Feature

Crossing Chronic Total Occlusions

Launched February 24, 2006 at the Third International Chronic Total Occlusion Summit (New York, NY) the Asahi Tornus® specialty catheter (Abbott Vascular Devices, Redwood City, CA) is a new catheter for crossing chronic total occlusions in both coronary and peripheral vasculature. Its design consists of several hair-thin stainless steel strands braided together, along with a safety-release valve at the proximal end to indicate when the device has reached maximum rotation, and a tapered distal tip with a radiopaque marker. The device is available in both 2.1 Fr for accessing lesions that are more difficult to navigate and 2.6 Fr for circumstances requiring more support to push through the lesion. Cath Lab Digest talked with Dr. Raj Dave about his thoughts on chronic total occlusions and experience with the Tornus. Dr. Dave, how long have you been using the Tornus specialty catheter? I have been using it for four months, primarily in chronic total occlusions (CTOs) of the coronary and peripheral arteries, especially the arteries below the knee as well as coronary arteries. Can you describe the CTOs you are treating? In the peripheral arteries, lesion length usually extends from 200 to 250 mm, and in the coronaries, it varies, ranging anywhere from 50 to 80 mm. All chronic total occlusions have some element of calcium; usually 50% of them are hard, calcified occlusions. How is the Tornus utilized? All total occlusions have hard caps at the proximal and distal ends. A 0.014 wire, especially the Asahi Miracle Bros and Confianza wires, is used primarily to navigate through the CTO, a critical step in success of this intervention. However, it is not possible to do so without a significant support catheter associated with the wire, and the Tornus is mainly used as the support catheter. Compared with some of the other support catheters on the market like the Transit catheter or a small balloon, the Tornus catheter has at least 60-70% more support and gives much more pushability, allowing you to go through the cap of the CTO and enter the lesion with the wire. That’s its main advantage. How would you compare the two sizes? I use the smaller size, the 2.1 Fr, mainly in the coronaries and vessels below the knee, while I use the larger size, 2.6 Fr, in the larger peripheral arteries such as the femoral or popliteal arteries. The critical distinction between the two is that the tip of the 2.1 Fr catheter is smaller than that of the 2.6 Fr catheter. Even though the 2.6 Fr catheter offers higher support, at times it can be too large for the coronary arteries. What are the different considerations when you are dealing with a coronary versus a peripheral CTO? There are significant differences between coronary and peripheral CTOs. In coronary circulation, the longer the CTO, the higher the failure rate. In peripheral circulation, the CTO tends to be very long, so using a catheter like the Tornus actually works extremely well, because you have to travel through a very long segment of lesion, which is typically very hard and full of calcium. How long and how intense is the manual rotation of the Tornus catheter to get through the lesion? There are certain critical considerations regarding movement of the catheter. It is made from 8 stainless steel wires, stranded over each other. You make 20 counterclockwise rotations, up to the maximum, in order to advance the catheter. As it moves forward, you stop torquing and try to advance your wire, and you keep advancing your catheter until you traverse the entire length of the lesion. What guidewires are you using in conjunction with the catheter? Guidewires, especially from the Asahi family, mainly Miracle Bros and Confianza, are very good. With the majority of CTOs, you cannot travel with a floppy steerable guidewire. The Miracle family of wires from Asahi help to get through the CTOs because they have different tips from 3 grams to 12 grams (3, 6, 9, and 12), and each has a different level of stiffness. I use incrementally higher-stiffness wires in conjunction with the Tornus device. Can you share a few case examples? I recently had a lower extremity case, a multi-segment occlusion with an occlusion in the superficial femoral artery (SFA). A short segment of the popliteal artery was patent, and then there was a very long segment of popliteal artery occlusion distally, with reconstitution of the peroneal artery below the knee. I had to use a 2.6 Fr Tornus in association with a Miracle 12-gram wire to go through the entire occlusion. A very hard, long area of occlusion requires much greater force than, for example, a 30 mm right coronary artery occlusion, which may not be that difficult to cross. I also recently had a very difficult right coronary artery CTO that I was able to cross with a Confianza ProWire. Even after placement of the wire, I could not pass a Transit catheter or a small balloon through the lesion because it was so hard and calcified. I made passes through the lesion with a 2.6 Fr Tornus catheter, creating enough room