Anil Arat

Dual Antiplatelet Therapy Monitoring for Neurointerventional Procedures Using a Point-of-Care Platelet Function Test: A Single-Center Experience

BACKGROUND AND PURPOSE: Growing evidence of the relationship between poor antiplatelet response and occurrence of clinical events elicited the need of monitoring the response which has not been part of our daily practice. We present our initial experience with a new point-of-care antiplatelet-function test (VerifyNow assay) in neurointerventional procedures. MATERIALS AND METHODS: Among the 106 consecutive patients from July 2006 to April 2007, ninety-eight met the inclusion criteria. Our preferred antiplatelet regimen was aspirin (325 mg daily) and clopidogrel (300 mg of loading dose followed by 75 mg daily) starting 5–10 days before the procedure. The test results were reported as aspirin-reaction unit (ARU) for aspirin and P2Y12 reaction units (PRU), baseline (BASE), and percentage inhibition for the P2Y12 assay and were summarized as mean ± SD of the values. We analyzed the effects of several factors of poor clopidogrel response (<40% inhibition). The occurrence of thrombotic events was recorded. RESULTS: The mean ARU of aspirin assays was 438.3 ± 47.9 (range, 350–632), and the response was poor in 2 patients (2.1%). For clopidogrel, the mean of the BASE, PRU, and percentage inhibition was 356.8 ± 56.3 (range, 234–495), 198.9 ± 104.4 (range, 8–401), and 45.2 ± 27.1% (range, 0–98), respectively. Forty-two patients (42.9%) showed poor response. Multivariate analysis showed greater body weight (81.9 Kg ± 19.1 kg versus 69.9 ± 15 kg) in the poor-response group. All 3 cases of intraprocedural thrombosis (3.1%) were observed only in the poor-response group. CONCLUSION: We observed a high frequency of poor clopidogrel responses in the neurointerventional setting. Routine monitoring of the drug response would be helpful for the early identification of poor antiplatelet responders so that we may modify the regimen and/or treatment plan.

Treatment of a Superior Sagittal Sinus Dural Arteriovenous Fistula with Onyx: Technical Case Report

OBJECTIVE: The endovascular treatment of a complex superior sagittal sinus dural arteriovenous fistula with ethylene vinyl alcohol copolymer (Onyx) in one session is described. CLINICAL PRESENTATION: A 54-year-old man presented with dizziness and a bruit. A cerebral angiogram demonstrated a superior sagittal sinus dural arteriovenous fistula with a patent superior sagittal sinus that was supplied via multiple branches of the external carotid arteries bilaterally and the left anterior and middle cerebral arteries. Drainage was mainly through the superior sagittal sinus and, only in part, retrogradely through the cortical veins. A decision was made to proceed with endovascular treatment followed by surgery. INTERVENTION: Transarterial injection of one pedicle of middle meningeal artery on both sides with Onyx resulted in complete obliteration of the dural supply and some of the pial supply to the malformation without complications. The superior sagittal sinus remained patent. Based on this result, surgical treatment was cancelled. The residual pial supply had disappeared by the 10-month angiographic follow-up examination and the patient remained neurologically intact and without symptoms. CONCLUSION: Definitive treatment may be attained with Onyx in dural arteriovenous fistulas. The potential of Onyx for use as a permanent embolic agent in dural arteriovenous fistulae needs to be investigated.

