Abstract: Coronary artery bypass grafting (CABG) is one of the conventional treatments of coronary artery disease. Though the artery grafts have its own superiority, autologous great saphenous vein is still commonly used. Ten years after operation, half of the vein grafts will be occluded and half of the remainder will often undergo severe pathological conditions. The poor long term patency of vein grafts has become the bottleneck of the efficiency of CABG. The restenosis of vein grafts resulting from neointima and atherosclerosis has become an urgent problem waiting to be resolved. As the study on the molecular mechanism and pathophysiology of the vein grafts disease develops, many therapeutic schedules have been made, including drug therapy, external stent, expanding solution and gene therapy. By contrast, gene therapy has a broader prospect. This article will have a review on the prevention of restenosis of the vein grafts after CABG.
ObjectiveTo evaluate the changes of the flow parameters before and after the anastomotic port exploration and dredging during coronary artery bypass grafting by using the transit time flow measurement (TTFM).MethodsA total of 167 patients who underwent continuous coronary artery bypass grafting and anastomotic port exploration and dredging surgery in Beijing Anzhen Hospital from 2018 to 2019 were enrolled in this study. There were 136 male and 31 female patients aged 41-82 (58.35±17.26) years. If the probe entered and exited the anastomotic port smoothly, it was recorded as a non-resistance group; if the resistance existed but the probe could pass and exit, it was recorded as a resistance group; if the probe could not pass the anastomotic port for obvious resistance, it was recorded as the stenosis group. In the stenosis group, the grafts were re-anastomosed and the flow parameters were re-measured by TTFM.ResultsA total of 202 anastomotic ports were carried out by exploration and dredging. Among them, 87 anastomosis (43.1%) were in the non-resistance group, and there was no significant change in the blood flow volume (BFV) and pulsatility index (PI) before and after exploration and dredging (6.16±3.41 mL/min vs. 6.18±3.44 mL/min, P=0.90; 7.06±2.84 vs. 6.96±2.49, P=0.50). Sixty-four anastomosis (31.7%) were in the resistance group, the BFV was higher after exploration and dredging than that before exploration and dredging (17.11±7.52 mL/min vs. 4.96±3.32 mL/min, P<0.01), while the PI was significantly smaller (3.78±2.20 vs. 8.58±2.97, P<0.01). Fifty-one anastomosis (25.2%) were in the stenosis group, and there was no significant change in the BFV and PI before and after exploration and dredging (3.44±1.95 mL/min vs. 3.48±2.11 mL/min, P=0.84; 10.74±4.12 vs. 10.54±4.11, P=0.36). After re-anastomosis, the BFV was higher (16.48±7.67 mL/min, P<0.01) and the PI deceased (3.43±1.39, P<0.01) than that before exploration and dredging.ConclusionThe application of anastomotic exploration and dredging can reduce the occurrence of re-anastomosis, and promptly find and solve the stenosis of the distal coronary artery, improve the poor perfusion of distal coronary, and thus improves the prognosis of patients.
External support stent is a potential means for restricting the deformation and reducing wall stress of the vein graft, thereby improving the long-term patency of the graft in coronary artery bypass surgery. However, there still lacks a theoretical reference for choosing the size of stent based on the diameter of graft. Taking the VEST (venous external support) stent currently used in the clinical practice as the object of study, we constructed three models of VEST stents with different diameters and coupled them respectively to a model of the great saphenous vein graft, and numerically simulated the expansion-contraction process of the vein graft under the constraint of the stents to quantitatively evaluate the influence of stent size on the radial deformation and wall stress of the vein graft. The results showed that while the stent with a small diameter had a high restrictive effect in comparison with larger stents, it led to more severe concentration of wall stress and sharper changes in radial deformation along the axis of the graft, which may have adverse influence on the graft. In order to solve the aforementioned problems, we ameliorated the design of the stent by means of changing the cross-sectional shape of the thick and thin alloy wires from circle into rectangle and square, respectively, while keeping the cross-sectional areas of alloy wires and stent topology unchanged. Further numerical simulations demonstrated that the ameliorated stent evidently reduced the degrees of wall stress concentration and abrupt changes in radial deformation, which may help improve the biomechanical environment of the graft while maintaining the restrictive role of the stent.
The saphenous vein graft (SVG) remains the most commonly used conduit in coronary artery bypass grafting (CABG), yet its limited long-term patency adversely affects patient outcomes. SVG failure is a multistage pathological process, characterized by early thrombosis, intermediate intimal hyperplasia, and late atherosclerotic degeneration. These changes are driven by endothelial dysfunction induced by ischemia-reperfusion and mechanical injury, smooth muscle cell phenotypic modulation, inflammatory activation, and conventional cardiovascular risk factors. Preventive strategies for SVG failure have increasingly focused on both surgical and pharmacological optimization. Surgical approaches include appropriate target vessel and anastomotic site selection, refinement of SVG harvesting techniques (notably the no-touch technique and endoscopic vein harvesting), optimization of graft configurations, and routine intraoperative graft flow assessment. Postoperative secondary prevention is essential, as antithrombotic and lipid-lowering therapies have been shown to reduce SVG occlusion. In addition, emerging therapies, including gene-based interventions, antiproliferative agents, novel graft preservation solutions, and external vein graft supports, show promise in improving SVG durability. Integrated multimodal strategies may further reduce SVG failure and improve long-term outcomes after CABG. This article provides a review of researches related to SVG failure, including the mechanisms of failure, intraoperative preventive measures, pharmacological prevention, and recent advances in treatment, aiming to offer insights for clinical diagnosis, treatment and future studies.