How I do it. Arteriovenous malformation management

Absence of skin discoloration after transarterial embolization of a subcutaneous auricular arteriovenous malformation with PHIL

BACKGROUND AND OBJECTIVE

One of the treatment options for arteriovenous malformations consists of embolization, with a choice of various embolic agents, with or without subsequent surgical excision. If embolization is offered without subsequent surgery, the embolic material will stay in situ, in which case the consistency and color become important in superficial lesions. The purpose of this case report is to describe if the use of a novel liquid embolic agent (PHIL) is well suited for treatment of superficial AVMs without subsequent surgery.

CASE DESCRIPTION

A 30-year-old male presented with a painful reddish, pulsatile swelling of the left ear that had been present for more than 10 years. Angiography confirmed an arteriovenous malformation supplied by the superficial temporal artery and the posterior auricular artery. The lesion was successfully treated by embolization with PHIL, through the superficial temporal artery. A minute residual shunt, from the posterior auricular artery, was accepted. Immediate disappearance of pulsatile tinnitus was reported. Moreover, return of normal skin color was observed without discomfort from the embolic deposits. This result has been stable throughout one year of clinical follow-up.

CONCLUSION

To our knowledge, this is the first case report describing PHIL embolization as a treatment option for superficial arteriovenous malformations without the necessity for subsequent surgery. The white color and rubbery consistency are beneficial characteristics of PHIL in treatment of subcutaneous lesions, especially in cosmetically relevant locations.

Superselective Intra-Arterial Ethanol Sclerotherapy of Feeding Artery and Nidal Aneurysms in Ruptured Cerebral Arteriovenous Malformations

In the endovascular treatment of cerebral arteriovenous malformations, ethanol sclerotherapy is seldom used due to safety concerns. However, when limited reflux of an embolic agent is permissible or when there is a long distance to the target, ethanol may be preferable. We reviewed 10 patients with 14 cerebral AVM feeding artery aneurysms or intranidal aneurysms treated with intra-arterial ethanol sclerotherapy at our institution between 2005 and 2014. All patients presented with acute intracranial hemorrhage. Thirteen of 14 aneurysms were treated primarily with 60%-80% ethanol into the feeding artery. Complete target feeding artery and aneurysm occlusion was seen in all cases; 8/13 (62%) were occluded by using ethanol alone. No retreatments or recurrences were seen. One permanent neurologic deficit (1/13, 7.7%) and no deaths occurred. In a subset of ruptured cerebral AVMs, ethanol sclerotherapy of feeding artery aneurysms and intranidal aneurysms can be performed with a high degree of technical success and a low rate of complication.

Interventional management of high-flow craniofacial vascular malformations: a database analysis and review of the literature

Background

High-flow craniofacial vascular malformations are uncommon, locally aggressive lesions that pose a therapeutic challenge.

Objective

To report our experience with the treatment of high-flow craniofacial vascular malformations.

Methods

After institutional review board approval was obtained, the neurointerventional databases of two institutions were retrospectively reviewed for vascular malformations from October 2010 to June 2015. All patients who had been treated for a high-flow craniofacial vascular malformation were included in the analysis. Clinical presentation, location, type, agent and techniques used, procedural complications, and clinical and imaging follow-up were included in the analysis.

Results

Eighteen patients (12 female and 6 male) harboring 21 high-flow vascular malformations met the inclusion criteria in our study. All patients were symptomatic. One patient had two separated arteriovenous malformations (AVMs) (one nasal and the other forehead/scalp), and one patient had three separated scalp lesions. One patient with a nasal AVM had capillary malformation-AVM syndrome. Overall, 13 AVM and 8 arteriovenous fistuli were treated in 31 targeted embolization procedures (ranging from 1 procedure to 4 procedures, mean 1.7 procedures). Onyx was the predominant agent used in 25 procedures. In 31 procedures, 1 procedural complication (skin ulceration) occurred. At the end of the last treatment session 14 of the 21 lesions were cured. Symptomatic control was achieved in all cases, with resolution or significant improvement of the symptoms (mean follow-up of 10 months).

Conclusions

High-flow craniofacial vascular malformations can be successfully managed with interventional techniques.