Focused RF hyperthermia using magnetic fluids

Heat therapies such as hyperthermia and thermoablation are very promising approaches in the treatment of cancer. Compared with available hyperthermia modalities, magnetic fluid hyperthermia (MFH) yields better results in uniform heating of the deeply situated tumors. In this approach, fluid consisting of superparamagnetic particles (magnetic fluid) is delivered to the tumor. An alternating (ac) magnetic field is then used to heat the particles and the corresponding tumor, thereby ablating it. However, one of the most serious shortcomings of this technique is the unwanted heating of the healthy tissues. This results from the magnetic fluid diffusion from the tumor to the surrounding tissues or from incorrect localization of the fluids in the target tumor area. In this study, the authors demonstrated that by depositing appropriate static (dc) magnetic field gradients on the alternating (ac) magnetic fields, focused heating of the magnetic particles can be achieved. A focused hyperthermia system was implemented by using two types of coils: dc and ac coils. The ac coil generated the alternating magnetic field responsible for the heating of the magnetic particles; the dc coil was used to superimpose a static magnetic field gradient on the alternating magnetic field. In this way, focused heating of the particles was obtained in the regions where the static field was dominated by the alternating magnetic field. In vitro experiments showed that as the magnitude of the dc solenoid currents was increased from 0 to 1.8 A, the specific absorption rate (SAR) of the superparamagnetic particles 2 cm apart from the ac solenoid center decreased by a factor of 4.5, while the SAR of the particles at the center was unchanged. This demonstrates that the hyperthermia system is capable of precisely focusing the heat at the center. Additionally, with this approach, shifting of the heat focus can be achieved by applying different amounts of currents to individual dc solenoids. In vivo experiments were performed with adult rats, where magnetic fluids were injected percutaneously into the tails (with homogeneous fluid distribution inside the tails). Histological examination showed that, as we increased the dc solenoid current from 0.5 to 1.8 A, the total burned volume decreased from 1.6 to 0.2 cm3 verifying the focusing capability of the system. The authors believe that the studies conducted in this work show that MFH can be a much more effective method with better heat localization and focusing abilities.

Distal Embolization After Stenting of the Vertebral Artery: Diffusion-Weighted Magnetic Resonance Imaging Findings

PurposeWe retrospectively evaluated our experience with stenting of the vertebral artery in an effort to determine the risk of distal embolization associated with the procedure.MethodsBetween June 2000 and May 2005, 35 patients with 38 stenting procedures for atherosclerotic disease of the vertebral origin in our institution were identified. The average age of the patients was 60.3 years (range 32–76 years). Sixteen of these patients (with 18 stents) had MR imaging of the brain with diffusion-weighted imaging and an apparent diffusion coefficient map within 2 days before and after procedure.ResultsOn seven of the 16 postprocedural diffusion-weighted MR images, a total of 57 new hyperintensities were visible. All these lesions were focal in nature. One patient demonstrated a new diffusion-weighted imaging abnormality in the anterior circulation without MR evidence of posterior circulation ischemia. Six of 16 patients had a total of 25 new lesions in the vertebrobasilar circulation in postprocedural diffusion-weighted MR images. One patient in this group was excluded from the final analysis because the procedure was complicated by basilar rupture during tandem stent deployment in the basilar artery. Hence, new diffusion-weighted imaging abnormalities were noted in the vertebrobasilar territory in 5 of 15 patients after 17 stenting procedures, giving a 29% rate of diffusion-weighted imaging abnormalities per procedure. No patient with bilateral stenting had new diffusion-weighted imaging abnormalities.ConclusionStenting of stenoses of the vertebral artery origin may be associated with a significant risk of asymptomatic distal embolization. Angiography, placement of the guiding catheter, inflation of the stent balloon, and crossing the lesion with guidewires or balloon catheters may potentially cause distal embolization. Further studies to evaluate measures to increase the safety of vertebral artery stenting, such as the use of distal protection devices or short-term postprocedural anticoagulation, should be considered for patients with clear indications for this procedure.

Percutaneous management of peripheral vascular malformations: a single center experience.

