CTA Evaluation of Basilar Septations: An Entity Better Characterized as Aberrant Basilar Fenestrations.

BACKGROUND AND PURPOSE: A basilar artery intraluminal septation is an exceedingly rarely reported, presumed congenital abnormality. In our clinical practice, we have occasionally noticed an intraluminal band within the inferior aspect of the basilar artery on CTA. Furthermore, we have noticed, at times, the presence of a punctate calcification associated with this finding. We hypothesized that what previous studies have called "basilar septations" in fact represent miniature and thus aberrant basilar fenestrations. MATERIALS AND METHODS: We retrospectively reviewed CTA studies obtained between January 1, 2017, and August 31, 2019. Identified intraluminal basilar abnormalities were classified as either basilar septations or basilar fenestrations. Association with other posterior circulation abnormalities was documented. RESULTS: A total of 3509 studies were examined. A basilar intraluminal abnormality was evident in 80 patients (2.3%). Of these 80 patients, 59 were classified as having a basilar fenestration (1.7%) and 21 were classified as having basilar septations (0.6%). Associated calcification was evident in 3 of the basilar fenestration cases and 13 of the basilar septation cases. CONCLUSIONS: Basilar septations most likely represent and should be referred to as aberrant basilar fenestrations. They should be interpreted as benign congenital incidental findings and should not be misinterpreted as focal dissections or arterial webs. Important variations in the morphology of aberrant basilar fenestrations exist, including areas of thinning, varying thickness, and nodularity. Therefore, when associated with calcification or nodularity, aberrant basilar fenestrations should not be confused with focal intraluminal thrombi or calcified or noncalcified emboli.

Complex-shaped platinum coils for brain aneurysms: higher packing density, improved biomechanical stability, and midterm angiographic outcome.

BACKGROUND AND PURPOSE: Five to 60% of coiled brain aneurysms recanalize, generally because of coil compaction. In vitro exclusive use of complex-shaped coils allows better packing of the aneurysmal sac and the neck as compared with helical coils. We report a single-center, prospective study using complex coils. Safety, packing density, and recanalization rate were evaluated. MATERIALS AND METHODS: Seventy-seven aneurysms were embolized using complex coils alone. Aneurysms had a volume of 265 mm3 (diameter: 7.1+/-3.3 mm) and a neck size of 4.1+/-1.8 mm (range: 1.5-12 mm). Average follow-up available in 31 patients was 10.5+/-7.6 months (range: 3-36 months). Primary angiographic endpoints included aneurysmal recanalization and (re)rupture. Primary adverse events included stroke or death. RESULTS: Complete or near-complete occlusion was achieved in all of the aneurysms but required balloon assistance in 24.6%. The packing density was computed as 37%+/-13%. No rerupture was observed during the follow-up interval. Recanalization was seen in 4 (12.9%) of 31. Two basilar tip aneurysms underwent a safe and complete recoiling. Periprocedural nondevice-related neurologic deficits were seen in 2 (2.9%) of 69 patients. CONCLUSIONS: The use of complex-shaped coils allows higher packing density, which may improve the recanalization rate. Basilar tip aneurysms remain a challenge.

Reduced Patient Radiation Exposure during Neurodiagnostic and Interventional X-Ray Angiography with a New Imaging Platform.

