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.     

The two-in-one model: a new variation of the arteriovenous malformation model in swine

We report a new variation of the well-established experimental arteriovenous malformation (AVM) model in swine. To provide high flow through the rete mirabile (nidus, RM) and thereby to reduce the rate of spontaneous thrombosis of the AVM, we performed an end-to-end anastomosis of the left common carotid artery (CCA) and the external jugular vein (EJV) microsurgically in three micropigs. After 1 and 4 months the animals underwent angiograms of the CCA and vertebral artery (VA). In all cases the diversion of the blood through the RM was patent, up to the 4 months follow-up. We observed an arteriovenous fistula (arteriovenous pseudomalformation, pAVF) between the VA and the EJV in each case at both 1 and 4 months. This modification of the well-known AVM model in the micropig could be used to monitor long-term changes after embolisation, avoiding the naturally high rate of spontaneous thrombosis. This two-in-one model is thus well suited for preclinical testing of embolic materials. Received: 2 December 1999 Accepted: 31 August 2000     

利用猪颅底奇网制作动静脉畸形模型的实验研究

目的 利用猪颅底奇网制作一种简单、经济的动静脉畸形模型.方法 通过显微外科手术,将猪一侧颈总动脉与颈内静脉或颈外静脉吻合,建成动静脉畸形模型.吻合术后行血管造影及组织学检查.结果 8头家猪手术后全部成活.血流自右侧咽升动脉流经奇网和对侧咽升动脉,进入颈内/外静脉.术后3周1头家猪死亡.另1头家猪1个月时吻合口闭塞.结论...     

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.     

DSA对脑动静脉畸形出血的预测分析

目的:探讨脑动静脉畸形(AVM)血管造影形态与出血关系,预测脑动静脉畸形(AVM)出血的危险性。方法:回顾性分析104例数字减影脑血管畸形资料。结果:穿支动脉供血、单支引流和深部引流、小病灶及位于基底节和后颅窝者易出血。结论:通过观察脑动静脉畸形(AVM)供血动脉(类型)、大小、位置、引流静脉数目及通畅情况,可以对脑动静脉畸形(AVM)的出血情况进行预测。     

Is a Swine Model of Arteriovenous Malformation Suitable for Human Extracranial Arteriovenous Malformation? A Preliminary Study

Objective

A chronic arteriovenous malformation (AVM) model using the swine retia mirabilia (RMB) was developed and compared with the human extracranial AVM (EAVM) both in hemodynamics and pathology, to see if this brain AVM model can be used as an EAVM model.

Methods

We created an arteriovenous fistula between the common carotid artery and the external jugular vein in eight animals by using end-to-end anastomosis. All animals were sacrificed 1 month after surgery, and the bilateral retia were obtained at autopsy and performed hematoxylin and eosin staining and immunohistochemistry. Pre- and postsurgical hemodynamic evaluations also were conducted. Then, the blood flow and histological changes of the animal model were compared with human EAVM.

Results

The angiography after operation showed that the blood flow, like human EAVM, flowed from the feeding artery, via the nidus, drained to the draining vein. Microscopic examination showed dilated lumina and disrupted internal elastic lamina in both RMB of model and nidus of human EAVM, but the thickness of vessel wall had significant difference. Immunohistochemical reactivity for smooth muscle actin, angiopoietin 1, and angiopoietin 2 were similar in chronic model nidus microvessels and human EAVM, whereas vascular endothelial growth factor was significant difference between human EAVM and RMB of model.

Conclusions

The AVM model described here is similar to human EAVM in hemodynamics and immunohistochemical features, but there are still some differences in anatomy and pathogenetic mechanism. Further study is needed to evaluate the applicability and efficacy of this model.     

胼胝体区脑动静脉畸形

目的 :探讨颅内胼胝体区脑动静脉畸形的病理基础、临床表现、脑血管影像特点及治疗效果。方法 :6例患者在数字减影血管造影 (DSA)监视下进行全脑血管造影 ,了解畸形血管团的位置、大小、供血动脉及引流静脉情况 ,然后给予血管内栓塞治疗或放射治疗。结果 :6例患者 ,4例应用漂浮导管技术行血管内栓塞治疗治愈 ;2例行X—刀治疗 ,1例治愈 ,1例因治疗时间短 ,未复查。结论 :胼胝体区脑动静脉畸形 ,发病年龄轻 ,出血危险性大 ,畸形团小 ,位置深 ,供血动脉少 ,引流静脉单一 ,治疗效果好     

