Guidewire tip
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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]
Overview
The tip of the coronary guidewire plays a critical role in determining the pushability, the steering, the tactile feel and torquability of the wire. There are two general types of guidewire tips.
- A tip coil which is flexible in shippable and is often used in workhorse wires
- A tip in which the guidewire core extends all the way to the tip of the guidewire yielding a stiffer and more torquable tip which comes at the risk of vessel perforation
Characterizing the Physical Characteristics of a Coronary Guidewire Using the Tip Load
One way of quantifying some of the physical features of a coronary guidewire is by using a strain gauge to measure the force needed to bend a wire when exerted on a straight guidewire tip, at a point 1 cm from the tip. Using this method, the tip loads in ascending order are (from less stiff to more stiff) 3 gm, 4.5 gm, 6 gm, 9 gm and 12 gm (ultra stiff). As stiffness increases the wire becomes prone to perforating the vessel.
Determinants of Tip Flexibility
There can be one or more joints made of different materials in the tips of guidewires. The number of joints and the nature of the joints can influence the clinical performance of the wires. These joints can serve as hinge points and bend during guidewire passage.
Core To Tip Guidewires
When the core is extended to the tip, that increases pushability, precise steering, tip control, tactile feel and torquability. This can be a useful feature for example in probing chronic total occlusions. If there is a two piece tip to the guidewire, then shaping is easy and the wire is likely to retain its shape, a property called “wire memory”.
Shaping Ribbon
Incorporation of a shaping tip yields a softer tip that allows for shape retention.
Spring Coil Tip
A spring coil tip may improve the performance of coronary guidewires. These tips are safer than hydrophilic coated or polymer tip wires and are associated with a lower risk of perforation.
Tip Cover
The tip can be covered in either a polymer or plastic. This covering can provide either lubricity or smooth tracking through vessel tortuosity. A polymer cover instead of a spring coil with hydrophilic coating may improve guidewire trackability but may reduce tactile feedback / feel. Examples of this design are the PT Graphix™ Intermediate Guide Wire, and the ChoICE PT wire.
”Combination” Tips
There are several types of combination tips available:
- Tip coils plus
- Intermediate coils
- Bare core
- Plastic cover
- Polymer
- Polymer over tip coils