BACKGROUND AND PURPOSE: Advancements in medical device and imaging technology as well as accruing clinical evidence have accelerated the growth of the endovascular treatment of cerebrovascular diseases. However, the augmented role of these procedures raises concerns about the radiation dose to patients and operators. We evaluated patient doses from an x-ray imaging platform with radiation dose-reduction technology, which combined image noise reduction, motion correction, and contrast-dependent temporal averaging with optimized x-ray exposure settings. MATERIALS AND METHODS: In this single-center, retrospective study, cumulative dose-area product inclusive of fluoroscopy, angiography, and 3D acquisitions for all neurovascular procedures performed during a 2-year period on the dose-reduction platform were compared with a reference platform. Key study features were the following: The neurointerventional radiologist could select the targeted dose reduction for each patient with the dose-reduction platform, and the statistical analyses included patient characteristics and the neurointerventional radiologist as covariates. The analyzed outcome measures were cumulative dose (kerma)-area product, fluoroscopy duration, and administered contrast volume. RESULTS: A total of 1238 neurointerventional cases were included, of which 914 and 324 were performed on the reference and dose-reduction platforms, respectively. Over all diagnostic and neurointerventional procedures, the cumulative dose-area product was significantly reduced by 53.2% (mean reduction, 160.3 Gy × cm2; P < .0001), fluoroscopy duration was marginally significantly increased (mean increase, 5.2 minutes; P = .0491), and contrast volume was nonsignificantly increased (mean increase, 15.3 mL; P = .1616) with the dose-reduction platform. CONCLUSIONS: A significant reduction in patient radiation dose is achievable during neurovascular procedures by using dose-reduction technology with a minimal impact on workflow.

Surpass Flow Diverter for Treatment of Posterior Circulation Aneurysms.

BACKGROUND AND PURPOSE: Flow diverters for the treatment of posterior circulation aneurysms remain controversial. We aimed to identify factors contributing to outcome measures in patients treated with the Surpass flow diverter for aneurysms in this location. MATERIALS AND METHODS: We conducted an observational study of 53 patients who underwent flow-diverter treatment for posterior circulation aneurysms at 15 centers. Key outcome measures were mortality, complete aneurysm occlusion, and modified Rankin Scale score at follow-up. RESULTS: At follow-up (median, 11.3 months; interquartile range, 5.9-12.7 months), 9 patients had died, resulting in an all-cause mortality rate of 17.3% (95% CI, 7%-27.6%); 7 deaths (14%) were directly related to the procedure and none occurred in patients with a baseline mRS score of zero. After adjusting for covariates, a baseline mRS of 3-5 was more significantly (P = .003) associated with a higher hazard ratio for death than a baseline mRS of 0-2 (hazard ratio, 17.11; 95% CI, 2.69-109.02). After adjusting for follow-up duration, a 1-point increase in the baseline mRS was significantly (P < .001) associated with higher values of mRS at follow-up (odds ratio, 2.93; 95% CI, 1.79-4.79). Follow-up angiography in 44 patients (median, 11.3 months; interquartile range, 5.9-12.7 months) showed complete aneurysm occlusion in 29 (66%; 95% CI, 50.1%-79.5%). CONCLUSIONS: Clinical results of flow-diverter treatment of posterior circulation aneurysms depend very much on patient selection. In this study, poorer outcomes were related to the treatment of aneurysms in patients with higher baseline mRS scores. Angiographic results showed a high occlusion rate for this subset of complex aneurysms.

Emergent Endovascular Management of Long-Segment and Flow-Limiting Carotid Artery Dissections in Acute Ischemic Stroke Intervention with Multiple Tandem Stents.

BACKGROUND AND PURPOSE: Although most cervical dissections are managed medically, emergent endovascular treatment may become necessary in the presence of intracranial large-vessel occlusions, flow-limiting and long-segment dissections with impending occlusion, and/or hypoperfusion-related ischemia at risk of infarction. We investigated the role of emergent endovascular stenting of long-segment carotid dissections in the acute ischemic stroke setting. MATERIALS AND METHODS: We retrospectively studied long-segment carotid dissections requiring stent reconstruction with multiple tandem stents (≥3 stents) and presenting with acute (<12 hours) ischemic stroke symptoms (NIHSS score, ≥4). We analyzed patient demographics, vascular risk factors, clinical presentations, imaging/angiographic findings, technical procedures/complications, and clinical outcomes. RESULTS: Fifteen patients (mean age, 51.5 years) with acute ischemic stroke (mean NIHSS score, 15) underwent endovascular stent reconstruction for vessel and/or ischemic tissue salvage. All carotid dissections presented with >70% flow limiting stenosis and involved the distal cervical ICA with a minimum length of 3.5 cm. Carotid stent reconstruction was successful in all patients with no residual stenosis or flow limitation. Nine patients (60%) harbored intracranial occlusions, and 6 patients (40%) required intra-arterial thrombolysis/thrombectomy, achieving 100% TICI 2b-3 reperfusion. Two procedural complications were limited to thromboembolic infarcts from in-stent thrombus and asymptomatic hemorrhagic infarct transformation (7% morbidity, 0% mortality). Angiographic and ultrasound follow-up confirmed normal carotid caliber and stent patency, with 2 cases of <20% in-stent stenosis. Early clinical improvement resulted in a mean discharge NIHSS score of 6, and 9/15 (60%) patients achieved a 90-day mRS of ≤2. CONCLUSIONS: Emergent stent reconstruction of long-segment and flow-limiting carotid dissections in acute ischemic stroke intervention is safe and effective, with favorable clinical outcomes, allowing successful thrombectomy, vessel salvage, restoration of cerebral perfusion, and/or prevention of recurrent thromboembolic stroke.

