Temporary Embolic Agent Research Articles

Comparing technical success and clinical outcomes of macrocatheter versus microcatheter in genicular artery embolization for knee osteoarthritis

PurposeThe purpose of this study was to evaluate the comparative effectiveness and safety of using macrocatheters versus microcatheters for genicular artery embolization (GAE) in the management of knee osteoarthritis (OA). The primary outcomes were technical success and adverse events during and immediately after the procedure. The secondary outcome was the clinical outcome over the follow-up period. Materials and methodsIn our retrospective analysis, we included 79 patients undergoing GAE for OA. Patients were categorized based on the catheter type used: microcatheter through macrocatheter or directly through macrocatheter. Key parameters, including technical success, adverse events, procedure duration, radiation exposure, and clinical outcomes (VAS and WOMAC scores), were assessed at 1st, 3rd, and 6th-month intervals. ResultsTechnical success stood at 100 % for the microcatheter group, with a slight reduction for the macrocatheter group at 91 % (p = 0.069). Procedure and fluoroscopy durations were significantly shorter in the macrocatheter group (p < 0.001). Additionally, the macrocatheter group demonstrated a marked reduction in radiation dose, with notably decreased air kerma values. Clinical outcomes, including VAS and WOMAC scores at the predefined intervals, revealed no significant disparities between the two cohorts. ConclusionIn GAE procedures utilizing a temporary embolic agent (imipenem/cilastatin), initiating the intervention with a macrocatheter can be deemed cost-effective, safe and advantageous for patients with less complex vascular anatomy, as it significantly reduces procedural and fluoroscopy times, thereby minimizing radiation exposure. Conversely, in patients with intricate vascular pathways, transitioning to a microcatheter enhances technical success.

Temporary Embolic Agents.

Temporary Embolic Agents.

In vitro study of the embolic characteristics of imipenem/cilastatin particles

BackgroundImipenem/cilastatin (IPM/CS) has long been administered intravenously as a carbapenem antibiotic. However, since this agent is poorly soluble in liquid, occasional reports have described its use as a short-acting, temporary embolic agent. The purpose of this study was to elucidate the characteristics of IPM/CS particles, which are thought to have pain-relieving effects against osteoarthritis-related pain, as an embolic agent.MethodsThree aspects of IPM/CS as an embolic agent were evaluated in vitro: particle size; particle shape; and change in particle size over time. For particle size, the long diameter was measured.ResultsMean particle size (n=244) was 29.2±12.0 µm (range, 1–60 µm). Shape (n=109) was round in 18.35%, elliptical in 11.93%, and polygonal in 69.72%, showing that most particles were polygonal. In observations of changes in particle size over time (n=9), particles had decreased to 75% of their original size at 82±10.7 min, 50% at 89.3±9.14 min, 25% at 91.3±8.74 min, complete dissolved at 91.8±9.02 min. A rapid shrinkage in diameter was seen in the final period.ConclusionsIPM/CS particles are ultrafine and the majority display a polygonal shape. This substance shows ultra-short embolic activity. This study revealed the characteristics of a substance that demonstrates an embolic effect not found in existing embolic materials.

Alteration of chronic inflammatory status by transarterial embolization in frozen shoulder evaluated by fluorine-18 fluorodeoxyglucose positron-emission tomography/computed tomography.

Frozen shoulder (FS) is speculated to have an inflammatory etiology. On angiography, abnormal angiogenesis is observed around the affected shoulder, suggesting a possible source of inflammation and pain. The effectiveness and safety of transarterial embolization (TAE) targeting abnormally proliferating blood vessels have been reported. This study investigated changes in chronic inflammatory and hypoxic status before and after TAE in FS by [18F]-fluoro-2-deoxyglucose (FDG) positron-emission tomography/computed tomography as a possible mechanism of the therapeutic response to TAE. Fifteen patients with unilateral FS, persistent for more than 6months, who were refractory to conservative treatments, underwent TAE using the temporary embolic agent imipenem/cilastatin. Patients underwent positron-emission tomography/computed tomography with FDG (as a biomarker of inflammation) before and 8weeks after TAE. Regional uptake was evaluated by the maximum standardized uptake value. The lesion-side-to-(contralateral-) normal-side uptake ratio was also calculated. Pain and functional scales, range-of-motion, and laboratory tests, including white blood cell, C-reactive protein, interleukin 6, vascular endothelial growth factor, and tumor necrosis factor α were evaluated. On FDG-PET, the average maximum standardized uptake value of the lesion-side was significantly greater than that of the normal-side (maximum standardized uptake value before TAE: 3.11±1.25 vs 1.95±1.15, P=.0001; 8-weeks post-TAE: 2.36±0.74 vs 1.78±0.69, P=.0002). The mean lesion-side-to-(contralateral-) normal-side uptake ratios before TAE (1.71±0.60) decreased after TAE (1.37±0.29, P=.011). The decrease of FDG uptake (-21.1±12.2%) showed a significant correlation with the change in the pain scale score (r=-0.56, P=.039) and extension score (r=-0.59, P=.026). Chronic inflammation in FS, as demonstrated by FDG uptake, was decreased after TAE. Thus, chronic inflammation is likely to be an underlying mechanism that should be targeted for symptomatic improvement of frozen shoulder.

