Introduction
Endovascular treatment for tibial arterial disease has grown in popularity through technological advancement and improvement in techniques, allowing increased success in treating difficult lesions. With growing evidence for decreased morbidity and mortality, as well as equivalent limb salvage rates following endovascular therapy when compared with open bypass surgery, tibial percutaneous transluminal angioplasty (PTA) is now commonly used as first-line treatment for infrapopliteal atherosclerotic disease.
The Inter-Society Consensus for the Management of Peripheral Arterial Disease (TASC) guidelines provide recommendations agreed upon by multiple medical, surgical, and radiological societies in Europe and North America for the diagnosis and treatment of peripheral arterial disease. These guidelines are based on disease complexity and anatomic locality, offering treatment recommendations ranging from endovascular therapy for the least severe TASC A lesions to surgical revascularization for the most severe TASC D lesions. Initially, the TASC II classification systems only included aortoiliac and femoropopliteal segment treatment recommendations, but more recently, an updated infrapopliteal classification was created to include management of tibial lesions ( Fig. 35.1 ). However, in these updated classifications, groups such as the Society of Vascular Surgery were not represented. For many vascular specialists, endovascular treatment for TASC C or D lesions is considered because patients with chronic limb-threatening ischemia secondary to tibial disease tend to have multiple comorbidities and may benefit from a less morbid procedure rather than a tibial or pedal bypass. Proper prevention and management of complications will ensure technical success during endovascular treatment of tibial lesions when open bypass is not an option.
Arterial Access
Technique
The most common complication following endovascular interventions is related to arterial access. Using an appropriate technique reduces risks of arterial access complications. For lower extremity endovascular interventions, arterial entry is frequently obtained by contralateral retrograde common femoral access. This access orientation allows full evaluation of inflow aortoiliac vessels without potential visual interference from the sheath. Additionally, it provides the operator more working room, stability, and accessibility to wires and catheters along the patient’s contralateral leg. However, for more severely calcified infrapopliteal lesions, ipsilateral antegrade common femoral access may prove to be beneficial, given more direct pushability of wires and catheters. High or narrow aortoiliac bifurcations can lead to difficulty in advancing sheaths up and over the bifurcation, and antegrade access can be used to avoid this anatomy. Retrograde tibial access is a useful technique for lesions that cannot be crossed in antegrade fashion. Brachial access can be considered for treatment of infrapopliteal lesions when femoral access is contra-indicated; however, for taller patients, the working length of the wires and catheters may be insufficient for treatment of distal lesions.
Retrograde Common Femoral Artery Access
Routine use of ultrasound guidance for arterial entry will help reduce access-site complications. Although arterial access can be obtained with aid of direct palpation of the common femoral artery, practice with ultrasound will prove to be invaluable when more precise access is required. In our practice, we use a micropuncture technique for all arterial access, which involves the use of a 21-gauge needle and a short 0.018″ guidewire. We find this technique especially useful when obtaining access in calcified vessels by being able to place the needle tip accurately into a less diseased part of the artery. Short 21-guage micropuncture needles are also commercially available for use during retrograde tibial or pedal access. Needle entry into the vessel should be at a 45-degree angle, although a steeper angle may be required for more calcified vessels. Dilation of the skin and subcutaneous fat tract with a hemostat will aid successful deployment of the closure device at the end of the case. Please see Chapter 1 for further details regarding femoral access.
Retrograde femoral access and placement of a 4-French sheath is generally sufficient to advance a catheter into the contralateral external iliac artery for initial diagnostic imaging. However, in patients with severe peripheral arterial disease, multilevel disease burden, or poor cardiac output, injection of contrast at the external iliac level may not reach the tibial vessels for clear imaging. Therefore, the catheter will need to be advanced into the superficial femoral artery. For tibial interventions, the sheath will need to be upsized to a least a long 5-French sheath and placed into the superficial femoral artery (SFA) or popliteal artery to allow passage of tibial balloons and/or stents. Once the sheath is in place, it is always flushed and locked with heparinized saline. Alternatively, a continuous infusion of heparinized saline through the sheath may be utilized. Systemic heparinization for a diagnostic procedure is generally not necessary; however, if interventions are to be performed, a systemic bolus of heparin at 100 units/kg is given to prevent thrombosis. Activated clotting times (ACTs) are obtained every 20–30 minutes throughout the case, and heparin is redosed as needed to obtain an ACT level greater than 300 seconds. We recommend achieving these higher levels of ACT, given reported intraprocedural thromboembolism rates during tibial intervention as high as 4%.
