Aneurysm rupture following treatment with flow-diverting stents: computational hemodynamics analysis of treatment

Abstract

Background and purpose: Flow-diverting approaches to intracranial aneurysm treatment had many promising early results, but recent apparently successful treatments have been complicated by later aneurysm hemorrhage. We analyzed 7 cases of aneurysms treated with flow diversion to explore the possible rupture mechanisms.

Materials and methods: CFD analysis of pre- and posttreatment conditions was performed on 3 giant aneurysms that ruptured after treatment and 4 successfully treated aneurysms. Pre- and posttreatment hemodynamics were compared including WSS, relative blood flows, vascular resistances, and pressures, to identify the effects of flow-diverter placements.

Results: Expected reductions in aneurysm velocity and WSS were obtained, indicating effective flow diversion from the sac into the parent artery, consistent with periprocedural observations. In each case with postaneurysm rupture, the result of flow diversion led to an increase in pressure within the aneurysm. This pressure increase is related to larger effective resistance in the parent artery from placement of the devices and, in 2 cases, the reduction of a preaneurysm stenosis.

Conclusions: Flow-diversion devices can cause intra-aneurysmal pressure increases, which can potentially lead to rupture, especially for giant aneurysms. This relates both to changes in the parent artery configuration, such as reduction of a proximal stenosis, and to the flow diversion into higher resistance parent artery pathways combined with cerebral autoregulation, leading to higher pressure gradients. These may be important effects that should be considered when planning interventions. Potentially dangerous cases could be identified with angiography and/or patient-specific CFD models.

Fig 1.

Rotational angiograms prior and immediately after stent placement and corresponding vascular models of 3 aneurysms associated with posttreatment rupture. Top row, patient 1, left to right: 3DRA before treatment, vascular pretreatment model, 3DRA without contrast after stent deployment, and vascular posttreatment model. Center row, patient 2, left to right: 3DRA before treatment, 3DRA without contrast after stent deployment, vascular posttreatment model, and stent design. Bottom row, patient 3, left to right: 3DRA before treatment, vascular pretreatment model, 3DRA after stent placement, and vascular posttreatment model.

Fig 2.

Rotational angiograms and computational models of 4 aneurysms successfully treated with flow diverters. Left to right: 3DRA image before treatment, computational model with stent in place, 3DRA without contrast showing the deployed stents, and follow-up 3DRA images. Rows top to bottom correspond to patients 4–7, respectively.

Fig 3.

Visualizations of the hemodynamics of patients 1–3 at peak systole before (left column) and after (right column) stent placement. Top to bottom: isovelocity surfaces, velocity color-coded streamlines, WSS distribution, and pressure distributions.

Fig 4.

Visualizations of the hemodynamics of patients 4–7 at peak systole before (left column) and after (right column) stent placement. Top to bottom: isovelocity surfaces, velocity color-coded streamlines, WSS distribution, and pressure distributions.

Fig 5.

Electric circuit analog.