Microcatheter Assists Brain Embolization Procedures

A novel microcatheter with a detachable tip mitigates the technical challenges of catheter retrieval during liquid embolization of brain arteriovenous malformations (bAVMs).

The Apollo Onyx Delivery Microcatheter was developed to enable physicians to choose the best catheter position for each procedure, and provide optimal navigability through complex distal anatomy. The proprietary detachable tip was designed to facilitate catheter retrieval in challenging environments during embolization procedures with the Onyx non-adhesive liquid embolic agent, comprised of ethylene vinyl alcohol (EVOH) copolymer dissolved in dimethyl sulfoxide (DMSO), and suspended micronized tantalum powder to provide contrast for visualization under fluoroscopy.


The DMSO solvent dissipates into the blood, causing the EVOH copolymer and suspended tantalum to precipitate in situ into a spongy, coherent embolus. Importantly, the microcatheter tip should be placed so that embolization of the bAVM occurs distal to any arterial vessels that supply normal brain tissue or cranial nerves. The Onyx Liquid Embolic System (LES) consists of a 1.5 mL vial of Onyx, a 1.5 mL vial of DMSO, and three 1 mL Onyx delivery syringes. The delivery Microcatheter is indicated for use in the neurovasculature and is used to access the embolization site.

The Onyx liquid is available in two product formulations, Onyx 34 (8% EVOH) and Onyx 18 (6% EVOH), which travels more distally and penetrates deeper into the nidus due to its lower viscosity. Final solidification occurs within five minutes for both formulations. The Apollo Onyx LES and Delivery Microcatheter are products of Covidien (Dublin, Ireland), and have been approved by the US Food and Drug Administration (FDA).

“Covidien is offering a new level of confidence for physicians by providing the only detachable tip microcatheter in the United States,” said Brett Wall, president of neurovascular at Covidien. “The Apollo Onyx microcatheter has the potential to improve patient outcomes by safeguarding the neurovasculature during catheter retrieval.”

“This new game-changing device will improve physicians’ options for treating patients with bAVMs,” said Alejandro Berenstein, MD, director of the center for endovascular surgery at Mount Sinai Health Systems (New York, NY, USA). “The Apollo Onyx micro catheter provides a very important added safety mechanism for catheter retrieval during Onyx LES embolizations of bAVMs, permitting a more complete treatment in a much safer manner.”

A bAVM occurs when a tangle of blood vessels in the brain or on its surface bypasses normal brain tissue and directly diverts blood from the arteries to the veins. A ruptured bAVM allows blood to leak into the brain or surrounding tissues, and reduces blood flow. Cerebral AVMs occur in less than 1% of the population, and in about half of the patients, the first symptoms are those of a stroke caused by bleeding into the brain.

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