Chitosan-nanoclay embolic material for catheter-directed arterial embolization

Minimally invasive transcatheter embolization is a common nonsurgical procedure in interventional radiology. It is used for the deliberate occlusion of blood vessels for the treatment of disease or injured vasculature, including vascular malformation and malignant/benign tumors. Here, we introduce a gel embolic agent comprising chitosan nanofibers and nanoclay with excellent catheter injectability and tunable mechanical properties for embolization. The properties of the gel were optimized by varying the ratio between each individual component and also adjusting the total solid content. The rheological studies confirm the shear thinning property and gel nature of the developed gel as well as their recoverability. Injection force was measured to record the force required to pass the embolic gel through a clinically relevant catheter, evaluating for practicality of hand-injection. Theoretical predicted injection force was calculated to reduce the development time and to enhance the physician's experience. The stability of occlusion was also tested in vitro by monitoring the pressure required to displace the gel. The engineered gels exhibited sterility, hemocompatibility and cell biocompatibility, highlighting their potential for transcatheter embolization.

The Use of Microspheres for Cancer Embolization Therapy: Recent Advancements and Prospective

Embolization therapy involving biomaterials has improved the therapeutic strategy for most liver cancer treatments. Developing biomaterials as embolic agents has significantly improved patients' survival rates. Various embolic agents are present in liquid agents, foam, particulates, and particles. Some of the most applied embolic agents are microparticles, such as microspheres (3D micrometer-sized spherical particles). Microspheres with added functionalities are currently being developed for effective therapeutic embolization. Their excellent properties of high surface area and capacity for being loaded with radionuclides and alternate active or therapeutic agents provide an additional advantage to overcome limitations from traditional cancer treatments. Microspheres (non-radioactive and radioactive) have been widely used and explored for localized cancer treatment. Non-radioactive microspheres exhibit improved clinical performance as drug delivery vehicles in chemotherapy due to their controlled and sustained drug release to the target site. They offer better flow properties and are beneficial for the ease of delivery via injection procedures. In addition, radioactive microspheres have also been exploited for use as an embolic platform in internal radiotherapy as an alternative to cancer treatment. This short review summarizes the progressive development of non-radioactive and radioactive embolic microspheres, emphasizing material characteristics. The use of embolic microspheres for various modalities of therapeutic arterial embolization and their impact on therapeutic performance are also discussed.

The Advantages of Non-Adhesive Gel-like Embolic Materials in the Endovascular Treatment of Benign Hypervascularized Lesions of the Head and Neck

OBJECTIVES

The use of non-adhesive gel-like embolic materials (NAGLEMs) in the endovascular treatment of hypervascularized formations in the head and neck is gaining in popularity because of a number of important characteristics involved. Their primary benefits are their capacity to penetrate diseased vasculature, effectively distribute, and, most importantly, remain controllable during the process. We reviewed the literature and evaluated the results of using NAGLEMs in comparison to other embolizing substances (namely, coils, glue, and particles) as alternative embolizing agents for patients receiving care at our clinic. The process comprised evaluating the safety, effectiveness, and technological elements of endovascular therapy used to treat two categories of hypervascular pathological abnormalities that were surgically corrected between 2015 and 2023. Arteriovenous malformations (AVMs) located in the head, neck, and paragangliomas with jugular/carotid body localization are combined by intense shunting blood flow and shared requirements for the embolic agent used in endovascular treatment (such as penetration, distribution, delayed polymerization, and controllability). An analysis of the literature was also conducted. Results showed 18 patients diagnosed with neck paragangliomas of the carotid body and jugular type. Five patients with arteriovenous malformation (AVM) of the face and neck were included, consisting of sixteen females and seven males with an average age of 55 ± 13 years. Endovascular procedures were performed using NAGLEMs (ONYX (Medtronic, Irvine, CA, USA), SQUID (Balt, Montmorency, France), and PHIL (Microvention, Tustin, CA, USA)) and dimethyl sulfoxide (DMSO)-compatible balloon catheters. All patients achieved complete or partial embolization of hypervascularized formations using one or more stages of endovascular treatment. Additionally, three AVMs of the face and two paragangliomas of the neck were surgically excised following embolization. In other instances, formations were not deemed necessary to be removed. The patients' condition upon discharge was assessed by the modified Rankin Scale (mRs) and rated between 0 and 2.

CONCLUSION

Currently, NAGLEMs are predominantly used to treat hypervascularized formations in the neck and head due to their fundamental properties. These properties include a lack of adhesion and a delay in predictable polymerization (after 30-40 min). NAGLEMs also exhibit excellent distribution and penetration throughout the vascular bed of the formation. Adequate controllability of the process is largely achieved through the presence of embolism forms of different viscosity, as well as excellent X-ray visualization.

