Hemodynamic effects of size and location of basilar artery fenestrations associated to pathological implications

Treatment of an intracranial aneurysm in the setting of fenestration of cranial division of the internal carotid artery: Technical considerations and a literature review

Although rare, cerebral arterial fenestration may present challenges in diagnosis and treatment. Here we present a case of a supraclinoid internal carotid artery (ICA) fenestration adjacent to an ICA aneurysm, successfully treated with balloon-assisted coil embolization. A female in her 50's presented with an acute subarachnoid hemorrhage from a ruptured left ICA-ophthalmic artery (OA) aneurysm. Digital subtraction angiography revealed a focal ICA fenestration distal to the posterior communicating artery (Pcom). The patient underwent successful coil embolization of the aneurysm using the balloon-assisted technique. No immediate hemorrhagic, thromboembolic, or neurological complications were observed. The patient was discharged in good condition after 2 weeks of hospitalization. A comprehensive literature review of 33 cases was subsequently performed to understand the characteristics of this condition. Cases involving the cranial division of the ICA forming the fenestration exhibited caliber differences significantly more frequently (p = 0.02). Embryological insights revealed distinctions between the cranial divisions of the ICA, influencing fenestration morphology and associated aneurysm formation. Endovascular treatment poses the risk of vascular injury, necessitating the identification of this variation and procedural planning.

Experimental and numerical investigation of the stenosed coronary artery taken from the clinical setting and modeled in terms of hemodynamics

The study was carried out to investigate the effect of the artery with different pulse values and stenosis rates on the pressure drop, the peristaltic pump outlet pressure, fractional flow reserve (FFR) and most importantly the amount of power consumed by the peristaltic pump. For this purpose, images taken from the clinical environment were produced as models (10 mm inlet diameter) with 0% and 70% percent areal stenosis rates (PSR) on a three-dimensional (3D) printer. In the experimental system, pure water was used as the fluid at 54, 84, 114, 132, and 168 bpm pulse values. In addition, computational fluid dynamics (CFD) analyzes of the test region were performed using experimental boundary conditions with the help of ANSYS-Fluent software. The findings showed that as PSR increases in the arteries, the pressure drop in the stenosis region increases and this amount increases dramatically with increasing effort. An increase of approximately 40% was observed in the pump outlet pressure value from 54 bpm to 168 bpm in the PSR 0% model and 51% increase in the PSR 70% model. It has been observed that the pump does more work to overcome the increased pressure difference due to increased pulse rate and PSR. With the effect of contraction, the power consumption of the pump increased from 9.2% for 54 bpm to 13.8% for 168 bpm. In both models, the Wall Shear Stress (WSS) increased significantly. WSS increased abruptly in the stenosis and arcuate regions, while sudden decreases were observed in the flow separation region.

Hemodynamics of different configurations of the left subclavian artery parallel stent graft for thoracic endovascular aortic repair

BACKGROUND AND OBJECTIVE

Parallel (chimney and periscope) graft technique is an effective approach for left subclavian artery (LSA) reconstruction in patients treated by thoracic endovascular aortic repair (TEVAR) for the inadequate landing zone. However, certain stent graft (SG) configurations may promote thrombosis and reduce distal blood flow, increasing risks of cerebral infarction and reintervention.

METHODS

In this paper, we first attempt to systematically evaluate the hemodynamic performances of different parallel graft techniques as potential determinants of complication risks. Based on the patient-specific 3D aortic geometry undergoing parallel graft technique, fifteen models in total for five kinds of LSA branched SG configurations (Forward, Backward, Extended, Elliptical and Periscopic) were designed virtually, and the hemodynamic discrepancies between them were analyzed by computational fluid dynamics.

RESULTS

Results show that flow rate of patients undergoing periscope technique reduces by half compared with chimney technique, suggesting that periscope SG may cause more serious flow obstruction to LSA, leading to stroke. For chimney stent structure, the extension length 0has little influence on energy loss and other parameters. Conversely, hemodynamic differences between the retrograde curvature and the antegrade curvature are significant (time average WSS: 47.07%), so the retrograde curvature might prompt SG displacement. Furthermore, the flatter chimney SG induces more aggressive hemodynamic forces, among which the difference of the maximum WSS between the flatter SG and nearly round SG reaches 65.56%, leading to the greater risk of vascular wall damage.

CONCLUSIONS

Results obtained might provide suggestions for physicians to formulate appropriate parallel graft technique schemes in TEVAR.

Multiphase Flow Hemodynamic Evaluation of Vertebral Artery Stenosis Lesions and Plaque Stability

BACKGROUND

Atherosclerosis is one of the main causes of vertebral artery stenosis, which reduces blood supply to the posterior circulation, resulting in cerebral infarction or death.

OBJECTIVE

To investigate stenosis rates and locations on the development of vertebral artery plaques.

METHODS

Stenosis models with varying degrees and positions of stenosis were established. The stenosis area was comprehensively analyzed using multiphase flow numerical simulation. Wall shear stress (WSS), blood flow velocity, and red blood cell (RBC) volume fraction were calculated.

RESULTS

Blood flow velocity in 30-70% stenosis of each segment tended to increase significantly higher than normal. Downstream of 50% stenosis exhibited turbulent flow; downstream of 70% displayed reflux. Severe stenosis increases the WSS and distribution area. The mixed area of high and low WSS appeared downstream of the stenosis. The RBC volume fraction at the stenosis increased (maximum value: 0.487 at 70% stenosis in the V4), which was 1.08 times the normal volume fraction. Turbulent and backflow regions exhibited complex RBC volume fraction distributions.

