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Essential equipment: Catheters
Purpose
Non-selective catheters with multiple sideholes are used for rapid injection of contrast into large–medium-sized arteries. Selective catheters may have sideholes or just a single endhole; they are shaped to allow the catheter to enter branch vessels or direct guidewires into them.
Description
Catheters come in a wide range of shapes, sizes and constructions. Simple rules govern catheter choice. Most interventional radiologists rely on a relatively small selection of catheters to perform almost all cases.
Catheter construction influences handling. You will need to experiment with different equipment until you find what works for you. Small-calibre catheters may be less traumatic in terms of the size of the puncture site but the cost is reduced ability to control rotation of the catheter tip in response to turning the catheter hub. This ‘catheter torque’ is also affected by many other factors, including catheter material, catheter length and the number of curves it has to negotiate.
Most non-selective angiograms can be performed with 3Fr catheters but selective catheterization, particularly if tortuous vessels are involved, usually requires 4Fr catheters or larger.
Construction considerations
Many of the common catheter shapes are available with different constructions. These change the handling characteristics markedly. In the absence of a known favourite, consider the following.
Braiding
Braided catheters have a wire reinforcement, which gives increased torque and some kink resistance. The downside is that they tend to be rather rigid and more prone to ‘ping in and out of vessels’.
Coating
Hydrophilic catheters (and wires) have a slippery coating when they are wet; this tends to be most useful at the extremes of scale, e.g. for inserting very large devices, such as stent grafts and when using coaxial microcatheter systems. Hydrophilic-coated catheters, when used in combination with a hydrophilic wire, can be advanced into small vessels of the distal arterial bed.
Visibility
It can be very difficult to see a small catheter in a large patient – opacity vs scatter. Some catheters have a barium coating or a platinum band to show the tip position.
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