Sebina Bulic, MD
The degree of carotid artery stenosis was, and remains focus of research in terms of surgical or interventional revascularization, primary or secondary stroke prevention. Also, plaque composition and identification of “vulnerable plaque” has been increasingly studied, for further risk stratification beyond the degree of luminal narrowing. Most of the available data is MRI based.
The authors used previously validated methodology using CTA and simple linear measurement of maximum soft plaque thickness on routinely acquired axial CTA images. Data acquired over 3 years (8/2009-8/2012) was analyzed. 6.2% or 76 patients out of 1224-screened patients had high-grade carotid artery stenosis (>70% stenosis) 45 patients or 59.2% of this cohort had TIA or stroke.
Mean values for the maximum total plaque thickness and maximum soft plaque thickness
were significantly higher in subjects with symptomatic carotid disease, whereas
maximum hard plaque thickness was found to be significantly higher in asymptomatic subjects. The degree of NASCET stenosis was not different between groups. For every 1 mm increase in maximum soft plaque thickness, there was approximately a 2.7 times greater likelihood (OR=2.7) of prior ipsilateral stroke or TIA (p<0.0001). For each 1 mm increase in hard plaque thickness, there was 45% (OR=0.55) decreased likelihood of prior ipsilateral stroke or TIA (p=0.007). It was found that maximum soft plaque thickness had the best ability to discriminate between symptomatic and asymptomatic subjects, with an optimal cutoff of 3.5 mm. This study also demonstrated excellent inter-observer reliability.
This study adds to the growing body of evidence on this topic, it is easy to perform, reproducible with excellent inter-observer reliability, however, given constant and dynamic changes in vulnerable plaque elements, prospective studies are needed for better identification of the population at greatest risk.