Elastase-induced aneurysms in rabbits: effect of postconstruction geometry on final size.

BACKGROUND AND PURPOSE: Elastase-induced aneurysms in rabbits have become an accepted model to study endovascular treatment. The size and shape of the resulting aneurysms may vary widely. Our goal was to predict the final aneurysm morphology on the basis of immediate postinduction geometry. METHODS: Thirty New Zealand white rabbits were used. Aneurysms were created at the origin of the right common carotid artery (CCA). Intraluminal incubation of elastase was applied to the origin of CCA with proximal balloon occlusion of the artery. The aneurysms were allowed to mature for 3 weeks and evaluated by digital subtraction angiography. We retrospectively measured neck diameter, dome height, and aneurysm diameter, as well as the angle between the parent artery and the main axis of the aneurysm neck. We performed correlation analysis with immediate postinduction geometry. RESULTS: The diameter of the origin of the CCA measured immediately after elastase incubation correlated positively to the mature aneurysm neck (P < .01). Moreover, the aneurysm neck both after the aneurysm creation and at 3-week follow-up had a positive correlation with the final dome height (P < .05). Finally, the dome height was related to the angle between the centerline of the innominate artery and axis of the aneurysm neck for dome diameter-to-neck ratio of <1.5 (P < .05). CONCLUSION: These results indicate that neck width immediately after creation and the curvature of the parent artery are linked to the final aneurysm dimensions, and we may be able to predict the size of aneurysm on the day of creation.

Acute and chronic swine rete arteriovenous malformation models: effect of ethiodol and glacial acetic acid on penetration, dispersion, and injection force of N-butyl 2-cyanoacrylate.

BACKGROUND AND PURPOSE: Liquid embolic agents are increasingly gaining importance in the embolization of cerebral arteriovenous malformations (AVMs). Currently, the most commonly used agent is N-butyl 2-cyanoacrylate (NBCA). Various NBCA mixtures, arterial hypotension, and Valsalva maneuver (increased positive end-expiratory pressure) during the injection of the acrylate have been used to address hemodynamic and architectural variations of an AVM; however, the precise in vivo polymerization, distribution, and kinetics of NBCA mixtures are unknown. We investigated the effect of different acrylate/Lipiodol mixtures and the addition of glacial acetic acid (GAA) on the penetration, dispersion, and injection force of NBCA. METHODS: A swine rete AVM model that has been described elsewhere was used for the embolization. In one subgroup of animals, embolization was performed immediately after construction of the AVM model. In a second subgroup, a chronic AVM model was used. GAA was added to the NBCA mixture to decrease the pH value of the solution and prolong the polymerization time. The addition of GAA allowed us to reduce the amount of Lipiodol, thereby reducing the viscosity of the mixture. A total of 30 swine were used for both the acute (n = 23) and chronic (n = 7) subgroups. The following mixtures of Lipiodol/NBCA and GAA (% vol/%vol + microL) were used for embolization: 80/20 + 0; 50/50 + 0; 50/50 + 5; 50/50 + 10; and 50/50 + 20. A total of six retia per mixture were used for the analysis. Glue injection pressure profiles were recorded in each experiment. High-resolution radiographic images obtained from the harvested retia were used to correlate the dispersion and depth of glue penetration with the AVM hemodynamics. The effect of different amounts of GAA on the glue dispersion and depth of penetration of the mixtures was also studied. RESULTS: Using the same pressure gradients, less viscous NBCA + GAA mixtures led to a deeper nidal penetration. The addition of 20 microL of GAA resulted in a three times higher penetration and dispersion of the NBCA mixture that was more homogenous. CONCLUSION: The viscosity of the liquid embolic agent used is an important limiting factor for an AVM embolization. Reducing the amount of Lipiodol improves nidus penetration. Quicker polymerization can be overcome by adding GAA, which reduces the pH of the mixture.