Non-invasive magnetic resonance-guided high intensity focused ultrasound ablation of a vascular malformation in the lower extremity: a case report

Introduction

Therapy of choice for symptomatic vascular malformations consists of surgery, sclerotherapy, or embolization. However, these techniques are invasive with possible complications and require hospitalization. We present a novel non-invasive technique, i.e., magnetic resonance-guided high-intensity focused ultrasound (MR-HIFU) ablation, for the treatment of a vascular malformation in a patient. This technique applies high-intensity sound waves transcutaneously to the body and is fully non-invasive. MRI guidance is the novel aspect of HIFU treatments and is used for exquisite delineation and localization of the lesion and accurate real-time temperature monitoring during tissue ablation. MR-HIFU is a well-established treatment option for uterine fibroids and is currently being investigated for, e.g., bone tumors, breast cancer, prostate cancer, and liver cancer. MR-HIFU of vascular malformations has not been a topic of research yet.

Case description

Volumetric MR-HIFU ablation of a vascular malformation in the lower extremity of an 18-year-old male patient was performed. Temperatures of 62–80 °C were reached in the target lesion with sonications of 4 × 4 × 8 mm using powers of 200 W for <20 s. At 1-month follow-up, the patient reported qualitatively sustained reduction of pain and normal motor function. Three-month follow-up imaging indicated successful nidus destruction, which resulted in reduction of >30 % of the tumor volume. After 13 months, pain score was reduced to <2 after extreme exertion for several hours and to 0 for daily activities.

Discussion and evaluation

Radiofrequency ablation and cryoablation are minimally invasive techniques that have been tried on low-flow vascular malformations with inconsistent results. Furthermore, both techniques require probe insertion, which is associated with risks of wound infection and hospitalization. Since MR-HIFU is truly non-invasive, these risks are negligible.

Conclusions

In conclusion, we reported a successful non-invasive treatment of a vascular malformation with MR-HIFU in a clinical patient including long-term follow-up data for the first time. The patient reported qualitatively sustained pain reduction up to 13 months post treatment.

Salvage treatment of hemorrhagic arteriovenous malformations in jaws

OBJECTIVE

To present our clinical experience on embolotherapy of arteriovenous malformations (AVMs) in jaws with acute hemorrhage.

MATERIALS AND METHODS

Twelve patients with a history of hemorrhage were selected for this study. Continuous interdental sling suture, digital pressure on the extraction socket, and iodoform gauze packed into the socket and fixed with sutures to the adjacent gum were used for temporary hemostasis before embolization. Fiberoptic bronchoscopy was used in all cases to facilitate endotracheal intubation. Absolute ethanol combined with coils was used as method of embolization.

RESULTS

Eight patients presented with intermittent interdental gum bleeding or controlled hemostasis before embolization. Four patients presented with torrential hemorrhage around the tooth, controlled by continuous pressure on the tooth and bilateral gum for temporary hemostasis. All patients were successfully salvaged before embolization. Ten of 12 patients were cured, and 2 had partial remission. Follow-up ranged from 12 to 26 months (mean, 16.5 months) for all patients, and there was no recurrence of the lesions.

CONCLUSIONS

The treatment of hemorrhagic AVMs of the jaw requires a multidisciplinary team approach; such cases can be successfully salvaged and stably controlled by embolization with coils and absolute ethanol.

The current approach to the diagnosis of vascular anomalies of the head and neck: A pictorial essay

Throughout the years, various classifications have evolved for the diagnosis of vascular anomalies. However, it remains difficult to classify a number of such lesions. Because all hemangiomas were previously considered to involute, if a lesion with imaging and clinical characteristics of hemangioma does not involute, then there is no subclass in which to classify such a lesion, as reported in one of our cases. The recent classification proposed by the International Society for the Study of Vascular Anomalies (ISSVA, 2014) has solved this problem by including non-involuting and partially involuting hemangioma in the classification. We present here five cases of vascular anomalies and discuss their diagnosis in accordance with the ISSVA (2014) classification. A non-involuting lesion should not always be diagnosed as a vascular malformation. A non-involuting lesion can be either a hemangioma or a vascular malformation depending upon its clinicopathologic and imaging characteristics.

