Essential equipment: Guidewires

Purpose

Guidewires are used in conjunction with catheters to navigate to a target, in addition they provide support and in the majority of cases, catheters, balloons and other devices are advanced into position over a previously positioned wire. Nearly all guidewires are constructed with a relatively flexible tip section of variable length and a less flexible shaft of variable stiffness. The performance of a guidewire depends on the relative properties of its tip and shaft.

Description

Guidewires broadly divide into functional groups:

• Non-steerable guidewires: these generally have a J-shaped or straight tip. They provide a supportive rail that allows the catheter to be advanced into position but are not designed to negotiate stenoses or select branch vessels.

• Steerable guidewires: these have shaped tips, the wire is constructed with good torque control so that when the shaft is rotated the tip turns a corresponding amount allowing responsive ‘steering’.

• Hydrophilic guidewires: these are mostly steerable wires, which have a slippery ‘hydrophilic’ coating. This allows the wire to cross even the tightest stenosis if used properly.

• Stiff guidewires: these are heavy-duty wires with particularly supportive shafts. A stiff wire may be required to support catheters/devices as they pass through occlusions/scar/fibrotic tissue or around challenging anatomy. The length of the flexible tip varies considerably and there is a transition between this and the stiff and more supportive wire shaft. In some wires, the transition point is visible on fluoroscopy as the flexible tip is usually more radio-opaque. Stiff wires are not normally used for primary selective catheterization but are introduced once a stable catheter position has been achieved.

• Hybrid guidewires: these are a more recent development combining a steerable floppy tip with a supportive shaft. As with all devices designed to do two things, they often are not quite as good as the original separate wires but they are pretty close and save both money and wire exchanges.