Rheological Properties of Non-Adhesive Embolizing Compounds-The Key to Fine-Tuning Embolization Process-Modeling in Endovascular Surgery

The study of polymers' rheological properties is of paramount importance both for the problems of their industrial production as well as for their practical application. Two polymers used for embolization of arteriovenous malformations (AVMs) are studied in this work: Onyx-18^® and Squid-12^®. Viscosity curve tests and computational fluid dynamics (CFD) were used to uncover viscosity law as a function of shear rate as well as behavior of the polymers in catheter or pathological tissue models. The property of thermal activation of viscosity was demonstrated, namely, the law of dependence of viscosity on temperature in the range from 20 °C to 37 °C was established. A zone of viscosity nonmonotonicity was identified, and a physical interpretation of the dependence of the embolic polymers' viscosity on the shear rate was given on the basis of Cisco's model. The obtained empirical constants will be useful for researchers based on the CFD of AVMs. A description of the process of temperature activation of the embolic polymers' viscosity is important for understanding the mechanics of the embolization process by practicing surgeons as well as for producing new prospective embolic agents.

Material characterization of GPX®: A versatile in situ solidifying embolic platform technology

Endovascular embolization is a minimally invasive procedure during which blood flow to targeted tissues is selectively occluded. The list of clinical indications for embolization continues to expand. Liquid embolic agents are injectable compositions that transition into a solid or semi-solid form when introduced into blood vessels. The mechanism that triggers the liquid-to-solid transition is a key distinguishing feature of liquid embolic agents. GPX is a waterborne liquid embolic agent comprising oppositely charged polyelectrolytes: polyguanidinum and inorganic polyphoshate. In situ solidification is driven by electrostatic condensation of the polyelectrolytes, triggered by ionic strength differentials. We report in vitro characterization of the material properties of GPX, it is in vivo effectiveness in acute animal studies, and its potential for chemoembolization. The viscosity of GPX can be varied over a wide range by adjusting the polyguanidinium MW and/or concentration. Formulation of GPX with either tantalum microparticles (30 wt%) or iodinated radiocontrast agents (300 mgI ml^-1) did not significantly change the flow behavior of GPX; the viscosity was independent of shear rate and remained within a clinically practical range (80-160 cP). Formulation of GPX with doxorubicin substantially increased viscosity at low shear rates and resulted in a power law dependence on shear rate. High contrast and effective vascular occlusion were demonstrated in both swine kidneys and rete mirabile. Contrast from iodinated compounds was temporary, dissipating within hours. The doxorubicin in vitro release profile was linear over 90 days. The results demonstrate that GPX is a versatile liquid embolic platform that can be formulated with a wide range of viscosities injectable at clinically practical flow rates, with either transient or permanent contrast, and that can provide prolonged zero-order delivery of doxorubicin to embolized tissues.

Initial clinical experience with N-hexyl cyanoacrylate for neuroendovascular embolization

OBJECTIVE

To report our initial clinical experience with N-hexyl cyanoacrylate (NHCA), a novel liquid agent for neurovascular embolization.

METHODS

Four paragangliomas were treated with percutaneous embolization using NHCA as the sole embolic material. In one dural arteriovenous fistula (dAVF), NHCA was used in combination with other embolic materials. Procedural specifics, complications and angiographic results were retrospectively evaluated.

RESULTS

Total or subtotal devascularization was obtained in 3 of the 4 paragangliomas. In the largest tumor, only partial devascularization could be achieved. The dAVF was completely occluded. Catheter entrapment did not occur. After dAVF treatment, the patient had an asymptomatic lacunar infarction, while there was no procedural morbidity related to paraganglioma treatment.

CONCLUSIONS

In this series, neurovascular embolization with NHCA was feasible and effective. It may be particularly beneficial for small and tortuous vessels that require low-profile catheterization and a slow and controlled polymerization. Further studies are necessary to prove the benefits of NHCA over established embolic agents.

The Minimally Invasive Treatment of Visceral Artery Pseudoaneurysms: A Retrospective Observational Single Centre Cohort Study on Glue Embolization

OBJECTIVE

The objective is to report a single centre experience in the embolization of visceral artery pseudoaneurysms with N-butyl-cyanoacrylate-methacryloxy sulfolane (NBCA-MS).

METHODS

A retrospective observational cohort study was conducted on data about all consecutive patients treated for visceral artery pseudoaneurysms in the Interventional Radiology Unit of SS Annunziata Hospital, in Taranto (Italy) between January 2016 and July 2020. Only patients treated with NBCA-MS embolization were included. Clinical and technical outcomes were evaluated during in-hospital stay and at 3-month follow-up by computed angiotomography (CTA).

