In December 2022, The GEST Group conducted a 2-day summit where physicians learned everything they need to know about using coils and how the materials and characteristics translate into clinical use.
Review of the Coil Summit
- Stainless Steel – early days, not used anymore
- Tungsten – outdated
- Polymer – outdated
- Platinum – main material used for modern coils
- Inconel – only one coil on the market for peripheral use (MReye, Cook)
Why platinum (92% Platinum, 8% Tungsten)
- It is highly radiopaque, biocompatible, flexible, malleable with minimal MRI or CT artifact.
- The primary structure is defined by the raw wire, the secondary structure by the coil diameter, and the tertiary structure by the 3D overall shape.
- Volume and stiffness can vary independently according to the raw wire structure, which explains why two coils with the same diameter may deploy differently.
- Small differences in the material will induce differences in softness, pushability, packability, and radial force.
- They are coils enlaced with fibers to promote biological response and support mechanical occlusion.
- Fibers reduce occlusion time, enhancing the mechanical action of bare coils.
- Fibers enhance thrombogenicity.
- They include Concerto, Interlock, Embold, Retracta, Flipper, Nester, Tornado and MReye.
- In contact with blood, hydrogen ions are released and water molecules form with the polymer causing it to expand.
- It is biologically inert and does not contain or produce biologics.
- Hydrogels are porous and compliant and allow natural tissue proliferation promoting endothelial formation.
- They do not rely on thrombus formation and can be used in coagulopathic patients.
- Azur HydroCoils systems expand 4-5 times when deployed.
- Coil systems include a delivery wire, a wire / coil connection and a coil.
- Pusher wires are made of Stainless Steel or Nitinol.
- The connection has to be predictable, durable, visible, and easy to use.
- Occlusion characteristics depend on the thrombogenicity and the packability of the coil.
- Coil manufacturing goes back to the 70’s.
- It initially started with the idea of mechanical obstruction.
- The goal of newer coils is also to minimize recanalization.
- Animal models show that vessels occluded by fibered coils contained 70% of thrombus with fibered coils and 40% with hydrogel-coated coils.
- Long-term recanalization may be lower if it is less reliant on thrombus-related occlusion.
- We must keep in mind thrombus resorption when coiling.
- Oversizing is important in venous coiling (>50%).
Measuring the Packing Density
- The goal is to have optimal cross-sectional occlusion to avoid recanalization.
- Initial aneurysm studies showed a minimal density of 20% to achieve occlusion.
- There is low level of evidence for a threshold.
- Coil compaction may be responsible for revascularization.
“As much as you can safely deploy”
- Prime the microcatheter: copious flushing prior to coil insertion.
- Secure the microcatheter and keep an eye on the diagnostic catheter.
- Avoid pushing wire into the coil pack.
- “One more coil”? If hesitant, wait and perform an angio. Occlusion may be delayed.
- Remove the pusher wire with care under scopic view.
- Remove the microcatheter with care when in contact with the packing.
Coil Catheter Compatibility at a Glance
During the coil summit, physicians expressed an interest in a quick guide to embolization coil-catheter compatibility. Thanks for Dr. Dania Daye, we are pleased to present the Coil/Catheter Compatibility at a Glance. Fill out the form to the right for immediate access to the guide.