Acute and chronic swine rete arteriovenous malformation models: hemodynamics and vascular remodeling.

BACKGROUND AND PURPOSE: An acute and a chronic arteriovenous malformation (AVM) model were developed by using the swine rete to study hemodynamics and vascular remodeling. The models were also used to study in vivo polymerization kinetics and the distribution of various N-butyl 2-cyanoacrylate (NBCA) and Lipiodol mixtures. METHODS: In the acute swine AVM model, retrograde flow through the left side of the rete was created by the placement of an endovascular shunt through the ipsilateral ascending pharyngeal artery. In the chronic model, flow was redirected retrograde through the left side of rete and ascending pharyngeal artery by creating an arteriovenous fistula between the ipsilateral jugular vein and the common carotid artery. After a period of at least 6 months, the entire head with the rete was connected to a perfusion loop driven by a peristaltic pump. A total of 30 swine were used for both the acute (n = 23) and chronic groups (n = 7). Hemodynamic parameters, including the flow and pressure drop across the rete, were recorded before NBCA embolization. Image processing was used on high-resolution radiographs of the explanted retia to measure the total rete length. Measurements of rete vessel calibers were based on histology. RESULTS: The pressure gradients across retia were higher in the chronic model than in the acute model, but they did not reach the level of statistical significance (23.7 +/- 12.0 mm Hg vs 15.4 +/- 1.4 mm Hg). The rete blood outflow was significantly higher in the chronic model compared with the acute one (139.9 +/- 100.3 mL/min vs 32.5 +/- 17.6; P = .03). The rete length in the chronic model was significantly higher than in the acute model (593.1 +/- 39.9 vs 401.3 +/- 65.2 pixel; P < .001). The average vessel diameter of the rete in the chronic group was 520 microm and 320 microm in the control animals. CONCLUSION: Increased pressure gradients and flow in the chronic swine rete AVM model may be related to increased size and decreased impedance. The resulting hemodynamic changes reflect a true flow-induced vascular remodeling rather than a simple change related to aging and size of the animal.

MR imaging of myeloperoxidase activity in a model of the inflamed aneurysm wall.

BACKGROUND AND PURPOSE: Although myeloperoxidase activity in vivo can be visualized by using noninvasive imaging, successful clinical translation requires further optimization of the imaging approach. We report a motion-sensitized driven-equilibrium MR imaging approach for the detection of a myeloperoxidase activity-specific gadolinium-containing imaging agent in experimental aneurysm models, which compensates for irregular blood flow, enabling vascular wall imaging in the aneurysm. MATERIALS AND METHODS: A phantom was built from rotational angiography of a rabbit elastase aneurysm model and was connected to a cardiac pulse duplicator mimicking rabbit-specific flow conditions. A T1-weighted turbo spin-echo-based motion-sensitized driven-equilibrium pulse sequence was optimized in vitro, including the addition of fat suppression and the selection of the velocity-encoding gradient parameter. The optimized sequence was applied in vivo to rabbit aneurysm models with and without inflammation in the aneurysmal wall. Under each condition, the aneurysms were imaged before and after intravenous administration of the imaging agent. The signal-to-noise ratio of each MR imaging section through the aneurysm was calculated. RESULTS: The motion-sensitized driven-equilibrium sequence was optimized to reduce flow signal, enabling detection of the myeloperoxidase imaging agent in the phantom. The optimized imaging protocol in the rabbit model of saccular aneurysms revealed a significant increase in the change of SNR from pre- to post-contrast MR imaging in the inflamed aneurysms compared with naïve aneurysms and the adjacent carotid artery (P < .0001). CONCLUSIONS: A diagnostic MR imaging protocol was optimized for molecular imaging of a myeloperoxidase-specific molecular imaging agent in an animal model of inflamed brain aneurysms.

