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Infrapopliteal Intervention Achieving revascularization below the knee. By David E. Cohen, MD ACCESS SITES
 Tips & Tricks: Procedural Tips for Infrapopliteal Intervention A successful procedure must begin with well-planned vascular access. This is usually performed through either a retrograde/contralateral femoral approach or through an antegrade/ipsilateral femoral approach. There are some considerations to think about when deciding on the approach to a particular case. There is a common misconception that contralateral access will not give the operator sufficient pushability to treat distal disease; this is not true with today's low-profile coaxial systems. If common femoral disease is present, achieving access via the contralateral common femoral artery is preferable. Lesions at the level of the ankle or below may not be reachable by interventional devices in tall patients using a contralateral approach. Patients with extremely calcified or angulated aortoiliac systems, or with previous aortobifemoral grafts, are usually not suitable for contralateral access. Patients who are obese or have proximal SFA disease are not good candidates for an antegrade approach. Contralateral approaches have the advantage of keeping access-related complications from having an impact on interventional sites. Using a long sheath that extends down to the level of the popliteal artery has the advantage of reducing contrast load and improving image quality. However, a sheath of this length should not be used if it impedes inflow around it or if the sheath tip lands distal to any important collateral vessels that may be essential for visualization of distal anatomy. If ipsilateral/antegrade access is used, use the femoral head as an anatomic landmark and always ensure a stiff wire is the first wire to be inserted (a soft wire might not provide sufficient support for sheath insertion). When making an antegrade femoral puncture, I find it useful to attach a Y-connector to the needle. This allows for easy contrast injections through the needle while simultaneously manipulating the wire into the SFA. Another useful tactic is to use a curved, long sheath for antegrade access, and then position the exteriorized proximal sheath as if it were a contralateral sheath and secure it to the drapes, which allows operators to work as though they are retrograde. IMAGING The tibial arteries can present daunting imaging challenges because of multiple vessels, multiple level occlusions, complicated networks of collaterals, slow-filling targets, and underlying bone. A moving patient can be prohibitive, and a carefully monitored propofol infusion can be helpful in this instance. Complex tibial interventions require meticulous imaging and careful interpretation of the anatomy to plan the approach. Careful, deliberate wire work is the key to success. Digital subtraction imaging is absolutely critical for interventions in this anatomy; cardiac "cine" has no place here. If your lab has roadmapping technology, familiarize yourself with it and use it liberally to help with guiding your wire through occlusions, precisely targeting the intervention and reducing contrast load. Image-summation software allows proximal (inflow) and distal (outflow) anatomy to be viewed in a single image in situations in which the proximal and distal anatomy fill with contrast sequentially rather than simultaneously. If your lab does not offer these technologies, get them! Other imaging tips include using the lowest magnification your lab offers to help map complex occlusive anatomy, using higher magnification and oblique views to help identify subtle stumps and oblique views to move tibial vessels off of underlying bony cortex; consider contrast injections from catheters positioned at the knee level to provide exquisite detail. Appropriate use of shutters and shielding is very helpful to maximize image quality. Be sure to always identify pedal runoff before and after the procedure. This step may require delayed views on the baseline angiogram. For contralateral access cases, try to set up the lab and position the patient so that the operator is standing opposite the leg being treated to avoid radiation exposure to the operator's hands during the procedure. In cases with complex tibial occlusive disease, take time to be sure you are properly defining the vessels, lesions, and target vessels. A clear understanding of the pathology is critical to a successful procedure. If an image in the upper calf does not clearly relate to an image in the lower calf, reimage the midcalf to clarify the anatomy. Be sure to take long imaging runs to identify slow-filling distal vessels. Also, be aware that tibial anomalies are fairly common, with unusual trifurcations and variations at the ankle level, as well. ANTICOAGULATION We prefer anticoagulation with bivalirudin in tibial cases because of its reliable effects and its antiplatelet activity. All patients should generally receive aspirin and clopidogrel after treatment. DEVICE SELECTION When crossing tibial occlusions, I exclusively use hydrophilic wires and almost never use .035-inch wires in the tibial arteries because they promote much spasm, which is not typically seen using .014-inch or .018-inch wires. My default crossing wire is a hydrophilic .018-inch wire. Straight-tipped wires are superior to angled-tip wires for traversing occlusions. These are straight vessels and require straight wires. When crossing a chronic total occlusion, always use a wire inside an appropriate support catheter, typically either a .018-inch or .014-inch support catheter. This technique provides wire support, the ability to exchange wires, and the ability to inject into the distal target after crossing to confirm intraluminal position. If the patient complains of pain during wire crossing, this always means your wire is subadventitial or perforating, so stop and take a look before moving ahead. Although using the Outback catheter in a tibial artery is not advisable, I have had success deploying the Outback somewhat blindly into occluded, nonvisualized, below-the-knee popliteal arteries, thereby successfully regaining access to the distally reconstituted tibial artery. Except perhaps for the most focal tibial lesions, debulking is likely superior to balloon angioplasty as the initial therapy. Debulking will avoid plaque shift at the trifurcation. If balloon angioplasty is used, I prefer long inflations at low pressures with balloons that are typically 2.5 to 4 mm in diameter. Debulking can be achieved with an excimer laser, with plaque excision, or, more recently, with orbital atherectomy, which appears ideally suited for heavily calcified vessels. For diffuse disease, longer balloons are superior to overlapping inflations with a short balloon. If balloons are used, peripheral balloons will be higher profile than "coronary" balloons, but the former is available in much longer balloon lengths. Think about what type of devices you anticipate using and choose an appropriate-diameter wire up front to accelerate the procedure. We always try to think two to three steps ahead; this planning helps to keep these cases from eating up time. Stents are not often needed in the tibials. Dissection is rare; however, if needed, be sure nitinol stents in the 3- to 4-mm-diameter range and in variable lengths are available. I am reluctant to place balloon-expandable stents in the calf because of the risk of stent crush and deformation. DISCUSSION The tibial vasculature has developed a largely undeserved reputation for being a risky bed for interventionists. These vessels are straight and highly predictable in their responses to manipulation, and they do not move around as much as coronaries. Thrombus is exceedingly rare there. Spasm can be avoided by using low-diameter wires, but if it occurs, intra-arterial nitroglycerin works well. Tibial artery perforations seem to worry many physicians because of compartment syndrome. However, tibial perforations can almost always be managed easily. Tibial artery perforations that occur as a result of guidewire penetration through an occlusion are benign because the vessel is occluded. Perforations that occur as a result of atherectomy can be sealed very effectively with prolonged (3 to 5 minutes) low-pressure (2 to 4 atm) inflations with a long, nominal-sized balloon, even without discontinuation of anticoagulation. Any time a patient complains of pain while you work in the tibials is cause to stop immediately and re-evaluate because it likely means that you are working in the adventitial space or beyond. It is very important to be sure that your work does not adversely affect distal target vessels, as this may limit future surgical options. CONCLUSION Working in the tibial space demands meticulous planning and technique and lots of patience. The reward is limb preservation, which has to be one of the most gratifying achievements we can accomplish. David E. Cohen, MD, is from Saint Joseph's Regional Medical Center in Paterson, New Jersey, and Seton Hall University School of Graduate Medical Education in South Orange, New Jersey. He has disclosed that he is a stockholder in Cardiovascular Systems, Inc. Dr. Cohen may be reached at (201) 265-5300; dcohen@cconj.com. |
