Coil variations include bare platinum, polymer coated (Matrix), and hydrogel coated coil (HydroCoil) coils.
In aneurysms Matrix coils were most likely to need retreatment. Retreatment rates were comparable for bare platinum and HydroCoils. Follow-up angiography demonstrated statistically significant attenuation of residual aneurysms for HydroCoils. Matrix group had the greatest and HydroCoils the least tendency to recanalize. Factors other than coil surface-coating may attenuate aneurysm recurrence 1).
See Coil migration