Laser Atherectomy in Peripheral Arterial Disease

The use of cold saline flush during laser atherectomy, still done today, was a critical addition. Laser does not work very well in a field that is filled with blood, because the blood absorbs the laser energy and reduces the effectiveness of the laser catheter. The cold saline flush associated with laser photoablative energy is the biggest advancement for this technique since laser atherectomy has been available. Several other updates have occurred in the laser catheter over a period of years. The second most important update has been the availability of the new Turbo elite catheters (Spectranetics Corporation, Colorado Springs, CO), recently released in the United States. These catheters provide an average of 26-36% more energy than conventional laser catheters. They are very effective in ablating atherosclerotic tissue as well as thrombus and hence increasing luminal diameter. In addition, the Turbo elite catheters have a PTFE coating on both sides of the catheter, which improves the trackability and flexibility of the device. How long have you been using laser atherectomy? Five years. I have used both the peripheral arterial and the coronary artery systems. Currently, in our practice, the primary use of laser atherectomy is related to peripheral arterial disease. However, we do use laser atherectomy in certain specific situations like vein graft disease, when a distal embolic protection device is not feasible, occasional cases of acute myocardial infarction with a large thrombus burden, for debulking bifurcation lesions and difficult coronary chronic total occlusion (CTO) cases where a balloon cannot be advanced post wire placement. How do the two systems (for peripheral and coronary) differ? They differ substantially. First, the coronary catheters are all monorail design in delivery configuration. Second, the coronary catheters are not continuous on lasers. Coronary catheters turn on for 5 seconds and automatically shut off for 10 seconds. Peripheral vascular disease treatment requires longer laser runs and so the peripheral arterial disease catheters are continuous lasers. The third important distinction between the two systems is that in the coronary arterial tree, laser atherectomy requires the crossing of the guidewire first, before you perform an ablation. In peripheral arterial disease, you don't have to cross first with the guidewire; instead you can directly apply the laser to the atherosclerotic tissue. Has adoption of laser atherectomy by peripheral vascular specialists been slow? I believe the contrary is true. Today, laser atherectomy is more frequently used in peripheral arterial disease than in coronary disease. At one point, laser atherectomy was quite popular in vein graft disease and bifurcations, but over a period of years, its use in the coronary arterial tree has substantially decreased. Its use in peripheral arterial disease has risen substantially. Laser atherectomy has not been a mainstream treatment in peripheral arterial disease, however, which I believe results from the combination of two things. One is the negative stigma that came from the early 1990s, before the appropriate technique was designed and the more flexible and powerful catheters were available. The early experience was mediocre, and it certainly does not represent the current technology. Second, similar to other devices in peripheral arterial disease, there is no level-1 evidence that laser atheterectomy improves total lesion revascularization (TLR) rate in peripheral arterial disease treatment. Certainly in our anecdotal experience, we find that doing laser atherectomy and modifying the plaque in the peripheral arterial disease improves the results of balloon angioplasty as well as allows for better stent expansion, leading to a long-term better outcome. Could you talk more about about prepping a lesion with laser atherectomy? Would you ever use it as a standalone device? Using photoablative energy, laser atherectomy vaporizes part of the plaque. It creates its own concentric lumen. In our experience, the use of adjunctive devices such as a plain balloon angioplasty or even a balloon angioplasty with plaque modification technology such as an AngioScore balloon after performing laser atherectomy, means less dissection, less need for stenting, and improved lumenal gain, resulting in a better patency rate long-term. Laser atherectomy is not designed for standalone use above the knee, since it currently cannot achieve more than a 4 mm lumen. There are some believers in standalone laser atherectomy, but that is not the right strategy. I do not think anyone is currently doing laser atherectomy alone; there are only a handful of physicians in the country who might recommend it. Generally, laser atherectomy is associated with other devices, like balloon angioplasty and/or stenting. Can you comment on the use of laser atherectomy in lesions prone to distal embolization and chronic total occlusions? I will cite an experience in the coronary tree to address the issue of distal embolization. In a recently completed trial with laser atherectomy called EXTENDED FAMILY, I examined laser atherectomy in patients with acute myocardial infarction. I presented data at the October 2006 TCT meeting which demonstrated that the myocardial