Core materials are chosen for having good torque transmission, which is also improved by a thicker core with more gradual distal taper.
tip shape ability
Importance increases as lesion complexity increases.
Nitinol is more difficult to shape, but can be reshaped; steel is easier to shape but can be ruined by being deformed.
Lubricity
Can ease wire passage in tight, calcified, severely tortuous lesions.
Tip or distal segment coating with silicon, hydrophilic coating, or polymer coating: “plastic jacketed” wires are the most lubricious but also the most dangerous; when combined with a stiff tip long dissections can be inadvertently created:hydrophilic requires water for activationhydrophobic does not require water for activation, allows feedback from distal tip so that excessive friction when creating a subintimal dissection or going below stent struts can be detected.
Tendency to prolapse
Can be important when negotiating angles >75°
A gradually tapering core with a smooth transition toward the tip improves support and tracking around bends; abrupt tapers and floppy cores are more likely to prolapse.
Visibility
The level of visibility becomes more important in obese patients or when angled working views are required.
Lubricious polymer‐coated nitinol wires can be difficult to see, platinum, steel, or tungsten markers at distal tip.
Tactile feedback
Provides the operator with essential nonvisual information, allows “palpation” of the lesion at the distal wire tip.
Hydrophylic wires provide poor tactile feedback; hydrophobic wires provide more feedback.
Tip stiffness
A soft gentle tip is essential for all “workhorse” wires; to reduce the risk of vessel trauma; stiffer tips are required for dedicated CTO wires.
More gradual distal taper, distal core material (e.g. high tensile steel).
