Andras Konya

New Embolization Coil Containing a Nitinol Wire Core: Preliminary In Vitro and In Vivo Experiences

PURPOSE To improve the stability of the standard stainless steel embolization coil by adding a nitinol wire core. MATERIALS AND METHODS With use of one coil with a nitinol wire core and one without one, stability and resistance to elongation were measured in vitro. Thirty-one factory-made stainless-steel macrocoils equipped with preshaped nitinol wire cores were acutely deployed into branches of the superior mesenteric artery (SMA) in five pigs (part I of the study). Fifteen homemade retrievable coils with thermal shape memory (TSM) nitinol wire cores were acutely deployed in the abdominal aortae or inferior venae cavae of four pigs (part II). Coils with a superelastic (SE) nitinol wire core (n = 9), a TSM nitinel wire core (n = 5), and without a core (n = 5) were compared in carotid embolization (part III). RESULTS In vitro, the expansile strength of the reinforced coils was significantly greater and elongation was significantly less than the standard coils (P <.01). In part I, coils were easily deployed via diagnostic catheters. In part II, ability to reposition the coils facilitated optimal coil configuration, which resulted in effective self-anchoring and occlusion. In part III, no coils with a SE core migrated, whereas one of five with a TSM core and three of five without reinforcement migrated immediately. The core significantly increased coil stability and postplacement configuration (P <.01). CONCLUSIONS Addition of a nitinol wire core increases the intravascular stability of the standard embolization coil by significantly enhancing expansile force and postplacement configuration. The wire core does not adversely affect the handling of the coil. The ability to reposition/retrieve the coil is a desirable feature.

Anchoring Coil Embolization in a High-Flow Arterial Model: A Pilot Study☆

PURPOSE To devise and test an occluding coil anchoring system to improve the safety of coil embolization. MATERIALS AND METHODS The anchoring system was attached to Gianturco embolization coils and investigated in 15 pigs. In the short-term studies, one 0.035-inch anchored coil (15-18 cm in length and 7-10 mm in diameter) was placed in the infrarenal portion of the abdominal aorta in each of 12 pigs with use of an 8-F catheter from the carotid approach. Aortography was performed before and up to 4 hours after coil placement. In the long-term studies, 0.028-inch anchored coils (8 cm in length and 5 mm in diameter) were placed in the left femoral and the right carotid arteries in each of three pigs with use of a 6-F catheter positioned from the right femoral approach. One week later, the animals were evaluated angiographically for coil migration and vascular occlusion. RESULTS Radiographically, the coils created a compact conglomerate on placement in all but one of the animals. No coil migration was noted during follow-up. Necropsy confirmed compact arrangement of the coils within the vessels and revealed effective anchoring of the device in all cases. CONCLUSIONS The anchoring coil has proved effective in making coil embolization safer, especially in a high-flow arterial model.

Preliminary Results with a New Vascular Basket Occluder in Swine

PURPOSE To experimentally evaluate a new self-anchoring vascular occlusion device suitable for use in large, high-flow vessels. MATERIALS AND METHODS A basket-shaped occluding device consisting of a nitinol frame (with or without polyester threads) covered with Dacron was evaluated in the common iliac arteries and abdominal aortae of normal pigs. One occluder was placed in each recipient vessel. Angiography was performed before and after placement of each occluder. RESULTS Precise placement of the device was achieved in all cases. Mechanically, all but one occluder worked dependably. Angiographically, devices without polyester threads produced only partial occlusion. Devices with threads produced complete occlusion in all but one abdominal aorta, in which partial occlusion occurred because the occluder opened asymmetrically. Complete iliac arterial occlusion occurred within 2-8 minutes of placement and aortic occlusion was achieved within 8-20 minutes. At necropsy, all devices were found to be securely anchored against the vascular wall. CONCLUSION Preliminary results indicate that this vascular basket occluder containing polyester threads is easy to place precisely, produces rapid embolization, and demonstrates good self-anchoring ability in a high-flow arterial model.

Comparison of the Texan Foreign Body Retrieval Device and the Amplatz Goose Neck Snare in Vivo and in Vitro

PURPOSE To compare the capturing ability of the Texan foreign body retrieval device with that of the Amplatz gooseneck snare in a swine model and to analyze their capturing mechanisms. MATERIALS AND METHODS The Texan device with a < or = 30-mm adjustable loop was compared with the 5-mm, 15-mm, and 35-mm Amplatz snares for retrieval of foreign bodies from the iliac vein, infrarenal aorta, inferior vena cava, and stomach. Capture times by two investigators were compared. RESULTS All 24 attempts with the Texan device were successful, as were 21 of 23 attempts with the Amplatz snare; two attempts with the 5-mm Amplatz snare were abandoned, and the failures were attributed to the suboptimal size of the snare. Other than the two abandoned attempts, there was no difference between the capturing performances of the Texan device and the 5-mm, 15-mm, and 35-mm Amplatz snares when they were compared side by side. In all vascular interventions, however, the Texan device performed significantly better in capture times than did the 5-mm and 15-mm Amplatz snare (P = .015). In all interventions, the Texan device performed significantly better in capture times than did all three sizes of the Amplatz snare (P= .012). CONCLUSION The overall performance of the Texan device based on its capturing ability was significantly better than that of the Amplatz snares. The adjustability of the loop and the more versatile capturing technique made capture and retrieval of foreign bodies easier.

