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

Arterioembolic Characteristics of Differentially Diluted CaHA-CMC Gels Within An Artificial Macrovascular Perfusion Model

BACKGROUND

Despite the recently increased incidence and improved awareness of filler-induced ischemic injuries, the arterioembolic behavior of filler products has not been well described.

OBJECTIVES

To evaluate the embolic behavior of varying dilutions of calcium hydroxylapatite-carboxymethylcellulose (CaHA-CMC) gel mixtures within an artificial macrovascular perfusion model of the proximal facial artery with correlation against published instances of ischemic injuries in the literature.

METHODS

CaHA-CMC gel mixtures were assessed through the Pulsatile Unit for the Laboratory Simulation of Arterioembolic Restrictions (PULSAR) system at different flow rates. The occlusive behavior, embolic particle size distributions, and morphological attributes were evaluated through direct photographic and videographic captures followed by digital image processing. The PubMed database was systematically queried for all published instances of CaHA-CMC-associated ischemic injuries.

RESULTS

Undiluted CaHA-CMC demonstrated highly cohesive behavior upon PULSAR inoculation, with a tendency toward proximal occlusion. Gel fragmentation resulted in a polydisperse embolic mixture averaging 0.151 ± 0.61 mm² (interquartile range: 0.006-0.022 mm²) in size. Product dilution had a profound effect on embolic behavior, with a significant reduction in average particle size (0.018 ± 0.03 mm²; interquartile range: 0.005-0.018 mm²; P < .0001) and complete elimination of proximally occlusive capacity for hyperdiluted mixtures compared with undiluted product (P = .002). Confirmed hyperdiluted CaHA-CMC-associated ischemic injuries represented only 3% of published reports, with a predominantly self-limited clinical course.

CONCLUSIONS

Embolized CaHA-CMC gels produce polydisperse particle mixtures with a preponderance of microparticles. Hyperdilution profoundly reduced the proximally occlusive potential of the product.

Penetration of Non-Adhesive Gel-like Embolic Materials During Dural Vessels Embolization According to Characteristics of Tantalum Powder

Tantalum powder is included in the composition of Non-Adhesive Gel-like Embolic Materials (NAGLEMs) for X-ray opacity. The duration of X-ray opacity during embolization is primarily associated with the particle size, which differs in the most used NAGLEMs-ONYX (Medtronic) and SQUID (Balt). NAGLEMs are widely used for the embolization of branches of the middle meningeal artery (MMA) in patients with chronic subdural hematomas (CSDHs). Considering the size (5-15 microns) of the target dural vessels, we assumed that not only the viscosity of NAGLEMs, but also the size and shape of tantalum granules may be important for the penetration of these gel-like embolic agents and determine their behavior. A notable discrepancy in size was observed. The medium-sized granules in the SQUID 18 sample (0.443 ± 0.086 microns, M ± SD) were found to be approximately ten times smaller than the tantalum granules in the ONYX 18 sample (5.2 ± 0.33 microns, M ± SD).Tantalum granules in SQUID 18 have a regular spherical shape; in ONYX 18 they have an irregular angular shape. When comparing the behavior of gel-like embolic agents of the same viscosity during MMA embolization in patients with CSDHs (an average age of 62.2 ± 14.3 years) in the group where SQUID 18 (n = 8) was used, the gel-like embolic agent in dural vessels demonstrated significantly greater penetration ability compared with the group where ONYX 18 (n = 8) was used. Accordingly, not only the viscosity of NAGLEMs, but also the size and shape of tantalum granules can have a significant effect on the penetration ability of gel compositions.

Dural arteriovenous fistula onyx embolization through a non-visible previously embolized pedicle

Cerebral dural arteriovenous fistulas (dAVFs) are commonly treated with endovascular embolization, either through arterial or venous routes in single or multi-staged procedures. Treatment outcomes depend on multiple factors, including the patient's clinical status, the anatomy of the malformation, and the operator's experience, but technical success is also highly dependent on choice of neurovascular devices and embolic agents. When transvenous routes are not feasible and the most obvious transarterial routes do not appear safe, deep knowledge of the dynamic fluid properties of liquid embolics can be a valuable asset. We present a case(video 1) in which a complex skull-base dAVF was completely occluded through a non-visualized previously partially embolized arterial feeder. It is a unique case in which the embolization takes advantage of the peculiar fluid dynamic properties of non-adhesive embolic agents (Onyx-Medtronic, Minnesota, USA) 18 and 34.1-3 neurintsurg;16/8/852/V1F1V1Video 1 Technical video presenting a dAVF completely cured through a non-visible previously embolized arterial pedicle.

OnyxTMGel or Coil versus Hydrogel as Embolic Agents in Endovascular Applications: Review of the Literature and Case Series

This review focuses on the use of conventional gel or coil and "new" generation hydrogel used as an embolic agent in endovascular applications. In general, embolic agents have deep or multidistrict vascular penetration properties as they ensure complete occlusion of vessels by exploiting the patient's coagulation system, which recognises them as substances foreign to the body, thus triggering the coagulation cascade. This is why they are widely used in the treatment of endovascular corrections (EV repair), arteriovenous malformations (AVM), endoleaks (E), visceral aneurysms or pseudo-aneurysms, and embolisation of pre-surgical or post-surgical (iatrogenic) lesions. Conventional gels such as Onyx or coils are now commercially available, both of which are frequently used in endovascular interventional procedures, as they are minimally invasive and have numerous advantages over conventional open repair (OR) surgery. Recently, these agents have been modified and optimised to develop new embolic substances in the form of hydrogels based on alginate, chitosan, fibroin and other polymers to ensure embolisation through phase transition phenomena. The main aim of this work was to expand on the data already known in the literature concerning the application of these devices in the endovascular field, focusing on the advantages, disadvantages and safety profiles of conventional and innovative embolic agents and also through some clinical cases reported. The clinical case series concerns the correction and exclusion of endoleak type I or type II appeared after an endovascular procedure of exclusion of aneurysmal abdominal aortic (EVAR) with a coil (coil penumbra released by a LANTERN microcatheter), the exclusion of renal arterial malformation (MAV) with a coil (penumbra coil released by a LANTERN microcatheter) and the correction of endoleak through the application of Onyx 18 in the arteries where sealing by the endoprosthesis was not guaranteed.

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.