RESULTS

Among 89 patients undergoing treatment for visceral artery pseudoaneurysm, a total of 58 (65.2%) patients (n = 32, 55.2% men; median age 45.8 years, range: 35-81) treated with NBCA-MS only were enrolled. Pseudoaneurysms were located in the renal artery (n = 18 cases, 31%), in the splenic artery (n = 27, 46.6%), in the intra-parenchymal hepatic artery (n = 3, 5.2%), in the common hepatic artery (n = 4, 6.9%) or in the pancreatic artery (n = 6, 10.3%). N-butyl-cyanoacrylate was diluted 1:1 with Lipiodol ultra-fluid, and mean volume injected was 0.6 ± 0.3 mL (range: 0.2-2.8 mL). Embolization was technically and clinically successful in all patients (n = 58, 100%) with an immediate total thrombosis of the pseudoaneurysm at the completion angiography. No systemic complications were noted in all cases. Five cases (8.6%) of non-target vessel embolization occurred without any clinical complication. No pseudoaneurysm recurrence was detected at the CTA control 1 day postoperatively. In one case (1.7%), a recurrence was detected 4 days after the initial treatment and successfully managed by a repeated NBCA-MS embolization. During the hospital stay, 56 patients recovered well but 2 (3.4%) died from multi-organ failure not related to the embolization. No recurrences were detected at the 3-month postoperative CTA in the remaining patients.

CONCLUSIONS

In properly selected patients affected with visceral artery pseudoaneurysms, NBCA-MS represents a definitive and safe embolization agent.

In Vivo Animal Study of a Highly Viscous N-butyl Cyanoacrylate Medical Adhesive for Intravenous Embolization

N-butyl cyanoacrylate (NBCA) is a liquid monomer that undergoes an exothermic polymerization reaction to form a solid upon initiation with hydroxyl anions. Recently, EGpresto, a highly viscous NBCA-based adhesive, has been developed for vascular-occlusion purposes. In this study, we investigated the heat of polymerization of EGpresto and compared the results with those of a low-viscosity NBCA glue. Results show that EGpresto exhibited a lower heat of polymerization (64 ± 7 °C vs. 34 ± 1 °C). This was due to its high viscosity, which resulted in a delayed polymerization time. To investigate the efficacy and safety of EGpresto for intravenous embolization, a 14 d in vivo animal test was conducted using three pigs. Five cc of EGpresto was injected into the epigastric vein of each animal. Complete postoperative vein occlusion was confirmed at 7 and 14 d by ultrasonographic visualization. After the animals were sacrificed, the operated and unoperated veins were exposed, and the injected adhesive was found without migration. During the histology, the injected adhesive was not found in the inner or outer vein walls, and the immune reactions seemed to be the only foreign-body reaction, showing that EGpresto is a non-toxic and safe intravascular embolic agent.

Liquid and Solid Embolic Agents in Gonadal Veins

Male varicocele and pelvic congestion syndrome (PCS) are common pathologies with high predominance in young patients, having a high impact on the quality of life and infertility. Lately, the use of different endovascular embolization techniques, with various embolizing agents, shows good technical results and clinical outcomes. With the aim of presenting the “state of the art” of endovascular techniques for the treatment of male varicocele and PCS, and to discuss the performance of the different embolic agents proposed, we conducted an extensive analysis of the relevant literature and we reported and discussed the results of original studies and previous meta-analyses, providing an updated guide on this topic to clinicians and interventional radiologists. We have also underlined the technical aspects for the benefit of those who approach this type of interventional treatment. Our review suggests promising results in both the endovascular embolic treatment of male varicocele and PCS; for varicocele, a success rate of between 70% and 100% and a recurrence rate of up to 16% is reported, while for PCS it has been found that technical success is achieved in almost all cases of endovascular treatment, with a highly variable recurrence rate based on reports. Complications are overall rather rare and are represented by periprocedural pain, migration of embolic media and vascular perforations: severe adverse events have been reported very rarely.

Endovascular treatment of cerebral dural arteriovenous fistulas with SQUID 12

BACKGROUND

Endovascular therapy with liquid embolic agents (LEAs) is the gold standard for the treatment of cerebral dural arteriovenous fistulas (cDAVFs). The aim of the study is to retrospectively evaluate effectiveness, safety, and midterm follow-up results of endovascular treatment of cDAVFs using SQUID 12.