Super-selective Gelfoam embolisation in high-flow priapism.

High-flow priapism is a rare condition with limited data in the literature, particularly in Australia. There is therefore no clear consensus regarding treatment. We aim to present our institutional network experience in managing this condition over the last decade with super-selective gelatin sponge (Gelfoam) embolisation of the internal pudendal artery. We retrospectively searched for and reviewed the patient records of all cases of priapism encountered within our multicentre institutional network over the last 10 years. Of these, the cases of high-flow priapism treated with embolisation were analysed in depth and compared with the current literature. Overall, 93 patients in our network were diagnosed with priapism from 1 January 2012 to 1 January 2022. And 89 of these patients (96%) had low-flow priapism and four patients (4%) had high-flow priapism. Of these four patients, two were treated within our network with super-selective Gelfoam embolisation of the internal pudendal artery. Following embolisation, both patients achieved rapid detumescence and returned to baseline premorbid erectile function. There was no report of recurrence or erectile dysfunction on follow-up. Super-selective embolisation of the internal pudendal artery should be considered as a treatment option for high-flow priapism, with Gelfoam as an appropriate temporary embolic agent of choice. We show that it was a safe and effective option for the patients treated in this series, enabling quick and long-term return to baseline erectile function. Our results support data provided by the limited number of cases in the literature.

Non-Permanent Transcatheter Proximal Renal Artery Embolization for a Grade 5 Renal Injury with Delayed Recanalization and Preserved Renal Parenchymal Enhancement

&lt;p&gt;Super-selective renal artery embolization is an increasingly popular technique for the management of traumatic, low-grade renal trauma. When performed in distal arterial branches, this intervention enables tissue preservation and arrest of hemorrhage, but it may not be practical in cases of multifocal, high-grade renal injuries. In such cases, surgical nephrectomy remains the more common treatment modality to ensure hemodynamic control. We present the unique case of a patient who presented in hemorrhagic shock following a major trauma that resulted in a grade 5 renal injury treated with complete renal artery embolization using Gelfoam, resulting in hemodynamic stabilization. Interestingly, imaging 1 month after embolization revealed residual enhancement of the inferior pole of the kidney, suggesting reconstitution of flow and partial renal salvage. Ultimately, transcatheter “nephrectomy” with careful selection of a temporary embolic agent may serve as a safe and efficient alternative to surgical nephrectomy with the added possibility of preserving partial renal perfusion and function in the emergent setting.&lt;/p&gt;

Characteristics of Imipenem/Cilastatin: Considerations for Musculoskeletal Embolotherapy

Imipenem/cilastatin (IPM/CS) is an antibiotic that has been applied as a temporary embolic agent in musculoskeletal (MSK) embolotherapy. While the therapeutic potential of IPM/CS as an embolic agent for pain relief has been demonstrated in osteoarthritis (OA) and tendinopathy, its characteristics, mechanism of action, and the manner in which a temporary embolic induces longstanding clinical effects remain unclear. This commentary summarizes what is known about IPM/CS, bridges knowledge gaps, and offers possible mechanisms by which its use could lead to MSK pain relief.