for subsequent balloon catheter advancement and DES placement. What have been your success rates in crossing CTOs with the Tornus? My overall success rate in the coronary arteries is about 75%. In the below-the-knee vessels, it is close to 90%. If you don’t cross the occlusion, do patients go on to surgery at that point? Not necessarily. There are certain patients whom we will continue to treat with medical therapy and see how they do. Some of these patients will have to go for bypass surgery if the CTO is not canalized, because there is really no other option. We will have a very small number of patients return for a second attempt. I would say about 40-50% of the time that we do a second attempt, we can get through the CTO. Sometimes with the catheters and wires, we can create a channel that may allow remodeling of the total occlusion. The next time around, we can then get into a better plane and get through. What’s the length of time between those two attempts? Minimally, 8-12 weeks, because that allows the lesion time to remodel itself. What do we know about patency rates? Patency rates depend on the location of the occlusion, how it was treated, and also the indication. There have not been any randomized trials in either coronary or peripheral circulation that compare one form of treatment to another. We are beginning to see many single-center as well as multicenter studies demonstrating excellent patency rates with DES in coronary CTOs. It has been shown in the literature that patients who have successful treatment of CTOs in the coronary arteries do much better over time than patients who have totally occluded arteries. Patients with occluded arteries are at higher risk of future cardiovascular events and a higher rate of coronary artery bypass grafting. Patients with chronic total occlusion in the peripheral arteries may be presented with either lifestyle-limiting claudication or a form of critical limb ischemia such as a non-healing ulcer or gangrene. With surgical revascularization of below-knee vessels, especially in small, diffusely diseased arteries and using prosthetic grafts, patency is very poor. Ideally, endovascular treatment should be the first choice of treatment, although operator experience in association with right tools are essential elements. In patients with tissue loss or non-healing ulcers, the focus is on the acute outcome rather than long-term patency, as the goal is healing of the ulcer. Even in claudicants, reports are now emerging about the use of drug-eluting stents in below-knee vessels. Small-size, specially designed Nitinol self-expanding stents and atherectomy are demonstrating good results in tibial vessels. Are you seeing more claudication patients versus critical limb ischemia patients? It depends on the individual practice. I see both, probably about 50:50, because we do a fair amount of CLI work in our practice. I work with podiatrists in our area, so I get a number of patients with non-healing ulcers who have severe peripheral arterial disease. Three months ago, I treated a patient who came in for a follow-up after intervention for a large ulcer on his foot. The below-the-knee vessel occlusions were treated with a Confianza wire and a Tornus catheter. The patient also had treatment with laser atherectomy as well as cryoballoon angioplasty. He had complete healing of the ulcer. How would you rate current physician awareness of peripheral vascular disease? I think we are seeing the slow development of a trend where physicians are sending us more patients in the early stages of peripheral arterial disease, still in the claudication stage. Yet there remains a large gap in physician understanding of the need for early intervention before this disease converges into a very long CTO. By this time, the patient is already having very severe symptoms and the lesion is very hard to treat, in comparison to a patient who may have diffuse disease or a severe stenosis and is in a claudication stage. There is still debate between the different societies for example, cardiovascular specialists and vascular surgeons as to when treatment is appropriate. I think those questions will be answered in the future with clinical trials. Are there any CTO-related clinical trials that you would like to see? Well, I would certainly like to see a well-designed, multicenter trial for CTOs in coronary arteries with a drug-eluting stent. We certainly want to see more clinical studies in the peripheral arterial circulation, including use of different technologies like laser atherectomy, FoxHollow atherectomy and cryoplasty. We need more multicenter trials with larger lesion lengths. All these devices have been approved in cases where the lesion length has been short, but we really want to see them in more complex settings. What are your future plans for your work with the Tornus catheter? We are planning to have a small, single-center registry using the Tornus catheter in the coronary as well as peripheral arteries. We’ll be looking at the success rate for crossing lesions and then comparing