METHODS

Between June 2017 and January 2020 the authors retrospectively reviewed clinical, demographic and embolization data of 19 consecutive patients with cDAVF who underwent embolization using SQUID 12. The number of arteries catheterized for each procedure, the total amount of embolic agent, the occlusion rate, the injection time, any technical and/or clinical complications were recorded. Mid-term follow-up with DSA was reviewed.

RESULTS

20 procedures were performed in 19 patients. A transarterial approach was accomplished in 19 procedure; a combined transvenous-transarterial approach was realized in 1 treatment. The average time of injection was 33 minutes (2-82 minutes), and the average amount of SQUID 12 was 2.8 mL (0.5-6 mL). Complete angiographic cure at the end of the procedure was achieved in 17 patients. No major periprocedural adverse events were recorded. Mid-term follow-up was achieved in 15 out of 19 patients and confirmed complete occlusion of the cDAVFs in 13/15 patients (87%); in 2 of the initially cured patients a small relapse was detected.

CONCLUSIONS

The treatment of the cDAVFs using SQUID 12 was effective and safe. The lower viscosity seems to allow an easier penetration of the agent with a high rate of complete occlusion of the cDAVFs.

Endovascular treatment for the control of active vaginal bleeding from uterine cervical cancer treated with radiotherapy

Background Endovascular treatment has become a significant therapeutic option for the management of intractable bleeding in gynecologic malignancies. However, the endovascular treatment types were almost never mentioned when active bleeding from different arteries was identified. Purpose To present angiographic details and evaluate clinical efficacy of endovascular treatments to control active vaginal bleeding in uterine cervical cancer patients treated with radiotherapy. Material and Methods In this retrospective study, six, consecutive cervical cancer patients treated with radiotherapy who underwent endovascular treatment for active vaginal bleeding were included. Angiographic findings, endovascular treatment details, and clinical outcomes were obtained. Results Ten endovascular procedures were technically successful, in which bleeding arteries were the internal iliac artery/its branches (n = 5), external iliac artery (EIA) (n = 3), uterine artery (n = 1), and superior rectal artery (n = 1), and bleeding manifested as contrast extravasation (n = 6), pseudoaneurysm (n = 1), or both (n = 3). Three of the four repeated procedures showed different bleeding sites from the primary ones. Stent graft was inserted to preserve the patency of the bleeding EIA in two patients. For another EIA rupture, both proximal and distal embolization were performed, followed by femoral-to-femoral bypass to preserve blood flow. Bleeding control within one month was achieved in 80% (8/10). One minor complication, mild transient pelvic pain, occurred in one patient. Conclusions Various endovascular treatment was feasible and effective to control active vaginal bleeding from cervical cancer. Repeated procedures showed commonly different bleeding foci and stent graft insertion was effective for preserving the patency of the large bleeding artery.

Menstruation recovery in scar pregnancy patients undergoing UAE and curettage and its influencing factors

This study aims to investigate the menstrual recovery outcome of scar pregnancy patients who received uterine artery embolization combined with curettage, and its influencing factors.The data of 119 patients with scar pregnancy, who received uterine artery embolization combined with curettage between December 2012 and December 2016 in Henan Provincival People's Hospital, were collected. The menstruation recovery of these patients was followed up, and factors that have influence on menstrual blood volume were analyzed using SPSS V.17.0.Follow-up data were available in 101/119 (84.9%) women. The median follow-up time was 22.7 months (range: 1.6-50.6 months); 58 (57.4%) patients had reduced menstrual blood volume, and 2 patients (2%) had amenorrhea. The proportion of patients with reduced menstrual blood volume, who were embolized with polyvinyl alcohol (PVA), PVA combined with gelatin sponge, and gelatin sponge between < and ≥33 years old was 41.7% versus 66.7%, 40% versus 57.1% and 60.6% versus 68.0%. The average age of patients with reduced menstrual blood volume (34.3 years) was greater than patients with normal menstrual blood volume (31.4 years), but the difference was not statistically significant (P = .07).Reduced menstrual blood volume can occur in scar pregnancy patients who received uterine artery embolization combined with curettage. The influence of the embolic agent PVA on menstrual blood volume depends on age, but the difference was not statistically significant.

