Hemodynamic characteristics in ruptured and unruptured intracranial aneurysms: a prospective cohort study utilizing the AneurysmFlow™ tool.

Background and purpose: Hemodynamic factors significantly influence the onset, progression, and rupture of intracranial aneurysms (IAs). Current rupture risk prediction scores focus primarily on the clinical, anatomical and morphological aspects. This study aimed to investigate the hemodynamic characteristics differences between ruptured and unruptured IAs.

Materials and methods: Conducted from July 2021 to July 2022, this prospective cohort study involved patients with ruptured and unruptured IAs undergoing digital subtraction angiography (DSA). Hemodynamic characteristics were assessed using the AneurysmFlow™ tool. Hemodynamic, clinical, anatomical and morphological parameters were compared between ruptured and unruptured IA groups.

Results: The study included 127 patients with 135 aneurysms (67 ruptured, 68 unruptured). Complex flow patterns (type 3 and 4) were observed more frequently in ruptured aneurysms compared to unruptured aneurysms (odds ratio [OR], 5.57; 95% confidence interval [CI], 2.49-12.45; P < 0.001) in univariate analysis, and were also more common in unruptured aneurysms associated with daughter sacs features (P = 0.015). The mean aneurysm flow amplitude (MAFA) was lower in ruptured aneurysms, and associated with lower flow velocity in the parent artery related to vasospasm. MAFA in the aneurysmal dome or any additional daughter sacs was lowest compared to other regions inside the aneurysms. The technical failure rate of AneurysmFlow™ measurements was 8.5% (12 out of 139 patients). Additionally, hypertension (OR, 0.42; 95% CI, 0.30-0.54; P < 0.001), bifurcation location (AcomA/ACA/MCA/PcomA/posterior circulation) (OR, 0.17; 95% CI, 0.05-0.29; P = 0.005), and irregular shape (OR, 0.19; 95% CI, 0.05-0.35; P = 0.012) were identified as independently associated with rupture.

Conclusions: Complex flow patterns identified on the AneurysmFlow™ tool are significantly more common in ruptured and unruptured aneurysms associated with daughter sac features. The lowest MAFA in the aneurysmal dome and daughter sacs likely indicates specific pathophysiological changes within the aneurysm wall associated with rupture incidence. Hypertension, bifurcation location, and an irregular shape are independently associated with the risk of rupture. Further multicenter studies with larger sample sizes are needed to validate these findings.

Abbreviations: ACA = anterior cerebral artery; AcomA = anterior communicating artery; IAs = intracranial aneurysms; ICA = internal carotid artery; MAFA = mean aneurysm flow amplitude; MCA = middle cerebral artery; PcomA = posterior communicating artery; RIAs = ruptured intracranial aneurysms; SAH = subarachnoid hemorrhage; UIAs = unruptured intracranial aneurysms.