Occlusive vascular disease associated with cerebral arteriovenous malformations

Selective carotid angiography and computed tomography were used in a study of the association of occlusive vascular disease with cerebral arteriovenous malformations in 13 patients. The arterial occlusions ranged from focal stenosis in the major artery supplying the malformation to complete occlusion of the supraclinoid internal carotid artery with subsequent development of "moyamoya" collaterals. The majority of the arterial occlusions were proximal to the vascular malformation. Some, however, extended distal to the major branch supplying the arteriovenous malformation (AVM). Selective angiography with subtraction techniques defines the distinct angioarchitecture of these AVMs and the associated stenoses and collateral telangiectases.     

Cerebral Hyperperfusion Syndrome after Endovascular Reconstruction of Carotid Artery in High-Flow Carotid-Jugular Fistula

We describe the occurrence of cerebral hyperperfusion syndrome (CHS) in a case of long-standing carotid-jugular fistula (CJF) treated by endovascular reconstruction of the carotid artery. A 43-year-old male with a high-flow CJF between the internal carotid artery (ICA) and internal jugular vein underwent endovascular reconstruction of the carotid artery using a stent graft. After treatment, the patient developed CHS. The patient succumbed to a large intracranial bleed in the left external capsule and parietal lobe on the fifth postoperative day. CHS following endovascular reconstruction of carotid artery is rare. We present the first reported case of CHS following endovascular reconstruction of ICA. A review of literature for patients treated by endovascular rerouting of blood flow to the cerebral parenchyma associated with hyperperfusion syndrome has been performed.     

Cerebral MR venography

This paper illustrates the technique and clinical use of cerebral MR venography (MRV). Dural sinus thrombosis is detected by both two-dimensional time-of-flight (TOF) and three-dimensional phase-contrast (PC) techniques. Venous angiomas are demonstrated by the three-dimensional PC method. The arterial feeders, nidus and draining veins of cerebral arteriovenous malformation (AVM) can be visualized on contrast-enhanced TOF three-dimensional MR angiogram. The high-flow draining veins of cerebral and dural AVMs, vein of Galen malformation and carotid cavernous fistula are better seen on contrast-enhanced three-dimensional gradient-echo MRV.     

Use of a new mixture for embolization of intracranial vascular malformations

Summary The internal carotid artery system in swine has a special anatomic configuration similar to a brain arterial-arterial malformation. The internal carotid artery breaks up into a multitude of fine channels (rete mirabile) situated at the base of the skull on the side of the hypophysis. This anatomic arterial model was used to analyze acute and chronic angiographic and histological changes after occlusion of the rete mirabile with I) avitene, II) avitene, and 50% ethanol, III) avitene, 30% ethanol and Polyvinyl alcohol, IV) avitene 50% ethanol and Polyvinyl alcohol, V) IBCA and VI) silk. Histopathological changes observed in the rete mirabile six weeks following occlusion demonstrated that a mixture of avitene, 30% ethanol and Polyvinyl alcohol and IBCA produced the best anatomic results. Embolization with avitene, PVA and ethanol induced a more bland histological reaction than the one observed with IBCA. Preliminary clinical experience with this mixture is reassuring in those cases in which the AVM was surgically resected. The partially thrombosed AVM was easily depressed and compressed by the neurosurgeon allowing for satisfactory hemostasis in and around the nidus of the AVM.This paper was presented in part at the International Symposium on Cerebral Stroke, Sendai, Japan, 1987     

Histopathologic characteristics of a chronic arteriovenous malformation in a swine model: preliminary study