Antegrade Common Femoral Artery Access
For ipsilateral antegrade access, precision in placing the arterial puncture over the femoral head is critical in preventing access site complications. Ultrasound visualization is important, not only for arterial entry but to direct the wire into the superficial femoral artery. Upsizing to a sheath should only be done once there is confirmation of SFA selection with the wire. Direct SFA access can be performed in certain situations where common femoral artery access is contra-indicated and the SFA is sufficient in diameter. In patients with a large obstructing pannus, it is helpful to reflect and to secure the pannus cranially with tape prior to prepping, draping, and attempting access.
Part of the difficulty of ipsilateral antegrade access is the directionality of wires toward the patient’s head, resulting in workspace limitations. Using a longer sheath and arching the extracorporeal portion of the sheath to the contralateral side to direct the wires along the contralateral leg is a helpful technique. Securing the sheath to the patient or the drapes will prevent accidental sheath dislodgement. If a sheath is dislodged during a procedure, it is important to replace and reinsert the inner sheath dilator before advancing the sheath into the artery to avoid damaging the tip of the sheath and injuring the artery. Upon completion of the procedure following either retrograde or antegrade common femoral access, manual pressure is usually sufficient to obtain hemostasis, given the small sheath size required for tibial interventions. Following manual compression and hemostasis, we require patients to lie flat for 1 hour per sheath size used.
Retrograde Tibiopedal Access
Retrograde percutaneous tibiopedal access has become an important tool for treating tibial lesions that cannot be crossed from an antegrade approach. Obtaining tibiopedal access can be challenging, given the small size and extensive calcification of these vessels. Initial antegrade run-off angiography will identify the location of distal reconstitution, which will be the target for retrograde access. This arterial entry point is then identified under ultrasound visualization and accessed using a short micropuncture 21-gauge needle ( Fig. 35.2A,B ). If access fails following multiple attempts, the artery may go into vasospasm. Intra-arterial injection of nitroglycerin through the antegrade sheath and warming the leg can help resolve the vasospasm. Nitroglycerin can be administered intra-arterially through the sheath or catheter in 100–200 µg increments. Hypotension is rarely seen when administering nitroglycerin directly to the infrapopliteal arteries.
Alternatively, retrograde access can be obtained under direct fluoroscopy using calcification as a roadmap or handheld contrast injections from the proximal catheter. However, this exposes the interventionalist to higher doses of radiation. Occasionally, patients are unable to remain comfortable and still for these procedures while under monitored sedation, and in those cases, general anesthesia may be useful. Following successful retrograde tibiopedal access with the micropuncture needle, the inner cannula of the micropuncture sheath is used as the tibial sheath ( Fig. 35.2C ). Alternatively, commercially available microsheaths can be used. However, we prefer the inner dilator alone to minimize the profile of the sheath in the tibial vessel. Following completion of the case and removal of all devices, hemostasis can be obtained via direct pressure over the tibial access point. Alternatively, inflation of a blood pressure cuff can be used for deeper accessed tibial vessels (e.g., peroneal) to achieve hemostasis. Closure devices should be avoided in these small vessels, given device-vessel size discrepancy and the risk of vessel narrowing and thrombosis.
Management of Complications
The most common complication from tibial endovascular interventions is access-site bleeding, followed by pseudoaneurysm, arteriovenous fistula, thrombosis/dissection, and distal embolization. To help triage access-site bleeding, an ACT level should be measured prior to sheath removal. For femoral access cases, bleeding following sheath removal can be controlled with direct manual pressure and reversal of heparin with protamine. Routinely, we deploy a closure device in the common femoral artery without heparin reversal. If we find continued bleeding after successful closure device deployment, we will then administer protamine. Alternatively, heparin can be allowed to wear off over 1–2 hours prior to sheath removal. As a general rule, 5 minutes of uninterrupted manual pressure per sheath size is recommended to obtain hemostasis in arteries without closure devices. If there is continued hemorrhage or hematoma expansion despite manual compression, surgical cut-down and repair of arteriotomy is indicated. In our institutional experience, the need for surgical cut-down following lower extremity access is very rare (<1%).
Similarly for retrograde tibial or pedal access, bleeding is controlled by direct manual pressure over the access site. Hemostasis can be confirmed by conventional angiogram if the proximal sheath or catheter is still in place. However, heparin reversal should only be done once the proximal sheath is removed, to avoid thrombosis. If manual pressure fails or if the tibial vessel is deeper within the calf, blood pressure cuff occlusion can be attempted.