Peripheral limb vascular malformations: an update of appropriate imaging and treatment options of a challenging condition

Peripheral vascular malformations encompass a wide spectrum of lesions that can present as an incidental finding or produce potentially life- or limb-threatening complications. They can have intra-articular and intraosseous extensions that will result in more diverse symptomology and present greater therapeutic challenges. Developments in classification, imaging and interventional techniques have helped to improve outcome. The onus is now placed on appropriate detailed preliminary imaging, diagnosis and classification to direct management and exclude other more common mimics. Radiologists are thus playing an increasingly important role in the multidisciplinary teams charged with the care of these patients. By fully understanding the imaging characteristics and image-guided procedures available, radiologists will be armed with the tools to meet these responsibilities. This review highlights the recent advances made in imaging and the options available in interventional therapy.

Neuropathy after sodium tetradecyl sulfate sclerotherapy of venous malformations in children

PURPOSE

To estimate the risk of nerve injuries and assess outcomes after sodium tetradecyl sulfate (STS) sclerotherapy of venous malformations (VMs) in children.

MATERIALS AND METHODS

Sclerotherapy is the treatment of choice for most VMs, but all sclerotherapy agents are associated with the risk of complications. Neuropathy is considered a rare but potentially serious complication of venous sclerotherapy. The institutional review board waived ethical approval for this retrospective review, in which 647 sclerotherapy procedures were performed in 204 patients (104 female and 100 male patients; mean age, 9 years 6 months [range, 6 months to 17 years 11 months]) as treatment for symptomatic VMs. Technical and clinical success of the treatment was evaluated. Complications were reviewed with a particular focus on nerve injury. Informed consent, specifying the risk of neuropathy, as well as pain, swelling, infection, risks of anesthesia, skin injury, nonresolution or worsening of symptoms, and possible need for further or multiple procedures, was obtained for all patients. Standard sclerotherapy techniques were used. Technical details of all procedures were recorded prospectively. Follow-up included immediate postprocedural assessment and outpatient clinic review. All nerve injuries were recorded. Patients were monitored and treated according to clinical need. Confidence intervals were calculated by using the Wilson method, without correction for continuity.

RESULTS

Treatment was technically successful in 197 of 204 patients (96.6%), and clinical success was achieved in 174 of 204 (85.3%). Thirty-seven of the 647 procedures (5.7%) resulted in a complication, including 11 cases of excessive swelling, nine cases of skin injury, two patients with infection, and two with pain. Motor and/or sensory nerve injuries occurred after seven procedures (1.1%). Five of the seven children had undergone at least one previous sclerotherapy procedure. Neuropathy resolved spontaneously in four patients and partially recovered in three, of whom two underwent surgery. Surgery included debridement of necrotic tissue, carpal tunnel decompression, and external neurolysis.

CONCLUSION

Nerve injury is an unusual but not rare complication of STS sclerotherapy. A degree of recovery, which may be complete, can be expected in most patients.

Arteriovenous malformations

Arteriovenous malformations (AVMs) are fast-flow vascular malformations composed of a complex vessel network directly connecting feeding arteries to draining veins. The intervening normal capillary network is absent. Proper diagnosis and treatment of AVMs is challenging and in need of an interdisciplinary team of experienced physicians. Careful analysis of the clinical features and evaluation of therapeutic options represent the basis for successful management of AVMs. This article will focus on the clinical and radiological findings and in particular on interdisciplinary management strategies of AVMs including minimally invasive endovascular and surgical treatment.

Pulmonary arterial hypertension secondary to ethanol sclerotherapy for renal artery embolization

Pulmonary arterial hypertension (PAH) has been reported as a major complication to consider and promptly manage in the use of ethanol sclerotherapy. Most of the available data on the development of PAH is derived from the use of ethanol for embolization of arteriovenous malformation, but it has been rarely reported in its other fields of application. We describe a case of outpatient renal artery embolization using ethanol, in which respiratory failure develops secondary to PAH despite adhering to safe practice protocols. We highlight the importance of pulmonary arterial pressure monitoring and the treatment steps to follow in order to avoid irreversible fatal outcomes.

Pelvic vascular malformations

Vascular malformations (VMs) comprise a wide spectrum of lesions that are classified by content and flow characteristics. These lesions, occurring in both focal and diffuse forms, can involve any organ and tissue plane and can cause significant morbidity in both children and adults. Since treatment strategy depends on the type of malformation, correct diagnosis and classification of a vascular lesion are crucial. Slow-flow VMs (venous and lymphatic malformations) are often treated by sclerotherapy, whereas fast-flow lesions (arteriovenous malformations) are generally managed with embolization. In addition, some cases of VMs are best treated surgically. This review will present an overview of VMs in the female pelvis as well as a discussion of endovascular therapeutic techniques.

