Endovascular Treatment of Infrapopliteal Lesions
An overview of the promising approaches to treating CLI and the role of debulking devices.
Chronic critical limb ischemia (CLI) generally results from advanced, multilevel atherosclerotic disease of the lower-extremity vasculature. Involvement of the tibioperoneal vessels is normally encountered (Figure 1). CLI presents with ischemic rest pain and progressive tissue loss. Historically, the gold standard for treatment of CLI has been surgical revascularization; however, this approach is limited to subjects with good distal target vessels and lack of severe comorbid condition. Several case series and the recent randomized BASIL trial1 have questioned the superiority of surgical revascularization and have confirmed the therapeutic role of tibioperoneal vessel interventions (TPVI) in this patient population. This is due to technical and technological advancements, which have resulted in improved safety and higher success rates of endovascular therapy for TPVI (Table 1).
The recently published BASIL trial demonstrated equivalent 6-month amputation-free survival in patients with CLI treated percutaneously.1 Furthermore, the endovascular approach was associated with lower 30-day morbidity and mortality. The initial strategy of attempting percutaneous revascularization was not found to hinder future surgical revascularization strategies. Arguably, TPVI should be the initial treatment of choice for CLI caused by infrapopliteal occlusive disease, especially if the life expectancy is less than 1 to 2 years and in patients with significant comorbidities. It is important to remember that the clinical success of this modality has been superior to its angiographic success because after wound healing was achieved, further restenosis may not be associated with recurrence of ulcers due to the presence of sufficient flow.2
Classically, infrapopliteal occlusive disease is not associated with lifestyle-limiting claudication. However, some patients will indeed have claudication with infrapopliteal occlusive disease, particularly those with concomitant pedal arch vessel disease. Traditionally, angioplasty for the treatment of intermittent claudication has been avoided in the past due to the concern over major complications. However, recent studies are beginning to question this long-standing dogma. A prospective study of TPVI in subjects with Rutherford class 2-3 demonstrated 89.4% procedural success (defined as less than 30% residual stenosis) after balloon angioplasty and stent placement (if deemed necessary). TPVI resulted in increased walking distance and ankle-brachial index. The complication rate was 5.8%, with no instances of amputation or surgery. The primary patency (on color-flow duplex or angiography) after 12 months was 66.3%.3
Appropriately planned access is an important part of the procedure (Table 2). Currently, the most common access methods are contralateral, antegrade ipsilateral, and rarely, retrograde tibial access.4
The contralateral approach is the most commonly used method. This approach allows for sufficient pushability in the majority of cases and is ergonomically less challenging. When additional backup is necessary, a guide catheter can be advanced to the level of the popliteal artery. This method also allows contrast injection closer to the region of interest, potentially allowing for less utilization of dye and improved imaging. The other advantage of the contralateral access approach is that during hemostasis, antegrade flow down the treated vessel is not impaired while the contralateral femoral artery is compressed.5
In some cases, the contralateral approach is not possible. In patients with an occluded iliac artery or previous aortoiliac reconstruction (either through surgery or stent placement), it may not be technically possible to gain access to the tibial vessels from the contralateral approach. In such cases, an antegrade approach may be preferred. Test angiograms or "road-mapping" through the introducer needle may aid in confirming that the guidewire is directed down the superficial femoral artery prior to sheath insertion. Comparatively, the antegrade access approach is associated with an increased complication rate.
The retrograde tibial access is an alternative approach used when usual antegrade or contralateral retrograde has been unsuccessful. This type of access requires sufficient caliber of anterior or posterior tibial artery below the ankle to allow a percutaneous approach. Access is obtained by using a 21-gauge micropuncture kit (Cook Incorporated, Bloomington, IN). The vessel is wired using a .014-inch or an .018-inch guidewire, and the inner component of a 4-F dilator is used to maintain the access. The micropuncture wire is then exchanged for an .018-inch angled Glidewire (Terumo Medical Corporation, Somerset, NJ), and the lesion is crossed in a retrograde fashion. This wire is advanced to the popliteal artery where it can be snared and exteriorized at the femoral artery.4
Adequate anticoagulation in below-the-knee intervention is crucial to minimize thromboembolic complications. An activated clotting time of 250 to 300 seconds should be maintained throughout the procedure. Some interventionists have advocated the use of bivalirudin. Allie et al studied the combination of bivalirudin and tirofiban as an anticoagulation method in peripheral intervention. This combination was a safe alternative to unfractionated heparin.6 Furthermore, infrapopliteal arteries are sensitive to manipulation, and intra-arterial use of vasodilators is recommended during the procedure.2 "No-reflow" is known to occur and can respond to nitroprusside, adenosine, and verapamil.
WIRE AND TECHNIQUES TO CROSS THE LESION
The leading cause of a technical failure is the inability to cross the lesion with the guidewire. Generally, in the tibial arteries, the .014-inch or .018-inch wire systems are utilized. Although a standard wire may be useful for stenotic lesions, occlusionsÑparticularly long occlusionsÑrequire a more aggressive approach. If initially unsuccessful with the standard wire, additional wire support can be provided by either a balloon or a catheter (eg, Quickcross, Spectranetics Corporation, Colorado Springs, CO). In a stepwise approach, hydrophilic wires of advancing stiffness are used. Hydrophilic wires have higher risk for perforation and should be used with caution and, once through the occlusion, exchange for a standard wire may be helpful. Ideally, an intraluminal approach is maintained; however, for longer occlusions, subintimal recanalization could be attempted.2
Primary balloon angioplasty has been used as the main revascularization modality in CLI.7 Generally, long balloons in 2.5-mm to 4-mm diameters are used, with prolonged (5-minute) inflations. Suitable lesions include short and discrete lesions, diffuse stenotic lesions, and occlusion <10 cm in tibioperoneal vessels. In a study by Dorros et al, this method was associated with 94% revascularization success, and limb salvage was achieved in 91% of subjects during 5-year follow-up. Compared to a surgical approach, this technique resulted in better outflow revascularization with a significant improvement in distal extremity perfusion, immediate relief of rest pain, and augmentation of ulcer healing.
