Background. Dilatative atherosclerosis is a rare form of degenerative process manifested by arterial aneurysms. It is believed that endothelial dysfunction is involved in dilatative atherosclerosis. For estimation of systemic endothelial dysfunction a standardized endothelium-dependent vasodilatation test can be used. Alteration of arterial wall in aneurysm can be visualized and estimated by high-resolution magnetic resonance imaging (MRI).
Aim. The aim of our study was to compare endothelial function and some MRI structural and morphological characteristics of dilatative atherosclerosis.
Hypotheses. 1. Endothelial function differs among groups. 2. MR signal from the vessel wall of popliteal aneurysm differs from that of atherosclerotic vessel wall. 3. MR signal from the vessel wall of popliteal aneurysm differs in comparison to the signal from nearby non-dilated site. 4. Thickness of the vessel wall at the dilated (aneurysmal) site equals to the thickness of non-dilated site of the same vessel.
Methods. We included 12 male patients with popliteal artery aneurysm (group A) and 9 male patients with classic atherosclerosis (group K). Endothelial function was estimated by endothelium-dependent vasodilatation test. In all patients a high-resolution cross-section MRI through two standardized locations was made. The distal location was knee-joint fissure in group K or the widest section of the aneurysm in the group A. The proximal location was at least six cm proximally to the distal one in the group K or a non-dilated section of artery in the group A. The data taken from MR images (average intensity of the signal, standard deviation of the signal and geometrical characteristics of the vessel wall) was then statistically compared.
Results. The comparisons of endothelium-dependent and endothelium-independent dilatation between groups showed no significant difference. The comparisons of normalized average vessel wall signal intensity (NIS) also showed no significant difference at both locations. However, we found that normalized standard deviation of the vessel wall MR signal (NSD) (a measure for homogeneity of the signal from vessel wall) was significantly different between groups in proximal as it was at the distal location. Comparing NIS of proximal and distal location of the vessel for every patient showed no significant difference. Comparing NSD of proximal and distal location for every patient also showed no significant. Comparing the proximal and distal vessel wall thickness we found significant thickening of the vessel wall in group A.
Conclusions. Endothelium-dependent vasodilatation test was impaired in both groups equally. Changes in vessel wall structure due to aneurysm in the same patient did not result in changes of its MR signal. NIS did not differ between both groups probably because the constituents of the vessel wall were the same; however the NSD was different probably due to different distribution of the vessel wall constituents. We found significant thickening of aneurysmal wall.