Role & Construction
1. The role of the guide catheter
The role of a guide catheter is to provide a stable channel for passing wires, balloons, stents and other equipment from the skin to the coronary arteries.
To achieve a stable platform the guide must overcome the friction when advancing material and oppose the force pushing it out of the artery. This ability to resist disengagement is called support or backup.
While doing this it also provides a way for visualising the artery with contrast injections, monitoring blood pressure, and a route to deliver medications directly into the coronary arteries.
2. Guide catheter shape and composition
Engineering these properties into a guide catheter requires consideration of both shape and composition.
Catheters are now available in different shapes and sizes. However, the initial catheters were all straight and needed heating and moulding into a shape suitable for each patient.
Over time some curves appeared more useful and pre-shaped catheters evolved, many of which are still in use today and retain the names of those who developed them.
3. Preshaped designs
There are now over 200 pre-shaped designs with some sharing similarities and forming the Judkins, Amplatz, and long-tipped catheter families.
Despite this choice, the bulk of left coronary procedures uses a long-tipped design such as an EBU type catheter and the majority of right coronary intervention use a Judkins right catheter.
4. Guide catheter components.
Constructing catheters from soft plastics, such as polyurethane, PEBA or PPA, allows them to be flexible and atraumatic. However, the need for thin walls that permit a larger internal diameter, or ID with the same outside diameter, or OD, for easy device passage reduces any built-in support.
Incorporating Nylon can increase stiffness, and reinforcement with a single or double wire braid improves strength, support, and torque control. However, highly reinforced catheters can cause vessel trauma, particularly to the coronary ostium.
Lubricious silicone coating on the inner surface reduces friction and enables smooth transit of wires and devices.