Abstract No. 14 Characteristics of imipenem–cilastatin as a temporary embolic agent for genicular artery embolization

Imipenem–cilastatin is an antibiotic traditionally used to treat gram-negative bacterial infections. Recently, this agent has been suggested as a temporary embolic agent in musculoskeletal conditions where there is joint hypervascularization, such as knee osteoarthritis. However, little is known about the characteristics of imipenem–cilastatin or its mechanism of action as a temporary embolic agent. This study aims to determine the characteristics of imipenem–cilastatin in vitro, to better understand how this agent could be most effectively applied for embolization in clinical practice. The size distributions and degradation rates of the particles as a function of time, temperature, concentration and suspension media were measured. Light microscopy assessed morphological changes, a Coulter counter measured particle size distributions, and ultraviolet-visible spectroscopy (UV-Vis) assessed the rate of Imipenem breakdown over time. In vitro flow phantoms were created to assess agent accumulation and degradation under flow. Imipenem–cilastatin in saline changed from a white cloudy solution to a transparent orange solution over a period of days, consistent with the expected degradation product of Imipenem. Coulter counter data and microscopy showed that initial particles were crystalline and polydisperse, from 1 μm to 50 μm in size, and degraded over time, with an increase in particles < 10 μm. UV-Vis and in vitro fow [sic] experiments are in progress and will contribute toward developing a model of embolic mechanism and degradation as a function of flow rate, physical and chemical properties. The degradation of imipenem–cilastatin were effectively measured in vitro, toward elucidating its future application as a temporary embolic agent for joint hypervascularization.

Biodegradable Polydioxanone Microspheres for Transcatheter Arterial Embolization: Proof of Principle

PurposeTo evaluate feasibility, embolization success, biodegradability, reperfusion, and biocompatibility of biodegradable microspheres (MS) made from polydioxanone (PDO) for transcatheter arterial embolization. Materials and MethodsUnilateral selective renal embolization of a segmental artery was performed in 16 New Zealand White rabbits with PDO-MS (100–150 μm and 90–315 μm). Animals were randomly assigned to different observation periods and underwent control digital subtraction angiography (DSA) and MR imaging immediately (n = 3), 1 week (n = 2), 4 weeks (n = 2), 8 weeks (n = 2), 12 weeks (n = 5), and 16 weeks (n = 2) after embolization. Kidneys were harvested for macroscopic and histologic analysis of embolization success, biodegradability, and biocompatibility. ResultsEmbolization was technically successful in 15 of 16 animals. One animal died of anesthesia-related circulatory failure. The 100–150 μm MS were injected easily through 3-F catheters; the 90–315 μm MS tended to clog with intermittent catheter obstruction. DSA and MR imaging showed successful target embolization in 13 of 15 animals. In 2 animals, the entire kidney was affected owing to catheter clogging, including a reflux of MS while flushing. Control DSA and MR imaging showed increasing vascular reperfusion with time. Macroscopic and histologic analysis revealed necrosis/infarction in areas in which embolization was achieved. MS were extensively degraded after 16 weeks, and overall inflammatory reaction was mild. ConclusionsBiodegradable PDO-MS induced effective embolization of target vessels while demonstrating good biocompatibility. MS increasingly dissolved at 16 weeks, partial reperfusion started at week 1, and complete reperfusion started at week 8, thus offering possible advantages as a temporary embolic agent.

Abstract No. 690 Magnetic resonance imaging–visible and triggered-degradable nanocomposite microsphere for on-demand temporary embolic agents

Temporary embolization of vessels plays a critical role in many angiographic procedures. However, predictability and reproducibility of vessel recanalization is limited, and in these situations permanent occlusion may be undesirable. The purpose of this study is to evaluate the feasibility of MRI visible and triggered degradable nanocomposite microspheres for a temporary embolic agent. Microspheres composed by superparamagnetic iron oxide nanocluster and alginate were fabricated with spray atomization and coagulation with CaCl2 solution. Size and morphology of the fabricated microspheres with different precursor concentrations and various distance between nozzle and spray were characterized by optical microscope and scanning electron microscope. MR T2 contrast effect of microspheres was measured with 7 T MRI. Triggered degradation of microspheres using various concentration of chelating agents (EDTA) was investigated. In vivo, hepatic arteries of New Zealand white rabbits (n = 3) were occluded by the intra-artery (IA) infused microspheres. Recanalization with a chelating agent were subsequently examined by angiography. The occlusion and recanalization of hepatic arteries were re-confirmed with a perfusion MR in Magnevist contrast-enhanced 3 T MR scans. Uniform-sized microspheres composed by 2%w/v sodium alginate and 5%w/w iron oxide were fabricated with 20 psi spray pressure. Iron oxide contributed to significant MR T2 contrast effect of the microspheres. Chelating agents (∼30 mM) rapidly dissolved the calcium crosslinked microspheres in both water and serum. In vivo angiography demonstrated fast recanalization of embolized right hepatic artery with the chelating agent. Finally, contrast-enhanced MRI showed the occlusion by microspheres and recanalization upon IA infusion of chelating agents. H&E and Prussian blue staining displayed dissolved microspheres in the tumor regions. Nanocomposite microspheres by a simple spray method demonstrated MRI visibility and fast triggered degradation in vitro and in vivo. Further studies will characterize this new on-demand temporary embolic agent.

