after the closure of the entry site, re-entry sites 1 through 3 became a new entry site whose flow pattern changed retrogradely, resulting in increased volume in the false lumen in the acute phase, whereas the flow at the previous re-entry sites from the true lumen to the false lumen decreased gradually, resulting in aortic remodelling with a reduction in the size of the false lumen: the preoperative, postoperative and 6-month postoperative mean flow volumes (ml/min) were 23, 254 and 173 at re-entry site 1; 59, 887 and 279 at re-entry site 2; and 303, 608 and 103 at re-entry site 3. The changes in the flow volume of the false lumen followed a similar trend expect for the area around the abdominal aorta., Conclusions: The volume of flow at the entry site was high, and closure of the primary entry site during thoracic endovascular aortic repair is very important. These changes in the flow volume of the re-entry sites and the false lumen may affect volume changes in the false lumen., (© The Author(s) 2018. Published by Oxford University Press on behalf of the European Association for Cardio-Thoracic Surgery. All rights reserved.)

Objectives: Inefficient aortic flow after the Norwood procedure is known to lead to the deterioration of ventricular function due to an increased cardiac workload. To prevent the progression of aortic arch obstruction, arch reconstruction concomitant with second-stage surgery is recommended. The aim of this study was to determine the indications for reconstruction based on numerical simulation and to reveal the morphology that affects the haemodynamic parameters., Methods: Fifteen patients who underwent the Norwood procedure or arch repair and Damus-Kaye-Stansel anastomosis were enrolled. The pressure gradient in aortic arch was 1.6 ± 3.9 mmHg (ranged from 0 to 12 mmHg) on catheter examination. Six patients who had prominent turbulent flow accompanied with a large flow energy loss index greater than 40 mW/m2 and high wall shear stress greater than 100 Pa underwent arch reconstruction., Results: After arch reconstruction, the energy loss index significantly decreased from 88.5 ± 50.0 mW/m2 to 23.1 ± 10.4 mW/m2 (P = 0.026) and wall shear stress significantly decreased from 194.5 ± 87.4 Pa to 60.3 ± 40.5 Pa (P = 0.0062). There were 3 late deaths due to heart failure caused by progressive atrioventricular valve regurgitation during the follow-up period (60 months). The systemic ventricular function was preserved in the remaining patients without any pressure gradients in the arch., Conclusions: Determining the surgical strategy for arch reconstruction based on numerical flow analysis may effectively reduce the ventricular load even if no stenosis or pressure gradients are observed on catheter examination or echocardiography., (© The Author 2017. Published by Oxford University Press on behalf of the European Association for Cardio-Thoracic Surgery. All rights reserved.)

Objectives: Coronary artery bypass grafting for multivessel disease requires an appropriate graft design to avoid the competition of flow between the graft and the native vessel in order to achieve a sufficient coronary flow and durable graft patency., Methods: Three-dimensional computational models of the left coronary artery were created based on the angiographic data. Three stenosis patterns of 75 and 90% combinations were created in the left anterior descending artery (LAD), the diagonal branch (Dx) and the circumflex artery (LCx). The left internal thoracic artery (LITA) was anastomosed to the LAD, and separate saphenous vein grafts (SVGs) were anastomosed to the Dx and the LCx in the 'Independent' model. The 'Sequential' model included sequential SVG anastomoses to the Dx and the LCx with a left internal thoracic artery-left anterior descending artery bypass, and Y-composite arterial grafts to LAD and Dx were created in the 'Composite' model., Results: The 'Independent' model had high reverse flow from the Dx to the LAD in systole, resulting in decreased LITA flow when Dx stenosis was mild. The 'Sequential' model also had reverse flow in diastole, resulting in additional LAD flow. The 'Composite' model distributed increased flow to the Dx when Dx stenosis was severe, resulting in decreased flow to the LAD., Conclusions: Systematic flow evaluation is beneficial for determining the optimal bypass graft arrangement in patients with multivessel disease. Individual SVG anastomoses to the Dx and the LCx are not desirable when Dx stenosis is not severe and a Y-composite arterial graft to the LAD and the Dx is not desirable when Dx stenosis is severe., (© The Author 2014. Published by Oxford University Press on behalf of the European Association for Cardio-Thoracic Surgery. All rights reserved.)