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| Basic Wire-Handling Strategies for Chronic Total Occlusions | 8/10
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 Figure
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Figure 11: Optimal point
to penetrate a distal fibrous cap in the LAD |
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Figure
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| Figure 12: Optimal point
to penetrate a distal fibrous cap in the RCA (a) LAO view; (b) RAO view; the pink area shows the optimal penetration point. |
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Figure
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| Figure 13: Optimal point
to penetrate a distal fibrous cap in the LCX (a) RAO view; (b) LAO view; the pink area shows the optimal penetration point. |
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3. Penetrating the distal fibrous cap:Before tackling the question of how exactly to make your penetration point with the wire, the first requirement is getting the wire tip to the point toward the target. Choosing the optimal point for the penetration is a skill best learned from experience. There are some kinds of distal fibrous caps however where experience isn’t a great help -such as, tapering CTOs and diffuse occlusions. With these, there is no correct way to get through the distal fibrous cap. In other words, there are some CTOs whose shape will themselves decide whether or not the distal fibrous cap will be penetrated. If the wire goes subintimal at this point, the chances of success are low. The emergence of the various kinds of stiff wires has not helped to solve this problem. Once again, if the wire is not in the right channel, pull back and try to find the right one before making the false lumen any larger.
Figures 11~13 show the optimal point to attempt a perforation when the CTO is one of those that ends abruptly. This will usually be on the myocardial mural side. This is important to remember. One thing to be aware of is that the end of the CTO occupies the inner part of the lumen more than the outer part, and is a 3-D dome-like shape, which doesn’t come out very clearly on a 2-D image such as fluoroscopy gives. So, be careful when the wire is touching the distal fibrous cap at the optimal perforation point, because in 2-D the wire can look as if it is already in the distal true lumen.In reality, the wire tip may not have lodged in the fibrous cap at all. In cases like these, experience may not be enough and extreme vigilance is the only way to be sure. In order to make the penetration at the correct point, it is necessary to carefully advance the wire from the central portion of the cap towards the distal lumen, and make sure that the wire is not being forced along an unnatural path. Otherwise the chances are that perforation will not be at the target site.
The most important thing of all, even after repeated attempts to make a penetration in the distal cap and even if the wire has been deflected by the fibrous cap, is to bring the wire tip back, try a different approach to the distal cap and try to locate a new channel. If this fails, pull back before making the false lumen even larger, and switch to a stiff or tapered wire. In order not to lose position at the distal fibrous cap, when changing wires, it is useful to leave the first wire in, and feed the second wire along parallel to it, continuously checking the relative positions of the wires.. Be careful that at a bend in the vessel, the position of the first wire does not block the way to the distal true lumen and obstruct maneuverability of the second wire.
If IVUS or the pathology suggests that the distal fibrous cap is softer than the hard tissue at the proximal fibrous cap, one might think that it will be easier to make the distal penetration. In practice, this may not be the case. Reasons for this could be that (1) the wire has already strayed into the sub-intima at the distal end, and it is hard penetrate through to the distal true lumen because the tissue there is thicker, or (2) that maneuverability at the distal end of the CTO is poor and that the distal fibrous cap moves as the wire tip does and it is difficult tp pin down a point to make the penetration.. For the former, all one can do is pull back and change the access route; while for the latter it is necessary to pin the fibrous cap down in order to get through. To do this, maneuver the wire as when trying to pierce through hard tissue at the proximal end of the CTO, only use a wire with a sharp stiff tip, and keep rotation to a minimum to position it securely at the perforation point.
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