Surpass flow diverter in the treatment of intracranial aneurysms: a prospective multicenter study.

BACKGROUND AND PURPOSE: Incomplete occlusion and recanalization of large and wide-neck brain aneurysms treated by endovascular therapy remains a challenge. We present preliminary clinical and angiographic results of an experimentally optimized Surpass flow diverter for treatment of intracranial aneurysms in a prospective, multicenter, nonrandomized, single-arm study. MATERIALS AND METHODS: At 24 centers, 165 patients with 190 intracranial aneurysms of the anterior and posterior circulations were enrolled. The primary efficacy end point was the percentage of intracranial aneurysms with 100% occlusion on 6-month DSA. The primary safety end point was neurologic death and any stroke through a minimum follow-up of 6 months. RESULTS: Successful flow-diverter delivery was achieved in 161 patients with 186 aneurysms (98%); the mean number of devices used per aneurysm was 1.05. Clinical follow-up (median, 6 months) of 150 patients (93.2%), showed that the primary safety end point occurred in 18 subjects. Permanent neurologic morbidity and mortality were 6% and 2.7%, respectively. Morbidity occurred in 4% and 7.4% of patients treated for aneurysms of the anterior and posterior circulation, respectively. Neurologic death during follow-up was observed in 1.6% and 7.4% of patients with treated intracranial aneurysms of the anterior and posterior circulation, respectively. Ischemic stroke at ≤30 days, SAH at ≤7 days, and intraparenchymal hemorrhage at ≤7 days were encountered in 3.7%, 2.5%, and 2.5% of subjects, respectively. No disabling ischemic strokes at >30 days or SAH at >7 days occurred. New or worsening cranial nerve deficit was observed in 2.7%. Follow-up angiography available in 158 (86.8%) intracranial aneurysms showed 100% occlusion in 75%. CONCLUSIONS: Clinical outcomes of the Surpass flow diverter in the treatment of intracranial aneurysms show a safety profile that is comparable with that of stent-assisted coil embolization. Angiographic results showed a high rate of intracranial aneurysm occlusion.

Microcatheter urokinase infusion in central retinal artery occlusion.

We treated 14 consecutive patients for acute central retinal artery occlusion. Eleven were treated with urokinase introduced through a microcatheter in the proximal segment of the ophthalmic artery. Fibrinolysis was succeeded by heparinization for two to three days. Instead of urokinase, we used tissue plasminogen activator in three patients. Vision improved markedly in four of the 14 patients. Five others had slight improvement of visual acuity, visual field, or both. In five patients, no change occurred. Such a recovery of visual acuity may be anticipated if treatment begins within the first few hours after the onset of central retinal artery occlusion. A control group of 41 consecutive patients treated conservatively showed almost no improvement in visual acuity. Eleven of these 41 patients were treated within the first six hours after the patient noticed the onset of blindness.

An orbital arteriovenous malformation in a patient with origin of the ophthalmic artery from the basilar artery.

An abnormal origin of the ophthalmic artery from the basilar artery, found in conjunction with an orbital arteriovenous malformation, is described. The successful treatment of the arteriovenous malformation by embolization through the ophthalmic artery is also reported.

Extended preoperative polyvinyl alcohol microembolization of intracranial meningiomas: assessment of two embolization techniques.

