Embolic coil with gradient stiffness

An embolization system comprising:

• a delivery catheter;
• an embolic coil releasably coupled to the delivery catheter, the embolic coil configured to be disposed within a lumen of the delivery catheter in a primary shape, and to form a secondary shape upon exiting the delivery catheter, the embolic coil having a proximal end and a distal end and formed from a continuous wire, the primary shape of the embolic coil formed by winding the continuous wire on a tapered mandrel such that the primary shape of the embolic coil is a spiral having an outer diameter that increases from a first outer diameter at the proximal end to a second outer diameter at the distal end that is larger than the first outer diameter;
• and
• wherein the embolic coil has a gradient stiffness profile transitioning from a first stiffness at the proximal end to a second stiffness at the distal end that is less than the first stiffness.

A method of manufacturing an embolic coil, comprising:

• providing a mandrel having a tapered outer diameter;
• wrapping a continuous wire around the mandrel to form a primary coil having a proximal end having a first outer diameter and a distal end having a second outer diameter larger than the first outer diameter, wherein the tapered outer diameter of the mandrel creates a gradient stiffness profile in the primary coil when released from the mandrel;
• removing the primary coil from the mandrel and forming a secondary shape including at least one loop or fold in the primary coil;
• heat treating the primary coil to set the secondary shape;
• and
• attaching a plurality of polymeric fibers between windings of the primary coil.