Background: The progression of intimal hyperplasia after carotid endarterectomy (CEA) is influenced by local hemodynamic factors. In our study we investigated associations between flow volume, velocity, shear stress and the intimal hyperplasia (IH) of the common carotid artery after CAE.

Methods: 1009 patients (60±15 years, 86% of which were male) who had had CEA between 2001 and 2011 were included in our study. Blood velocity, internal diameter, flow volume and intima-media thickness were measured using standardized duplex ultrasound examination at 3, 6, 9 and 12 months after operation. Shear stress was calculated as blood viscosity multiplied by blood velocity divided by internal diameter.

Results: The maximum progression of IH was observed at 3 months (1,4±0,4 mm). Afterwards progression IH decreased and stabilized at 12 months. Mean shear stress at bifurcation after CEA was 16,6±2,3 dynes/cm² and was inversely related to internal diameter of common carotid artery at reconstruction site. Low mean shear stress correlated with low flow volume (r=0,56 P<0.0001). IH was inversely associated with shear stress (r=0,37 P<0.0001) and flow volume (r=0,35 P<0.0001).

Conclusions: This study demonstrates that low shear stress could lead to progression of IH after CEA. Strong correlation between flow volume and shear stress supports the conclusion that reduced flow volume can cause intimal hyperplasia. Artificial increase in artery’s diameter, especially with patch, leads to the development of intimal hyperplasia through decrease of shear stress.