PURPOSE: To evaluate the efficacy of preoperative meningioma devascularization with small polyvinyl alcohol (PVA) particles. METHODS: In 34 patients with intracranial meningiomas, CT, MR, 1H MR spectroscopy, MR volumetric measurements, intraoperative ultrasound, and histopathologic findings were used to compare the efficacy of two embolization techniques: 1) administration of 150- to 300-microns PVA particles in the usual suspension, and 2) administration of 50- to 150-microns PVA particles in a highly diluted suspension. RESULTS: Angiography after embolization demonstrated the total elimination of tumor blush in all patients. Contrast-enhanced MR after the administration of 150- to 300-microns PVA particles revealed a reduction of tumor enhancement in only two out of 14 patients. Only after the use of small particles could significant tumor necrosis be depicted on MR and confirmed histopathologically after surgery. In 12 of 20 patients, 30% to 95% of the whole tumor was necrotic with 17% to 20% reduction of tumor volume in four cases, leading to recovery from the initial neurologic deficits. In three of 20 patients without sufficient steroid medication before the treatment, tumor swelling occurred. Postembolization MR disclosed a tumor volume increase of 10% to 20% in these patients. 1H MR spectroscopy of the tumors showed an increase of lactate and aliphatic lipid compounds after embolization, indicating tumor infarction. Surgical removal of effectively embolized meningiomas without significant blood loss was possible. The appearance of the tumor at operation, ultrasound examination, and the histopathologic examination of different parts of the tumor confirmed the preoperative MR findings suggesting necrosis. CONCLUSION: Extended microembolization with 50- to 150-microns PVA particles improves the surgical treatment of meningiomas, as compared with larger particle embolization. It may also be the only treatment required in older or high-risk patients. The protective effect of steroid medication before the endovascular treatment of meningiomas is suggested by our study.

Self-expanding nitinol stents in canine vertebral arteries: hemodynamics and tissue response.

PURPOSE: To evaluate the hemodynamics and tissue response associated with stent placement in low-flow-velocity arteries. METHODS: Six self-expanding nitinol stents (5.5 mm caliber) were implanted transfemorally within the proximal segments of vertebral arteries (2.5 mm diameter) in six adult dogs during anticoagulative protection. RESULTS: Control angiograms demonstrated patency and 20% dilatation of all stented arteries. One artery was partially thrombosed 1 week later and subsequently showed a 50% stenosis. Throughout the observation period (4 to 9 months after stenting), the other five arteries remained patent without significant narrowing (< or = 15%). Small cervical muscle branches originating from the vertebral arteries within the stented segments remained patent. No major branch occlusions of the vertebrobasilar system were detected. Stent migration or kinking did not occur. MR studies of the brain 4 months after implantation revealed no infarcted areas. These findings were confirmed with brain sections. Stented artery specimens showed delayed stent dilatation. A comparison of the total mean thickness of intima covering the five 30- to 40-mm stents removed at 4, 6, and 9 months showed no significant difference (338, 332, and 389 microns, respectively). Histologic findings verified the macroscopic impression of a thicker intima at the inner curve of the stented artery segments and at the junctions of the stent filaments. The shortest (10 mm) stent had the thinnest neointimal growth (155 microns). Stented vessels showed compression of the media with atrophy, but without necrosis or perforation. Scanning electron photomicrographs revealed intact endothelial cell linings with typical elongated cells. CONCLUSIONS: No significant risk of thromboembolic events exists after implanting these nitinol stents in nonatherosclerotic vertebral arteries in dogs. Thicker neointimal growth after stenting may result from either low wall shear stress with possible flow separation or from changes in the shape and size of the stent, or both.

Europium fluorescence to visualize N-butyl 2-cyanoacrylate in embolized vessels of an arteriovenous malformation swine model.

