Guidewire desirable performance characteristics

Overview
There are several performance characteristics of coronary guidewires that make them effective. These desirable performance characteristics are described below.

Steerability
The tip of a coronary guidewire must be curved and must be able to be turned or "torqued" to follow the course of the vessel down which it is being placed.

Trackability
A coronary guidewire must be capable of being readily advanced around curves in the coronary arteries, and must have sufficient strength or support to allow devices to likewise go around these curves in the coronary artery.

Torquability
The tip of the guidewire must be able to be pointed in different directions by the operator to change directions, to go into sidebranches, to cross asymmetric or eccentric lesions, to avoid stent struts and to go around corners and bends in the coronary artery. When the operator rotates the guidewire outside the body, the ability of the guidewire to translate this motion into a similar motion at the tip is called torquability. This is the ability of the coronary guidewire to transmit rotational forces from the operators hand to the tip and the optimal performance is for this rotation of the coronary guidewire to be translated to the tip in a one-to-one fashion. The operator will often use his hand to twist or maneuver the wire, however, the torquability of the wire may be further improved by the use of a “torquer” or a “pin vise” or “steering tool”.

Support
The support of coronary guidewire refers to the ability of the coronary guidewire to allow a bulky device to track through bends in the coronary artery and to be to be delivered across the blockage without buckling or kinking of the wire. If the operator is attempting to advance a balloon or stent down the artery, and if the guiding catheter backs out of the coronary artery and if the guidewire also works its way from a distal position to a proximal position and backs out of the body, then this may be a sign of a "lack of guidewire support". Calcified and tortuous right coronary arteries often require guidewires that offer improved support to maneuver a balloon or a stent to a distal lesion in the right coronary artery.

Flexibility
Flexibility refers to the ability of the coronary guidewire to bend with direct pressure. The flexibility of the wire is determined mainly by the distance from the tip of the central core to the distal tip of the wire. Flexibility is an important performance characteristic that minimizes vascular trauma.

Stiffness
Stiffness of the guidewire depends upon the diameter, trackability and torque control of the guidewire. Stiffer wires give better torque control and straighten the vectors of forces pushing the wire, balloon or a stent. Stiff quagmires may allow devices to be delivered through tortuous and calcified vessels with greater ease. A stiffer wire can be useful in crossing chronic total occlusions as well as when delivering a stent or balloon in a straight segment and can work against delivering a stent or balloon in a tortuous or an angulated segment. Stiffer wires are more likely to cause pleating artefacts and also slice through the intima in a “cheese cutter” effect. This "cheese cutter" effect has been observed with the "Iron Man" wire.

Tactile Feedback
Tactile feedback refers to the “feel” of the wire tip’s behavior as perceived by the operator. Tactile feedback is better appreciated with coil tipped wires, whereas polymer tipped wires it may be minimal or absent, making inadvertent perforation, dissection or subintimal diversion into a plaque more likely.

Malleability
Malleability refers to the ability of the coronary guidewire to be shaped or bent without breaking.

Radio-opacity and Visibility
Radio-opacity refers to the visibility of a coronary guidewire under fluoroscopy and cineangiography. It is a critical characteristic of the guidewire so that the leading tip of the guidewire can be identified. Platinum at the end of the wire provides radio-opacity to the tip. One of the limitations of increased radio-opacity or visibility throughout the length of the guidewire is that the guidewire may mask the presence of a tear or dissection in the artery.