Pure Ethiodized Oil as a Capillary Embolic Agent with and without Ethanol-ethiodol Mixture in the Rabbit Kidney: Embolic Efficacy and Temporal Histopathologic Findings

PURPOSE To determine the extent of ablation and the temporal histopathologic findings associated with selective arterial injection of pure Ethiodol in the normal rabbit kidney, with or without arterial occlusion of the main renal artery. MATERIALS AND METHODS In 19 rabbits, 27 kidneys were embolized by injecting 0.6 mL of pure Ethiodol into the main renal artery to achieve capillary stasis. A 9:1 ethanol-ethiodized oil mixture was then injected into 17 of the 27 kidneys until complete arterial stasis was accomplished. Macro- and microscopic evaluation was performed 10 minutes to 6 weeks and 60 minutes to 1 week, respectively, for kidneys with and without arterial occlusion. RESULTS Ethiodol followed by ethanol-Ethiodol mixture (mean +/- standard deviation, 0.37 mL +/- 0.03) caused complete and permanent arterial stasis in all 17 kidneys. Thrombosis of the large arteries occurred initially. Ischemic coagulative necrosis of renal tubules and damage to glomeruli were detected 2 hours after embolization. Within 24 hours, the glomeruli and most tubules of the cortex and medulla were necrotic. Without arterial occlusion, the arteriocapillary bed of the kidneys was completely patent, with normal contrast medium excretion. Ethiodol was observed in glomeruli and interstitial capillaries from 60 minutes to 1 week and caused mild acute glomerulitis from day 1. The lesions were confined to the glomeruli, and no significant parenchymal changes were observed. CONCLUSIONS In the rabbit, selective arterial injection of pure Ethiodol produces complete renal ablation within 24 hours if prompt and permanent occlusion of the arterial compartment guarantees its permanent capillary retention.

Comparison of two foreign body retrieval devices with adjustable loops in a swine model.

The purpose of the study was to compare two similar foreign body retrieval devices, the Texan™ (TX) and the Texan LONGhorn™ (TX-LG), in a swine model. Both devices feature a ≤30-mm adjustable loop. Capture times and total procedure times for retrieving foreign bodies from the infrarenal aorta, inferior vena cava, and stomach were compared. All attempts with both devices (TX, n = 15; TX-LG, n = 14) were successful. Foreign bodies in the vasculature were captured quickly using both devices (mean ± SD, 88 ± 106 sec for TX vs 67 ± 42 sec for TX-LG) with no significant difference between them. The TX-LG, however, allowed significantly better capture times than the TX in the stomach (p = 0.022), Overall, capture times for the TX-LG were significantly better than for the TX (p = 0.029). There was no significant difference between the total procedure times in any anatomic region. TX-LG performed significantly better than the TX in the stomach and therefore overall. The better torque control and maneuverability of TX-LG resulted in better performance in large anatomic spaces.

Superselective Arterial Catheterization in the Rabbit

RATIONALE AND OBJECTIVES To improve the safety and success of selective and superselective arterial catheterization in the rabbit. METHODS A 2-F catheter introducer system was devised that consisted of the sheath of an 18-gauge, 5.1-cm sheath needle and a hemostatic valve attached to the hub of the sheath. The system was tested in 14 adult male New Zealand white rabbits with regard to ease of insertion and facilitation of superselective arterial catheterization. RESULTS The introducer system was easily placed in all rabbits, and no bleeding was seen around the sheath at the puncture site. Preshaped 2-F polyethylene catheters were readily inserted through the assembly and sheath. The valve prevented bleeding from around the catheter, and the side-arm flush tube served as a route for heparinization. The system greatly facilitated the manipulation of 2-F angiographic catheters. CONCLUSION Use of the introducer system with a 2-F polyethylene angiographic catheter improved the success of selective and superselective arterial catheterization in the rabbit.

New Retrievable Coil Anchors: Preliminary In Vivo Experiences in Swine

PurposeTo design and test retrievable coil anchors to improve the safety and efficacy of coil embolization.MethodsFifty-two 0.038-inch homemade retrievable stainless steel coils were equipped with one of four different pre-shaped nitinol anchors and tested in 38 pigs. All coils with the anchor were completely retrieved and redeployed 3–18 times (median 7 times) prior to release. Types 1 and 2 anchored coils were acutely deployed in the external iliac arteries (n = 10 each), and chronically tested (1 week) in the common carotid arteries (n = 6 each). Larger type 1 (n = 4), type 3 (n = 6), and type 4 (n = 4) anchored coils were acutely deployed in the abdominal aorta. The largest type 1 anchors (n = 6) were acutely tested in the inferior vena cava.ResultsAll anchored coils were successfully retrieved and repositioned several times. All but two coils formed a compact plug and there was no coil migration except with two mechanically defective type 3 anchors.ConclusionThe use of retrievable anchors allowed the coils to be retrieved and repositioned, prevented coil migration, and enabled compact coil configuration.