Keywords
1. Carotid Stenting Neointimal Hyperplasia
2. Computational Fluid Dynamics Carotid
3. Hemodynamics Carotid Angioplasty
4. Carotid Bifurcation Geometry
5. Wall Shear Stress Carotid Artery
In a groundbreaking study published in the Circulation Journal, researchers have identified carotid bifurcation geometry as a critical predictor of neointimal hyperplasia (NIH) following carotid angioplasty and stenting (CAS), a procedure used to treat carotid stenosis. The findings of the study, detailed in a July 2020 issue (Volume 83, Issue 7), shed new light on the nuances underlying this common vascular intervention, with the potential to improve patient outcomes significantly.
Introduction
Carotid stenosis, characterized by the narrowing of the carotid arteries, poses a significant risk for ischemic stroke, one of the leading causes of morbidity and mortality worldwide. CAS has become a viable therapeutic option for patients, especially those at high risk for complications with the traditional carotid endarterectomy. Despite the procedural advancements in CAS, NIH – the abnormal growth of tissue inside the stent – remains a limitation, often leading to restenosis.
The Study
The study in question, conducted by an international team helmed by Xinke Yao of Southeast University’s School of Biological Science & Medical Engineering, employed computational fluid dynamics (CFD) to understand the impact of carotid bifurcation geometry on NIH formation. Yao and colleagues meticulously analyzed both idealized models and patient-specific models derived from digital subtraction angiography (DSA) of 25 patients who underwent bilateral CAS.
Research Methodology
The researchers employed synthetic models to simulate the blood flow dynamics within the carotid artery bifurcations, examining a range of geometries to understand the effects of varying internal carotid artery (ICA) angles on local hemodynamics.
Simultaneously, the team reconstructed patient-specific models using DSA images, enabling them to observe actual hemodynamic conditions within the arteries post-intervention, such as time-average wall shear stress (TAWSS) and oscillatory shear index (OSI).
Findings
Yao’s team’s multi-faceted analysis revealed a significant negative correlation between ICA angle and favorable local hemodynamics in their idealized models. This suggests that certain geometrical predispositions may increase the likelihood of aberrant flow patterns that can promote NIH.
More striking were the results obtained from the patient-specific models. The researchers found a clear distinction in hemodynamic conditions between patients who exhibited asymmetric NIH following CAS, compared to those with more uniform tissue regrowth. High OSI values and low TAWSS, indicators of disturbed flow, were frequently noted at NIH sites.
The NIH-asymmetric group exhibited more pronounced differences in geometric features compared to the NIH-symmetric group, highlighting geometrical variations as potential local risk factors for NIH. Notably, there were larger differences in OSI percentage area (10.56±20.798% vs. -5.87±18.259%, P=0.048) and the ratio of external carotid artery (ECA) to common carotid artery (CCA) diameter (5.64±12.751% vs. -3.59±8.697%, P=0.047) within the NIH-asymmetric group.
Implications
The discovery that carotid bifurcation geometry can influence blood flow dynamics, and consequently the development of NIH, underscores the importance of meticulous, personalized pre-operative planning for patients undergoing CAS. The potential for predicting NIH risk based on geometry and hemodynamics may allow for strategic alterations in procedural technique or stent design to mitigate this risk.
References
1. Yao, X., Dai, Z., Zhang, X., Gao, J., Xu, G., & Cai, Y., et al. (2019). Carotid Geometry as a Predictor of In-Stent Neointimal Hyperplasia – A Computational Fluid Dynamics Study. Circulation Journal, 83(7), 1472-1479. DOI: 10.1253/circj.CJ-18-1152
2. Harloff, A., Simon, J., Brendecke, S., Assefa, D., Helbing, T., Frydrychowicz, A., & Weiller, C. (2010). Complex plaques in the proximal descending aorta: an underestimated embolic source of stroke. Stroke; a journal of cerebral circulation, 41(6), 1145-1150.
3. Li, Z., Taviani, V., Tang, H., Abilez, O. J., & Zarins, C. K. (2009). The flow field along the entire length of mouse aorta and primary branches. Journal of Biomechanical Engineering, 131(9), 091002.
4. Malek, A. M., Alper, S. L., & Izumo, S. (1999). Hemodynamic shear stress and its role in atherosclerosis. Jama, 282(21), 2035-2042.
5. Parodi, J. C., & La Mura, R. (2008). Predictors of carotid stent restenosis: a systematic review and a comprehensive account of clinical studies. Journal of Cardiovascular Surgery, 49(3), 345-354.
Conclusion
The study by Yao and colleagues is a pioneering effort in the pursuit of tailored treatment modalities for carotid stenosis, providing key insights into the relationship between vessel geometry and post-stenting complications such as NIH. As evidence mounts that personalized medicine holds the key to better patient outcomes, this research reaffirms the value of precision in intervention planning and the need for advanced computational modeling in the vascular domain. Paving the way for more efficacious and safe CAS procedures, the team’s work could significantly contribute to reducing the global burden of ischemic strokes caused by carotid stenosis and its associated interventions.