Documentation of bilateral pedal pulse examination prior to lower extremity endovascular intervention is important, especially since contralateral femoral access is commonly used. New findings of a cool, pulseless, or mottled limb at the completion of case or worsening foot pain is worrying for access site thrombosis or dissection. Access-site thrombosis is confirmed by intraoperative duplex ultrasound. If thrombosis is suspected prior to sheath removal, a contrast injection through the sheath will aid in diagnosis. However, injection through the sheath in this instance should only be performed if there is good back bleeding from the sheath side port demonstrating that the sheath itself is not thrombosed. If there is sheath thrombosis, the sheath may be removed over the wire and replaced. For femoral artery access-site thrombosis, surgical cut-down, thrombectomy, and repair of vessel are generally required. In selected cases when surgical cut-down of the groin is high risk or contra-indicated, gaining contralateral access and treatment using lysis, PTA, and stenting can be considered.
Femoral access site pseudoaneurysms can present as groin swelling, with or without an obvious hematoma or pulsatile groin mass. Retrograde tibial access-site pseudoaneurysms can present with swelling and, in very rare circumstances, can lead to compartment syndrome. Any patients with worrying findings on examination following access procedures should receive a groin or leg duplex ultrasound. Duplex ultrasound helps diagnosis and guidance for treatment options. Small pseudoaneurysms <2 cm can be observed and will usually thrombose spontaneously in the absence of systemic anticoagulation. Femoral and tibial pseudoaneurysms can be initially managed by direct manual pressure or ultrasound-guided compression, particularly if recognized immediately while the patient is sedated. Compression of a pseudoaneurysm in an unsedated patient is often not well tolerated. Open surgical repair of a pseudoaneurysm is indicated if the pseudoaneurysm is not anatomically amendable to thrombin injection or if the pseudoaneurysm is rapidly expanding, causing overlying skin necrosis, or is infected. Lower extremity fasciotomies may be required if compartment syndrome develops.
Treatment of Tibial Lesions
Techniques
Nonocclusive Tibial Stenosis
Angiographic evaluation of tibial vessels begins with quality arteriography. Imaging of diseased tibial vessels will often be diagnostically inadequate, with a flush catheter placed high in the aortoiliac vessels. For more detailed tibial vessel evaluation, contrast injection should be done following selective catheterization of the common femoral artery, distal superficial femoral artery, or popliteal arteries. The more distal the catheter is placed, the less contrast is required and the clearer the images become. In patients with chronic limb-threatening ischemia, contrast injection can result in a significant amount of ischemic pain. This pain is possibly caused by displacement of the limited blood supply or from the osmolarity of the contrast itself. Use of diluted isomolar nonionic contrast tends to cause the least patient discomfort.
Occasionally, patients are unable to stay still for the images under monitored sedation because of the pain, resulting in motion artifact. Placing an imaging delay following contrast injection can help reduce motion artifact. If the patient is still unable to stay still despite radiolucent restraints or increasing amounts of sedatives, the case will need to be completed with general anesthesia. To avoid these delays, it is important to assess and identify preoperatively patients who cannot tolerate an awake procedure, such as those with dementia, the elderly, or those with severe rest pain. In these patients, intervention under general anesthesia is preferred. Alternatively, cases performed with anesthesiologists can be started under monitored sedation with transition to general anesthesia during the case if needed.
It is important to remember that angiographic images are two-dimensional and lesion contours can be misrepresented when visualized in certain orientations. Imaging with different oblique projections can help clarify lesions. Obtaining tibial duplex ultrasound studies preoperatively can be helpful in identifying target lesions and for case planning. Additionally, intraoperative duplex can be performed to verify lesions that are found on outpatient imaging but not seen on arteriography and to demonstrate the presence or absence of a hemodynamically significant residual stenosis. Use of pressure wires to measure gradients across stenoses can also be performed; however, the routine use of this technique is expensive and the benefits have yet to be clearly elucidated.