Cardiovascular collapse due to right heart failure following ethanol sclerotherapy: a case report

Ethanol sclerotherapy for the treatment of low-flow vascular malformations can cause catastrophic cardiopulmonary complications, including pulmonary embolism and pulmonary hypertension, that can result in right heart failure and fatal arrhythmias, leading to death. We here report a case of abrupt cardiovascular collapse that developed immediately following ethanol sclerotherapy in 31-year-old female patient who had a large arteriovenous malformation in her leg. Anesthesiologists should be aware of the fatal cardiopulmonary complications that are associated with ethanol sclerotherapy and consider the use of invasive hemodynamic monitoring, such as pulmonary artery pressure monitoring, when large doses of ethanol are required.

Vascular anomalies: classification, imaging characteristics and implications for interventional radiology treatment approaches

The term vascular anomaly represents a broad spectrum of vascular pathology, including proliferating vascular tumours and vascular malformations. While the treatment of most vascular anomalies is multifactorial, interventional radiology procedures, including embolic therapy, sclerotherapy and laser coagulation among others, are playing an increasingly important role in vascular anomaly management. This review discusses the diagnosis and treatment of common vascular malformations, with emphasis on the technique, efficacy and complications of different interventional radiology procedures.

Endovascular embolization strategy for renal arteriovenous malformations

BACKGROUND

Renal arteriovenous malformations (AVMs) are rare vascular malformations that cause hematuria. Treatment for renal AVMs has evolved from open nephrectomy to transcatheter arterial embolization (TAE).

PURPOSE

To retrospectively evaluate efficacy and adverse events of TAE for renal AVMs.

MATERIAL AND METHODS

We examined 12 patients (three men, nine women; mean age, 56 years) with renal AVM with gross hematuria, who underwent 14 sessions of treatment, using various embolization materials (liquid embolization agents, gelatin sponge, and coils). Among the 12 patients, 10 had cirsoid AVMs, eight of which were high-flow lesions. The remaining two patients had aneurismal AVMs. We assessed technical and clinical success, and also complications. All patients were followed for 7-92 months (mean, 48 months).

RESULTS

Technical success was obtained in all patients. Primary clinical success was obtained in all patients; however, recurrence was observed in two patients who were treated with coils alone. A second session of TAE led to the sustained relief of symptoms. Clinical success rate was significant better (P = 0.045) when coils combined with other agents or liquid agents were used, than when only coils were used. No major complications occurred in any of patients; post-embolization syndrome and deterioration of renal function were not observed.

CONCLUSION

TAE treatment was safe, effective, and provided a good outcome, except when only coils were used as the embolization agent.

Intraarterial polidocanol injection for the treatment of peripheral arteriovenous malformations

PURPOSE

The purpose of this study was to investigate the efficacy and safety of intraarterial transcatheter administration of polidocanol as an alternative treatment for peripheral arteriovenous malformations (AVMs).

METHODS

The study comprised 10 patients (six males and four females) with a mean age of 28.8 years (range 8-52 years). All patients had trunk or extremity AVMs. Following the administration of general anesthesia or intravenous (IV) sedation, the patients underwent staged intraarterial polidocanol sclerotherapy with or without additional embolizations for their AVMs. The administration of polidocanol was executed by intraarterial infusion through a microcatheter or by direct percutaneous entry into the nidus under ultrasound guidance.

RESULTS

A total of 19 sessions were accomplished in 10 patients. Polidocanol was used alone in six of the 19 sessions. In 13 sessions, polidocanol was used in combination with another agent (including n-butyl cyanoacrylate (NBCA), lipiodol, and ethanol) and/or coils. In two sessions, polidocanol was administered percutaneously under ultrasound guidance directly into the nidus documented by arteriography. No major complications occurred.

CONCLUSION

Intraarterial transcatheter administration of polidocanol alone or in combination with other agents is a safe and effective alternative treatment for peripheral AVMs.

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.