blush scores after laser atherectomy and all other adjunctive treatments were higher than any other study which may have used embolic protection devices or thrombus removal devices. This list includes four different studies: X-AMINE, AIMI, EMERALD and REMEDIA. The myocardial perfusion was superior because laser atherectomy resulted in less embolization and better thrombo-ablation. Laser is not only effective in ablating the atherosclerotic tissue, but it is also very effective in ablating thrombus. I remember two years ago at my interventional meeting, C3 (Capital Cardiovascular Conference), there was an acute limb ischemic case with a patient who had an acutely clotted stent in his popliteal artery, and we treated it with a 2.5 mm Turbo laser catheter (Spectranetics Corp.). After the first laser pass, there was restoration of flow, with a minimal amount of thrombus left in the vessel. Distal embolization is substantially less with this device than with any other atherectomy catheters, one quality that puts laser in a different category than many other atherectomy devices. In regards to CTOs, the applicability and success of laser atherectomy depends on where the CTO is located. Let's talk first about peripheral arterial CTOs. The step-by-step technique where we use laser energy without first advancing the wire, the laser can create a channel through a CTO, although I must caution that there are certain limitations that still exist. First, laser is more effective in doing a step-by-step atherectomy technique when the artery is straight, than when the artery takes a large bend or curve. In tortuous arteries, it is difficult to maintain the catheter position and perform a step-by-step technique, which may lead to a catheter exit extravascularly. Most CTOs contain fibrocalcific, collagenous and thrombotic tissue. Before the final treatment, which is most likely a nitinol self-expanding stent, especially in the superficial femoral artery, laser atherectomy provides debulking, modifying the plaque so the stent can be better expanded. I have seen many procedures where a CTO was crossed with a guidewire, followed by balloon angioplasty and stenting, with a result where several areas within the self-expanding stent were not fully expanded. Laser atherectomy prior to stent placement will make a substantial difference in those cases where we can obtain the proper stent expansion. Now let me address CTOs in the coronary arteries. In Europe, a special laser wire is being investigated for crossing CTOs. Occasionally, it is difficult to traverse a balloon through a CTO after placement of a guidewire. A 0.9 mm excimer laser catheter works extremely well over the guidewire and will create a channel to allow and facilitate the advancement of other interventional devices, i.e., balloons and stents. What percentage of CTOs are you seeing in the cath lab? In peripheral arterial disease, the chronic total occlusion rate is very high. I would say more than 60% of patients with peripheral arterial disease present with CTOs. In the coronaries, on average, 20% have CTOs. What about distal embolization concerns? Distal embolization concerns are higher in peripheral arterial disease than in coronary artery disease, especially with CTOs. We do not usually see a large amount of distal embolization with CTOs in the coronary arteries because it is mainly fibrocalcific tissue and with balloon expansion, this tissue can be compressed against the vessel wall and then covered by the stent. Especially in a calcified lesion, distal embolization is an issue. Rotational atherectomy as well as newly emerging orbital atherectomy are excellent devices for calcified lesions in peripheral arteries. Rotational atherectomy is now used very rarely, secondary to not having availability of large-size burrs. With this type of atherectomy, microembolization into the distal vascular bed is a concern. A recent thrombotic lesion or occasionally a chronic total occlusion may potentially have a higher degree of thrombotic material. These patients may also have a higher likelihood of distal embolization. We are investigating use of embolic protection devices (EPD) in the vascular tree to prevent this problem. The currently available EPDs are largely inadequate for the peripheral arterial tree and newer devices will have to be designed and investigated. How have TLR rates with laser atherectomy use compared to surgery or balloon angioplasty? I think it is unfair to compare laser atherectomy to balloon angioplasty, since laser atherectomy is not a device that should be used as a standalone device, unless it is used in small vessels below the knee. However, for below-the-knee vessels, there is no current, level-1, controlled randomized trial which compares laser alone to the balloon angioplasty alone. It would be a very difficult study to do. In our practice, when we perform laser atherectomy even in a very small, diffusely diseased, below-the-knee artery, we still perform balloon angioplasty in addition to laser atherectomy. For comparisons with surgery, the LACI trial did not compare TLR rate, but rather limb salvage rate. Historically, critical limb ischemia patients are poor surgical candidates and the limb salvage rate with surgery is very poor. This is especially true in diabetic patients with small distal target