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| Basic Wire-Handling Strategies for Chronic Total Occlusions | 7/10
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2. Getting the wire to the distal end of the CTO: As there is no easy way to master the technique of getting the wire to the distal end of the CTO, it really is a question of trial and error and learning from mistakes. If inside the CTO there is a portion of surviving lumen, or a recanalization channel, these can serve as guides, Conversely, if one goes down one of the bridging collaterals, or new vessels in the media or adventitia by mistake, there is risk of perforating the vessel itself Thus, great care has to be taken. Calcification can also be a good guide to vessel course. Whether the path is signposted or not, sensitivity to resistance at the tip of the wire is crucial. What tells you that the wire tip is in the lumen, is a gravelly sensation caused by contact with the relatively harder tissue there. As I have mentioned above, it is sometimes hard to sense this feeling with anything heavier than a Miracle 6g. Also, even if the vessel is dead straight, proceed with caution as is there is no guarantee that the channel being navigated will be as straight. Care is especially required in the RCA, where even a very small deviation can send one burrowing down a false lumen. Remember as I said before, when this happens, the only thing to do is pull back and try to tell from the feel of things where the right path is.
If the wire tip repeatedly creates a false lumen, one is unlikely to get a better result with the same or an identical wire. Before making the false lumen even bigger, it is best to change the shape of the curve or change to another wire altogether. Changing wires in this situation can be difficult but this is an indispensable part of basic CTO wire technique. You will also find that once a wire has forged a channel, it is usually possible to pass another different wire along it, but one needs to be 100% confident that he will be able to locate the channel with the new wire. The parallel wire technique can be usefulIf wire handling is tricky, which is often the case when there is a false channel, or when the vessel shape is not conducive. There are also times when the balloon catheter and wire are inside the CTO but the tip passes into a false lumen. When proximal bends in the vessel obstruct wire maneuverability, one option is to inflate the balloon at the proximal point, while passing the wire through the CTO. Before doing this, make sure you do not dilate a false lumen.
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 Figure
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| Figure 9: Wire positioning
at bends If you position your wire on the outer portion of the bend, especially when you are using a stiff wire, it is quite easy for the wire to pass out of the lumen into the sub-intima; if it keeps going, you can end up making a large false lumen. |
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In the event that a vessel bend causes one to make a false lumen, it is best to avoid switching to a stiff wire or a stiff tapered wire because that increases the risk of perforating the vessel itself and reduces the chances of finding another channel through the lumen. In many cases, to stop making the false lumen even bigger, it is a good idea to switch form a stiff wire to a softer one, once a route into a new channel is opened. Positioning the wire at the outer part of the curve of the bend can often cause the tip to enter the subintima (Figure 9). It is better to position the curve at the inner part of the vessel bend.
If the cause of the false lumen is
not connected with a bend in the vessel, it will often be the case that the
wire’s path has been obstructed by hard tissueand passed into the sub-intima.
The best thing to do in that case is pull back proximal to the point where the
wire entered the false lumen, and switch to a stiff wire (Miracle 6g or up)
or a stiff tapered wire. A Conquest wire will normally be the best bet, when
one gets a good feel of the way to go from resistance at the wire tip. The important
thing is not to go any further forward as soon as it is evident that the wire
is in a false lumen. If it is impossible to find a new channel,the last available
option, is to carry the wire down a false lumen and then tryi to force a way
into the true lumen from the false lumen (i.e. from the sub-intima). This is
technically an extremely difficult undertaking, and should be avoided wherever
possible.
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Figure
10
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| Figure 10: How to make a
new channel inside a CTO (a) Looking for the part of the hard tissue where the wire-tip gets stuck; (b) Feeding the wire through to the point where the tip bends slightly. With stiff wires like the ACS Standard, and even harder wires, be careful as the wire-tip doesn’t bend all that much, as can be seen from the figure; (c) Rotating the wire (in this example, clockwise, less than 180°) while slightly pulling back, and (d) just as the wire straightens, rotating and advancing it back along the channel. |
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Figure 10 illustrates how to pull back and look for a new channel. This involves rotation as well as careful forward and backwards maneuvers with the trick being not to over-rotate. While it should be relatively easy to find and advance along a different channel with a stiff wire or a tapered wire, over-rotation may take the wire down a new false lumen or widen an existing one. The curve of the tip should also be kept as small as possible, except when the false lumen has already been enlarged.
When making a new channel, it is important to understand its position relative to existing channels, The parallel wire method, may be useful in this situatioin.
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