Flow Simulations to Establish the Relationship Between the Inflow Zone in the Neck of a Cerebral Aneurysm and the Positions of Struts

2016 ◽  
Author(s):  
Kazuhiro Watanabe ◽  
Hitomi Anzai ◽  
Makoto Ohta
Keyword(s):  
Reduction Rate ◽  
Flow Simulation ◽  
High Flow ◽  
Parent Artery ◽  
High Porosity ◽  
Critical Area ◽  
Flow Reduction ◽  
Fine Mesh ◽  
Parent Artery Occlusion ◽  
The Relationship

Flow-diverter (FD) stent implantation is an attractive treatment for cerebral aneurysms because of its low level of invasiveness. FD stent has a fine mesh structure, and the aim of FD implantation is to reduce the blood flow in an aneurysm by covering the aneurysm orifice. However, the fine mesh of the implant poses the risk of parent artery occlusion. One approach for avoiding this risk is to use a stent with a higher porosity. Previous studies have shown that placing a strut to disturb the inflow entering an aneurysm can promote a higher reduction in aneurysm flow. However, Hirabayashi et al. reported that a high-porosity stent can be sensitive to misdeployment in flow reduction. We hypothesized that a positioning error in flow reduction was sensitive to the relative position of the strut to the inflow configuration. In this study, we performed flow simulation to investigate the relationship between the inflow zone of the aneurysm neck and the positions of struts. Lattice Boltzmann (LB) flow simulation was performed to allow a comprehensive study of strut positions. Two rectangular solids were used as the strut model. Steady flow simulation was applied to models based on ideal and realistic three-dimensional (3D) aneurysm geometry, changing two strut positions along the neck plane. For both models, velocity boundaries were imposed on the inlet and a constant pressure boundary was imposed on the outlet. Average flow velocity in an aneurysm was calculated to evaluate the dependency of the flow reduction effect on the deployment position. We analyzed aneurysm flow using the following three strategies to observe the relationship between flow configuration, strut configuration, and flow reduction. Analysis A: Flow reduction rate (Rf) with one strut. A strut was moved from the proximal to the distal neck (perpendicular deployment) or from outside to inside (parallel deployment). Analysis B: Rf with two struts. One strut (strut A) was fixed in a specific position on the neck plane. The other (strut B) was moved along the neck plane in parallel to strut A. Analysis C: Rf with two struts. Strut B was located on the distal or inner side of strut A. The distance between the two struts was changed, and the two struts were moved along the neck plane while maintaining that distance. From the results of Analyses A and B, we confirmed a critical area in the inflow zone that maintained a high flow reduction regardless of the position of the second strut. The results of Analysis C confirmed that there were several distances between the struts at which flow reduction was almost constant. This constant reduction was maintained when one of the struts was located in the critical area, whereas the reduction was disturbed if both struts were located outside the area. These results suggest that the influence of positioning errors can be reduced by constantly placing at least one strut in a critical area, resulting in a high flow reduction. This may lead to optimal stent porosity for flow reduction and robustness of deployment.

Optimization of Strut Placement in Flow Diverter Stents for Four Different Aneurysm Configurations

2014 ◽  
Vol 136 (6) ◽  
Author(s):  
Hitomi Anzai ◽  
Jean-Luc Falcone ◽  
Bastien Chopard ◽  
Toshiyuki Hayase ◽  
Makoto Ohta
Keyword(s):  
Arterial Occlusion ◽  
Flow Simulation ◽  
Flow Diverter ◽  
Optimal Placement ◽  
Parent Artery ◽  
High Porosity ◽  
Mesh Structure ◽  
Flow Reduction ◽  
Fine Mesh ◽  
Flow Diverter Stent