BACKGROUND AND PURPOSE: The experimental induction of histologic transformations in microvessels of similar caliber to those of nidus vessels of cerebral arteriovenous malformations (AVMs) has not been attempted previously. Our goal was to examine preliminarily the histopathologic characteristics of nidus vessels and the angiographic features of a chronic AVM model in swine. METHODS: AVM models were fashioned from bilateral carotid retia mirabilia of seven swine after the surgical formation of large unilateral carotid-jugular fistulas. One AVM model was made for immediate use, whereas in the other six, follow-up angiography was obtained at varying intervals (2 to 180 days) after model creation. Light and electron microscopy, immunohistochemistry (using monoclonal antibodies against smooth muscle actin and PC10 against proliferating cell nuclear antigen), and histometry were performed on the nidus vessels of three swine: one acutely created, one 2 months old, and one 6 months old. RESULTS: Vascular dilatation and tortuosity of the main arterial feeder and draining vein were evident angiographically as early as 4 days after AVM creation, and were maximal in the 6-month-old model. Compared with the acutely created nidus vessels, those in the two chronic models revealed disrupted and attenuated elastica and intimal hyperplasia that was focal ("cushions") or generalized, leading to luminal occlusion. Variable numbers of cells in the tunica media of chronic nidus vessels contained smooth muscle actin. PC10/proliferating cell nuclear antigen immunoreactivity was observed in the endothelium and subendothelial layers. Histometry showed increases in intimal hyperplasia and medial thickness in the chronic vessels. CONCLUSION: Nidus vessels in this chronic swine AVM model exhibited striking histologic changes similar to those seen in cerebral AVMs. The induced vessel growth seen angiographically and histologically in components of the chronic AVMs was consistent with the presence of persistently raised intravascular hemodynamic loads. This preliminary feasibility study suggests that the realistic histologic characteristics of this chronic AVM model are an attractive feature, and if confirmed in future, more comprehensive, studies would be of benefit in accurate histopathologic interpretation of the effects of superimposed experimental embolotherapy or radiosurgery. This model may provide a useful experimental tool to study the dynamic cellular and tissue events that dictate the development and natural history of AVMs.     

Demonstration of an early draining vein by MR angiography

We present a case of an arteriovenous malformation (AVM) where standard MR angiography demonstrated an enlarged basal vein of Rosenthal. The lenticulostriate branches of the middle cerebral artery were suggested but not conclusively shown, as the feeders of the AVM. Therefore, it could not be determined whether the enlarged vein was part of an AVM or of a venous angioma. By using a saturation pulse inferior to the image volume including the basal vein of Rosenthal and the middle cerebral artery, the transmission of "black blood" to the basal vein of Rosenthal was demonstrated. This implied early venous draining, which confirmed that the lesion represented an AVM.     

Spontaneous regression of cerebral arteriovenous malformations: clinical and angiographic analysis with review of the literature

Spontaneous regression of cerebral arteriovenous malformation (AVM) is rare and poorly understood. We reviewed the clinical and angiographic findings in patients who had spontaneous regression of cerebral AVMs to determine whether common features were present. The clinical and angiographic findings of four cases from our series and 29 cases from the literature were retrospectively reviewed. The clinical and angiographic features analyzed were: age at diagnosis, initial presentation, venous drainage pattern, number of draining veins, location of the AVM, number of arterial feeders, clinical events during the interval period to thrombosis, and interval period to spontaneous thrombosis. Common clinical and angiographic features of spontaneous regression of cerebral AVMs are: intracranial hemorrhage as an initial presentation, small AVMs, and a single draining vein. Spontaneous regression of cerebral AVMs can not be predicted by clinical or angiographic features, therefore it should not be considered as an option in cerebral AVM management, despite its proven occurrence.     

Determination of cerebral blood flow with a phase-contrast cine MR imaging technique: evaluation of normal subjects and patients with arteriovenous malformations.

This study evaluated a phase-contrast cine magnetic resonance (MR) imaging technique capable of simultaneously allowing determination of velocity and volume flow rate (VFR) in both carotid arteries and the basilar artery. Forty patients were studied; 24 were neurologically normal, and 16 had intracerebral arteriovenous malformations (AVMs). In the normal group, mean basilar flow was significantly less than mean carotid flow. Mean velocity and VFR showed a significant decline with age in the basilar artery. Carotid artery flow and total cerebral blood flow did not decline with age. In the AVM patients, flow and velocity measurements were significantly elevated in all three arteries. Flow in the carotid artery ipsilateral to the AVM was significantly greater than flow in the contralateral carotid artery. VFR increased in all three arteries with increasing AVM volume. Four patients underwent partial embolization, and a corresponding decrease in flow was observed. Phase-contrast cine MR imaging provides rapid, simultaneous, noninvasive velocity and VFR measurement in the major intracranial arteries.     

Epilepsy associated with cerebral arteriovenous malformations: a multivariate analysis of angioarchitectural characteristics.

