Multivariate predictors of intracranial aneurysm rupture by regression analysis of Willis circle variation and hemodynamic forces alteration arised from vascular structural abnormity

Abstract

Objective To explore the effect of Willis circle variation and hemodynamic forces alteration arised from vascular structural abnormity on intracranial aneurysm (IA) rupture using 3D-digital subtraction angiography (DSA) and transcranial color Doppler (TCCD) detection. Methods Two hundred and twenty-three patients with IA, admitted to and conformed by DSA in our hospital from November 2010 to November 2011, were divided into ruptured IA group (n=182) and un-ruptured IA group (n=41). The 3D-DSA was applied in all patients to carefully evaluate the aneurysm sizes, locations, and morphous features, and to confirm the presence of A1 dominance and Willis circle variation. Moreover, aneurysmal neck area, diameter of parent artery, angle between A2 segments of bilateral anterior cerebral artery, angle between aneurysmal longitudinal axis and parent artery, aortic diameter (AD) and aspect ratio (AR) were measured with assistance of 3D-DSA images. Besides, TCCD was applied to all patients, and the hemodynamic parameters were recorded to calculate wall shear stress (WSS) and mechanical stretch. The risk factors of IA rupture were analyzed by receiver operating characteristic (ROC) curve and multivariate Logistic regression with emphasis on Willis circle variation and hemodynamic forces alteration. Results Whether it was in ruptured IA group or in un-ruptured IA group, the incidence rate of variation of anterior Willis circle was higher than that of variation of posterior Willis circle. A1 dominance on the left side was the most common asymmetry. As compared with those in un-ruptured IA group, statistically elder age, smaller AD, larger angle between aneurysmal longitudinal axis and parent artery, decreased WSS and increased mechanical stretch in the ruptured IA group were noted (P<0.05). ROC curve indicated that angle between aneurysmal longitudinal axis and parent artery, AD, WSS and mechanical stretch could be used to evaluate IA rupture (area under the curve: 0.606、0.618、0.396、0.637). Age (OR=8.618, 95% CI: 2.866-25.917, P=0.000), hypertension (grade III OR=16.320, 95% CI: 1.628-163.556, P=0.018), angle between aneurysmal longitudinal axis and parent artery (OR=3.053, 95%CI: 1.131-8.242, P=0. 028), AD (OR=5.638, 95%CI: 1.507-20.251, P=0.008) and mechanical stretch (OR=4.230, 95% CI: 1.554-11.516, P=0.000) were risk factors of IA rupture. A1 dominance (OR=0.242, 95% CI: 0.074-0.785, P=0.018), small aneurysms (2-5 mm, OR= 0.207, 95% CI: 0.054-0.788, P=0.002) and WSS (OR=0.021, 95% CI: 0.060-0.672, P=0.009) were identified as protective factors. Conclusions Willis circle variation exists in IA patients. Age, hypertension (grade III), angle between aneurysmal longitudinal axis and parent artery, AD and mechanical stretch are risk factors of IA rupture, while A1 dominance, small aneurysm (2-5 mm) and WSS are identified as protective factors. Accurate assessment of these factors is of great clinical significance for the prevention and treatment of IA in the future. Key words: Intracranial aneurysm; Hemodynamic factor; Rupture; Willis circle variation; Risk factor