Decoding the Impact of Vortex Dynamics on Carotid Artery Health: Swirling Safeguards Against Atherosclerosis

Cardiovascular disease is still the number one cause of death around the world, with atherosclerosis playing a major role in conditions like strokes and heart disease. When it develops in the carotid arteries (vessels in the neck that deliver blood to your brain) especially at the carotid artery bifurcation, it becomes a serious risk for ischemic strokes. The way atherosclerotic plaques form—blocking or restricting blood flow to the brain—has been studied for years. However, there is still a lot we do not fully understand about the biomechanics behind it. While researchers know that low wall shear stress (WSS) is a major trigger for plaque buildup, the role that vortex structures inside the artery play in shaping these stress levels has not been studied in detail. To truly get ahead of atherosclerosis risk, scientists need to look more closely at how these swirling blood flow patterns behave in both healthy and disease-prone arteries. One of the biggest challenges in vascular research is the sheer complexity of blood flow in areas where arteries split. The carotid bifurcation is one of those zones where blood is constantly pulsing, creating vortex structures that appear and disappear throughout each heartbeat. These vortex patterns directly affect the cells lining the arteries, influencing whether plaques start forming. So far, computational fluid dynamics has been a great tool for studying blood flow, but most studies have only looked at average WSS over time rather than zooming in on the changing nature of vortices and how they break down over time. Another challenge is that research has not separated the effects of artery shape from actual blood flow conditions. Most studies compare healthy arteries to diseased ones, but they do not always break down whether geometry alone is responsible for increased plaque risk or if abnormal blood flow patterns are just as important. Some people might have arteries with high-risk geometries, like a wider bifurcation angle, but never develop plaques. Others with “normal” artery shapes might still end up with dangerous buildups due to changes in pressure gradients or flow distribution. Because these factors are not well separated in existing research, it is tough to determine who is truly at risk based on their artery structure alone.

To bridge this gap, a new study published in Physical Review Fluids—led by Professor Michael Plesniak with Dr. Nora Caroline Wild and Associate Research Professor Kartik Bulusu at George Washington University, they created three different carotid artery models: one modeled after an average healthy individual, another based on a disease-prone artery shape, and a third hybrid model that kept the healthy artery structure but imposed disease-prone flow conditions. Dr. Wild explained, “We used clinical data from the literature to design realistic geometries that captured the main features of healthy and disease prone patient populations, this makes these findings applicable beyond a single patient-specific case.” This allowed them to tease apart whether anatomy or blood flow conditions had a bigger influence on vortex formation and, ultimately, the development of plaque-promoting shear stress patterns. The team ran simulations of pulsating blood flow through the three different artery models so they could track how vortices formed, evolved, and eventually disappeared over the course of a heartbeat. The researchers used the lambda-2 (λ₂) criterion, a widely recognized method for pinpointing vortex cores, and monitored how these swirling structures changed over time. They found that the exact moment a vortex appeared depended mostly on the shape of the artery, however, how long the vortex lasted and how quickly it faded away was driven more by the actual flow conditions, such as how blood split between branches and the pressure differences along the artery walls. This was a key discovery because it showed that while anatomy plays a role in shaping blood flow, it is the forces within the blood itself that determine whether these disturbances stick around long enough to create conditions that encourage plaque buildup. The authors also focused on vortex circulation and expansion—essentially, how much space these swirling structures occupied and how strong they were. The team calculated the circulation strength of the “main vortex” (a flow pattern that is larger compared to the other concomitant smaller-sized vortices) in each model and noticed a clear pattern. In the disease-prone artery, vortices formed earlier in the heartbeat cycle but also disappeared much more quickly than those in the healthy model. In fact, in the healthy artery, the main vortex remained intact for about 75% of the cycle, while in the disease-prone model, it lasted only 25% before breaking down. Even more interesting was what happened when the unhealthy flow conditions were applied to the healthy artery shape—the main vortex also faded faster, proving that the way blood moves, rather than just the shape of the artery, plays a huge role in early vortex decay. This was a significant finding because it suggested that a high internal carotid artery blood flow rate and a stronger pressure gradient near peak systole might be strong indicators of a higher risk for atherosclerosis. Moreover, the researchers took a closer look at where exactly these vortices formed and how much space they occupied in the internal carotid artery sinus, a region known to be especially vulnerable to plaque buildup. They found that in disease-prone arteries, the main vortex started larger but shrunk and disappeared much faster, leading to an unstable flow environment where shear stress levels changed unpredictably. This was a major concern because the cells lining blood vessels depend on steady shear forces to stay healthy. When these forces fluctuate too much or drop too low, it can trigger plaque formation.

In conclusion, the research work led by Professor Michael W. Plesniak, alongside Dr. Nora Caroline Wild and Associate Research Professor Kartik V. Bulusu, is an important advancement in our understanding of how blood flow mechanics contribute to atherosclerosis. More importantly, their findings open the door to better diagnostic tools and early intervention strategies for cardiovascular disease. The study suggests that the risk of atherosclerosis may have less to do with artery shape alone and more to do with how blood actually moves through the vessel. This challenges the long-standing belief that structural abnormalities are the main culprit, shifting the focus toward fluid mechanics as a key factor in vascular health. One of the most exciting takeaways from this study is the possibility of new, non-invasive ways to assess atherosclerosis risk. Right now, doctors rely on tools like Doppler ultrasound and MRI, which focus mainly on blood flow speed and artery narrowing. However, these methods do not account for the detailed vortex structures that influence shear stress, which plays a big role in plaque formation. By incorporating vortex-based risk assessment into medical imaging, doctors could spot early signs of plaque buildup long before arteries actually start to narrow. This could allow for early treatments that dramatically lower the chances of stroke and other cardiovascular issues. The authors want to emphasize that “the significance of this result is that disease prone flow conditions that are expected to play a significant role in atherosclerotic plaque formation caused by early deterioration of the beneficial vortex structures, could be observable in medical imaging and thus lead to earlier disease detection through medical imaging.” The study also has implications for medical device design. Manufacturers of stents and vascular grafts could use the new findings to improve their designs, ensuring that implants work with the body’s natural blood flow rather than disrupting it. This could help create longer-lasting devices with a lower risk of complications like thrombosis (blood clots) and restenosis (re-narrowing of arteries), both of which are major issues in cardiovascular treatments today. Additionally, the methods could be of valuable contribution to the broader field of biofluid mechanics and applied to other parts of the body, like coronary arteries and peripheral blood vessels, where similar blood flow disturbances might contribute to vascular disease.