BACKGROUND AND PURPOSE: Standard tissue staining using the lipid dye Oil-Red-O has been previously applied to stain vessel specimens, which were embolized with a mixture of n-butyl 2-cyanoacrylate (NBCA) and oil (Lipiodol). That technique, however, results in nonspecific and nonquantitative staining that does not provide the necessary differentiation between NBCA and Lipiodol. We present an innovative staining procedure that quantifies NBCA within treated tissues. METHODS: An arteriovenous malformation (AVM) model in swine was used to evaluate the polymerization characteristics of various ratios of Lipiodol/NBCA/glacial acetic acid (GAA) mixtures. To determine the depth of NBCA penetration within the AVM model and to characterize the polymerization patterns of various mixtures within the vessel, histologic cross- and longitudinal sections were prepared for microscopy. These paraffin-embedded tissue sections were stained with a europium aryl-beta-diketone complex (TEC) to improve differentiation between NBCA and Lipiodol. Quantification of NBCA and Lipiodol within the lumen of rete cross-sections was accomplished using image analysis software to determine percent luminal area occluded by embolization. RESULTS: Upon application of TEC, intense europium fluorescence was seen when the tissue samples were excited by low-power UV light (excitation at 365 nm; emission at 614 nm). The area of europium intensity within the lumen corresponded to NBCA concentration, and addition of GAA aided the NBCA distribution throughout the lumen without affecting fluorescence intensity. It was seen that NBCA could be easily differentiated from Lipiodol and that quantification could be readily performed on these sections because of the improved differentiation. For the case of a 50:50 (vol. %) mixture with an added 20 microL of GAA, luminal area distribution of Lipiodol, NBCA, and blood products was 42.6 +/- 3.5%, 33.8 +/- 5.7%, and 23.7 +/-2.7%, respectively. CONCLUSION: The rare earth metal europium, when added as a fluorescent chelate compound to histologic tissue sections, allowed for differentiation between NBCA and Lipiodol with good detail. These results have facilitated further characterization of NBCA polymerization for the use of AVM embolization.

Self-expanding and balloon-expandable stents in the treatment of carotid aneurysms: an experimental study in a canine model.

PURPOSE: To assess the efficacy of metal stents for the treatment of different forms and sizes of carotid aneurysms. METHODS: A total of 14 experimentally constructed aneurysms in dogs were treated with transfemorally placed balloon-expandable tantalum and self-expanding nitinol stents. RESULTS: In 10 cases, stenting produced either immediate complete occlusion of the aneurysm (n = 7) or complete delayed thrombosis after 7 to 10 days (n = 3). In two cases treated with balloon-expandable tantalum endoprostheses, repeated angiography showed a persistent aneurysmal neck with a diameter of 1 mm. No incompletely occluded aneurysms were visible after implantation of nitinol stents. Nine-month angiographic follow-up revealed maximal stenosis of the stented vessel segment of up to 40% after placement of tantalum endoprostheses. However, no more than 15% stenosis followed the deployment of nitinol stents. Histologic examination confirmed these findings. Significantly greater intimal fibrocellular tissue growth surrounded tantalum filaments than nitinol filaments, which were covered with a smooth, thin neointimal layer. In two carotid arteries a subtotal and total occlusion of the parent vessel occurred after the insertion of a tantalum and nitinol stent, respectively. No recanalization of completely occluded aneurysms or delayed migration of a stent was observed. CONCLUSIONS: Porous, tubular self-expanding nitinol stents may become the treatment of choice for broad-based and fusiform aneurysms of the internal carotid artery. However, blood flow dynamics of the aneurysms must be studied carefully in order to select an appropriate mesh size for complete occlusion while preserving the parent vessel. Improvements in the introducing system, stent material, and stent shape are required for simple implantation and reduction of intimal hyperplasia.

Modification of a previously described arteriovenous malformation model in the swine: endovascular and combined surgical/endovascular construction and hemodynamics.

BACKGROUND AND PURPOSE: The rete mirabile in swine has been proposed as an arteriovenous malformation (AVM) model for acute experimental studies through surgical creation of a large carotid-jugular fistula. This report describes two endovascular modifications to simplify the surgical creation and provides hemodynamic parameters for the AVM model. METHODS: An AVM model was created in 29 animals to study n-butyl 2-cyanoacrylate polymerization kinetics. The common carotid artery (CCA) was punctured and a guiding catheter was inserted tightly into the origin of the ascending pharyngeal artery (APA). The CCA was ligated proximal to the catheter to create a pressure drop across the rete, which represented the AVM nidus. The catheter hub was opened whenever needed and served as the venous drainage of the AVM nidus. The contralateral APA served as the arterial feeder. Instead of the surgical ligation of the CCA, a temporary balloon occlusion was performed in three animals. RESULTS: A mean pressure gradient of 14.9 +/- 10.5 mm Hg (range, 4-42 mm Hg) was measured across the rete. The mean flow rate was 30.4 +/- 14.2 mL/min (range, 3.5-46 mL/min), as measured at the venous drainage. CONCLUSION: The endovascular and combined surgical-endovascular rete AVM model in swine is easy to construct and is less time-consuming than are the currently used models for acute experimental studies. Hemodynamic parameters can be monitored during the entire experiment and correspond to values found in human cerebral AVMs.