PURPOSETo identify the morphological vascular characteristics of cerebral arteriovenous malformations (AVMs) that predict a clinical presentation of epilepsy.METHODFifteen angioarchitectural characteristics of brain AVMs were selected for assessment in 100 consecutive patients referred to our institution for endovascular treatment. In this population, 47% of the AVMs were diagnosed as a consequence of epilepsy. The angioarchitectural characteristics and population demographics were statistically analyzed by means of multivariate analysis.RESULTSThe following six parameters were found to be the most predictive of epilepsy: cortical location of the AVM, feeding by the middle cerebral artery, cortical location of the feeder, absence of aneurysms, presence of varix/varices in the venous drainage, and association of varix and absence of intranidal aneurysms. Three factors were not among the most predictive factors of epilepsy but were significantly associated with the onset of seizures: AVM feeding by the external carotid artery, a temporal cortical location, and a parietal cortical location.CONCLUSIONDetailed analysis of the angioarchitecture of intracranial AVMs has helped us identify features that strongly correlate with epilepsy. This may aid in future understanding of the physiopathologic mechanisms in epilepsy associated with AVMs, and in identifying goals of treatment for epileptogenic AVMs.     

A novel two-stage technique for construction of experimental aneurysms

A two-staged technique for construction of experimental aneurysms in swine is described. The jugular vein is initially anastomosed to the carotid artery. Spontaneous hypertrophy of the vein is modeled by placing restraining sutures to create a fusiform aneurysm. Subsequent endovascular closure of this aneurysm leaves a sidewall aneurysm pouch. Staging allows maturation of the anastomosis, and the technique provides additional targets for endovascular training. Trial has been successful in three animals.     

Occlusion of arteriovenous malformations of the cavernous sinus via the superior ophthalmic vein

The treatment of five patients with dural arteriovenous malformations (AVMs) of the cavernous sinus via the superior ophthalmic vein (SOV) is reported. The procedure was performed by transcutaneous puncture of the SOV under the guidance of real-time digital subtraction angiography. Complete resolution of the ocular symptoms was achieved in all cases. Angiograms after embolization showed complete obliteration of the malformation in four cases and partial obliteration in one. This method can cure dural AVMs of the cavernous sinus, with preservation of blood flow in the internal carotid artery. It is particularly indicated when the SOV is enlarged and when (1) dural AVMs of the cavernous sinus are fed by small branches of the internal carotid artery or direct carotid cavernous fistulas with small tears; (2) dural AVMs of the cavernous sinus are fed by multiple branches from both the internal and external carotid arteries, one or both sides; or (3) dural AVMs of the cavernous sinus or direct carotid cavernous fistulas recur after trapping of the internal carotid artery. Transcutaneous puncture and catheterization of the SOV was performed safely with the aid of digital subtraction angiography. The SOV approach was able to treat the fistula with preservation of the internal carotid artery.     

Congenital right internal mammary artery to portal vein arteriovenous malformation

Neonatal cases of systemic artery to portal venous system arteriovenous malformations (AVMs) can present unique challenges in terms of diagnosis, management, and treatment. Prompt identification of these AVMs is necessary for minimizing long-term sequelae and optimizing prognosis. Our report describes the diagnosis and successful endovascular coil embolization of a congenital right internal mammary artery (IMA) to portal vein AVM in a young infant initially presenting during routine fetal screening with an incidentally discovered congenital thoracic vascular abnormality.     

颅底及颈段脊髓血管畸形的介入检查

目的 :为介入栓塞治疗及手术治疗提供重要依据 ,从而防止误诊、漏诊病例的发生。方法 :对我院近期 3 0例疑有颅底及颈段脊髓血管畸形患者的临床表现、MRI影像特点、介入检查资料进行分析。结果 :3 0例患者均具有颅底及颈段脊髓血管畸形的临床表现及磁共振影像特点 ,经行选择性全脊髓血管造影、必要时行全脑血管造影证实 2 9例为颅底及颈段脊髓血管畸形 (其中 2 7例畸形团来自颈部血管供血及胸段脊髓血管等多支血管供血 ;2例来自颈外动脉系统供血 )。另外 1例开始被误诊为颅底及颈段脊髓血管畸形 ,后进行全脑血管造影发现为由颈内动脉原始听动脉供血的硬脑膜动静脉瘘向脊髓髓周静脉引流而造成MRI的留空信号。结论 :为了防止误诊及漏诊病例的发生 ,应对双侧的锁骨下动脉、椎动脉、肋颈干、甲状颈干、上胸段肋间动脉或全脊髓血管及颈外动脉进行造影检查 ,必要时还应进行全脑血管造影。