A modern technique for the treatment of cerebral aneurysms involves insertion of a flow diverter stent. Flow stagnation, produced by the fine mesh structure of the diverter, is thought to promote blood clotting in an aneurysm. However, apart from its effect on flow reduction, the insertion of the metal device poses the risk of occlusion of a parent artery. One strategy for avoiding the risk of arterial occlusion is the use of a device with a higher porosity. To aid the development of optimal stents in the view point of flow reduction maintaining a high porosity, we used lattice Boltzmann flow simulations and simulated annealing optimization to investigate the optimal placement of stent struts. We constructed four idealized aneurysm geometries that resulted in four different inflow characteristics and employed a stent model with 36 unconnected struts corresponding to the porosity of 80%. Assuming intracranial flow, steady flow simulation with Reynolds number of 200 was applied for each aneurysm. Optimization of strut position was performed to minimize the average velocity in an aneurysm while maintaining the porosity. As the results of optimization, we obtained nonuniformed structure as optimized stent for each aneurysm geometry. And all optimized stents were characterized by denser struts in the inflow area. The variety of inflow patterns that resulted from differing aneurysm geometries led to unique strut placements for each aneurysm type.

scholarly journals Cerebral revascularization for the management of complex intracranial aneurysms: a single-center experience

2019 ◽  
Vol 131 (4) ◽  
pp. 1297-1307 ◽  
Author(s):  
Eric S. Nussbaum ◽  
Kevin M. Kallmes ◽  
Jeffrey P. Lassig ◽  
James K. Goddard ◽  
Michael T. Madison ◽  
...  
Keyword(s):  
Intracranial Aneurysms ◽  
Case Series ◽  
Artery Occlusion ◽  
High Flow ◽  
Cerebral Revascularization ◽  
Low Flow ◽  
Parent Artery ◽  
Team Approach ◽  
Parent Artery Occlusion

OBJECTIVEBecause simple intracranial aneurysms (IAs) are increasingly treated endovascularly, neurovascular surgery has become focused on complex IAs that may require deconstructive aneurysm therapy with concomitant surgical bypass. The authors describe the decision-making process concerning cerebral revascularization and present outcomes that were achieved in a large case series of complex IAs managed with cerebral revascularization and parent artery occlusion.METHODSThe authors retrospectively reviewed the medical records, including neuroimaging studies, operative reports, and follow-up clinic notes, of all patients who were treated at the National Brain Aneurysm Center between July 1997 and June 2015 using cerebral revascularization as part of the management of an IA. They recorded the location, rupture status, and size of each IA, as well as neurological outcome using the modified Rankin Scale (mRS), aneurysm and bypass status at follow-up, and morbidity and mortality.RESULTSThe authors identified 126 patients who underwent revascularization surgery for 126 complex, atheromatous, calcified, or previously coiled aneurysms. Ninety-seven lesions (77.0%) were unruptured, and 99 (78.6%) were located in the anterior circulation. Aneurysm size was giant (≥ 25 mm) in 101 patients, large (10–24 mm) in 9, and small (≤ 9 mm) in 16 patients. Eighty-four low-flow bypasses were performed in 83 patients (65.9%). High-flow bypass was performed in 32 patients (25.4%). Eleven patients (8.7%) underwent in situ or intracranial-intracranial bypasses. Major morbidity (mRS score 4 or 5) occurred in 2 (2.4%) low-flow cases and 3 (9.1%) high-flow cases. Mortality occurred in 2 (2.4%) low-flow cases and 2 (6.1%) high-flow cases. At the 12-month follow-up, 83 (98.8%) low-flow and 30 (93.8%) high-flow bypasses were patent. Seventy-five patients (90.4%) undergoing low-flow and 28 (84.8%) high-flow bypasses had an mRS score ≤ 2. There were no statistically significant differences in patency rates or complications between low- and high-flow bypasses.CONCLUSIONSWhen treating challenging and complex IAs, incorporating revascularization strategies into the surgical repertoire may contribute to achieving favorable outcomes. In our series, low-flow bypass combined with isolated proximal or distal parent artery occlusion was associated with a low rate of ischemic complications while providing good long-term aneurysm control, potentially supporting its wider utilization in this setting. The authors suggest that consideration should be given to managing complex IAs at high-volume centers that offer a multidisciplinary team approach and the full spectrum of surgical and endovascular treatment options to optimize patient outcomes.

