Midterm Recanalization after Arterial Embolization Using Hydrogel-Coated Coils versus Fibered Coils in an Animal Model
The number of available coils on the market continues to increase with variations on the basic principle of creating a mechanical obstruction to cause occlusion. Both fibered and hydrogel-coated coils (HydroCoils) are available with the purpose of enhancing the effectiveness of the mechanical blockade. HydroCoils are well documented in neuro-interventional aneurysm coiling showing decreased recanalization rates. The purpose of this study was to evaluate the angiographic and pathologic effects of HydroCoils and fibered coils within the internal iliac arteries and renal arteries of a sheep model. Comparison time points included 1 week, 1 month, and 4 months.
0.018-inch detachable and 0.035-inch pushable HydroCoils (Azur; Terumo, Tokyo Japan) were compared with 0.018-inch detachable fibered coils (Interlock; Boston Scientific, Marlborough, Massachusetts) and 0.035-inch pushable fibered coils (Nester; William Cook Europe, Bjaeverskov, Denmark). In 12 sheep, the left internal iliac was coiled with 0.035-inch coils and the right renal artery with 0.018-inch coils. Selective angiograms were performed immediately following coil embolization, and subsequently at 7 days, 1 month, and 4 months. Pathologic evaluation was performed at 4 months. There was no statistical difference in recanalization rates at the 7 day interval. However, at one month, there was a 50% (6 of 12 arteries) occlusion rate with fibered coils compared to 100% (12 of 12) with HydroCoils. At 4-months, vessel occlusion was 25% (3 of 12) with fibered coils compared to 80% (8 of 10) with HydroCoils. In both groups, recanalization was higher in the renal arteries (occluded with 0.018-inch coils) compared to the internal iliac arteries (using 0.035-inch coils). On pathologic examination, the occlusion plug was 77% thrombus and 23% metal with fibered coils versus 36% thrombus, 15% metal, and 49% hydrogel.
Figure 3 and 4. 3) Photographs of tissue sections of 0.035-inch HydroCoils occluding an iliac artery at 4 months. Complete occlusion is visible. The coil (arrows) represented 22% of the lumen surface, the hydrogel (green asterisks) represented 51%, and thrombus (red asterisks) represented 27%. Artefactual detachments are seen around the coil loops. 4) Photographs of tissue sections of 0.035-inch fibered coils occluding an iliac artery at 4 months. Complete occlusion is visible. The coil (arrows) represented 21% of the lumen surface, and thrombus (asterisks) represented 79%. Dacron fibers are difficult to identify.
With increasing products available for permanent embolization, including coils and plugs, there is increasing competition for utilization in specific cases and for space on your shelves. Performance, sizing choices, versatility, and cost-effectiveness are all important factors in product choice. Bare metal and fibered coils are known to have recanalization over time, likely due to clot resorption. HydroCoils were created to combat this phenomenon with the outer hydrogel polymer expanding with exposure to blood and fill a larger portion of the lumen. This is again demonstrated in this study along with decreased recanalization rates at 1 and 4 months. This study is limited due to the small number of arteries embolized (6 in each category), the nature of an animal model, and short follow up (4 months). Long term degradation of the hydrogel or adjacent inflammatory reaction may effect durability past 4 months. Additionally, cost considerations with HydroCoil use and clinical consequences of recanalization was not addressed. With future research in vivo and with increased follow up duration, HydroCoils could be proven to have superiority compared to standard bare metal and fibered coils which could have significant effect on what you choose to stock and deploy next.
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Fohlen A, Namur J, Ghegediban H, et al. Midterm Recanalization after Arterial Embolization Using Hydrogel-Coated Coils versus Fibered Coils in an Animal Model. J Vasc Interv Radiol. 2018.
David M Mauro, MD
Department of Radiology
Vascular and Interventional Radiology
University of North Carolina