Not every vascular target is well suited to coils or plugs. Complex, high-flow lesions such as arteriovenous malformations (AVMs) often have irregular, branching architecture that benefits from an embolic agent capable of flowing into and casting the shape of the abnormal vessel network itself. Ethylene vinyl alcohol copolymer, commonly abbreviated EVOH, is one of the most established liquid embolic chemistries used for this purpose, and understanding how it behaves helps explain its role in modern embolization practice.
What Is an EVOH Liquid Embolic Agent?
EVOH liquid embolic agents are a category of injectable embolic material formulated from ethylene vinyl alcohol copolymer dissolved in a solvent, most commonly dimethyl sulfoxide (DMSO). When the liquid is injected into a blood vessel and comes into contact with blood and surrounding tissue fluid, the solvent diffuses away and the copolymer precipitates out of solution, solidifying in place to form a cohesive, spongy cast that conforms to the shape of the vessel it was injected into. This casting behavior is what distinguishes liquid embolics from solid devices like coils or plugs, which occupy space rather than conforming to it.
Why Is Radiopacity Important, and How Is It Achieved?
Because the liquid embolic is injected under continuous imaging guidance, the operator needs to see exactly where the material is flowing in real time to avoid unintended spread into non-target vessels. EVOH-based agents commonly incorporate a radiopaque additive — tantalum powder is a widely used option — suspended within the formulation to enhance visibility under fluoroscopy during injection. This tantalum-enhanced visibility allows the interventional radiologist or neurointerventionalist to track the leading edge of the embolic material as it fills the target vessel architecture.
How Does the Injection Technique Work?
EVOH liquid embolic injection is typically performed through a microcatheter that has been navigated to the target vessel, and the microcatheter itself must be compatible with the DMSO solvent used to keep the polymer in solution prior to injection, since DMSO can damage certain catheter materials. Injection is generally performed slowly and incrementally, with the operator pausing frequently to assess the pattern of embolic material distribution on imaging before continuing, since controlled, gradual casting reduces the risk of the material migrating into non-target vessels.
Where Are EVOH Liquid Embolics Used?
EVOH liquid embolic agents are most commonly discussed in the context of treating brain and spinal arteriovenous malformations, where their ability to penetrate and cast the nidus (the tangled vessel core of an AVM) is particularly valuable. They are also used in some peripheral and visceral embolization applications where complex vessel architecture makes coils or plugs less practical. The decision to use a liquid embolic versus a solid device depends on the specific vascular anatomy and treatment goal, determined by the treating physician.
What Concentrations Are Available, and Why Does Concentration Matter?
EVOH liquid embolics are typically supplied in different concentrations, which influences how quickly the material precipitates and how far it penetrates into smaller vessel branches before solidifying — lower concentrations tend to flow further into small vessels before casting, while higher concentrations solidify more rapidly near the injection point. Selecting the appropriate concentration for a given lesion is part of the pre-procedural planning done by the treating physician based on the specific vascular architecture being treated.
LIBRO: INVAMED's EVOH Liquid Embolic Agent
INVAMED manufactures LIBRO, an EVOH-based liquid embolic agent offered in 6% and 8% concentrations, formulated with tantalum for enhanced visibility under fluoroscopic guidance during controlled vessel casting procedures. More information on INVAMED's embolization portfolio, including liquid embolic technologies, is available on the INVAMED embolization products page. Availability and indications vary by country, and the Instructions for Use (IFU) should always be consulted by treating clinicians.
Device availability and regulatory status vary by country. Please contact INVAMED or your authorized local distributor for current regulatory information applicable to your region.