CONCLUSION

Flow velocity, WSS, and RBC volume fraction at the stenosis increase with stenosis severity, increasing plaque shedding. Narrow downstream spoiler and reflux areas possess low WSS and high erythrocyte volume fractions, accelerating plaque growth.

The first reported case of left renal vein fenestration

PURPOSE

Vascular fenestrations are mostly seen in the arterial system and cerebral vessels, but they can be seen rarely in the venous system. In this article, we aimed to present the first case of left renal vein fenestration, which has not been previously reported in the English literature to the best our knowledge.

METHODS

Computed tomography angiography (CTA) examination was performed on a 40-year-old male patient who presented with rectal bleeding, and iron deficiency anemia, detected hemorrhoids in colonoscopy, and was planned for superior rectal artery embolization.

RESULTS

In CTA examination, a fenestration in the middle part of the left renal vein was detected. The fenestrated segment length was measured approximately 3 cm. The diameter of anterior and posterior channels were 7.66 and 6.01 mm, respectively. The 2.85 mm diameter inferior segmental artery of the left renal artery was passing between the anterior and posterior channels of the fenestrated segment, and there was a slight indentation of this artery to the posterior canal.

CONCLUSION

Although venous fenestrations are rare, they can also be seen in the renal venous system, and can be detected with CTA. It is important for radiologists to be aware of this situation, to increase its detectability and to prevent iatrogenic injury in possible surgical procedures. And also as in our case, left renal vein fenestration may be one of the causes of microscopic hematuria.

Anatomical variations of human vertebral and basilar arteries: A current review of the literature

The vertebral artery originates from the subclavian artery and is divided into four segments (V1-V4). In its intracranial segment (V4), the two vertebral arteries join to form the basilar artery, an unpaired medium-sized artery. However, apart from this typical description, several anatomical variations may occur in the human body. Although in some cases such variations may be asymptomatic, they may be also associated with several pathological conditions, neurological complications, surgical complications, and increased risk of developing vascular diseases. Therefore, it is crucial to obtain sufficient information on the anatomy and variants of both arteries to prevent such complications and ensure the safe completion of surgical and radiological treatments. For this reason, we reviewed studies published up to January 2022 concerning the reported variations of the vertebral artery and basilar artery regarding their origin, course, length, and diameter. We believe that the thorough presentation of these variations would help surgeons worldwide during their daily clinical and surgical practice.

Association of cerebral infarction with vertebral arterial fenestration using non-Newtonian hemodynamic evaluation

PURPOSE

Cerebral artery fenestration is a rare vascular anomaly, but its existence has been increasingly documented. The association of cerebral infarction and fenestration is of great clinical interest, and the exact underlying mechanism remains unclear. This study aims to identify risk factors contributing to cerebral infarction by computational hemodynamics analysis.

METHODS

Eight patients with image findings of fenestration structure were recruited in this research, in which four suffered fenestration-related cerebral infarction (A series) while the other four (B series) were set as control matched by the fenestration size. Three-dimensional models were reconstructed from the MRA images and computational simulations with non-Newtonian flow model were performed to get interested hemodynamic characteristics.

RESULTS

The blood flow pattern was relatively separated along two channels of fenestration in series A compared with series B cases in Group 1-2, however, no significant difference was shown in Group 3-4. Quantitatively, planes were cut in the middle of fenestrations and the ratio of mass flow rate and area was calculated at systolic peak. Results showed that the side of the dominant blood supply was opposite between A and B series, and the dominant side was also opposite between small and large fenestrations. In infarction cases, the basilar top was distributed with larger areas of detrimental hemodynamic indicators and a larger concentrated high viscosity region.

CONCLUSION

The flow division condition throughout the fenestration structure has a key impact on further flow redistribution and flow pattern. The blood viscosity has the potential to be a useful tool in identifying the risk factors for cerebral infarction and more emphasis should be placed on the hemodynamic environment at superior cerebellar arteries.

Hemodynamic Differences Between Basilar Artery Fenestration and Normal Vertebrobasilar Artery: A Pilot Study

Background: Basilar artery fenestration has been proposed as a contributor to ischemic stroke, as unique flow patterns induced by fenestration may be related to thrombus formation or insufficiency. This study aimed to evaluate the hemodynamics of basilar artery fenestration (BAF) using computational fluid dynamics (CFD).

Methods: Patients with BAF and normal vertebrobasilar system were recruited and separately evaluated using CFD. Specific geometric vascular models were reconstructed based on 3D-rotational angiography (3D-RA). Patients were divided into the BAF group and control group (i.e., patients with the normal vertebrobasilar system). Hemodynamic and geometric variables were calculated and compared between groups using Student's t-test or Wilcoxon rank-sum test.

Results: Overall, 24 patients were included, with 12 patients each in the BAF group and the control group. The BAF group had a significantly smaller basilar artery diameter than the control group (3.1 ± 0.51 vs. 3.76 ± 0.4, p = 0.002). Compared to the control group, the BAF group had higher values of maxOSI (median, 0.3 vs. 0.09, p = 0.028), TAWSSG (median, 983.42 vs. 565.39, p = 0.038) in the flow confluence, higher SAR-TAWSSG in bifurcation (median, 70.22 vs. 27.65, p = 0.002) and higher SAR-TAWSSG in basilar artery (median, 48.75 vs. 16.17, p < 0.001) of the vertebrobasilar artery.

Conclusions: This pilot study suggested that hemodynamic differences between BAF and normal vertebrobasilar artery across multiple shear flow parameters. The disturbed flow in the BAF may increase the risk of thrombus formation, plaque instability, and subsequent ischemic cerebrovascular events. These should be confirmed by future studies.