Angiographic Revascularization after Bariatric Embolization in a Swine Model

This study evaluated fundal arteriole angiographic revascularization after embolization with embolic microspheres of 3 different diameters in a swine model (16 swine, 31 arterioles). In the 50-μm group, 7 of 11 (64%) arterioles recanalized completely, 3 of 11 (27%) arterioles recanalized partially, and 1 of 11 (9%) arterioles had collateralization (no recanalization). In the 100- to 300-μm group, 7 of 10 (70%) arterioles recanalized completely and 3 of 10 (30%) arterioles) recanalized partially. In the 300- to 500-μm group, 7 of 10 (70%) arterioles recanalized completely, 1 of 10 (10%) arterioles recanalized partially, and 2 of 10 (20%) arterioles had collateralization. No difference was found between the groups in the degree of recanalization (P = .64). All embolized arterioles exhibited some degree of angiographic revascularization, irrespective of the microsphere size.     

Bariatric Arterial Embolization with Non-spherical Polyvinyl Alcohol Particles for Ghrelin Suppression in a Swine Model

CardioVascular and Interventional Radiology - To evaluate the effect of bariatric arterial embolization (BAE) with non-spherical polyvinyl alcohol (PVA) particles on systemic ghrelin levels, weight...     

Targeting and Recanalization after Embolization with Calibrated Resorbable Microspheres versus Hand-cut Gelatin Sponge Particles in a Porcine Kidney Model

PurposeTo report on polyethylene glycol hydrogel-based resorbable embolization microspheres (REM) that were synthesized to resorb in < 24 hours, before inflammation and vascular remodeling, to achieve a complete arterial recanalization and to compare targeting and recanalization of REM of 300–500 µm, 500–700 µm, and 700–900 µm with hand-cut gelatin sponge particles (GSP).Materials and MethodsEight pigs underwent polar renal artery embolization with REM or GSP. Angiograms were obtained before embolization and 10 minutes and 7 days after embolization before pigs were sacrificed to determine the occlusion level, the percentage of occlusion, and the recanalization rate for each product. The distribution of embolic material was assessed in pathology, and infarction rate of the kidneys was measured.ResultsREM of 300–500 µm occluded more distal vessels than REM of 500–700 µm and 700–900 µm. At day 7, the recanalization rate was complete for the larger REM, whereas it was about 60% for the two smaller sizes. REM were completely degraded, with no residual material or inflammation. GSP occluded more proximal arteries than REM of 700–900 µm, were partly degraded at day 7, and were accompanied by a foreign body reaction in proximal and distal arteries. GSP recanalized at 79%. The infarction rate was higher with the two smaller sizes of REM and with GSP than with the largest REM.ConclusionsREM of different sizes targeted different occlusion levels in kidney arteries. GSP provided an extended occlusion level without actual targeting. Regardless of embolic material used, angiographic recanalization of renal arteries depended on the extent of necrosis. REM of 700–900 µm demonstrated the lowest infarction rate and the best recanalization rate.     

Long-Term Histopathologic and IVUS Evaluations of a Novel Coiled Sheet Stent in Porcine Carotid Arteries

Carotid angioplasty with stent placement has been proposed as an alternative method for revascularization of carotid artery stenosis. A novel stent with a laser-cut, rolled sheet of Nitinol (EndoTex Interventional Systems, Inc., Cupertino, CA) has been developed to customize treatment of stenotic lesions in carotid arteries utilizing a single stent, designed to adapt to multiple diameters and to tapered or nontapered configurations. The purpose of this study is to evaluate the conformability and vascular response to a novel stent in a chronic porcine carotid model using serial three-dimensional intravascular ultrasound (IVUS) analysis as well as histological examination. Ten Yucatan pigs underwent stent implantation in both normal carotid arteries with adjunctive balloon angioplasty. Three-dimensional IVUS analysis was performed before stent implantation, after adjunctive balloon angioplasty, and at follow-up [1 month (n = 6), 3 months (n = 6), or 6 months (n = 8)]. Histological examination (injury score, percent plaque obstruction, and qualitative analysis) was also performed. All stents were successfully deployed and well apposed in different sized vessels (lumen area range: 19–30 mm²). Volumetric IVUS analysis showed no significant difference between the lumen areas before stent implantation and after adjunctive balloon angioplasty and no stent area change at each follow-up point compared to immediately postprocedure. Histological examination revealed minimal injury and neointimal hyperplasia at each follow-up point. In the chronic porcine carotid model, the novel stent system demonstrated good conformability, resulting in minimal vessel injury and neointimal formation. Hideaki Kaneda and Fumiaki Ikeno Contributed equally to the work     

