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Principles of using catheters and wires


Knowing the equipment is a great start but it comes into its own if you know how to use it. Remember wires go first, and the initial step of most procedures is to establish safe guidewire access to the target zone.

Alarm

Exceptions to the catheter follows the wire are: manoeuvring a pigtail up and down the aorta and moving catheters up and down the aorta to allow them to engage a branch vessel – even then, take care in a diseased aorta.

Achieving a selective position or negotiating complex anatomy usually requires catheters and wires working together.

Using guidewires and catheters together: a step-by-step guide

This section is about the use of guidewires and catheters together to navigate from A to B. This assumes that you have already managed to pass a wire through the puncture needle ( Ch. 8 ) and then achieved access with a sheath ( Ch. 14 ). Guidewire and catheter selection is discussed in the essential equipment chapter ( Chs. 11 and 12 ). We are assuming here you know what to ask for but not necessarily how to use it – in fact: ‘all the gear – no idea’.

Advancing the guidewire

Very often, a J-tip or steerable wire can be advanced to close the target site without need for a catheter. J-wires tend to stay in major vessels but steerable wires, such as the angled Terumo, will often stray from the path, and readily enter branch vessels.

As the guidewire is advanced, pay attention to detect any resistance to the passage of the wire. Learning to feel an increase in resistance as soon as it occurs is a key skill in intervention. This is an adjunct to using fluoroscopy.

Alarm

Use fluoroscopy to keep on track and detect deviation before causing a problem.

Troubleshooting

The wire does not go where you expect it to

This happens when it enters a branch or collateral or is no longer in the lumen.

  • If the wire is moving freely, then simply pull the wire back, rotate the shaft of the wire and advance under fluoroscopy.

  • If the wire repeatedly takes the same (wrong) path: advance a catheter over the wire and carefully aspirate to make sure there is backflow. Use a gentle contrast injection to determine your position. If in a branch vessel, pull back into the main vessel and rotate the catheter when advancing the wire to avoid the offending branch.

  • If there is no backflow then you are either wedged or extraluminal. Pull the catheter back aspirating as you go until there is backflow and then check again.

Advancing a catheter over a guidewire

The catheter follows the wire when it is being introduced and advanced except during proximal vessel selective catheterization.

  • Hold the wire close to the skin.

  • Ask your assistant to load the catheter onto the wire until it reaches your fingers.

  • Extend the wire so that it is in a straight line and hold the wire close to the catheter hub keeping it under tension.

  • Start to advance the catheter into the sheath a few centimetres at a time. Always manipulate it just a few centimetres away from the sheath.

  • Keep the wire fixed in position with your right hand.

  • As the catheter gets further in, reposition your hand to maintain tension in the guidewire.

  • Fluoroscope over the wire tip when you advance the catheter and try to maintain a constant position.

Troubleshooting

The catheter sticks on the wire before it reaches the sheath

This is most likely with a hydrophilic wire that has become dry. Use a wet sponge to wet the wire. Catheters can stick on conventional wires usually when there is a blood clot or a piece of gauze stuck to it. Clean as above. If the catheter still will not advance, try to take it off the wire, flush it and clean the wire.

The catheter does not advance once it is in the patient

Fix the catheter and wire and ask the radiographer to pan the C-arm down from the wire tip while screening. Try to see if there is an obvious cause such as a kink or loop in the catheter. The reason may not be obvious in the case of a very tight stenosis.

  • If there is a kink, you will probably need to exchange the wire for a new one. Consider whether a stiffer wire would be more appropriate.

  • If there is a loop, it is normally necessary to pull the catheter and wire back together until they straighten out.

  • If there is a known tight stenosis, e.g. you are planning to treat it, then if possible keep the wire across it. If there is room, insert some more wire to improve stability and try again. If this fails, you may need to change to a low profile system.

Maintaining your position

  • When you are not manoeuvring, keep a hand on the catheter/wire close to the access site.

  • Remember that hydrophilic wires are incredibly slippery when wet and sticky when they dry out. Keep the wire lubricated and make sure you are still holding it. Take care when ‘letting go’ of a dry wire, as it may be attached to your glove.

Tip

Always assume that your assistant is determined to pull the guidewire out during catheter exchanges. Get a grip!

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