The use of the cutting balloon in the infrapopliteal arteries was associated with a 20% rate of intimal dissection and inadequate hemodynamic result, necessitating use of adjunctive stenting.8 Cutting balloons, however, may have niche uses, such as treating ostial lesions, or lesions from neointimal hyperplasia.
The PolarCath (Boston Scientific Corporation, Natick, MA) can be used in the tibial arteries. The PolarCath uses nitrous oxide to inflate the angioplasty balloon to 8 atm, in 2-atm increments. By using nitrous oxide, the balloon is cooled to –10°C, which theoretically may result in a more controlled angioplasty, less need for adjunctive procedures (particularly stenting), and less restenosis. The smallest-diameter PolarCath is 2.5 mm, with a maximum length of 8 cm.
Data regarding the use of stents in the infrapopliteal arteries have been limited. The most common reasons to use stents in this area are flow-limiting dissection9 and vascular recoil. Small-diameter (4-mm) self-expanding stents are available (Xpert, Abbott Vascular Devices, Abbott Park, IL). The use of drug-eluting stents (sirolimus-eluting stents) in the infrapopliteal artery has been compared to bare-metal stent placement in a prospective study of 58 patients. The use of sirolimus-eluting stents was associated with improved 6-month patency rates (92% vs 68%, respectively, P<.002). This was associated with statistically significant reduction of target vessel revascularization at 6 months.10 Future technology may address the problem of in-stent restenosis in the lower extremity by using bioabsorbable stents with drug-eluting capability.11
The excimer laser light (at 308 nm) removes plaque by photoacoustic ablation. The excimer laser delivers, via a flexible fiberoptic catheter, ultraviolet energy in short pulses. This technology allows for plaque ablation and reduces the potential for embolic complications. Recently, the results of the LACI trial were published, which showed 86% procedural success with the use of an excimer laser (Spectranetics Corporation) in subjects with high risk for surgical intervention due to the presence of prohibitive comorbidities or inadequate target vessels or saphenous veins.12 This study demonstrated a 6-month limb salvage rate of 93% of the limb intervened upon. The advantage of the laser is that it may facilitate recanalization of difficult-to-cross chronic occlusions. Furthermore, in complete occlusions, one can use a "step-wise" approach of lasing, and then probing with the wire for the true lumen, until successful recanalization. Adjunctive balloon angioplasty is commonly required after lasing due to the catheter size.13
The SilverHawk (FoxHollow Technologies, Redwood City, CA) is an excisional atherectomy device that has been used for TPVI. In a study by Kandzari et al, use of the device in the setting of CLI resulted in a 99% procedural success and prevented an amputation in 82% of patients at 6 months.14 In this study, 40% of the lesions were in the tibioperoneal vessels or dorsalis pedis artery. Adjunctive therapy was needed in less than one fifth of the patients. Compared to balloon angioplasty, excisional atherectomy theoretically results in a higher luminal gain, without plaque displacement and vessel injury. It is promoted that excisional atherectomy can be used as a standalone therapy. Restenosis after atherectomy using the FoxHollow device is approximately 22% at 6-month follow-up, with cumulative event-free survival at 76.9% across several below-the-knee vessel beds,15 although there have been no large prospective trials with routine angiographic follow-up. Distal embolization has been reported with the device.
In the study by Soder et al,16 the mortality rate after percutaneous transluminal angioplasty was 1.7%, which compares favorably to a perioperative mortality rate of 1.8% to 6% for distal bypass surgery.2 The 30-day mortality rate was 2.9% after endovascular therapy and 5.6% after surgery in the BASIL trial.1 The arterial perforation rate can occur up to 3.7% and is more common in diabetic and elderly subjects. This complication can be addressed by balloon tamponade with or without reversal of the anticoagulation. Other major complications occur at 2% to 6% and include access-site hematoma, acute arterial occlusion from embolization or "no-reflow," and amputation. Iatrogenic arterial occlusion can be secondary to spasm, dissection, or distal embolization. Antispasmodic agents, stents, and thrombolysis with or without aspiration thrombectomy could be used to help resolve the condition.2
The endovascular approach to infrapopliteal arterial disease can be a safe and effective method to address this problem. The interventions should be thought out in a deliberate manner, and the lesions should be approached systematically, in a stepwise fashion. Several devices are capable of restoring patency of the tibial vessels. Ultimately, the acute procedural success usually drives the clinical result of ulcer healing.
Ali Morshedi-Meibodi, MD, is a vascular medicine, endovascular, and cardiology fellow at Loyola University in Maywood, Illinois. He has disclosed that he holds no financial interest in any product or manufacturer mentioned herein. Dr. Morshedi-Meibodi may be reached at (708) 216-4466.
Robert S. Dieter, MD, RVT, is assistant professor of vascular, endovascular, and interventional cardiology at Loyola University in Maywood, Illinois. He has disclosed that he holds no financial interest in any product or manufacturer mentioned herein. Dr. Dieter may be reached at (608) 262-2122; firstname.lastname@example.org.