PURPOSE To review the therapeutic results of the combination of embolization and sclerotherapy, with or without surgery, in patients with peripheral vascular malformations (PVMs). MATERIALS AND METHODS A total of 40 patients (24 males and 16 females) with PVMs, who were treated via percutaneous embolization (transarterial [TA] versus direct puncture [DP]) and sclerotheraphy between March 2003 and September 2009, were included in this retrospective study. The mean age was 28 years (range, 6-66 years), and 9 patients (7 boys, 2 girls) were ≤18 years of age (range, 6-18 years). The 40 patients experienced 40 PVMs, of which 15 were localized to an upper extremity, 13 to a lower extremity, 7 to the axial body, and 5 to the pelvis. A total of 22 PVMs were high-flow, whereas 18 were low-flow. Indications for treatment included pain, swelling, extremity function loss, and cosmetic concerns. RESULTS A total of 85 embolization/sclerotheraphy sessions were performed (2.1 sessions per patient). For the 22 high-flow PVMs, 53 treatment sessions were completed (2.4 sessions per lesion). Of the high-flow PVMs, 10 were treated via embolization only (7 DP, 2 TA, 1 DP and TA), 5 via alcohol sclerotheraphy only (2 DP, 2 TA, 1 DP and TA) and 7 via a combination of embolization and sclerotheraphy (3 TA, 4 DP and TA). The agents of embolization and sclerotherapy were n-butyl cyanoacrylate (n=22 patients), Onyx® (n=12 patients), and alcohol (n=19 patients). A total of 18 low-flow PVMs were treated in 32 sessions (1.8 sessions per lesion), all via the direct puncture approach. Of the low-flow PVMs, 11 were treated with embolization only, 6 with sclerotheraphy only, and 1 with a combined approach. In 16 patients (6 high-flow versus 10 low-flow), after a mean of 2.1 sessions (range, 1-9 sessions), the percutaneously treated lesions were excised by surgery without any major complications. In the 24 patients who did not have surgery, the lesions significantly decreased in size and the complaints from these patients improved. In four patients, skin ulcerations were identified, two of these patients needed surgical grafting; whereas in one patient, sciatic nerve paralysis developed after trans-arterial embolization and recovery was achieved in six months. CONCLUSION Percutaneous treatment of PVMs by embolization and sclerotheraphy is a safe and effective method, provided that appropriate lesion classification and treatment agent selection are performed.

Preliminary experience with squid: a new liquid embolizing agent for AVM, AV fistulas and tumors.

AIM The aim of the present study was to analyze our experience with a new liquid embolic agent, Squid, for the treatment of cerebral vascular lesions. MATERIAL AND METHODS We present 28 patients who were treated with two formulations of Squid (Squid 18 and Squid 12). The lesions included 16 arteriovenous malformation (AVM)s (Spetzler-Martin grade 2 in 8, 3 in 6 and 4 in 2), 9 arteriovenous (AV) fistulas, 2 tumors (glomus tumor and angiofibroma) and 1 AICA aneurysm. Of the 9 patients presenting with hemorrhage, 6 were AVM, 2 were AVF and 1 was aneurysm. RESULTS The total obliteration rate of the AVMs was 37.5%. Fistulas were closed completely after combined treatment with surgery in 6 out of 9 patients, and one was sent to radiotherapy. There was no mortality. Two reported hemorrhages and thromboembolic complications resulted in permanent deficits in 3 patients. Pathologic examination revealed mild inflammatory reaction with infiltration of polymorphonuclear cells in 5 patients in whom surgery was performed immediately after embolization. Technical problems such as rupture, inability to remove or premature occlusion of the microcatheter related to the embolic agent were not recorded. CONCLUSION Squid is a safe and effective embolic agent for treatment of cerebral AVMs, AV fistulas, tumors and aneurysms with satisfactory obliteration rate.

Management of Vertebral Stenosis Complicated by Presence of Acute Thrombus

A 44-year-old male presented with multiple punctate acute infarcts of the vertebrobasilar circulation and a computed tomographic angiogram showing stenosis of the right vertebral origin. A digital subtraction angiogram demonstrated a new intraluminal filling defect at the origin of the stenotic vertebral artery where antegrade flow was maintained. This filling defect was accepted to be an acute thrombus of the vertebral origin, most likely due to rupture of a vulnerable plaque. The patient was treated with intravenous heparin. A control angiogram revealed dissolution of the acute thrombus under anticoagulation and the patient was treated with stenting with distal protection. Diffusion-weighted magnetic resonance imaging demonstrated no additional acute ischemic lesions. We were unable to find a similar report in the English literature documenting successful management of an acute vertebral ostial thrombus with anticoagulation. Anticoagulation might be considered prior to endovascular treatment of symptomatic vertebral stenoses complicated by the presence of acute thrombus.