scholarly journals Internal carotid artery occlusion may affect long-term quality of life in patients with high-flow carotid cavernous fistulas

2019 ◽  
Vol 26 (1) ◽  
pp. 83-89 ◽  
Author(s):  
Rong-Qin Dai ◽  
Wei-Xing Bai ◽  
Bu-Lang Gao ◽  
Tian-Xiao Li ◽  
Kun Zhang
Keyword(s):  
Quality Of Life ◽  
Artery Occlusion ◽  
High Flow ◽  
Parent Artery ◽  
Parent Artery Occlusion ◽  
Carotid Cavernous Fistulas ◽  
Headache Impact

Purpose To investigate the mid- and long-term effects of parent artery occlusion on the carotid cavernous fistula and on the quality of life of patients. Materials and methods One hundred and twenty-six patients with high-flow direct carotid cavernous fistulas were enrolled. The modified Rankin scale scores, the headache impact test and the short form health survey scores were used to evaluate the patients' clinical status. Results Fifty-two patients had parent artery occlusion, while the rest of the 74 patients had embolization of carotid cavernous fistulas with parent artery preservation. No periprocedural complications occurred. Eighteen patients in the parent artery occlusion group had low perfusion symptoms within two weeks following embolization, and three patients had Horner's syndrome on the ipsilateral side. At two months' follow-up, the patients with parent artery occlusion had a significantly ( P < 0.05) greater proportion of headache than patients with parent artery preservation. At 12 months, no significant ( P > 0.05) difference existed in the headache impact test scores in both groups. At 36 months' follow-up, the patients with parent artery occlusion had decreased SF-30 scores in all the eight health domains compared with patients treated with parent artery preservation, with a significant ( P < 0.05) lower score in general health, vitality and bodily pain in the parent artery occlusion compared with the parent artery preservation group. No recurrence was shown in patients with parent artery occlusion, but nine (12.2%) patients were recurrent in patients with parent artery preservation. Conclusion Parent artery occlusion may affect the quality of life of patients with carotid cavernous fistulas despite being an effective treatment option for high-flow direct fistulas.

Early echocardiographic modifications after flow reduction by proximal radial artery ligation in patients with high-output heart failure due to high-flow forearm arteriovenous fistula

2020 ◽  
Vol 21 (5) ◽  
pp. 753-759
Author(s):  
Barbara Maresca ◽  
Fausta Barbara Filice ◽  
Sara Orlando ◽  
Giuseppino Massimo Ciavarella ◽  
Jacopo Scrivano ◽  
...  
Keyword(s):  
Heart Failure ◽  
Arteriovenous Fistula ◽  
Radial Artery ◽  
Reduction Rate ◽  
Left Ventricular ◽  
High Flow ◽  
Evaluation Tool ◽  
Artery Ligation ◽  
Flow Reduction ◽  
High Output

