Imbalanced flow changes of distal arteries: An important factor in process of delayed ipsilateral parenchymal hemorrhage after flow diversion in patients with cerebral aneurysms

Abstract

Background and objective: Hemodynamic forces may play a role in symptomatic delayed ipsilateral parenchymal hemorrhage (DIPH) of intracranial aneurysm (IA) after flow diverter placement. We aimed to investigate the hemodynamic risk factors in the postsurgical DIPH process.

Methods: Six patients with internal carotid artery (ICA) aneurysm developed to DIPH and 12 patients without DIPH (1:2 matched controls) after flow diverter were included between January 2015 to January 2019. Postsurgical hemodynamics of distal arteries (terminal ICA, middle cerebral artery (MCA), anterior cerebral artery (ACA)) were investigated using computational fluid dynamics, as well as the hemodynamic alteration between pre- and post-treatment. The DIPH related and unrelated distal arteries (either MCA or ACA) were discriminated and compared. Definition of imbalance index is the difference in increased velocity post-flow diverter between MCA and ACA and was used to evaluate the blood flow distribution of distal arteries.

Results: The mean and maximum flow velocities in the terminal ICA increased significantly after treatment in both groups. In DIPH group, the increase rate of mean velocity in the DIPH-related artery was significantly higher than that in DIPH-unrelated artery after the treatment (20.98 ± 15.38% vs -6.40 ± 7.74%; p = 0.028). Between the DIPH and control group, the baseline characteristics were well matched. However, a higher imbalance index of mean velocity was found in DIPH group (27.38 ± 13.03% vs 10.85 ± 14.12%; p = 0.031).

Conclusion: The mean velocity of DIPH related artery increased more, and the imbalance in increased blood flow distribution of distal arteries might play an important role in DIPH after flow diverter of IAs.

Keywords: Intracranial aneurysms; delayed ipsilateral parenchymal hemorrhage; endovascular treatment; flow diverter; hemodynamics.

Figure 1.

The measurement section in patient-specific aneurysm model: the measurement section was the test plane of ICA (yellow), the MCA (red) and ACA (blue).

Figure 2.

The comparison of increase rate of velocity between DIPH related artery and unrelated artery.

Figure 3.

Comparison of the imbalance index of distal arteries in velocity between DIPH group and control group. The imbalance index of mean velocity between the DIPH and the controls showed statistically significant difference, and the median value was 25.8 and 3.7.

Figure 4.

An ophthalmic segment aneurysm (DIPH 3 in Supplemental Digital Content 1) of right internal carotid artery was treated with the first-generation PED assisted coiling. (a, b) The aneurysm showed residual sac filling at postprocedural immediate angiography(B). CT images showed the coiled aneurysm and DIPH at ipsilateral temporal lobe was found at 2 days later after the procedure (c). In hemodynamic simulation, the velocity on the cross section of terminal internal carotid artery was increased significantly compared with preprocedural results. (Increase rate =10.3%) (d, arrows) Furthermore, the flow velocity of DIPH related artery (middle cerebral artery) have significant increasing after PED treatment (Increase rate =19.6%) (e, arrows), while the velocity of DIPH unrelated artery (anterior cerebral artery) showed no significant change (Increase rate =0.9%) (f, arrows). The imbalance index of distal arteries was 18.7%.

Figure 5.

An ophthalmic segment aneurysm without DIPH (Control 5 in Supplemental Digital Content 1) of left internal carotid artery was treated with the first-generation PED assisted coiling. (a, b) The aneurysm showed residual sac filling at postprocedural immediate angiography (b), and complete occlusion at 6 months follow-up (c). In hemodynamic simulation, the velocity on the cross section of terminal internal carotid artery was increased significantly compared with preprocedural results. (Increase rate =11.1%) (D, arrows) Furthermore, the flow velocity of distal arteries (middle cerebral artery and anterior cerebral artery) have also significant increasing after PED treatment (Increase rate =13.5% and 12.8% respectively) (e, f, arrows) The imbalance index of distal arteries was 0.7.