Interventional embolization therapy of puerile congenital deep femoral arteriovenous fistula

This study aimed to investigate the treatment efficiency of interventional embolization therapy in puerile congenital deep femoral arteriovenous fistula. A retrospective analysis was conducted for 9 cases of congenital deep femoral arteriovenous fistulae treated in our department in the past 5 years. B-ultrasound examination indicated that all puerile patients suffered from deep femoral arteriovenous fistulae, which was confirmed by angiography examination. For all patients, endovascular interventional embolization therapy was conducted and angiography re-examination was implemented after 4 weeks. If there were residual orificium fistulae, the interventional embolization therapy was conducted again. In the 6 month to 2 year follow-up period, improvement of clinical symptoms was observed. Following interventional embolization, 9 cases of deep femoral arteriovenous fistulae were completely occluded and the clinical symptoms were improved. No relapses occurred. In addition, after three embolization treatments, the disease condition of one case was controlled well and the disease condition did not progress. Interventional embolization therapy has a number of advantages, including simple surgery and reliable treatment efficacy. Therefore, it is worthy of promotion and application in the clinic.

Acute cor pulmonale and right heat failure complicating ethanol ablative therapy: anesthetic and radiologic considerations and management

Ethanol is an effective ablative agent used for the treatment of certain solid organ tumors and vascular malformations (VMs). The egress of ethanol beyond the target tissue can be associated with significant changes to the cardiopulmonary system that can lead to cardiac arrest. This article reviews the contemporary role of ethanol in tumor and VM treatment and discusses the physiological mechanisms of acute pulmonary hypertension and cardiovascular collapse. The importance of periprocedural recognition of the hemodynamic changes that can occur with the use of ethanol and the treatment of this condition are discussed.

Extensive bilateral arteriovenous malformations of the mandible successfully controlled by combined endovascular and transcutaneous angio-embolization: case report and review of the literature

We report a unique case of extensive bilateral arteriovenous malformation (AVMs) in a child's mandible, discuss treatment options and review literature. A healthy 8 year-old girl presented with bright blood of unknown source found on her pillow. Three large AVMs involving the symphyseal region and bilateral mandibular bodies were found on angiography. Due to the extent of surgical resection required, the patient underwent a series of endovascular and transcutaneous angio-embolization. In cases of extensive intraosseous AVMs, serial embolization procedures can be successful in controlling episodes of hemorrhage and allow for bone remineralization. A multidisciplinary approach by otolaryngologists and neurointerventional radiologists can optimize the results.

Peripheral vascular tumors and vascular malformations: imaging (magnetic resonance imaging and conventional angiography), pathologic correlation and treatment options

Vascular anomalies are classified into vascular tumors (infantile hemangioma) and vascular malformations. Vascular malformations are divided into slow flow and high flow subtypes. Magnetic resonance imaging helps in classification and assessing extent and distribution. Conventional angiography also known as digital subtraction angiography is pivotal in assessment of fine vascular details and treatment planning. Imaging correlates well with histopathology. We review recent development in imaging techniques of various vascular anomalies most of which are affecting the peripheral system which potentially may broaden understanding of their diagnosis, classification and treatment.

Anesthesia for endovascular neurosurgery and interventional neuroradiology

This article outlines the roles of the anesthesiologist in the management of patients undergoing invasive endovascular procedures to treat vascular diseases, primarily of the central nervous system. This practice is usually termed interventional neuroradiology or endovascular neurosurgery. The article emphasizes perioperative and anesthetic management strategies to prevent complications and minimize their effects if they occur. Planning the anesthetic and perioperative management is predicated on understanding the goals of the therapeutic intervention and anticipating potential problems.

Head and neck arteriovenous malformations: results of ethanol sclerotherapy

BACKGROUND AND PURPOSE

Peripheral AVM is a locally aggressive disease with a high tendency to recur; its treatment is complex, especially in the anatomically delicate head and neck area. Here, we report results of ethanol sclerotherapy for head and neck AVM and discuss its potential use for peripheral AVM.

MATERIALS AND METHODS

We retrospectively assessed degree of AVM eradication, complications, and clinical or imaging signs of recurrence for 19 patients treated with ethanol sclerotherapy for head and neck AVM (1 intraosseous, 18 soft-tissue AVMs).

RESULTS

Of the 19 patients, 11 had complete eradication of arteriovenous shunting at DSA, with 1 recurrence (mean follow-up 15 months), and for 7 patients, treatment is ongoing. During 59 treatment sessions, 12 patients experienced 14 complications, 1 leading to permanent functional damage.

