It is estimated that more than 10 million Americans currently have some form of peripheral arterial disease. One of the largest peripheral arterial disease patient groups are those who suffer from lifestyle-limiting and limb-threatening disease of the superficial femoral artery (SFA). Stenting is now commonly employed as a treatment for stenoses and occlusions of the SFA. Two dedicated devices have been approved for this indication and several more are currently undergoing clinical investigation. To date, comparative data from randomized studies of SFA stenting versus percutaneous transluminal angioplasty (PTA) are limited and have failed to demonstrate the superiority of stenting over PTA in this vascular bed. In addition, there are many unanswered questions regarding the long-term durability of stents in this location, as well as the potential implications of stent fracture. The RESILIENT Trial, which began enrollment in July 2004, is a prospective, randomized, multicenter trial designed to evaluate the safety and efficacy of SFA stenting using a modern, self-expanding nitinol stent (Lifestent NT, Edwards Lifesciences, Irvine, CA) compared to balloon angioplasty alone. Phase 1 of the RESILIENT trial enrolled 20 patients, all of whom received the Lifestent NT. Enrollment in phase 2, the pivotal randomized arm of the trial, is ongoing. This article summarizes the preliminary findings from phase 1 of the RESILIENT Trial.

PHASE 1 DESIGN AND BASELINE CHARACTERISTICS

The feasibility phase of the prospective, multicenter RESILIENT Trial was designed to evaluate the safety of the LifeStent NT self-expanding stent in the treatment of stenoses or occlusions of the SFA and proximal popliteal artery. Twenty patients were enrolled and treated with the LifeStent NT System at six sites in the US. Inclusion criteria included claudication (Rutherford category 1-3), de novo or restenotic (non-stented) stenoses or occlusions in the SFA or proximal one-third of the popliteal artery, lesion length <150 mm (single or tandem), and at least one patent runoff vessel to the foot.

Seventy-five percent of the patients were male, and the mean age was 70.5±9.9 years. Ten patients (50%) had diabetes, and 80% were smokers. Ninety percent had hypercholesterolemia and 85% were hypertensive. All patients were either Rutherford category 2 (70%) or 3 (30%) at presentation. The target limb ankle-brachial index (ABI) was 0.76±0.26, and the mean lesion length was 83.7±28.6 mm. Two-thirds of all lesions were calcified, and 23.8% were total occlusions. A mean of 1.8 stents per patient were implanted.

ACUTE AND MIDTERM RESULTS

There were no incidences of in-hospital death, stroke, myocardial infarction, emergent surgical revascularization, significant distal embolization, or thrombosis. At 30 days, the target limb ABI had improved to 0.97±0.15. Seventy-five percent of patients for which 30-day data were available (12 of 16) were asymptomatic (Rutherford category 0), and 25% (4 of 16) were classified as Rutherford category 1. Clinical success was 100%.

At 6 months, the target limb ABI was 0.94±0.11. Eighty percent of patients (12 of 15) were Rutherford category 0, 13.3% (2 of 15) were category 1, and 6.7% (1 of 15) were category 2. Clinical success remained 100%, and primary patency by duplex ultrasound was 93.3% (14 of 15). There have been no reinterventions, and very importantly, no stent fractures have been identified (0 of 17) on radiographic follow-up.

Quality-of-life assessments such as the Walking Impairment Questionnaire and SF-8 also showed significant improvement at 6 months. Pain indices, walking distances, stair climbing, and walking speed scores all improved approximately twofold from baseline. SF-8 tests showed marked improvement in physical and mental scores, which increased from 40.5±9.1 to 50.0±9.5 (P= .0016) and 47.0±11.7 to 50.7±8.6 (P=.3228), respectively.

RESILIENT PHASE 1 IN CONTEXT

Results from the SIROCCO trials have generated much interest in SFA stenting. Although the long-term restenosis rates in the drug-eluting stent arm of the SIROCCO trial were not as low as the investigators had hoped, the results observed in the bare-metal control arm were surprisingly good with 6-month angiographic restenosis rates in SIROCCO I and II of 23.5% and 7.7%, respectively. A problem that was brought to light in the SIROCCO trial was the frequent occurrence of stent fracture when multiple nitinol stents are implanted into the SFA and popliteal artery. The magnitude of this problem was further supported by the findings from the European FESTO trial. Preliminary data from phase 1 of the RESILIENT Trial have been promising in this regard, with a 0% fracture rate at 6 months versus 6.9% in the SIROCCO II DES arm and 10.7% in its bare-metal control arm. The 6-month duplex derived restenosis rate of 6.7% in RESILIENT phase 1 also compares favorably with the 6-month angiographic restenosis rate from the bare-metal control arm of SIROCCO II.

The acute and 6-month data from RESILIENT's feasibility phase are encouraging. Longer-term data and forthcoming results from the pivotal phase 2 randomized portion of this trial will provide us with much needed information about the effectiveness of nitinol stents in the SFA compared to balloon angioplasty alone. Important additional data regarding the risk of stent fracture with this newer, more flexible nitinol stent design will be generated.

John R. Laird, Jr, MD, is Director of Peripheral Vascular Interventions at the Cardiovascular Research Institute, and is Assistant Clinical Professor of Medicine at Georgetown University Medical Center, Washington, DC. He is also the Co-Director of the Center of Vascular Care at the Washington Hospital Center, Washington, DC. Dr. Laird may be reached at (202) 877-5975; John.R.Laird@medstar.net.