Principles of crossing stenoses and occlusions

Many interventional procedures have the primary aim of managing narrowings or blockages to restore flow of blood, urine, bile, air or even bowel contents. Once access into the appropriate lumen has been achieved, the basic principles of catheters and wires are used to navigate through the diseased segment. This chapter is concerned with the mechanics of getting across to the other side. Success is largely governed by:

• Having a ‘map’ of the lesion: this is a combination of pre-procedure imaging combined with per-procedure imaging, using contrast to outline the lesion and any key anatomical structures.

• Choosing the right weapons: a combination of sheaths, guide catheters, shaped catheters and guidewires.

• Achieving a position of strength: this usually means a stable catheter position ideally with mechanical advantage, just in case you need to push to cross an occlusion. Stability begins with the choice of access site and is supplemented by the use of sheaths and guide catheters.

• Perseverance: sometimes you can traverse the most difficult lesion in a matter of seconds. Try to look as though you are not too surprised at your luck when this occurs. However, success often takes time, this is much easier if you have prepared the patient for a longer procedure and ensured they have adequate analgesia.

• Reassessing the situation: if you have been trying without success for a while. Stop and think – is there anything you could be doing differently? It often helps to phone a friend at this stage, two heads can be better than one and sometimes a fresh approach is all that is needed.

• Knowing when to stop: OK, so this is normally associated with failure but there is a time to give up before causing any harm. Revisiting a case on another occasion is often successful, particularly when there has been chronic obstruction in a non-vascular system. A period of drainage can let oedema settle down and subsequent catheterization becomes much easier.

Crossing stenoses

Even the tightest stenosis can be negotiated with patience, a little skill and the right tools. Simple stenoses are readily negotiated with a guidewire alone: most operators will choose a steerable hydrophilic wire in the first instance but a Bentson wire can be used in conjunction with a curved catheter ( Fig. 31.1 ).

Key steps

• Centre the image intensifier over the lesion and obtain a ‘map’ of the stenosis at appropriate magnification.

• Start with the catheter 2–5 cm from the stenosis and advance the guidewire.

• Use your catheter and wire together to steer towards the apex of the stenosis.

• Take your time and do not use force. Hold the wire loosely, and gently probe with the tip until it engages.

• Use a pin-vice to steer the wire to advance through and across the lesion.

Tip

A pin-vice makes it much easier to steer and control a hydrophilic wire. There is nothing macho about struggling without one, however, if none is to hand, dry the wire to allow you to grip it. Be careful! A dry wire will stick to your gloves and is easily pulled out!

This sounds simple but longer and more complex stenoses, especially those located on bends or at the origin of a vessel, can be very challenging. In longer lesions, the key is to steer through the narrow segment, using a shaped catheter and a curved hydrophilic wire.

Once you have crossed the lesion

Remember that the hydrophilic wire, which was great for crossing the lesion, is now a liability as it is readily pulled out. Exchanging for a conventional wire after negotiating the lesion is infinitely safer. To exchange the wire, fix it in position with the tip in sight. Advance a catheter through the lesion, remove the hydrophilic wire and inject contrast to confirm intraluminal position and then put in a suitable wire, such as a 3-mm J-wire or a stiffer wire, such as an Amplatz.

Troubleshooting

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