Intravenous Vasopressin for the Prevention of Nontarget Gastrointestinal Embolization during Liver-directed Cancer Treatment: Experimental Study in a Porcine Model

PurposeThe aim of this study was to evaluate the potential for intravenous vasopressin to reduce the risk of nontarget gastrointestinal embolization during transcatheter liver-directed cancer therapies in a porcine model.Materials and MethodsAn angiographic catheter was used to select the celiac or common hepatic artery under fluoroscopic guidance in six anesthetized pigs. After angiography of the hepatic and splanchnic territories was performed, technetium-99m macroaggregated albumin (^99mTc-MAA) was injected through the catheter. Serial arteriograms were obtained before, every 5 minutes during, and after peripheral intravenous vasopressin infusion at 0.4 U/min for a minimum of 20 minutes. After 10 minutes of infusion, indium-111 (¹¹¹In)-MAA was injected through the arterial catheter. Quantitative comparisons of liver and gastrointestinal activity using dual-isotope single-photon emission computed tomography (SPECT)/CT imaging were performed.ResultsCatheter angiography demonstrated reduced blood flow to the splanchnic vasculature while maintaining blood flow through the hepatic arteries during vasopressin infusion. Angiographic findings correlated with the relative distribution of ^99mTc-MAA (before the vasopressin infusion) and ¹¹¹In-MAA (after the vasopressin infusion) on SPECT/CT. The increased ratio of liver to gastrointestinal tract activity during the vasopressin infusion was statistically significant (6.2:11.4, respectively; P = .018).ConclusionsIntravenous vasopressin reduces arterial blood flow to the splanchnic vasculature while preserving hepatic arterial blood flow in a healthy porcine model. Intraprocedural vasopressin administration has the potential to benefit liver-directed cancer therapies by enhancing tumor targeting as well as preventing the unintended delivery of bland embolic, chemoembolic, or radioembolic agents into the gastrointestinal vascular territories.     

Bariatric Arterial Embolization for Obesity: A Review of Early Clinical Evidence

CardioVascular and Interventional Radiology - Obesity is a worldwide public health epidemic that leads to increased morbidity, mortality, and cost burden to health care. Although bariatric surgery...     

Porous Gelatin Particles for Uterine Artery Embolization: An Experimental Study of Intra-Arterial Distribution, Uterine Necrosis, and Inflammation in a Porcine Model

Purpose

We evaluated the location of porous gelatin particles (GP; Gelpart; Nippon Kayaku/Astellas, Tokyo, Japan) within the arterial vasculature and their acute effects on uterine necrosis and inflammation after uterine artery embolization (UAE) in swine.

Materials and Methods

Adult nonpregnant pigs (n = 6) were allocated to either 1- (n = 3) or 2-mm GP (n = 3). Superselective and bilateral embolization of the uterine arteries was performed. All animals were killed 1 week after UAE. Macroscopic and microscopic findings, including the level of arterial occlusion and their effect on uterine necrosis and inflammation, were analyzed.

Results

All UAE procedures were completed without severe complications. The macroscopic necrosis was seen in two animals in the 2-mm group with an extent of <50%. The location of the occluded arteries did not differ significantly between groups. The median diameters of the occluded arteries were 449 μm (95% confidence interval [CI] 417–538 μm) in the 1-mm GP group and 484 μm (95% CI 370–560 μm) in the 2-mm GP group. As for microscopic necrosis, no statistically significant difference was observed. The qualitative inflammatory reaction was significantly greater in the 2-mm GP group than in the 1-mm group (p < 0.001).

Conclusions

Both 1- and 2-mm GP occluded the arteries relevant to the target diameter for UAE in porcine uterus, presumably due to the plastic deformity. Both sizes of GP were associated with limited areas of necrosis; however, evaluation of inflammatory reaction was preliminary. Further study with adequate evaluation of inflammatory reactions is suggested.     

