Wall Shear Stress Differences Between Arterial and Venous Coronary Artery Bypass Grafts One Month After Surgery

Cardiac tissue engineering: an emerging approach to the treatment of heart failure

Heart failure is a major health problem in which the heart is unable to pump enough blood to meet the body's needs. It is a progressive disease that becomes more severe over time and can be caused by a variety of factors, including heart attack, cardiomyopathy and heart valve disease. There are various methods to cure this disease, which has many complications and risks. The advancement of knowledge and technology has proposed new methods for many diseases. One of the promising new treatments for heart failure is tissue engineering. Tissue engineering is a field of research that aims to create living tissues and organs to replace damaged or diseased tissue. The goal of tissue engineering in heart failure is to improve cardiac function and reduce the need for heart transplantation. This can be done using the three important principles of cells, biomaterials and signals to improve function or replace heart tissue. The techniques for using cells and biomaterials such as electrospinning, hydrogel synthesis, decellularization, etc. are diverse. Treating heart failure through tissue engineering is still under development and research, but it is hoped that there will be no transplants or invasive surgeries in the near future. In this study, based on the most important research in recent years, we will examine the power of tissue engineering in the treatment of heart failure.

In a rat model of bypass DuraGraft ameliorates endothelial dysfunction of arterial grafts

Coronary artery bypass surgery can result in endothelial dysfunction due to ischemia/reperfusion (IR) injury. Previous studies have demonstrated that DuraGraft helps maintain endothelial integrity of saphenous vein grafts during ischemic conditions. In this study, we investigated the potential of DuraGraft to mitigate endothelial dysfunction in arterial grafts after IR injury using an aortic transplantation model. Lewis rats (n = 7-9/group) were divided in three groups. Aortic arches from the control group were prepared and rings were immediately placed in organ baths, while the aortic arches of IR and IR + DuraGraft rats were preserved in saline or DuraGraft, respectively, for 1 h before being transplanted heterotopically. After 1 h after reperfusion, the grafts were explanted, rings were prepared, and mounted in organ baths. Our results demonstrated that the maximum endothelium-dependent vasorelaxation to acetylcholine was significantly impaired in the IR group compared to the control group, but DuraGraft improved it (control: 89 ± 2%; IR: 24 ± 1%; IR + DuraGraft: 48 ± 1%, p < 0.05). Immunohistochemical analysis revealed decreased intercellular adhesion molecule-1, 4-hydroxy-2-nonenal, caspase-3 and caspase-8 expression, while endothelial cell adhesion molecule-1 immunoreactivity was increased in the IR + DuraGraft grafts compared to the IR-group. DuraGraft mitigates endothelial dysfunction following IR injury in a rat bypass model. Its protective effect may be attributed, at least in part, to its ability to reduce the inflammatory response, oxidative stress, and apoptosis.

Hemodynamics and Wall Mechanics of Vascular Graft Failure

Blood vessels are subjected to complex biomechanical loads, primarily from pressure-driven blood flow. Abnormal loading associated with vascular grafts, arising from altered hemodynamics or wall mechanics, can cause acute and progressive vascular failure and end-organ dysfunction. Perturbations to mechanobiological stimuli experienced by vascular cells contribute to remodeling of the vascular wall via activation of mechanosensitive signaling pathways and subsequent changes in gene expression and associated turnover of cells and extracellular matrix. In this review, we outline experimental and computational tools used to quantify metrics of biomechanical loading in vascular grafts and highlight those that show potential in predicting graft failure for diverse disease contexts. We include metrics derived from both fluid and solid mechanics that drive feedback loops between mechanobiological processes and changes in the biomechanical state that govern the natural history of vascular grafts. As illustrative examples, we consider application-specific coronary artery bypass grafts, peripheral vascular grafts, and tissue-engineered vascular grafts for congenital heart surgery as each of these involves unique circulatory environments, loading magnitudes, and graft materials.

Abnormal Wall Shear Stress Area is Correlated to Coronary Artery Bypass Graft Remodeling 1 Year After Surgery

Coronary artery bypass graft surgery is a common intervention for coronary artery disease; however, it suffers from graft failure, and the underlying mechanisms are not fully understood. To better understand the relation between graft hemodynamics and surgical outcomes, we performed computational fluid dynamics simulations with deformable vessel walls in 10 study participants (24 bypass grafts) based on CT and 4D flow MRI one month after surgery to quantify lumen diameter, wall shear stress (WSS), and related hemodynamic measures. A second CT acquisition was performed one year after surgery to quantify lumen remodeling. Compared to venous grafts, left internal mammary artery grafts experienced lower abnormal WSS (< 1 Pa) area one month after surgery (13.8 vs. 70.1%, p = 0.001) and less inward lumen remodeling one year after surgery (- 2.4% vs. - 16.1%, p = 0.027). Abnormal WSS area one month post surgery correlated with percent change in graft lumen diameter one year post surgery (p = 0.030). This study shows for the first time prospectively a correlation between abnormal WSS area one month post surgery and graft lumen remodeling 1 year post surgery, suggesting that shear-related mechanisms may play a role in post-operative graft remodeling and might help explain differences in failure rates between arterial and venous grafts.