Planning the sequence of tibial revascularization and selecting the number of vessels to be treated depends on indication for treatment, condition of the patient, and pattern of atherosclerotic disease. In general, for both chronic limb-threatening ischemia and claudication, revascularization of a single tibial vessel is sufficient if it provides adequate flow to the wound, either directly or through large collaterals. Based on a review from our institution, multiple-vessel tibial intervention for chronic limb-threatening ischemia, including patients with tissue loss, does not improve outcomes in terms of rates of reintervention, major amputation, or restenosis compared with single-vessel intervention. In general, revascularization by angiosome does not apply to patients with chronic limb-threatening ischemia, given deviation from normal anatomy and redistribution of arterial perfusion away from the diseased vessels. We base tibial intervention instead on initial angiographic interpretation of the best vessel that will supply the lesion in question. Although in-line flow to the lesion is best, reperfusion through a collateral vessel is preferred over revascularization based on angiosome distribution, in particular when that vessel is occluded in the foot or has poor flow to the wound based on diagnostic imaging. Overall selection of the appropriate tibial vessel for revascularization is based on vessel accessibility and disease burden. Choosing a vessel that is most amenable to endovascular therapy, such as a short-segment TASC A stenosis, can result in a more durable effect than treatment of a long-segment, heavily diseased vessel.
Using an 0.014″ wire, a nonocclusive tibial lesion can be carefully crossed. Because atherosclerotic lesions are irregular, using an instrument to mold a curve onto the tip of a straight 0.014″ wire can help direct the wire to the desired direction. A large variety of wires are currently available on the market with varying stiffness, including those with tapered and weighted tips. For severe stenosis, where a lumen exists, we will choose a hydrophilic wire, such as Command 14 (Abbott Laboratories. Abbott Park, IL) or Choice PT (Boston Scientific, Malborough, MA). For chronic occlusions we will choose a weighted, tip wire such as Miracle Bros or Confianza (Asahi Intecc, Seto-shi, Japan). A torque device will help improve steerability of the wire through a lesion and 0.014″ or 0.018″ catheters, such as CXI support (Cook Medical, Bloomington, IN) or Quick-cross (Spectranetics, Colorado Springs, CO) catheters, can be fed over the wire for support and help direct the wire through an area of stenosis. Additionally, it is often helpful to use the 0.018 CXI support catheter through a 0.035″ catheter, such as Navicross (Terumo, Somerset, NJ), in a telescoping fashion to provide additional support. Additionally, a balloon catheter can be used in place of a support catheter to aid in lesion crossing by reducing the need for multiple catheter exchanges. Advancement of the sheath closer to the lesion will aid in overall stability of the system.
After crossing the stenosis, maintaining wire access is imperative to the success of the case by preventing multiple wire passes across a lesion. Multiple wire passes can result in thrombosis and dissection of the vessel. The tip of the wire should be visualized on live fluoroscopy at all times, especially during catheter exchanges, to avoid inadvertent wire advancement, causing distal vessel injury or perforation. Digital zoom can be utilized to focus on the area of interest while the wire tip is visualized simultaneously on the non-magnified image. Use of the digital zoom setting avoids the increased radiation associated with live fluoroscopic magnification.
Starting with 260–300 cm exchange length wires instead of shorter 145–180 cm length wires will ensure adequate working length for stable exchanges of balloons and catheters, especially with over-the-wire catheters and devices. Monorail catheter systems allow the wire to exit from the catheter closer to the tip of the device to facilitate quicker catheter exchanges with less wire manipulation. However, the monorail system has less pushability compared with the over-the-wire system. The Advance LP monorail balloon system (Cook Medical, Bloomington, IN) does have a longer over the wire segment (50 cm) before the wire exits the catheter, potentially allowing better pushability. When using this system through a sheath parked in the popliteal artery, most or all of the length of balloon catheter outside a sheath will be over the wire, while the monorail portion will remain within the sheath, thereby maintaining the benefits of a monorail system over long catheter lengths (170 cm). To prove intraluminal positioning of the wire once a tibial lesion is crossed, the tip of the wire should be seen freely advancing and rotating. For additional verification, a 0.014″ or 0.018″ catheter can be advanced over the wire and pass the lesion to perform a contrast injection.
Tibial balloon PTA has been widely accepted for treatment of tibial atherosclerotic disease. Prolonged balloon dilation for 2–3 minutes with gradual balloon deflation to reduce elastic recoil may help prevent intimal dissection. Balloon length and size are selected based on measurements on diagnostic arteriography. Treatment of long tibial lesions with a single long balloon instead of multiple inflations with shorter balloons may also help reduce the risk of dissection and thrombosis. Tibial PTA results in flow occlusion through the vessel. Therefore, performing multiple short balloon inflations instead of single balloon inflation will add additional ischemia time. Additionally, in small tibial vessels, the balloon catheter itself is often occlusive in the vessel without balloon inflation. To prevent thrombosis, it is important to maintain ACT levels greater than 300 during tibial PTA and remove PTA catheters promptly.