Duplex Ultrasound-guided Direct Percutaneous Management of Pseudoaneurysm of Branch of Segmental Renal Artery: Technique and Its Outcome

To describe the role of duplex ultrasound imaging (DUI) in prompt diagnosis of pseudoaneurysm (PSA) of a branch of the segmental renal artery (b-SRA) and to evaluate outcomes of DUI directed percutaneous embolization. Forty-five patients were referred to us for the management of intractable renal hematuria. A total of 20 cases (44.44%) had developed PSA after nephrolithotomy, 12 cases (12.66%) had developed PSA after guided renal biopsies, 6 cases (13.33%) had developed PSA following road side trauma, and 2 cases (4.44%) of the tuberous sclerosis complex had developed PSA. Three cases (6.66%) of arteriovenous and 2 cases (4.44%) of arteriocalyceal fistulae had been excluded from the study. DUI-guided direct percutaneous management (DPM) was done as a 4-step process. First is the identification of PSA sac in the neck and offending b-SRA. Second is the puncture of PSA sac with 18 g puncture needle under DUI. Subsequently, manual injection of temporary embolic agent was done followed by N-butyl cyanoacrylate glue. Thrombosis of the PSA sac was confirmed by absent flow on DUI. Forty cases of b-SRA were managed successfully in a single session and followed up by clinical findings, DUI, and computed tomography angiography. There was no need for the second session of DPM, transarterial embolization, or surgery in this cohort. Twelve cases (30%) had developed a mild fever and were managed conservatively. All 40 cases had no evidence of renal hematuria after follow-up of 3 months. DUI-guided DPM is a safe, feasible, cost-effective, and nephron-sparing promising alternative to TAE or surgery for management of PSA of b-SRA.

Developing an in situ forming polyphosphate coacervate as a new liquid embolic agent: From experimental design to pilot animal study

A radiopaque temporary liquid embolic agent was synthesized from polyphosphate (PP) coacervates and optimized using a design of experiments approach. Variables studied were: strontium substitution (0–15mol%), barium substitution (0–15mol%), PP concentration and degree of polymerization of the polyphosphate (Dp). The viscosity, radiopacity and cell viability of the resulting coacervates were measured for 60 formulations and response surface modeling was used to determine the optimum coacervate that maximized radiopacity and cell viability. The optimum coacervate made from PP with a large Dp (9.5g NaPP/100mL, 2.2mol% Sr, 9mol% Ba and 3.8mol% Ca) was taken forward to a pilot animal trial. In this rabbit model, PP embolic agent successfully occluded the central auricular artery with promising biocompatibility. Further study is required to optimize the cohesiveness and clinical effectiveness of PP as an in situ setting temporary embolic agent. Statement of significanceThis article describes the development of a new radiopaque temporary liquid embolic agent from the optimization using design of experiments to a pilot animal study. Embolization is a minimally invasive interventional radiology procedure used to block blood flow in a targeted blood vessel. This procedure is used to treat many conditions including: tumors, aneurysms and arteriovenous malformations. Currently, no inherent radiopaque embolic agents are available in the clinic, which would allow for direct imaging of the material during the procedure and follow up treatment.

