Polyvinyl Alcohol Embolic Microspheres

Polyvinyl Alcohol Embolic Microspheres are compressible hydrogel microspheres made from polyvinyl alcohol (PVA) that are used to block blood flow in blood vessels. They are delivered via catheter under fluoroscopic visualization and are indicated for embolization of arteriovenous malformations (AVMs), hypervascular tumors, and uterine fibroids. The microspheres are supplied sterile in glass vials in sizes ranging from 75–1200 μm, available in blue-dyed or clear formulations.

The subject device is nearly identical to the predicate (CalliSpheres/8Spheres) in polymer composition (PVA), storage media (0.9% sodium chloride), sterilization method (moist heat), non-resorbable nature, and delivery mechanism (1.7–4.0 Fr catheters). Key differences include: the subject device has a smaller minimum particle size (75 μm vs. 100 μm), greater compressibility (50% vs. 30% by diameter), offers 3 mL/6 mL configurations not available in the predicate, and has a longer shelf life (3 years vs. 2 years). Both use the same radiopacity method and are packaged in borosilicate glass vials.

ISO 10993 series (biocompatibility: cytotoxicity, sensitization, irritation, acute systemic toxicity, hemolysis, pyrogen, muscle implantation); ISO 10993-17:2023 and ISO 10993-18:2022 (chemical characterization and toxicological risk assessment); USP-NF 2025 standards (sterility <71>, endotoxins <85>, water content <731>, pH <791>); ASTM D4169-22 (transportation testing); ASTM F1929-15 (dye penetration); ASTM F1980-21 (accelerated shelf-life aging); ISO 17665:2015 (steam sterilization validation).

The subject device is substantially equivalent because it uses the identical fundamental technology (PVA suspension polymerization) and has the same indications for use as the cleared predicate. The smaller minimum particle size (75 vs. 100 μm) does not raise safety or effectiveness concerns because smaller microspheres have already been cleared for similar indications with the same basic design. All non-clinical testing (performance, biocompatibility, sterility, shelf-life, and animal efficacy studies) demonstrated the subject device performs as safely and effectively as the predicate. The differences in compressibility, shelf-life, and available configurations represent minor design variations that do not affect the fundamental safety or performance profile.