The superficial femoral artery still represents one of the major challenges facing endovascular specialists. Dennis Gable, chief of Vascular Surgery, Heart Hospital Baylor Plano, Plano, USA, and Thomas Zeller, head, Department of Angiology, Universitäts-Herzzentrum Freiburg, Bad Krozingen, Germany, are both specialists in the treatment of femoropopliteal disease, but use very distinct approaches for endovascular revascularisation of the superficial femoral and popliteal segment. They spoke to Vascular News about the strategies and devices they use in these lesions.
Currently, what are the main challenges in the treatment of superficial femoral artery lesions?
Thomas Zeller: The main challenge in the treatment of superficial femoral artery disease is severe calcification which is the main predictor for acute and long-term treatment failure. Even if the use of re-entry devices and retrograde access techniques allow crossing severely calcified lesions in almost all cases, acute recoil limits the durability of the intervention. Residual stenosis has been identified as predictor for loss of patency. Even dedicated stents with high compression resistance are not able to result in residual stenosis less than 30% in such lesions. Plaque excision or plaque modulation in such lesions is limited by the mostly subintimal crossing attempt.
Dennis Gable: I feel the main issues in treatment of superficial femoral artery lesions are for providers to choose which device to use in their patient and for which lesions. Cost of different devices is also a big issue especially in the current healthcare environment of cost reduction/control. Most physicians will use what they are “comfortable” with or what they have “experience” with but many of the devices out on the market have very little data to back up their use. Many devices quote results of patency or target lesion revascularisation at 12 months but longer follow-up is more beneficial and we are finally seeing some studies/devices that have data out through three and four years.
If one reviews and really studies the available data, several things come in to play. First, many of the devices and studies that quote treatment of “long” lesions really only offer data to support use in lesions up to 10 or 11cm. I would call that a medium length lesion as opposed to long lesions of 20–30cm. While many of the stents available have comparable results for medium lesions, none have shown consistent outcomes in long lesions over 10 to 12cm with patency or target lesion revascularisation beyond 24 months except the Viabahn stent. Conversely, for medium lesions under 10cm and given the cost of the device, Viabahn has no different outcomes than many of the bare metal stents and therefore is likely not worth the cost difference in treatment of these shorter lesions. There are some patients in the recent Zilver PTX study that have longer lesions of over 20cm but the mean lesion length in the study is 9.9cm and the patients in the “registry” arm do not offer any reliable level 1 or 2 data simply due to it being a registry report. Some of the devices available are currently reimbursed very well and therefore are very popular but there is very little data (if any reliable data) that supports a reasonable patency beyond 12 months. The use of these devices, especially given their high cost, is questionable in my opinion.
Finally, I feel that we often are grading device success based on target lesions revascularisation or patency but perhaps we should be evaluating these treatment modalities in new studies going forward for limb salvage and quality of life as well in order to determine the best “treatment modality” to use.
When do you recommend the use of angioplasty alone and when do you use a primary stenting strategy?
Thomas Zeller: In the era of drug-eluting balloons, provisional stenting should be the preferred treatment strategy in lesions which are not severely calcified or ulcerated. Spot stenting should be performed only in case of flow-limiting dissection or a residual stenosis >50%. Primary stenting should be reserved to lesions with irregular morphology, eccentric calcification and lesions where a thrombus should be fixed. The stent with the best mechanical properties for calcified lesions is the Supera stent which essentially mandates sufficient predilatation, which could even be performed with a drug-eluting balloon.
Dennis Gable: I use angioplasty alone in lesions under 3–5cm or if the treatment vessel (superficial femoral artery) is less than 5mm diameter. I think the use of primary stenting or atherectomy in small vessels generally will have poor and predictable failure at 6–12 months. In shorter lesions under 3–5cm, I think angioplasty alone offers the best “bang for the buck” for patency and limb salvage. I typically use primary stenting for lesions over 5cm or in calcified lesions as I feel this offers better long-term success. We have not yet had ready access to drug-eluting technology as they do in Europe.
How are you using PTA, stents, drug-eluting stents, and drug-eluting balloons in the SFA?
Thomas Zeller: In my own practice plain balloon angioplasty as a standalone procedure is not used anymore for the treatment of femoropopliteal lesions but for predilatation where indicated. Drug-eluting balloons have completely replaced the uncoated balloons as primary treatment strategy—drug-eluting balloons are sufficiently reimbursed in Germany. If a lesion needs a scaffold but no particular compression resistance and is not yet predilated with a drug-eluting balloon we use a drug-eluting stent. If the lesion is severely calcified or involve the popliteal artery we implant Supera stents. For lesions with insufficient acute treatment result after drug-eluting balloon angioplasty, we implant traditional slotted tube nitinol stents.
Dennis Gable: As previously outlined, I currently use plain balloon angioplasty only for small vessels and/or shorter lesions under 3–5cm. I currently do not use any drug-eluting balloons or stents in the superficial femoral artery. We have little access to these devices in our area but I remain intrigued over the possibilities and continue to watch for ongoing studies and results.
With so many stents available on the market, how do you choose the best devices to have in your tool box?
Thomas Zeller: We are following the published evidence regarding patency data and fracture resistance of a device. Additionally, due to intensive study activities, we have different investigational devices on stock. As mentioned, it is essential to have a drug-eluting balloon available—currently Zilver PTX is the only one available. In addition, for calcified lesions and the popliteal artery, the Supera stent should be on stock. As a third stent type, a slotted tube nitinol stent with good fracture resistance and patency data such as LifeStent or Complete SE stent are available. As bailout and special indication device, we have the Viabahn endoprosthesis on stock. A potential additional interesting device, the BioMimics stent, is not yet commercially available.
Dennis Gable: My treatment algorithm, if you will, for treatment of superficial femoral artery disease is certainly not perfect but I feel it gives my patients good and reliable results. I typically treat small arteries (<5mm diameter) and lesions under 3–5cm with angioplasty alone with stent placement only for dissection or failed angioplasty (recoil). I will treat lesions 3–10cm with bare metal self-expanding stent placement. I favour the LifeStent, Complete or Absolute stent.
Beyond 10cm, I feel the best available data for long-term patency is in using Viabahn. Although this device has some techniques that need to be adhered to in order to allow for success, if one follows these recommendations, the outcomes are reproducible and quite good over the long term both for limb salvage and primary/secondary patency. I believe these stents have best and strongest data available when compared to all other devices.
Do you think there is a growing interest in the development of new devices for the superficial femoral artery and popliteal lesions, and less for below-the-knee interventions?
Thomas Zeller: I do not believe so. There are more unmet needs existing below the knee than above the knee. We do not yet have any efficient stent device dedicated to the below-the-knee artery needs. It should be flexible (self-expanding), drug-eluting, with small stent strut diameters. For short lesions, coronary drug-eluting stents do a good job in the tibial arteries excluding the distal vessel segment and the foot arteries. However, for longer lesions we do not have an efficient device yet—bare 4F nitinol stents offer no better patency data than plain balloon angioplasty.
Dennis Gable: I believe there continues to be high interest in the treatment of superficial femoral artery/popliteal artery with these devices and new devices but also believe there continues to be growing interest in the treatment of tibial artery lesions as well. The tibial artery anatomy will likely be the next frontier to be studied for treatment by interventional means.