that rate to our previous experience before Tornus to see if there is a substantial improvement in our chances of success. I think we will find that the success rate is much better with the use of this catheter, because it provides much better support. It’s easy to use and has a radiopaque marker at the tip. There is also a wire lumen through the catheter, so it is not a blinded device. Raj Dave, MD, can be contacted at rdintervention@yahoo.com Dr. Jeffrey W. Moses was kind enough to talk with Cath Lab Digest regarding his work with the Tornus and crossing CTOs. Dr. Moses, how long have you been using the Tornus catheter? Since early February 2006. We are doing mainly coronary work. What is the process for patient selection for CTO revascularization? It is emerging that in the major vessels, definitely in the LAD and probably in the right coronary artery, that revascularizing CTOs is associated with reduced mortality in patients with coronary disease, especially in LADs, but in multi-vessel disease patients as well. Treatment of single-vessel LAD and multi-vessel disease patients with CTOs, which is usually in the RCA, seems to have an advantage in mortality. Obviously we do have to treat patients who are symptomatic, who have large ischemic zones, but not exclusively. Are there patients who would not be appropriate for CTO revascularization? Well, if it’s a small vessel without symptoms of ischemia, non-viable myocardium (that’s still speculative) and also those lesions that we currently consider very technically impossible: without visible distal vessels, very long, heavily calcified lesions or very tortuous vessels. When do you utilize the Tornus? The Tornus is predominantly for those lesions where you can’t cross with a balloon. Some people would have tried to use a Rotablator or a laser; the Tornus is a very easy and low-cost, simple substitute. It is more effective in previously uncrossable lesions. I should note that we don’t use the Tornus exclusively for CTOs. We use it for some uncrossable lesions in other circumstances, i.e., very severe, long, calcified lesions where you can’t cross with a balloon, but it’s mainly encountered in total occlusions. How are you using the two sizes of the Tornus (2.1 Fr and 2.6 Fr)? The 2.1 Fr doesn’t give as much support, but obviously there’s a lower crossing profile. If the wire has already completely crossed and it’s very difficult crossing with a balloon, we’ll try the 2.1 Fr size, and then potentially step up to the 2.6 Fr. If we really feel we need the backup, then we’ll start with the 2.6 Fr. If the vessel is very tortuous, the 2.6 Fr is a little more rigid, so then we’ll start with the 2.1 Fr. It’s important to note that with the smaller size catheter, you don’t want to go more than 20 rotations of the catheter before you unscrew it, so to speak, and with the larger, not more than 40. How often do you find yourself coming close to that limit? Not often. It’s pretty effective; I’ve been really surprised. Are there any clinical trials you’d like to see done regarding CTOs in general? There is a randomized trial, the OAT Trial, looking at occlusions post-MI (not high-risk occlusions) to see if the outcomes are positive in the post-MI period. In terms of the chronic period, I would like to see a clinical follow-up of patients randomized to complete revascularization of CTOs irrespective of symptoms or ischemia from the CTO. That would be an interesting trial. Does planned use of the Tornus affect your initial choice of guidewire? No, not really. The guidewire strategy is by and large separate from the Tornus strategy. Although you can screw the Tornus into the proximal part of the lesion to give you a really good platform, so you may not need the heavier duty guidewire. You may be able to use a less stiff wire to cross the lesion than you would otherwise, because the Tornus can give you backup. Are success rates improving? Oh, unmistakably. We are achieving success rates of about 90% using the Tornus device with a retrograde approach. If you don’t cross the lesion, what next? It really depends on the circumstances. We may send the patient for surgery only if we have a highly symptomatic lesion, say in the LAD, or if we were trying to do complete revascularization in a complex case. For example, perhaps it’s a large right coronary where we decided that if we can’t open up this large right, then there is no point in doing angioplasty on the other that situation may be another indication. It’s not frequent, but that may be because the success rate is high enough that surgery itself is infrequent. What are your future plans for work with the Tornus? Right now we are just in an informal experimentation stage. We’ve been using it for just a few months in a variety of circumstances. I think we still need to get more experience and a better feel for the catheter. We are broadening our indications for work beyond CTOs, so it may cut into some of our Rotablator use. Dr. Moses can be contacted at jm2456@columbia.edu
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