Background: Arteriovenous fistula (AVF) for haemodialysis (HD) induces a volume/pressure overload which impairs bi-ventricular function and increases systolic pulmonary arterial pressure (PAPS) and left ventricular mass (LVM). In the presence of high blood flow (Qa) AVF (> 1.5 L/min/1.73 m2) and cardio-pulmonary recirculation (>20%), high-output congestive heart failure (CHF) may occur and AVF flow reduction is recommended. Proximal Radial Artery Ligation (PRAL) is an effective technique for distal radio-cephalic (RC) AVF flow reduction. Methods: we evaluated six HD and four transplant patients with high-flow RC AVF and symptoms of CHF who underwent PRAL. We compared echocardiographic (ECHO) findings before (T0) and 1 and 6 months (T1,T6) after PRAL. Preoperative ECHO was performed before (T0b) and after AVF anastomosis manual compression (T0c). Results: At T1 AVF flow reduction rate was 58.4% ± 13% and 80% of patients reported improved CHF symptoms. ECHO data showed an improvement of tricuspid annular plane systolic excursion (TAPSE) at T1 (p = 0.03) and a reduction of PAPS at T6 (p = 0.04). TAPSE improved after AVF anastomosis compression during preoperative ECHO (p = 0.03). Delta of TAPSE at the dynamic manoeuvre at T0 directly correlated with early (1 month after PRAL, p = 0.01) and late (6 months after PRAL, p = 0.04) deltas of TAPSE. Conclusions: AVF flow reduction after PRAL induces immediate regression of CHF symptoms, early improvement of TAPSE and late improvement of PAPS, suggesting a prevalent right sections involvement in CHF. Preoperative TAPSE modification after AVF anastomosis compression could represent a useful evaluation tool to determine which patients would benefit of PRAL.

Revascularization and Parent Artery Occlusion for Giant Internal Carotid Artery Aneurysms in the Intracavernous Portion Using Intraoperative Monitoring of Cerebral Hemodynamics

Neurosurgery ◽  
2006 ◽  
Vol 58 (1) ◽  
pp. 43-50 ◽  
Author(s):  
Yoshitaka Kubo ◽  
Kuniaki Ogasawara ◽  
Nobuhiko Tomitsuka ◽  
Yasunari Otawara ◽  
Shunsuke Kakino ◽  
...  
Keyword(s):  
Carotid Artery ◽  
Middle Cerebral Artery ◽  
Artery Bypass ◽  
Superficial Temporal Artery ◽  
Temporal Artery ◽  
Artery Occlusion ◽  
High Flow ◽  
Parent Artery ◽  
Bypass Grafting ◽  
Parent Artery Occlusion

Abstract OBJECTIVE: Therapeutic parent artery occlusion with or without revascularization is a useful surgical technique for the management of a giant aneurysm located in the intracavernous portion of the internal carotid artery (ICA). The purpose of the present study was to determine whether intraoperative cortical blood flow (CoBF) monitoring during surgical parent artery occlusion could identify patients who required bypass with a saphenous vein graft (high flow bypass). METHODS: Eleven patients with a giant aneurysm located in the intracavernous portion of the ICA underwent superficial temporal artery-middle cerebral artery bypass. CoBF was monitored intraoperatively in all patients using a thermal diffusion flow probe. The lowest CoBF during test occlusion of the ICA under functioning superficial temporal artery-middle cerebral artery bypass was determined, and the ratio of the value to the CoBF immediately before test occlusion of the ICA was calculated in the frontal and temporal lobes. When the CoBF ratio in the frontal or temporal lobe was less than 0.9, high flow bypass grafting was elected. RESULTS: Of the eleven patients undergoing superficial temporal artery-middle cerebral artery bypass, five patients underwent concomitant high flow bypass grafting. Postoperative cerebral ischemic events did not occur in any patient over a follow-up period ranging from 3 to 60 months. Postoperative cerebral angiography showed resolution of the aneurysm and patency of the bypass in all patients. CONCLUSION: Intraoperative CoBF monitoring using a thermal diffusion flow probe during surgical parent artery occlusion for giant intracavernous carotid artery aneurysms can identify patients who require concomitant high flow bypass grafting.