Microdroplet tracking using biplane digital subtraction angiography for cerebral arteriovenous malformation blood flow path and velocity determinations.

High-speed biplane angiography is used to determine the path and velocity of microdroplets of contrast material in three dimensions. By allowing more accurate determination of detailed blood flow in feeding vessels and draining veins of cerebral arteriovenous malformations than available with standard angiography, the new method offers the potential for more accurate treatment and further study of neurovascular/cerebrovascular hemodynamics. The first study of the method is presented.

Initial experience with collagen-filled Guglielmi detachable coils for endovascular treatment of experimental aneurysms.

PURPOSE: To evaluate the effectiveness of Guglielmi detachable coils (GDCs) filled with collagen threads in the permanent treatment of experimental aneurysms. METHODS: Seventeen side-wall aneurysms were surgically constructed in the canine common carotid artery; six were treated with conventional GDCs and 11 with collagen-filled GDCs. One aneurysms was removed at 1 week, the others were studied by digital subtraction angiography for a period of 8 to 12 weeks. Longitudinal sections of all aneurysms were examined by light microscopy. RESULTS: Angiograms obtained throughout the follow-up period showed no significant difference between aneurysms treated with conventional GDCs and those treated with collagen-filled GDCs. Light microscopy revealed a dense meshwork of newly formed collagen and fibroblasts near the collagen-filled GDCs, whereas a loose cellular meshwork surrounded the conventional GDCs at 8 and 12 weeks after treatment. CONCLUSION: Collagen threads within GDCs do not noticeably improve angiographic treatment of experimental aneurysms; however, these threads did induce local proliferation of fibroblasts and production of collagen within the aneurysmal cavities.

Effects of a mixture of a low concentration of n-butylcyanoacrylate and ethiodol on tissue reactions and the permanence of arterial occlusion after embolization.

OBJECTIVE: Cyanoacrylates are the most commonly used liquid embolic agents. For embolization of arteriovenous malformations, a mixture of a low concentration of n-butylcyanoacrylate (NBCA) and Ethiodol (Savage Laboratories, Melville, NY) has been recommended for deeper penetration of the nidus. Dilution of NBCA, however, might result in different degrees of tissue reaction and might influence the permanence of vessel occlusion, with an increased risk of vessel recanalization. We compared tissue reactions induced by different NBCA/Ethiodol mixtures and analyzed the permanence of their embolic effects. METHODS: NBCA was diluted with Ethiodol to prepare the following standard solutions: Mixture A, low concentration (NBCA/Ethiodol ratio of 20:80); Mixture B, high concentration (50:50). The study was designed in two parts, because tissue reactions after embolization are considered to be a combination of foreign body reactions to solidified material and reactions to the injured blood vessel. Foreign body reactions were studied by intramuscularly injecting both glue mixtures into the backs of 18 rats. Specimens were obtained at various times after implantation. Immunohistochemical analysis and esterase staining were used to detect macrophages and neutrophils, respectively. The densities of these inflammatory cells were calculated and statistically compared. To study the degree of vascular wall injury and the permanence of embolic effects, the renal arteries in 48 rabbits were embolized with NBCA Mixture A or B. Six specimens for each group were obtained at various times after embolization. RESULTS: There was no significant difference in foreign body reactions between groups treated with Mixtures A and B, at any time. However, the macrophage density was larger for both groups at 3 months versus 3 days and for the group treated with Mixture B at 3 months versus 2 weeks. There was no difference in the degree of vessel wall injury. None of the embolized vessels demonstrated evidence of recanalization. CONCLUSION: The low concentration of NBCA induced a tissue response similar to that of the high-concentration form. Embolized vessels exhibited no greater incidence of recanalization. Therefore, embolization of arteriovenous malformations with diluted NBCA may be safe.