Gradient of luminal narrowing of internal carotid artery on atherosclerotic plaque as risk factor for cerebral ischemic damage

Aim. To study the clinical significance of the gradient of narrowing of arterial lumen (GNL) for atherosclerotic stenosis of the internal carotid artery (ICA) as a risk factor for ischemic brain damage.

Material and methods. We proposed a new parameter of hemodynamic severity of ICA atherosclerotic stenosis — GNL. It calculated as ratio of the difference in the ICA cross section areas on the stenotic lesion and the near non-stenotic region to the distance between them: Snorm — Sstenosis)/Dnorm — stenosis, mm2 /mm. We examined 25 patients with advanced atherosclerosis and with uni(n=22) or bilateral (n=3) ICA stenosis >50% according to European Carotid Surgery Trial, and 11 individuals without ICA stenosis. Each participant underwent magnetic resonance angiography (MRA) of the carotid arteries with reconstruction of the arteries from C6-C7 level to the parietal bones, and the GNL was calculated. The thickness of the baseline slice was 0,8-1 mm. Each subject also underwent cerebral magnetic resonance imaging (MRI) in T1-, T2-, PD-, flair-weighted protocols.

 Results. Patients were divided into groups: group 1 (n=12) — without ischemic injury in the ICA system, and group 2 (n=13)  — with MRI signs ischemic injury history. The groups did not differ in proportion of stenosis (74,9±4,25% and 77,8±3,8%, p<0,05), ICA lumen area on the stenotic lesion (1,05±0,18 mm² and 1,14±0,17 mm² , p<0,05) and the ICA diameter at the non-stenotic region (4,30±0,32 mm and 4,9±0,29 mm, p<0,05). In control group, GNL was <0,75 mm² /mm. Groups 1 and 2 significantly differed (2,47±0,41 mm² /mm and 4,60±0,51 mm² /mm, p<0,02). In group 2, 12 out of 13 patients had GNL >3,35 mm² /mm, and, in group 1, 9 out of 12 — less than 3,35 mm² /mm. GNL did not correlate significantly with other parameters of ICA stenosis. Two patients with the highest GNL in each group (5,5 and 8,6 mm² /mm) had a fatal ischemic stroke within six months

Conclusion. Firstly, proposed parameter of stenosis hemodynamic severity GNL is independent, informative and prognostically important indicator for carotid artery atherosclerotic lesion.

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