The different forms of catheter are designed to accommodate viewing different areas of anatomy, and the manoeuvring of interventional devices through the vascular system. Standard catheters (JL, JR) are named after Dr Melvin Judkins, their inventor. These pre-shaped catheters remain almost unchanged since first production in 1968.
French sizing is used to indicate the outer diameter of the device. 1 French unit is equivalent to 0.33mm, and different sizings have different pros and cons attributed to them. Historically, 6F catheters didn’t possess internal dimensions a large as those found in an 8F device, but in many modern 6F catheters this difference is now negligible.
Given the potentially long nature of any given procedure, catheters may be required to be held in place, so devices offer Back-Up Support, of which there are two types; active and passive.
Active Support uses the curve of the catheter and the shape of the anatomy, where the curvature of the device is created using the aortic root, whereas Passive Support puts more reliance on the catheter composition itself.
6F devices provide active support, and require a smaller puncture wound, but as they use a smaller volume of contrast, visualisation is poorer than larger sizes. 7F – 8F devices are better with regard to arterial visualisation (they use more contrast), but require a larger puncture in order to be inserted.
There are many more catheters used in angiography, but these varieties presented below are fairly common.
The JL catheters possess three curves, and are assigned numbers which, in the left, indicate the distance between the primary and secondary curves, such 3.5cm, 4cm, and 5cm. In the right, the numerical value denotes the length of the secondary curve. This is where the names JL3.5 and JR4 come from.
The Judkins Left catheter is designed to enable easy seating in the ostium of the left main stem, by following the outer lumen of the aorta. The Judkins Right catheter is curved in such a way as to allow the tip to engage the ostial RCA with only a small rotation, once advanced through the vessel.
Extra Backup catheters offer greater support for engagement with the Left Main ostium, on account of the broad secondary curve
These catheters are designed to pass PCI equipment through the vessel, and as such are usually larger and stiffer than diagnostic catheters. They perform three main functions:
- Balloon-Stent delivery: The catheter sits inside the coronary artery, allowing balloon-stent catheters to passed through its distal end so as to be positioned at the site of the lesion
- Contrast injection: Like diagnostic catheters, guide caths allow for dye injection to visualise the target area and lesion
- Pressure monitoring: The lumen of the guiding cath allows measurement of the aortic pressure throughout the procedure