Fig. 8.1
One case of tubular dissections. Arrows indicate the contrast-induced dissection
The principle information we can obtain from this dissection classification is regarding the location of the micro-catheter or the OTW balloon within the vessel architecture. A tubular dissection suggests that the distal tip of the over the wire (OTW) balloon is in the subintimal space of a main branch or a big side-branch and the contrast is homogenously distributed over a wide area between the media and the adventitia. This type of dissection is associated with a higher chance of re-entry into the true lumen. The following step is breaking hydrodynamically or mechanically the flap of the occlusive dissection in order to connect the false with the true lumen.
On the other hand, a storm cloud dissection, suggests that the distal tip of the OTW balloon is pointed towards the subintimal space of a small side-branch: the storm cloud angiographic appearance is probably caused by an injection of contrast in a branch so small that it is not capable to contain even a very small amount of contrast. When a storm cloud appears, it is mandatory to stop the injection as any further amounts of contrast can cause a perforation.
A storm cloud dissection needs to be converted to a tubular one using appropriate manoeuvres: the OTW balloon should be pulled back in order to position it in the main vessel, in a more favourable and wider spot capable of containing a greater amount of contrast. Once this is confirmed with a small injection (showing a tubular dissection), and the course of the main branch is delineated, the operators can insert an appropriately shaped guidewire in the OTW balloon (or microcatheter), steering it towards the direction of the main vessel, avoiding the small side-branch.
Hence, by analysing the characteristics of the dissection operators can make informed decision about when and how to continue with the procedure.
Alternative Uses of the Intraocclusional Injection of the “Carlino Technique”
With the increase of our experience and confidence we discovered other utilities of the subintimal contrast injection manoeuvre. Failure to cross a lesion with a guidewire or a balloon is most often due to severe calcification at the occlusion site that can be quite challenging to overcome. Several strategies have been proposed [3], and can be summarized into two categories: (1) strategies that increase guide-catheter support and (2) strategies that provide lesion modification. Strategies that increase guide-catheter support include (i) deep guide intubation, (ii) use of guide-catheter extensions, such as the Guideliner catheter (Vascular Solutions) and the Guidezilla (Boston Scientific), and (iii) use of various anchor techniques (such as side-branch anchor and distal anchor). Those techniques are described in Chap. 12 of this book.
Strategies that involve lesion modification include (i) “rupturing” small balloons, advanced as far as possible into the lesion in an attempt to modify the proximal cap (a technique often called balloon-assisted microdissection (BAM) or also “grenadoplasty”), (ii) use of various microcatheters, such as Tornus (specifically designed to “screw into” resistant lesions, creating a channel), Corsair or Finecross, and (ii) use of laser or the Crosser catheter (Flowcardia, Inc) or rotational atherectomy.
Injecting contrast into the occlusion is an alternative strategy that can lead to lesion modification. Soft plaque consists of cholesterol-laden cells and foam cells with loose fibrous tissue and a network of neovascular channels and is more frequent in younger occlusions (<1 year old) [4]. Soft plaque is more likely to allow wire passage either directly through tissue planes or via neovascular channels into the distal lumen. Conversely, hard plaques are more prevalent with increasing CTO age and are characterized by dense fibrous tissue and often contain large fibro-calcific regions without neovascular channels [5]. Areas of calcification frequently occur even in CTOs <3 months of age, although the extent and severity of calcification increase with occlusion duration. Older (>1 year) occlusions are more likely to deflect guide-wires into the subintimal area, creating dissection planes. This age-related increase in calcium and collagen content of CTOs in part explains the progressive difficulty during PCI in crossing older occlusions.
Fig. 8.2
Two cases of storm cloud dissections. Line A: here a proximal CTO of a right coronary artery treated using the contrast-guided STAR technique. Being in the sub-intimal space, the operator applied the contrast guided STAR technique, injecting contrast and producing a storm cloud dissection (yellow arrow). At this point he slightly pulled back the balloon, adjusting the position of its tip and identified the course of the vessel but a small amount of contrast continued towards the dissection and increased the storm cloud effect. However, at the same time, it surprisingly produced a re-entry into the true distal lumen. This demonstrates that the storm cloud dissection is not a perforation, because otherwise the contrast would have gone into the pericardial space, which is a low-pressure chamber by comparison with the resistance offered by the vessel. But what is even more interesting and surprising is that following stent implantation the side branch appears to be absolutely healthy, with no evidence of perforation or residual contrast staining. In the line below we can see a Storm Cloud dissection appeared during a CTO treatment using the contrast guided STAR technique. This picture could be confused with a perforation. But an orthogonal image of the storm cloud dissection compared to the previous one shows a peri-adventitial distribution of the contrast excluding the perforation one might have suspected looking at the previous picture. Both cases illustrate recanalization after storm cloud dissection and excellent final angiographic result after stenting with drug eluting stents
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