Association of ophthalmic origin aneurysms with abnormally-enhanced hemodynamic stresses at the arterial wall

Abstract

Purpose

To investigate hemodynamic parameters associated with ophthalmic aneurysms using computational fluid dynamic (CFD) analysis.

Materials and methods

Sixty patients with or without ophthalmic origin aneurysms were enrolled, including 30 patients with and 30 patients without ophthalmic aneurysms. The demography, vascular diameter and angles, and hemodynamic parameters were analyzed.

Results

The bifurcation angle between the ophthalmic artery and internal carotid artery (ICA) distal segment was significantly (P < 0.0001) greater in patients with than those without ophthalmic aneurysm (140.7 ± 16.3 vs. 120.8 ± 16.1). The hemodynamic parameters were all significantly decreased on aneurysm dome compared with those at the direct flow impingement zone (FIZ) after virtual aneurysm removal, including the dynamic pressure (0.36 ± 0.49 vs. 0.58 ± 0.40 Pa), total pressure (29.88 ± 3.37 vs. 32.94 ± 1.64 Pa), velocity angle (1.02 ± 1.62 vs. 1.66 ± 0.27 degree/s), vorticity (606.72 ± 254.12 vs. 853.84 ± 261.78 1/s), WSS (0.78 ± 0.30 vs. 1.11 ± 0.30 Pa), and strain rate (613.93 ± 233.21 vs. 870.78 ± 231.21 1/s). The total pressure profile was like a parabola, and the profiles of WSS and dynamic pressure were characteristic of one minimal value and two peaks. The greatest total pressure and minimal shear stress and dynamic pressure were at the FIZ center, and as blood flowed distally, the total pressure decreased rapidly while the other parameters quickly increased to peaks. The WSS peak distance was significantly (P < 0.05) positively correlated with the bifurcation angle (ophthalmic/distal ICA angle) in patients with (R = 0.59 and P = 0.004) or without (R = 0.55 and P = 0.009) ophthalmic aneurysms. The WSS peak distance was significantly (P < 0.05) positively correlated with the summit total pressure in patients with ophthalmic aneurysms (R = 0.49 and P = 0.02) rather than in patients without aneurysms or in the total patients. Transverse line 4 was located in the FIZ center, lines 1–3 on the distal ICA wall, lines 5–7 on the ophthalmic artery wall, and from transverse line 4 to line 1 or to line 7, the total pressure significantly (P < 0.0001) decreased while all the other hemodynamic parameters significantly (P < 0.0001) increased. Transverse line 5 on oe peak had significantly (P < 0.01) greater dynamic pressure, velocity angle, WSS, vorticity and strain rate than those on transverse line 3 on the other peak.

Conclusion

Enlarged bifurcation angle between the ophthalmic artery and distal ICA segment significantly increases the hemodynamic parameters at the bifurcation apex and may contribute to the formation of ophthalmic aneurysms, which is to decrease the abnormally elevated hemodynamic parameters at the bifurcation apex.