vessels. In the LACI trial, laser atherectomy was performed in 155 limbs. At 6 months, there was a more than 93% limb salvage rate. When you compare laser atherectomy to a surgical procedure, especially in terms of limb salvage rate, it is substantially superior. Blockages are vaporized and absorbed into the bloodstream. Are there any further effects on the vessel or blood from the vaporized pieces, or is that the end of the story? That is correct. There are no effects I know of. Could you talk about potential complications? There are two main complications. One is perforation. If you use laser atherectomy in a very tortuous segment and push too hard to advance the catheter, you may potentially perforate. Second, if you don't use an appropriate technique with continuous cold saline flush, then you may see a high risk for dissection. Extremely rarely, you may have some distal embolization, because of the advancement of the wires, but in comparison to any other atherectomy devices, the risk is extremely small. There are two methods for saline flush. The first option is through the sheath, and the second involves connecting the saline line to the laser catheter with the use of a toughy valve, thus allowing you to flush through the laser catheter itself. I use both methods. When you use the saline flush with appropriate technique, you rarely see complications. What is the learning curve with this device? There definitely is some learning curve, and two important aspects need to be mentioned. First is, of course, the setup, because it is important to have the saline flush. Second, it is important to be cognizant of the speed with which the device is being advanced in the artery. It should be no more than 0.5 mm/sec. If it is any faster, then you are not allowing for the appropriate ablative energy to really work on the vessel, and are just dottering the lesion. Slow advancement and the saline flush are integral to procedural success, as well as understanding how to increase the energy level on the catheter as the case unfolds and the appropriate sizing of the catheters. Despite all this, the learning curve, in my opinion, is very small. After a small number of cases, anyone can master this technique. Using a step-by-step technique to recanalize CTOs certainly requires substantially more experience. Outside of CTO work, laser atherectomy is a fairly simple procedure. Can you share more about how you utilize laser atherectomy in your practice? In our practice, the use of laser atherectomy continues to evolve in a variety of different scenarios. First, it covers standard atherectomy to debulk a variety of peripheral arterial obstructions, including those in the superficial femoral and popliteal arteries, and especially the below-the-knee vessels. In addition, we use it for patients with in-stent restenosis, where it is extremely effective in debulking the neointimal tissue. Third, for acute limb ischemia, we may first perform a laser atherectomy to remove some of the thrombus and restore some flow before we consider doing a thrombolytic infusion. In our own experience, we have found this strategy has reduced our thrombolytic infusion time. In the coronary arteries, distal, diffusely diseased degenerate vein grafts respond very nicely to laser atherectomy. Occasionally, we will use laser atherectomy for initial debulking in the CTO to allow passage of the other devices such as balloons or stents. We may occasionally use laser atherectomy in acute myocardial infarction and bifurcation lesions. In acute myocardial infarction, laser has been shown to improve myocardial blush and hence viability and LV remodeling. In bifurcations, we use it for debulking in the main branch and occasionally a side branch to allow for better stent expansion in both branches. What changes are you anticipating for future generations of the device? I am the national PI of a current study called the CELLO trial. This trial is investigating a custom guide catheter (Turbo-Booster, Spectranetics Corp.) for use with the laser catheter. The custom guide catheter is designed to allow the laser to directionally ablate tissue within large vessels to obtain a larger lumen. The current Turbo elite catheter, which at 2.5 mm is the largest catheter available, creates an average 3 mm lumen in firm tissue. With the Turbo-Booster device permitting directional ablation of tissue, we will have better lumen achievement, since tissue will be removed more effectively. This catheter will prove even more beneficial in in-stent restenotic lesions. The second next-generation adaptation with the laser technology would be to merge visualization technology with the laser catheter, which will also allow better imaging within the vessel to determine where the ablation is required. Other applications will be investigated in the future, especially for venous thrombosis, potential use in A-V dialysis grafts, and perhaps a few years ahead, treatment of acute stroke, where a very small, flexible catheter can be utilized to thrombectomize distal intracranial vessels. Dr. Dave can be contacted at rdintervention (at) yahoo. Com The 2007 C3 meeting will be September 10-12, 2007, at the Harrisburg Hilton in Harrisburg, Pennsylvania. More information is available at www.ccmcme.com/c32006/

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