The infrainguinal vascular bed poses unique challenges to today's interventionist. Although the endovascular specialist's armamentarium has expanded greatly in recent years, the results of these newer modalities leave many of us still looking for durable and predictable results. The trinity of durability, economic viability, and preservation of potential bypass targets has largely remained elusive.

THE PROBLEM
The management of infrainguinal arterial occlusive disease has evolved to consist primarily of endoluminal interventions. The superficial femoral artery (SFA) provides unique challenges not seen in other vascular beds. It is an artery of intermediate size (anywhere from 3 to 7 mm) that tends to develop diffuse disease that can span up to 30 cm or more.

There are unique forces at work on the SFA. Depending on the position of the leg, the SFA can be exposed to flexion forces, torsion, or contraction. The adductor hiatus tethers the artery and can result in arterial compression. These anatomical dynamics are not seen elsewhere and present distinct challenges when planning an intervention that will obtain a durable result.

Angioplasty remains, for the most part, the gold standard to which other endoluminal interventions are compared. Often, angioplasty may not be the ideal modality because results in some instances, however, are not as durable as we may like. Immediate technical success can be challenged by elastic recoil of the artery, creation of significant flow-limiting dissections, or restenosis. In response to these potential sequelae, additional therapeutic modalities have been introduced as adjunctive strategies or used as primary interventional strategies.

Stenting in the SFA may be performed to address the complications of angioplasty, namely flow-limiting dissections and elastic recoil, but it has yet to be shown to dramatically reduce the incidence of restenosis or increase patency rates. Flexion forces concentrated at the bifurcation of the common femoral artery and in the popliteal artery at the knee joint also create unique treatment challenges.

Atherectomy has undergone many iterations over the years and continues to be touted as a viable alternative to primary angioplasty. In theory, atherectomy makes sense, but it has not been proven to have longterm benefits over angioplasty alone, and lesions may need postdilatation after the mechanical disruption of the plaque. Atherectomy devices may also potentially result in embolization that can threaten the tenuous tibial outflow seen in many of these patients.

CRYOPLASTY THERAPY: A POTENTIAL SOLUTION
Boston Scientific Corporation's CryoPlasty Therapy has been introduced as an alternative to traditional angioplasty in treating this unique infrainguinal vascular bed. A single-patient-use inflation unit is used to forcibly inject liquid nitrous oxide into a triple-layer angioplasty balloon. The nitrous oxide undergoes a phase change to a gas and draws in energy. As the balloon inflates to 8 atm, the surface temperature is driven down to -10°C.

In theory, the addition of cold therapy may affect the outcome of simple angioplasty by altering the vessel's response to dilation and by inducement of smooth muscle cell (SMC) apoptosis. Results from in vitro studies have shown that arterial SMCs were found to be susceptible to freeze-induced apoptosis at a temperature range of -5° to -15°C.1 Theoretically, a reduction in organized SMC apoptosis could alter the intimal hyperplastic response at the area being treated.

Laird et al published the initial safety data on CryoPlasty Therapy in 102 patients. Eighty-four percent (86/102) of the lesions treated were in the SFA. In all limbs treated, a 94.1% (96/102) initial technical success rate was reported. Fewer than 10% (9/102) of treated lesions required stenting.2 Follow-up of this initial group was extended and revealed durable results, with freedom from target lesion revascularization of 75% at 1,253 days by Kaplan-Meier estimate.3 The BTK Chill trial studied primary CryoPlasty Therapy treatment of below-the-knee occlusive disease in CLI patients and yielded similar results.4

POTENTIAL ADVANTAGES OF CRYOPLASTY THERAPY
CryoPlasty Therapy was designed to offer a novel approach to the challenges of the peripheral vasculature, including infrainguinal interventions. Clinical data have demonstrated good immediate technical success characterized by a low rate of dissection and an infrequent need for stenting.3 In theory, the addition of cold therapy to standard angioplasty may alter the vessel's response to injury through SMC apoptosis.

Stenting the infrainguinal arteries can, in some instances, limit subsequent bypass options. A stent placed at the adductor hiatus can force any subsequent bypass to be performed below the knee, which can lead to a decrease in primary patency. An infrapopliteal stent can greatly limit potential bypass targets and potentially convert a below-knee popliteal artery bypass to a tibial artery bypass. In patients who might have progressed to bypass or those with limited bypass targets, CryoPlasty Therapy may provide an alternative.

In a recent publication by Bakken et al, in which the use of CryoPlasty Therapy as a stand-alone technology was compared to angioplasty in 124 patients with TASC C/D lesions, a 67% cost reduction in the patients treated with CryoPlasty Therapy versus those treated with angioplasty was reported. In their retrospective analysis, the cost reduction was attributed to the decreased use of stents in patients treated with CryoPlasty Therapy (22% [10/39] vs 75% [70/85]).5

Bakken et al also reported that the modes of failure between angioplasty and CryoPlasty Therapy were different. The primary mode of failure in the CryoPlasty Therapy group was restenosis rather than occlusion, whereas the angioplasty group primarily failed because of occlusion, making endoluminal revascularization difficult and leading to more bypass procedures in this group. The patients treated with CryoPlasty Therapy in this retrospective review developed restenosis and tended to have endoluminal options for revascularization in addition to potential bypass options. The investigators concluded that CryoPlasty Therapy was a viable stand-alone therapy for these more complex lesions.

CONCLUSION
Because endoluminal interventions have evolved, it is rare that I will use primary angioplasty in a standalone fashion. The potential complications of elastic recoil, clinically significant dissections, and restenosis encouraged me to use adjunctive therapeutic modalities and to search for other primary interventional strategies. CryoPlasty Therapy offers a unique variation on primary angioplasty with the addition of cold therapy, and clinical data have shown an infrequent need for stenting, as well as durable results that can be economically viable and may also preserve potential bypass targets.2,3,5

Colleen J. Moore, MD, is with the Division of Vascular Surgery, Southern Illinois University School of Medicine in Springfield, Illinois. She has received no financial compensation for participation in this supplement. Dr. Moore may be reached at (217) 545-7983; cmoore@siumed.edu.

  1. Isner JM, Kearney M, Bortman S, et al. Apoptosis in human atherosclerosis and restenosis. Circulation. 1995;91:2703-2711.
  2. Laird JR, Jaff MR, Biamino G, et al. Cryoplasty for the treatment of femoropopliteal arterial disease: results of a prospective, multicenter registry. J Vasc Interv Radiol. 2005;16:1067-1073.
  3. Laird JR, Biamino G, McNamara T, et al. Cryoplasty for the treatment of femoropopliteal arterial disease: extended follow-up results. J Endovasc Ther. 2006;13:II52-II59.
  4. Das TS, McNamara T, Gray B, et al. Primary CryoPlasty Therapy provides durable support for limb salvage in critical limb ischemia patients with infrapopliteal lesions: 12- month follow-up results from the BTK Chill Trial. J Endovasc Ther. 2009;16(suppl 2):II19-II30.
  5. Bakken AM, Saad WE, Davies MG. Cryoballoon angioplasty broadens the role of primary angioplasty and reduces adjuvant stenting in complex superficial femoral artery lesions. J Am Coll Surg. 2008;206:524-532.