CONCLUSIONS

Ethanol sclerotherapy has potential for complete eradication of head and neck AVM with low recurrence within the first year after completion of treatment. Complete eradication may require several treatment sessions during which complications should be minimized with careful techniques.

Low-dose contrast-enhanced time-resolved MR angiography at 3T: diagnostic accuracy for treatment planning and follow-up of vascular malformations

AIM

To assess the accuracy of low-dose contrast-enhanced time-resolved 3T magnetic resonance angiography (MRA) for the morphological and functional assessment of vascular malformations (VM), and to evaluate its diagnostic potential for the depiction of treatment-induced changes.

MATERIALS AND METHODS

Twenty-five patients with known VM underwent MRA to evaluate the location and extent of lesions and their haemodynamic characteristics. Three-dimensional (3D) T1-weighted time-resolved sequences were acquired following the administration of 0.05mmol/kg of gadobenate dimeglumine. VM were classified according to their morphology and haemodynamic characteristics. All patients thereafter underwent conventional angiography to confirm the diagnosis and to treat the lesions (embolization or sclerotherapy). Follow-up MRA was performed 30 days after treatment to assess morphological and functional changes. A visual analogue scale (VAS) was used to clinically assess the severity of symptoms before and after therapy.

RESULTS

Based on haemodynamic characteristics, VM were classified as predominantly arterial [4 (16%)], artero-venous [19 (76%)] or venous [2 (8%)]. Twenty-three (92%) lesions were classified as high-flow VM and two (8%) as low-flow VM. Intralesional thrombosis was present in 17 (68%) lesions before therapy and in 10 lesions (40%) after therapy. The median VAS scores were 5±1 before treatment and 4±2 after treatment. Very good correlation (Spearman's correlation coefficient: rho=0.87; p=0.000) was noted between the reduction of lesion size on follow-up MRA and pain relief as assessed by VAS.

CONCLUSION

Low-dose contrast-enhanced time-resolved 3T MRA can be used to define morphological and functional aspects of VM accurately during treatment planning and follow-up, and can identify post-therapy changes that positively correlate with treatment outcome.

Endovascular management of high-flow arteriovenous malformations

This article describes the various methods of endovascular management of high-flow arteriovenous malformations. Concepts of patient management and various therapies for vascular malformations are discussed. Nontraumatic acquired arteriovenous malformations, arteriovenous fistulae, and endovascular treatment of arteriovenous malfromations are described.

A Step-by-Step Practical Approach to Imaging Diagnosis and Interventional Radiologic Therapy in Vascular Malformations

Within vascular anomalies, vascular malformations are those present at birth that grow with the patient and exhibit abnormal dilated vascular channels lined by mature endothelium. Vascular tumors, the other group of vascular anomalies, demonstrate endothelial hypercellularity. Vascular malformations are further divided into low-flow varieties (capillary, venous, and lymphatic malformations) and high-flow varieties (arteriovenous malformation and fistula). All malformations exhibit a predictable group of clinical patterns that vary in severity and rate of progression. The interventional radiologist must incorporate this clinical data with characteristic ultrasound and magnetic resonance findings to arrive at a diagnosis. One must then decide in a multidisciplinary fashion, based on objective clinical criteria and image-based morphology, if the patent is a candidate for intervention. Sclerotherapy is a technique used to treat vascular malformations whereby an endothelial-cidal agent is introduced into the endoluminal compartment to initiate vascular closure. The high flow rate of an arteriovenous malformation requires the incorporation of superselective transarterial, direct, and transvenous access with flow reduction techniques to deliver adequate dose of sclerosant and embolic to the nidus. Satisfactory outcomes are seen in over half of all malformations patients. Similar treatment-related complications are seen between malformations but are lowest in lymphatic and highest in arteriovenous malformations.

Complications of embolization

Embolization is a remarkably versatile procedure used in nearly all vascular and nonvascular systems to treat a wide range of pathology. The published literature is rich with studies demonstrating the enormous therapeutic potential offered by embolization procedures, and the possibilities continue to expand with the advent of new embolization agents and techniques. Unfortunately, with this variety and innovation comes a wide spectrum of potential complications, not always easy to classify and summarize, associated with embolization. This article reviews the procedures and associated complications of arterial and venous embolization procedures, organized by vascular distribution.