Intimal Thickening after Placement of a Neuroform Stent: Its Incidence and Relation to Angiographic Follow-up Results of Aneurysm Embolization

Little attention has been given to the intimal thickening of the parent artery associated with the use of Neuroform stent. The purposes of this study were are to analyze quantifyanalyze the incidence of the parent artery intimal thickening the incidence and pattern of luminal changes, to to see somedetermine possible predictors of the phenomenonof the intimal thickening, to to evaluate the its effectthe phenomenonrestenosis on the aneurysm treatment results. We reviewed the initial and six-month follow-up angiographic images in 32 intracranial aneurysm patients treated with Neuroform stent and coilsin wide-necked aneurysm treatment. The initial embolization results were evaluated by the Raymond and Roy classification. The angiographic changes from immediate post-embolization to the six-month follow-up were classified as ‘improved’, ‘unchanged’ and ‘worse’. The occurrencerates of parent artery intimal thickening was observed. Any perceivable change in the stented segment of the parent artery was considered as ‘intimal thickening’ and any change of ≥50% as ‘significant thickening’. Fisher exact tests and logistic regression analysis were applied to determine the relation between the occurrence of the intimal thickening and several variables. The incidence of the intimal thickening was 18.8% (6/32) and of significant thickening, 3.1% (1/32). The change in angiographic occlusion of the aneurysm was ‘improved’ in 40.6% (13/32), ‘unchanged’ in 37.5% (12/32), and ‘worse’ in 21.9% (7/32). Among the variables, patients age (≥55) and follow-up angiographic results (‘improved’) correlated with the occurrence of the intimal thickening. Of notable finding was all six cases with intimal thickening of the parent artery were associated with ‘improved’ in their follow-up angiographic result. Neuroform-associated intimal thickening usually occurs in younger patients and is frequently associated with improved angiographic result of the aneurysm embolization on follow-up.

Angiographic Morphometry of Internal Carotid Artery Circulation in Turkish Children.

AIM Knowledge of cerebrovascular morphology is integral in planning neuroendovascular interventions, especially for procedures involving placement of stents, flow diverters or stentrievers. There is insufficient data on angiographic normative values of cerebral circulation in the pediatric age group since angiograms are uncommonly performed in children except for arteriovenous malformations in which arterial dimensions are larger than normal. We aimed to measure the diameters of internal carotid circulation (ICC) arteries on digital subtraction angiograms of pediatric patients and determine the growth trends. MATERIAL AND METHODS This is a retrospective cross-sectional study measurements of ICC arteries of 64 pediatric patients (4-122 months) with retinoblastoma undergoing intra-arterial chemotherapy. RESULTS Petrous, cavernous, supraclinoid and choroidal segments of internal carotid artery (ICA) and anterior cerebral artery (ACA) diameters had significant correlation with age. Most of the growth was noted in the first 36-48 months of life. Middle cerebral artery (MCA) diameter did not show significant correlation with age. 87% of the adult diameter of the MCA was attained in the first 6 months of life. ICC arteries reached 81% to 99% of adult sizes in the first 48 months of life. On the contrary, the main iliac artery was only 59% of the adult diameter at this age group. CONCLUSION Use of current intracranial stents in children appears tolerable due to the growth pattern of ICC arteries. Based on this data, the current armamentarium of intracranial stents or stent-like devices is sufficient to cover the need in the pediatric population.

Silk Device for the Treatment of Intracranial Aneurysms. Part 1: Peri-Procedural Results, Technical Aspects and Learning Curve.

AIM We evaluated the procedural outcomes of intracranial aneurysm treatment with the Silk device and its relation with operator experience. We also detailed some technical points we learned throughout our experience. MATERIAL AND METHODS One hundred and six consecutive patients with intracranial aneurysms treated using Silk (BaltExtrusion, Montmorency, France) stent between October 2010 and November 2013 were included. Patients were evaluated in terms of age, sex, aneurysm size, location, technical success, and adverse events. RESULTS There were 106 patients (71 female) undergoing 116 procedures with a mean age of 49.8 (range: 3-78 years). Mean aneurysm size was 10.7±8.0 (range, 2-40 mm). Technical success of the procedures was 96.5%. Adverse event rate was 11.2%. Among adverse events, there were 4 adverse events without complications, 2 mild complications, 7 severe complications, 4 of which resulted with death. The adverse event rate was significantly higher during the first half of the operators experience. The rate of adverse events seemed to stabilize after around 50 patients. Adverse events, regardless of the presence or absence of a clinical complication, were more frequent in aneurysms larger than 18.5 mm. CONCLUSION Safety of flow-diverter (FD) placement for intracranial aneurysms increases with operator experience. Training programs in endovascular management of cerebrovascular diseases and relevant fellowship curricula must be adapted to include sufficient flow diverter experience. The learning curve needs to be kept in mind when studies comparing different FD devices or those comparing other treatments to FDS are planned.