Qingdao Central Hospital: rupture sites of MCA aneurysms show low wall shear stress in 15 patients
CFD simulations on CT angiography data from 15 patients showed that intraoperatively confirmed rupture points had lower wall shear stress and higher oscillatory shear than the sac, while pressure did not differ.
Researchers at Qingdao Central Hospital compared the hemodynamic environment at the rupture point of middle cerebral artery aneurysms with that of the aneurysm sac and the parent artery. The study, based on preoperative CT angiography data from 15 patients with ruptured aneurysms, was published in Frontiers in Neurology frontiersin.org
Frontiers in Neurologyfrontiersin.orgOpen source ↗. Rupture regions were identified during surgery.
According to the authors, the rupture point was characterised by low time-averaged wall shear stress (TAWSS) and a high oscillatory shear index (OSI), rather than by elevated pressure.
Method: CT-based flow simulation
Three-dimensional vessel geometries were reconstructed from the preoperative scans. Transient computational fluid dynamics (CFD) simulations were run under rigid-wall and Newtonian-fluid assumptions. From them the authors computed TAWSS, OSI, pressure and flow streamlines.
Values were compared across three locations: the parent artery, the aneurysm sac and the rupture point. The authors used the Friedman test and pairwise Wilcoxon signed-rank tests with Bonferroni correction (p < 0.0167). No daughter sac, bleb or secondary lobulation was found on the reconstructions or at surgery frontiersin.org
Frontiers in Neurologyfrontiersin.orgOpen source ↗.
Results: shear stress, oscillation, pressure
TAWSS decreased monotonically from the parent artery (median 9.97 Pa) to the aneurysm sac (4.58 Pa) and then to the rupture point (2.14 Pa); all pairwise p ≤ 0.003. Rupture-point TAWSS was lower than sac TAWSS in 14 of 15 patients.
OSI was higher at the rupture point than in the sac (p = 0.0003) and the parent artery (p = 0.0002). The sac and the parent artery did not differ (p = 0.252). Rupture-point OSI exceeded sac OSI in 13 of 15 patients. The rupture region coincided spatially with the low-TAWSS and high-OSI areas of the sac.
Pressure was higher at the rupture point (p = 0.005) and in the sac (p = 0.009) than in the parent artery. Between the rupture point and the sac it did not differ at the corrected threshold (p = 0.027). The Friedman test was significant for all three parameters: TAWSS p < 0.0001, OSI p = 0.0004, pressure p = 0.0011 frontiersin.org
Frontiers in Neurologyfrontiersin.orgOpen source ↗.
The authors concluded that CTA-based CFD resolves region-level differences between the rupture region, the sac and the parent artery. The work was carried out at Qingdao Central Hospital together with two other Qingdao hospitals.
