Hemodynamic Characteristics of Ruptured and Unruptured Multiple Aneurysms at Mirror and Ipsilateral Locations

Abstract

Background and Purpose Different hemodynamic patterns have been associated with aneurysm rupture. The objective was to test whether hemodynamic characteristics of the ruptured aneurysm in patients with multiple aneurysms were different from unruptured aneurysms of the same patient. Materials and Methods A total of 24 mirror and 58 ipsilateral multiple aneurysms with one ruptured and the other(s) unruptured were studied. Computational fluid dynamics models were created from 3D angiographies. Case-control studies of mirror and ipsilateral aneurysms were performed using paired Wilcoxon tests. Results In mirror pairs, the ruptured aneurysm had more oscillatory wall shear stress (WSS) (p=0.007) than the unruptured one, and tended to be more elongated (higher aspect ratio), although this trend only achieved marginal significance (p=0.0302 one-sided test). In ipsilateral aneurysms, ruptured aneurysms had larger maximum WSS (p=0.0501), more concentrated (p=0.0007) and oscillatory WSS (p=0.0001), stronger (p=0.0001) and more concentrated inflow jets (p=0.0001), larger maximum velocity (p=0.0003), and more complex flow patterns (p=0.0001) compared to unruptured aneurysms. Additionally, ruptured aneurysms were larger (p=0.0001), more elongated (p=0.0001), had wider necks (p=0.0003), and lower minimum WSS (p=0.0002) than unruptured aneurysms. Conclusions High WSS oscillations and larger aspect ratios are associated with rupture in mirror aneurysms. Adverse flow conditions characterized by high and concentrated inflow jets, high, concentrated and oscillatory WSS, and strong, complex and unstable flow patterns are associated with rupture in ipsilateral multiple aneurysms. In multiple ipsilateral aneurysms, these unfavorable flow conditions are more likely to develop in larger, more elongated, wider necked, and more distal aneurysms.

Shear stress and aneurysms: a review

“…These ruptured aneurysms were found to have greater maximal and lower minimal shear stress compared to their unruptured counterparts. 8 The gradient of the WSS has been found to have an effect on cells of the vascular wall, as Dolan et al have demonstrated that a negative WSSG may antagonize the effect of high WSS on gene expression. 10 An additional theory by Meng et al is that both high and low WSS drive aneurysm growth and rupture, with regions of low WSS with high oscillatory shear index undergoing inflammatory cell-mediated destructive remodeling, and regions of high WSS with a positive WSSG undergoing mural cell-mediated remodeling.…”

Systematic review of hemodynamic discriminators for ruptured intracranial aneurysms

“…The first set of exclusion criteria were as follows: (a) CFD-unrelated (n = 5), (b) rupture-point-known (n = 10), (c) discriminator-unrelated (n = 26), (d) small number of aneurysms (less than 30) (n = 28), and (e) WSS or OSI undisclosed (n = 11), yielding a total of 32 studies. The second set of exclusion criteria were as follows: (f) location-specific (n = 14), (g) locationundefined (n = 2), (h) size-restricted (n = 1), and (i) metaanalysis (n = 2), yielding a total of 13 studies [38,39,[45][46][47][48][49][50][51][52][53][54][55]. Setting a specific location and size was avoided since those factors are known to be related to the aneurysm rupture rate and may lead to a possible bias; however, casematching studies based on location and size were permitted.…”

“…From the 13 included studies [38,39,[45][46][47][48][49][50][51][52][53][54][55], the following data were extracted: (1) year of publication, (2) study design, (3) location of aneurysms, (4) number of aneurysms, (5) number of ruptured aneurysms, (6) aneurysmal size, (7) aneurysmal aspect ratio, (8) aneurysmal WSS, (9) aneurysmal normalized WSS (NWSS), (10) aneurysmal OSI, and (11) aneurysmal LSA%. The mean (or median), p value, and area under the curve (AUC) from a receiver operating characteristic (ROC) analysis of these geometric and hemodynamic indexes were extracted.…”

“…Finally, the coefficient of variation (CV = SD/Mean) was calculated, and its average between ruptured and unruptured aneurysms was used to quantify the variability between groups. Table 1 summarizes the univariate analyses of 13 studies (3,692 aneurysms) [38,39,[45][46][47][48][49][50][51][52][53][54][55]. The percentage of ruptured aneurysms ranged from 30% to 50%.…”

Novel Models for Identification of the Ruptured Aneurysm in Patients with Subarachnoid Hemorrhage with Multiple Aneurysms

“…Several morphologic and hemodynamic parameters have been found to differ significantly between ruptured and unruptured aneurysm cohorts in patients with multiple IAs, albeit with conflicting findings. [9][10][11][12][13][14][15] These studies have generally relied on univariate and multivariate regression analyses of pooled data of ruptured and unruptured IAs. Although such methods model the general probability of aneurysm rupture, they are not tailored for identifying which aneurysm ruptured in patients with SAH with multiple aneurysms.…”