Water-soluble Polyvinyl Alcohol Microspheres for Temporary Embolization: Development and in Vivo Characteristics in a Pig Kidney Model

To preliminarily examine whether solubility of water-soluble polyvinyl alcohol (PVA) microspheres in blood plasma changes in proportion to their degrees of saponification. The study also examined their feasibility as a temporary embolic agents in the pig renal artery. Three types of PVA microspheres with the degrees of saponification of 97 mol% (S97), 98 mol% (S98), and 99 mol% (S99) were prepared. Seven kidneys in seven miniature pigs were embolized and divided into three groups so there would be at least two kidneys for each type of PVA. One animal in each group was euthanized immediately after angiography at 3 hours after embolization and the other one at 7 days after. In addition, one animal embolized with S99 microspheres was euthanized at 21 days after embolization. With S97 microspheres, the vascular network had recovered to the preembolic state by 3 hours after embolization. With S98 microspheres, blood flow in the third-order branch had been restored in the same period. With S99 microspheres, the second- and lower order branches remained occluded until 21 days. Histopathologic specimens harvested at 3 hours revealed only a trace of PVA for S97 microspheres. With S98 microspheres, the vascular lumen was still found to be filled with PVA gel. With S99 microspheres, swollen microspheres densely filled the vascular lumen even on day 21. Dissolution process in vitro and the duration of arterial occlusion in vivo were possibly related to the degree of saponification of PVA. This result may support feasibility of PVA microspheres as a temporary embolic agent.

Angiographic Embolization for Gastroduodenal Hemorrhage

To examine the safety, efficacy, and predictors of outcome of angiographic embolization in the management of gastroduodenal hemorrhage. Retrospective record review. University-affiliated tertiary care center. All of the patients were referred after endoscopic treatment failure. Surgery was not immediately considered because of poor surgical risk, refusal to consent, or endoscopist's decision. Patients with coagulopathy, hemobilia, and variceal or traumatic upper gastrointestinal tract bleeding were excluded from review. Between January 1, 1996, and December 31, 2006, 70 embolization procedures were performed in 57 patients. Technical success rate (target vessel devascularization), clinical success rate (in-hospital cessation of bleeding without further endoscopic, radiologic, or surgical intervention), and complications. The technical success rate was 94% (66 of 70 angiographies). The primary clinical success rate was 51% (29 of 57 patients), and the clinical success rate after repeat embolization was 56% (32 of 57 patients). Two factors were found to be independent predictors of poor outcome by multivariate analysis: recent duodenal ulcer suture ligation (P = .03) and blood transfusion of more than 6 units prior to the procedure (P = .04). There was no predictive value for angiographic failure based on age, sex, prior coagulopathy, renal failure at presentation, immunocompromised status, multiple organ system failure, empirical (blind) embolization, and use of permanent vs temporary embolic agents. Repeat embolizations were helpful for postsphincterotomy bleeding. Major ischemic complications (4 patients [7%]) were associated with previous foregut surgery. Angiographic embolization for gastroduodenal hemorrhage was associated with in-hospital rebleeding in almost half of the patients. Angiographic failure can be predicted if embolization is performed late, following blood transfusion of more than 6 units, or for rehemorrhage from a previously suture-ligated duodenal ulcer.

Temporary vascular occlusion with poloxamer 407

There is a need for safe and reversible occlusions during percutaneous endovascular procedures. Poloxamer 407 is a non-ionic surfactant with rapid reversible sol–gel transition behaviour. The safety and efficacy of this polymer as a temporary embolic agent was investigated. First, dissolution time after gelation of poloxamer was determined in an in vitro model. Then, transient poloxamer occlusion of renal and pulmonary arteries of seven dogs was followed by serial angiograms. Macroscopic and pathological changes were studied 1 week later. This experiment was repeated in similar arteries in one pig, and in auricular arteries of two rabbits. Poloxamer dissolution after in vitro polymerization was completed within 1–20 h, depending on concentrations. In vivo poloxamer 22% injections led to complete occlusion, followed by full recanalization within 10–90 min without complication. The only biochemical effect of poloxamer occlusions was transient elevation of triglyceride levels. There were no pathological abnormalities at 1 week. Poloxamer 407 could be used as an embolic material for temporary occlusions.

Uterine artery embolisation of myomas: Preliminary results of gelatin sponge pledgets as the embolic agent

SummaryUterine artery embolisation is rapidly gaining widespread acceptance as an alternative to surgery for the treatment of symptoms related to uterine myomas We used gelatin sponge pledgets to embolise 13 women with symptomic uterine myomas Our results suggest that the effectiveness of this temporary embolic agent is similar to that of polyvinyl alcohol (PVA) If larger studies corroborate this finding, we may be able to offer this procedure to women who wish to preserve their fertility.