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| Basic Wire-Handling Strategies for Chronic Total Occlusions | 10/10
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It is sometimes hard to get a clear idea from coronary angiography about the tissue at the entry to the proximal edge of a CTO. CTOs are especially hard to assess in the ostial LAD, when the LAD is totally occluded immediately after the bifurcation of a large diagonal branch or septal branch; in the RCA, when the occlusion occurs just after the bifurcation of the right ventricular branch, or ostially at the posterior descending artery orposterolatreral branch; or in the LCX straight after the obtuse marginal. In cases like these, the location of the occlusion can be confirmed by inserting an IVUS catheter into a side-branch. IVUS will be useless,unless the catheter can be placed well into the side branch, or when there is heavy calcification in the vessel wall at the CTO ostium or side-branch.
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 Figure
20
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| Figure 20: Locating the CTO
ostium with IVUS In this patient, the proximal RCA has a very tight bend and with CAG it is very hard to get a good view of the area where the right ventricular branch forks from the main trunk. As you pull back the IVUS catheter and the mirror, the images obtained allow you to locate the CTO ostium. |
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One use for IVUS is first to use it to check the CTO ostium, then under flouroscopy the transducer position at whichthe CTO ostium is evident.This position can then be used to check on the position of the CTO ostium (Figure 20). The position of the CTO ostium can be confirmed from longitudinal positions, but it it will be often hard to see it clearly on the axial view. This will not usually be a problem if coronary angiography is used.
When the wire has re-entered the
true lumen from a false lumen, IVUS can demonstrate where the wire entered,
or where exactly the false lumen was made (especially whether it went through
the sub-intima or not). Similarly, when the wire is in a side-branch, it is
important to establish the location of any plaque build-up at the bifurcation
of side-branch and parent vessel, and to know whether rotablator or DCA are
needed to pass the wire through, and whether that is safe or not. IVUS is the
best way to get this information.
It is important to bear in mind, while developing wire handling skills for CTOs, that acquiring the ability to tackle these lesions is a gradual process. To put it another way, the chances are remote that an operator with experience in less than 100 CTO patients, will be able to successfully tackle a several year-old CTO. Of course, the low initial success rate will put off some operators from doing CTOs altogetherThe high incidence of complications is another disincentive. In this text, I have not dealt with how to reduce and prevent complications associated with CTO lesions. CTOs are different from normal lesions in the sense that there is a very low risk of dangerous coronary occlusion, but conversely, there are other complications peculiar to CTOs. A good grounding in normal interventional procedures is an important starting point.
As experience with CTOs expands to include more indications, it should first be possible to achieve a success rate of 90% for CTOs three months old or less. For CTOs older than three months, the operator should expect gradually to work up from tapered occlusions to abruptly closing CTOs, from CTOs with no tight bends to moderately tortuous ones, from CTOs less than 20mm long to longer CTOs, and from occlusions up to a year to ones even older than that. And as I said at the beginning, making sure you have a solid grasp of how to read the lesions and a good understanding of all the pitfalls and important details is crucially important before you begin to tackle CTOs.
Finally, I have, in this text, concentrated entirely on wire handling and not the handling of the other devices used in intervention for CTOs. It goes without saying that good CTO technique also requires the operator to possess a greater degree of skill and ability, than even is required for normal intervention, for guide catheter postioning and selection, crossing difficult lesions with balloons, implanting stents, and using the Rotablator and DCA.
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