Comparison of Soluble Gelatin Sponge Particles and Tris-acryl Gelatin Microspheres for Bariatric Arterial Embolization in Swine

The purpose of this study was to compare complications and the number of ghrelin-expressing cells (GECs) after bariatric arterial embolization (BAE) using soluble gelatin sponge particles (SGSs) or tris-acryl gelatin microspheres (MSs) in swine. Twelve swine underwent embolization of gastric fundal arteries with SGSs (n = 4) or MSs (n = 4) or underwent saline infusion (n = 4, control group). One week later, the number of gastric ulcers and the percentage of GECs were compared among the 3 groups. There were no ulcers in the SGS and control groups. Two swine in the MS group had 4 large ulcers (12–50 mm in size). The mean percentages of GECs were significantly lower in the SGS (2.7% ± 0.9%) and MS (2.5% ± 1.0%) groups compared with the control group (3.7% ± 1.3%; P = .038 and P = .016, respectively). SGSs may be safer than MSs for BAE while inducing a similar reduction of GECs in swine.     

Transarterial Embolization of Liver Cancer in a Transgenic Pig Model

PurposeTo develop and characterize a porcine model of liver cancer that could be used to test new locoregional therapies.Materials and MethodsLiver tumors were induced in 18 Oncopigs (transgenic pigs with Cre-inducible TP53^R167H and KRAS^G12D mutations) by using an adenoviral vector encoding the Cre-recombinase gene. The resulting 60 tumors were characterized on multiphase contrast-enhanced CT, angiography, perfusion, micro-CT, and necropsy. Transarterial embolization was performed using 40–120 μm (4 pigs) or 100–300 μm (4 pigs) Embosphere microspheres. Response to embolization was evaluated on imaging. Complications were determined based on daily clinical evaluation, laboratory results, imaging, and necropsy.ResultsLiver tumors developed at 60/70 (86%) inoculated sites. Mean tumor size was 2.1 cm (range, 0.3–4 cm) at 1 week. Microscopically, all animals developed poorly differentiated to undifferentiated carcinomas accompanied by a major inflammatory component, which resembled undifferentiated carcinomas of the human pancreatobiliary tract. Cytokeratin and vimentin expression confirmed epithelioid and mesenchymal differentiation, respectively. Lymph node, lung, and peritoneal metastases were seen in some cases. On multiphase CT, all tumors had a hypovascular center, and 17/60 (28%) had a hypervascular rim. After transarterial embolization, noncontrast CT showed retained contrast medium in the tumors. Follow-up contrast-enhanced scan showed reduced size of tumors after embolization using either 40–120 μm or 100–300 μm Embosphere microspheres, while untreated tumors showed continued growth.ConclusionsLiver tumors can be induced in a transgenic pig and can be successfully treated using bland embolization.     

Evaluation of a Hydrogel Liquid Embolic Agent in a Porcine Mesenteric Hemorrhage Model

PurposeTo evaluate the ability to achieve hemostasis of a new liquid embolic agent in a porcine mesenteric artery hemorrhage model.Materials and MethodsAn anticoagulated porcine mesenteric artery hemorrhage model was created using a transarterial approach. Arterial hemorrhage was the result of aspiration needle punctures and simultaneous radiofrequency current application. Ten injured mesenteric arteries in 8 swine were treated. The hydrogel liquid embolic agent under investigation, an aqueous-based and in situ polymerizing liquid embolic agent, was used to treat actively bleeding sites. At 7 days, confirmation angiography was performed, followed by necropsy.ResultsThe mesenteric arterial injuries produced persistent and angiographically visible hemorrhage before initiating embolic therapy. Arteriovenous fistulae were observed in 4 cases. Embolization led to hemostasis in 10 of the 10 bleeds (100%). The mean embolic agent delivery time was 5.3 minutes (range, 1–15 minutes) with a mean embolic agent volume of 2.9 mL (range, 0.8–5.2 mL) delivered to achieve hemostasis. Notably, 40% of the treatments embolized the injury in the artery at the treatment site while leaving the native arterial lumen patent for the 7-day term of survival. All animals survived with no clinical evidence of hemorrhage through 7 days. Necropsy did not reveal evidence of ischemia within the bowel, liver, or lung.ConclusionsA new hydrogel liquid embolic agent was found to achieve rapid and durable hemostasis in an animal model of acute mesenteric hemorrhage.