Balloon preparation is important in preventing air embolus if the balloon ruptures during PTA. This is performed by negative aspiration of air from the catheter and passively refilling the catheter shaft with diluted contrast media. Following PTA, it is important to confirm balloon deflation radiographically before removing the catheter. Having an assistant hold the sheath while walking off the balloon will prevent sheath dislodgement and help maintain wire access. Again, the tip of the wire should be visualized during the removal of the catheter. A completion angiogram is then performed to evaluate the success of the PTA treatment and to identify dissection, distal embolization, or arteriovenous (AV) fistula complications. Residual stenosis can be treated with repeat PTA or stenting.
Other adjuncts available for use in infrapopliteal lesions include drug-eluting stents (DES), drug-coated balloons (DCB), mechanical atherectomy devices, cryoplasty, cutting balloons, and laser atherectomy devices. Multiple European randomized controlled trials have shown benefit for infrapopliteal DES over PTA and bare metal stents (BMS) in terms of patency and freedom from reintervention. However, improvement in major amputations or overall mortality has been inconsistent among these trials. There are currently no FDA approved DES for tibial vessels in the United States. Given this unavailability, DESs approved for coronary use are sometimes used off-label in tibial vessels.
The benefit of DCB therapy for infrapopliteal lesions is less clear. Whereas some studies have shown lower rates of 1-year restenosis, others found a trend toward higher amputation rates. Regardless, there are no FDA approved DCB for tibial vessel in the United States and the smallest peripheral DCB is 4.0 mm in diameter, which is too large for use in most tibial vessels. Use of cutting balloons and atherectomy devices can lead to successful outcomes, depending on the operator’s experience with these techniques. However, evidence for these devices is currently limited to smaller retrospective studies with short follow-up and conflicting outcomes. In our practice, we do not use atherectomy devices given the risk of embolization, lack of evidence for benefit, and difficulty with successful use of distal filters in small tibial vessels. In patients who are not candidates for bypass, we occasionally use rotational atherectomy in situations where small balloon catheters will otherwise fail to pass a calcified lesion or would burst upon inflation.
Chronic Occlusions
Treatment of tibial artery occlusions can be challenging, depending on the degree of calcification and length of occlusion. Initial attempts for crossing occlusions are performed using 0.014″ or 0.018″ wires. Small back and forth movements can facilitate finding a soft spot in the occlusion. If this fails, rapidly spinning the wire like a drill with constant forward pressure can be successful. Advancing an 0.14″ or 0.18″ microcatheter over the wire and placing it directly against the occlusion will help generate more support and force for advancing the wire. Multiple wires are commercially available and designed to traverse tibial occlusions. Using a hydrophilic tipped wire or switching from a 0.14″ to a 0.35″ diameter wire can also be effective for stiffer occlusions. However, we rarely do this because of the increased risk of inadvertent vessel perforation.
Subintimal techniques are used if more traditional methods fail. If the subintimal plane is entered while trying to cross an occlusion, attempts are made to re-enter the reconstituted lumen distally. If the wire cannot be advanced any further to the reconstituted portion of the distal artery, we advance a microcatheter to the end of the wire so that progress is not lost and then switch out with a new wire and try to cross the remainder of the occlusion. If no further progress can be made, we pull the wire and catheter back to the top of the occlusion and attempt in a different plane. If the occlusive lesion is successfully crossed, subintimal PTA is then performed, and stenting may occasionally be needed.
Retrograde tibial access is very helpful in cases where antegrade crossing of the occlusion fails ( Fig. 35.3 ). We now turn to retrograde access quickly if antegrade attempts are difficult. As described previously, a micropuncture needle is used to access the reconstituted portion of the distal tibial artery under ultrasound or live fluoroscopic guidance. Through the inner cannula of the micropuncture sheath, a long 0.14″ or 0.18″ wire is advanced through the occlusion in retrograde fashion. If there is still difficulty crossing the occlusion, the inner cannula sheath can be replaced with a 0.014″ catheter, such as a CXI catheter (Cook Medical, Bloomington, IN). Advancement of a catheter to the lesion will add additional support for the wire. Once the wire crosses through the occlusion and into true lumen proximally, the wire is then advanced into and through the antegrade sheath ( Fig. 35.4A ). If there is difficulty feeding the wire into the antegrade sheath, a snare device can be used to grab the wire. This technique is referred to as subintimal arterial flossing with antegrade–retrograde intervention (SAFARI). Placement of a hemostat at the retrograde access site to secure the wire will help prevent accidental wire pull-through and may be useful as a “body floss” technique to pass catheters, if there is resistance. From this point, antegrade PTA with or without stent of the tibial occlusion can be performed.