Uterine fibroid embolization with acrylamido polyvinyl microspheres: prospective 12-month clinical and MRI follow-up study

Background Uterine fibroid embolization (UFE) is an effective minimally invasive treatment aimed to obtain complete fibroid infarction. Purpose To evaluate the degree of fibroid infarction after embolization with acrylamido polyvinyl alcohol microspheres (Bead Block). Material and Methods This prospective study included 26 pre-menopausal women in the period October 2013 to January 2015. UFE with the use of Bead Block microspheres 700-900 µm was obtained until flow stasis was achieved. Contrast-enhanced magnetic resonance imaging (MRI) was used to define residual contrast enhancement in the total fibroid burden and enhancement >10% was defined as insufficient embolization. The dominant fibroid volume and total uterine volume changes were assessed. Clinical outcome was analyzed using the quality of life questionnaire (UFS-QOL). Results Twenty-four of the 26 patients (92%) had a technically successful UFE with complete flow-stop in both uterine arteries. Twenty-two of the 26 patients (85%) completed 3 months of MRI control and 20 patients (77%) completed 12 months of MRI control. There were 16 of 22 patients (73%) with complete fibroid burden infarction and/or without residual contrast enhancement of the fibroids of more than 10% at 3 months of control. Six of 22 patients (27%) had insufficient fibroid burden infarction with residual contrast enhancement of more than 10%. Twenty-two and 18 of 26 patients completed the 3-month and 12-month questionnaire, respectively. UFS-QOL analyses showed that 91% of the patients had significant clinical improvement. Conclusion Sixteen of the 22 patients had complete fibroid burden infarction using Bead Block microspheres (700-900 µm); however, unacceptably high insufficient fibroid burden infarction in almost one-fourth of the patients were recorded.

Possible toxicity following embolization of congenital giant vertex hemangioma: case report

The authors describe the case of a 3-year-old boy with a giant congenital vertex hemangioma who underwent presurgical embolization with Onyx (ethylene-vinyl alcohol copolymer dissolved in dimethyl sulfoxide) and Glubran ( N-butyl-2-cyanoacrylate). This vascular tumor had no intracranial vascular communication as assessed by pre-embolization MRI and catheter angiography. All embolizations were performed by direct percutaneous injection. One week following the last embolization procedure the child presented with a 24-hour history of ataxia and extrapyramidal tremor. He was diagnosed with a possible immune-mediated reaction to Onyx or Glubran, which was treated with an urgent surgical excision of the hemangioma followed by intravenous administration of immunoglobulin and steroids. To the authors' knowledge, this is the first case of possible immune-mediated toxicity secondary to either Onyx or Glubran administration. This case highlights the need for awareness of potential toxic reactions to these embolic agents in the treatment of hemangiomas in the pediatric patient.

Efficacies of uterine artery embolization for symptomatic uterine fibroids using gelatin sponge: a single-center experience and literature review

AIM

The aim of this study was to retrospectively analyze the efficacies of uterine artery embolization (UAE) using gelatin sponge for symptomatic uterine fibroids.

METHODS

A series of 60 consecutive premenopausal women underwent UAE using gelatin sponge particles or porous gelatin particles. Patients were routinely followed up at 1, 3, 6, and 12 months after the procedure and asked to report any procedure-related complications. At each follow-up, an original clinical questionnaire was completed by the patients to evaluate changes in fibroid-related symptoms. Pelvic magnetic resonance imaging was performed before and at 3 and 12 months after the procedure, and the changes in volume of the dominant fibroid were calculated.

RESULTS

Bilateral UAE was successfully performed in all the patients. Median age was 45 years (range 34-53 years), and median follow-up period was 25.2 months (range 1-116 months). At the 3- and 12-month follow-up, the dominant fibroid volumes were found to be significantly decreased by 33.4% (95% confidence interval [CI]: 24.9-41.1) and 48.4% (95% CI: 40.7-56.1) compared to baseline volumes, respectively. Excluding patients not having menorrhagia or bulk-related symptoms, at 12 months 49 of 50 (98%) women showed improvement in menorrhagia, and 45 of 47 (95.7%) women showed improvement in bulk-related symptoms. During the follow-up period, ten patients (16.7%) required further interventions including two patients who had undergone hysterectomy. No sequelae were experienced by any of the patients.

CONCLUSION

UAE using gelatin sponge was associated with a high clinical success rate and good fibroid volume reduction compared to UAE using other embolic agents.

Effect of transarterial embolization for post-partum hemorrhage on subsequent pregnancy

Although pregnancy after transarterial embolization (TAE) has occasionally been reported, gelatin sponge was used as the embolic agent in most of these cases. Reports on the effect of TAE with permanent embolic agents such as N-butyl cyanoacrylate or coil on subsequent pregnancies are rare. We describe placenta accreta associated with difficult hemostasis in two patients who became pregnant after TAE with permanent embolic agents. In pregnancy after TAE with permanent embolic agents, placenta accreta occurs frequently and well-developed collateral vessels are highly likely, resulting in difficult hemostasis. Although the acceptability of pregnancy after TAE with permanent embolic agents is controversial, patients should be informed that pregnancy is extremely high risk.