Successful obliteration and shrinkage of giant partially thrombosed basilar artery aneurysms through a tailored flow reduction strategy with bypass surgery

2011 ◽  
Vol 114 (4) ◽  
pp. 1028-1036 ◽  
Author(s):  
Susumu Miyamoto ◽  
Takeshi Funaki ◽  
Koji Iihara ◽  
Jun C. Takahashi
Keyword(s):  
Basilar Artery ◽  
Artery Occlusion ◽  
Parent Artery ◽  
Reduction Strategy ◽  
Flow Reduction ◽  
Parent Artery Occlusion ◽  
The Mean ◽  
Residual Blood ◽  
Complete Thrombosis

Object The authors evaluated the efficacy of a new flow reduction strategy for giant partially thrombosed upper basilar artery (BA) aneurysms, for which proximal parent artery occlusion is not always effective. Methods Eight consecutive patients with severely symptomatic, partially thrombosed, giant upper BA aneurysms were treated with a tailored flow reduction strategy, or received conservative therapies. The flow reduction strategy comprised isolation of several branches from the upper BA at their origins with bypasses in addition to parent artery occlusion. Results The median follow-up period of all 8 patients was 15.0 months (range 4–31 months). In 6 patients treated with flow reduction, the mean decrease in residual blood lumen was −10.7 mm (95% CI −19.7 to −1.7 mm; p = 0.029) and the mean decrease in diameter of the aneurysms was −11.5 mm (95% CI −25.1 to 2.1 mm; p = 0.082). Complete or virtually complete thrombosis was achieved in all but 1 aneurysm (83%) and shrinkage was observed in 4 (67%). In those in whom complete or virtually complete thrombosis was achieved, significant shrinkage of the aneurysm was observed (mean decrease in diameter −14.8 mm; 95% CI −28.8 to −0.8 mm; p = 0.043). Improvement or stabilization of symptoms occurred in 67% of the patients who received flow reduction treatment. Both patients who received conservative treatment had unfavorable outcomes. Conclusions The flow reduction strategy is effective at promoting complete thrombosis of the aneurysm. This strategy can also induce shrinkage of the aneurysm if successful thrombosis is achieved. Although the neurological outcome of the treatment appears favorable considering its intractable nature, further study of the treatment is necessary to confirm its clinical efficacy and safety.

Peripheral intracranial aneurysms: management challenges in 60 consecutive cases

2009 ◽  
Vol 110 (1) ◽  
pp. 7-13 ◽  
Author(s):  
Eric S. Nussbaum ◽  
Michael T. Madison ◽  
James K. Goddard ◽  
Jeffrey P. Lassig ◽  
Leslie A. Nussbaum
Keyword(s):  
Intracranial Aneurysms ◽  
Artery Occlusion ◽  
Neurological Deficits ◽  
Parent Artery ◽  
Branch Points ◽  
Aneurysm Neck ◽  
Vertebrobasilar System ◽  
Parent Artery Occlusion ◽  
Major Branch ◽  
Proximal Occlusion

Object The authors report the management and outcomes of 55 patients with 60 intracranial aneurysms arising distal to the major branch points of the circle of Willis and vertebrobasilar system. Methods Between July 1997 and December 2006, the authors' neurovascular service treated 2021 intracranial aneurysms in 1850 patients. The database was reviewed retrospectively to identify peripherally located intracranial aneurysms. Aneurysms that were mycotic and aneurysms that were associated with either an arteriovenous malformation or an atrial myxoma were excluded from review. Results The authors encountered 60 peripheral intracranial aneurysms in 55 patients. There were 42 small, 7 large, and 11 giant lesions. Forty-one (68%) were unruptured, and 19 (32%) had bled. Fifty-three aneurysms were treated surgically by using direct clip reconstruction in 26, trapping or proximal occlusion with distal revascularization in 21, excision with end-to-end anastomosis in 3, and circumferential wrap/clip reconstruction in 3. Coils were used to treat 6 aneurysms, and 1 was treated by endovascular parent artery occlusion. Overall, 49 patients had good outcomes, 4 were left with new neurological deficits, and 2 died. Conclusions Peripherally situated intracranial aneurysms are rare lesions that present unique management challenges. Despite the fact that in the authors' experience these lesions were rarely treatable with simple clipping of the aneurysm neck or endovascular coil occlusion, preservation of the parent artery was possible in most cases, and the majority of patients had a good outcome.

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