EVOH copolymer embolization relies on a solvent-exchange precipitation mechanism to transform a liquid polymer solution into a solid embolic cast inside a target blood vessel. This technology underlies non-adhesive liquid embolic agents used in AVM and hypervascular tumor treatment, including INVAMED's LIBRO system. This guide walks through the underlying chemistry and procedural implications for interventional physicians.
What Is Ethylene Vinyl Alcohol Copolymer?
Ethylene vinyl alcohol (EVOH) copolymer is a polymer that is soluble in dimethyl sulfoxide (DMSO) but insoluble in water and blood. This solubility difference is the foundation of the embolic mechanism: as long as the EVOH remains dissolved in DMSO, it stays in liquid form, but once the DMSO is displaced by an aqueous environment, the polymer precipitates out of solution.
Manufacturers typically suspend a radiopaque agent, such as micronized tantalum powder, within the EVOH-DMSO mixture so the embolic material can be visualized under fluoroscopy during and after injection.
How Does the Precipitation Process Occur?
When the EVOH-DMSO solution is injected into a blood vessel through a microcatheter, the DMSO begins to diffuse outward into the surrounding blood and tissue fluid. As DMSO concentration drops within the injected column, the EVOH copolymer loses solubility and precipitates from the outside in, forming a solid, spongy, coherent cast that fills the vessel lumen and conforms to its contours.
This "outside-in" precipitation is a key procedural feature: the outer surface of the injected column solidifies first, forming a semi-solid shell, while the interior may remain more fluid briefly, allowing continued controlled injection and distal penetration under physician judgment.
What Are the Procedural Implications?
Because the precipitation process is gradual and diffusion-dependent, EVOH copolymer embolics generally allow a different injection technique compared to instantaneous-polymerizing adhesive agents:
- Staged injection: physicians can often pause and reassess distribution under imaging between injection increments.
- DMSO compatibility: the syringes, catheters, and hubs used must be compatible with DMSO, as this solvent can degrade certain plastics; confirming compatibility against the product IFU is essential.
- Injection rate control: injection rate and technique influence how far the agent penetrates before precipitating, which affects treatment planning for complex vascular networks.
What Should Be Considered Before the Procedure?
Patient and lesion selection for EVOH copolymer embolization is determined by the treating physician using diagnostic imaging, including angiography, to characterize the target vessel anatomy. As with any embolization technique, non-target embolization, vessel perforation, and other procedural risks exist and should be weighed against anticipated clinical benefit on a case-by-case basis.
Frequently Asked Questions
Why is DMSO used as the solvent for EVOH embolics?
DMSO is one of the few solvents capable of fully dissolving EVOH copolymer while remaining miscible with blood, allowing the solvent-exchange precipitation mechanism to function. Its diffusion properties are central to how the embolic column forms.
Does EVOH copolymer embolization work the same way in all vessel sizes?
The underlying precipitation chemistry is consistent, but injection technique, vessel anatomy, and flow dynamics all influence how a physician approaches embolization in different vessel calibers and locations. Individual procedural planning is determined by the treating physician.
How is the embolic material visualized during injection?
Radiopaque components, such as tantalum powder, are suspended within the EVOH-DMSO solution so the physician can track the embolic cast under fluoroscopic imaging in real time as it precipitates and fills the target vessel.
Related INVAMED Resources
- LIBRO Non-Adhesive Embolization Agent
- Embolization Products at INVAMED
- MicroCATH Neurovascular Catheter Family
Medical Disclaimer: This article is provided for general informational and educational purposes only and does not constitute medical advice, diagnosis, or treatment recommendation. It is not a substitute for consultation with a qualified healthcare professional. Product indications, availability, and regulatory status vary by country. Always refer to the official Instructions for Use (IFU) and consult a licensed physician for guidance specific to your situation. INVAMED devices are intended for use by trained healthcare professionals.