Tell us about your work treating chronic total occlusions (CTOs).
I have been treating CTOs for nearly a decade. As the field progresses, we continue to utilize newer and better techniques that increase procedural success and improve patient safety. Five years ago, it became clear that the retrograde approach led to high rates of complications such as perforations and the antegrade approach was determined to be the safest approach. However, challenges remain even when performing the antegrade approach in terms of understanding the individual anatomy, proximal cap of the CTO, amount of calcification in the vessel, vessel tortuosity, and branching. We often started CTO procedures via the antegrade approach because we were not certain of these factors and thus not confident enough to push our wires, catheters, and balloons. To improve our procedural confidence, we decided to integrate computed tomography angiography (CTA) into our CTO procedures, and have now been involved in this particular work and research for about five years.
How do you incorporate CTA in CTO procedure planning?
We regularly have patients with a CTO referred to us who have undergone prior unsuccessful attempts at treatment of the lesion. At the point when the patient comes to our clinic, we arrange for a planning CTA. Once performed, we sit down with an imaging cardiologist and an in-house Siemens Healthineers CTA expert who helps bring the CT images to the cath lab. syngo CTO guidance software (Siemens Healthineers) creates a roadmap of the lesions using the CT images which are then overlaid on the cath lab fluoroscopic images (CT Fusion, Siemens Healthineers). At the pre-procedure planning stage, we fuse these two types of images and spend considerable time with our imaging experts in order to review the anatomy of the CTO vessel. We seek to better understand the direction of the artery and any involved branches, as well as aspects such as lesion length, the extent of calcification, and how the CTO could be approached retrograde. Before this technology was available, we had to learn all these things when the patient came to the cath lab for their actual procedure. CTA really provides an extra dimension of visualization, while the CTO guidance software supports us in planning the procedure and understanding potential complications, even before we stick the groin.
How do you use CT Fusion when the patient is in the cath lab for a CTO procedure?
The synchronization and overlay of CT with fluoroscopy is also very handy when we are actually doing the procedure. There is real excitement in being able to import CTA images onto the cath lab screen to guide us as we attempt to open the vessel. Not only can we overlay the images based upon appropriate cardiac cycles and phases, allowing adjustment for cardiac motion, but we can also map the actual course of the vessel. It is almost like a GPS, showing us where to make a right or a left turn, or that we can go forward here, we should push harder here, or don’t push at all. Remember that on fluoro, we can only see the segment of the vessel that is open; after that, it is a blind course. The use of CT Fusion allows us to proceed both more aggressively and safely. As we go on with the procedure, the CT images will come up in the background behind the x-ray, which allows us to determine, for example, if we are exactly within the vessel wall architecture or not.
How has the use of CT Fusion affected your procedures?
Knowing where to go in the artery definitely has helped us reduce both the length of the procedure and the amount of radiation. It has also significantly reduced the amount of contrast used because now that we know the direction of the vessel, we don’t have to keep injecting more contrast. Instead, we can push a wire confidently by following the roadmap generated by the CTA images. We have had successful cases where historically we would have stopped, but now we are able to proceed. At the same time, the CT-fluoro overlay reduces the amount of cases done from a retrograde approach, so we avoid stopping the case in order to bring the patient back another day to go from the retrograde collaterals, which as you can imagine, increases the potential risk for complications. Many patients are referred to us specifically for retrograde CTO PCI, because an initial antegrade approach was unsuccessful. However, with the use of CT-fluoro overlay, we can often successfully use antegrade techniques for previously unsuccessful cases.
What aspects of CTO-related procedures are better on CTA vs fluoroscopy and vice versa?
If there is an ambiguous cap or if side branches are very close to the proximal cap, the CTA allows us to better orient ourselves. In terms of assessing the nature of the actual CTO cap, while CTA is helpful, here we rely more on the cath lab fluoroscopy, because the cap can be better visualized with fluoro versus CTA. Other nuances include the angle of the cap, the bluntness of the cap, and the side branch origin, all of which certainly can be very well visualized by CTA. As you can imagine, one benefit is that during the live case flow, we are required to inject less contrast, because we already know and can see where a side branch is going. We will literally draw lines on the screen showing where to go. For example, we draw a green line to show the course of, for example, a right coronary artery to its occluded portion. We draw a yellow or a red line where any of the branches come off the vessel and the angles. If the wire follows the non-green lines, we know we are going the wrong way. As I mentioned, it is almost like having a GPS showing us which way to drive. Another amazing advantage of CT Fusion technology is that as the detector is rotated to look from different angles, let’s say from left anterior oblique (LAO) to right anterior oblique (RAO) or cranial and caudal, the CT images rotate alongside the fluoroscopy. It definitely reduces the amount of radiation exposure to our patients.
Any final thoughts?
CT-fluoro overlay may seem like futuristic technology, but the more we use it, the more it becomes clear how it simplifies our workflow and increases the safety of CTO procedures, resulting in higher success rates. We have seen an increased use of the antegrade technique. Retrograde access and wiring should be saved as a last-effort option, because going through the collaterals via this approach brings a high risk of perforation and donor artery complications. It is also obviously a much longer procedure, with a higher amount of contrast and radiation required in order to perform this approach. Certain patients may just have lesions that are only suitable for retrograde approach, but we are now using it more often when an antegrade approach is unsuccessful. If success via the antegrade approach can be made more likely through the integration of CTA with fluoroscopy, it should hopefully reduce the need for the retrograde approach and its accompanying higher rate of complications. As we are able to present more data, I hope that there will be greater penetration of integrative technology, especially in CTO procedures, but even complex coronary percutaneous intervention (in addition to CTO) or other vascular spaces may benefit.
AT CA NAM-742
The statements herein are based on results that were achieved in the doctor’s unique setting. Because there is no “typical” hospital or laboratory and many variables exist (e.g., hospital size, samples mix, case mix, level of IT and/or automation adoption, experience) there is no “typical” hospital or laboratory and many variables exist (e.g., hospital size, samples mix, case mix, level of IT and/or automation adoption, experience) there can be no guarantee that other users will achieve the same results.