24-month outcomes from the Xpert-BTK study hail dedicated BTK stent as safe and efficient

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According to the 24-month results from the Xpert-BTK Study, the Xpert nitinol self-expanding below-the-knee (BTK) stent (Abbott Vascular) is an efficient tool for the treatment of BTK lesions. However, angioplasty (PTA) for treatment of BTK-lesions should be the first approach, and only in case of failure or suboptimal outcomes followed by bail-out stenting with dedicated BTK stents (e.g. balloon-expandable or self-expanding), explained Dr Marc Bosiers, Belgium, in his presentation at CIRSE.

The study was a prospective, multi-centre, non-randomised clinical trial which aimed to assess the safety and performance of the 4F Self Expanding Xpert for the treatment of infrapopliteal lesions in patients with chronic critical limb ischaemia (CLI). Patients with stenotic (>50%) or occlusive BTK arteries were recruited, with a lesion length of <10cm. A maximum of two lesions in one or more BTK vessels was an essential part of the inclusion criteria, along with patients presenting with symptomatic critical limb ischaemia (Rutherford 4–6), and patients with one stenosed and patent artery were also included on the pre-condition that the stenosed artery supplies the wounded area.

Patients excluded were those with lesion lengths that required more than two stent implants, more than two infrapopliteal lesions in the same limb, previously implanted stent(s) or angioplasty (PTA) at the same lesion site, and inflow-limiting arterial lesions that were left untreated.

The study showed that at two years, primary patency was achieved in 54.4% and limb salve in 90.8% of patients (n=94: 46.8% were diabetic). Two-year survival was 71.9%. Stratifying the outcomes for lesion location (proximal vs. distal),  there was no significant difference in primary patency (56.8% vs. 52.3%, respectively). However, limb salvage was significantly better for patients treated with proximal compared to distal BTK-lesions (95.1% vs. 81.1%, respectively).

The study initially ran for 12 months, then was extended for another 12 months. In the 12-month initial report (May 2005 – December 2005), 51 CLI patients were enrolled and the primary endpoint was one-year angiographic patency, as well as absence of >50% stenosis on QVA (Quantative Vessel Analysis). The 24-month extension (May 2005 – Nov 2007) study involved 94 CLI patients, and the primary endpoint was two-year duplex patency and absence of >50% stenosis. Secondary endpoint was two-year limb salvage rate.

In his concluding remarks, Bosiers said, “The Xpert stent is an efficient tool for the treatment of below-the-knee lesions. Limb salvage rates are better for proximal compared to distal lesions.”

AMS not ready for primetime
In a separate presentation, Bosiers discussed the six-month analysis of the Absorbable Metal Stent (AMS) Insight study, which showed that although AMS technology can be safely applied, it did not demonstrate efficacy in long-term patency over standard angioplasty in the infrapopliteal vessels.

The study was designed to investigate the impact of the implantation of AMS in the infrapopliteal arteries, measuring patency by angiography at six months. One hundred and seventeen patients with 149 lesions with critical limb ischaemia (CLI) were randomised to implantation of an MS (n=60, 74 lesions) or stand-alone angioplasty (n=57, 75 lesions) The primary safety endpoint was defined as absence of major amputation and/or death within 30 days after index intervention and the primary efficacy endpoint was the six-month angiographic patency rate as confirmed by core-lab QA.

 Present and future clinical view on lower limb treatment
According to the TransAtlantic Inter-Society Consensus (TASC) recommendations, recent Level-1 studies with current generation stents support the endovascular strategy for TASC A and B lesion classification for the treatment of peripheral arterial occlusive disease (PAOD), said Dr Marc Bosiers at the EuroPCR meeting held in Barcelona in May. He added that new investigational stents might further expand endovascular possibilities towards TASC C and D.

TASC A – FAST
The Femoral Artery Stenting Trial (FAST) trial was designed to evaluate treatment with balloon dilatation compared with stenting among patients with superficial femoral artery (SFA) disease and chronic limb ischaemia. Patients were randomised to treatment with balloon dilatation (PTA) (n=121) or stenting (n=123) with a self-expanding nitinol stent (Luminexx – Bard).

The primary endpoint of binary restenosis on Doppler at 12 months did not differ between groups (31.7% of the stent group and 38.6% of the PTA group, p=.377). Target lesion revascularisation by one year occurred in 14.9% of the stent group and 18.3% of the PTA group (p=.595). Stent fractures had occurred by one year in 12% of patients. The conclusion reached was that among patients with SFA disease, treatment with stenting was not associated with a difference in binary restenosis at 12 months compared with balloon dilatation.

TASC B – Improved design and improved results
Improvements in stent design, such as reorientation of stent bridges has lead to improved adaption to torsion, explained Bosiers. The first generation design contains stent rings connected with longitudinally oriented bridges. However, the latest generation stent design contains stent rings that are connected with helically oriented bridges, improving torsion adaption and hence results.

  • RESILIENT Trial – The prospective, randomised, controlled RESILIENT Trial (Randomized Study Comparing the Edwards Self-Expanding LifeStent vs.Angioplasty-alone In LEsions INvolving The SFA &/or Proximal Popliteal Artery), was designed to assess PTA vs. the triple helix nitinol LifeStent (Bard, former Edwards). Two-hundred and six patients were enrolled, and randomised 2:1. The most important endpoints were Duplex-based patency and stent fractures. At one year, primary patency was achieved in 38% in patients receiving PTA alone, compared with 80% in the stent group (one-year fracture rate: 3%).
  • ABSOLUTE Vienna Trial – The main endpoints of the Absolute Vienna Trial were Duplex-based patency and stent fractures. The prospective, randomised, controlled study evaluated PTA vs. the Absolute nitinol stent (Abbott Vascular), and at two years, patency was achieved in 31% of the PTA/stent group vs. 54% for the stent alone group. The fracture rate at two years was 2%.

Following the encouraging outcomes from the RESILIENT and ABSOLUTE trials, Bosiers explained that longer stents have become available. The first generation stents were relatively short, would often overlap when required to cover total lesion length, and increased stiffness and fracture risk would occur at stent overlap. The latest generation of stents, up to 20cm in length, have the ability to minimise fracture risk. Bosiers presented the six-month interim results of the Durability trial, which was the first study to specifically test the performance of long stents (10–15cm) in long SFA lesion

  • Durability Study – The main endpoints of the Durability study, were Duplex-based patency and stent fractures. The prospective, non-randomised, study evaluated the Protégé Everflex stent (ev3), and at six months, patency was achieved in 91% of the patients with a stent fracture rate of 6%.

TASC C and D – Will surgery be abandoned?
For treatment of femoropopliteal artery disease, Bosiers strongly believed that surgery will not be abandoned and will in fact remain the gold standard. However, he said that new active stent coatings offer new indications, such as those investigated the Zilver PTX study (Paclitaxel-eluting Zilver stent of Cook) and the STRIDES study (Everolimus eluting Dynalink-E stent of Abbott Vascular) for the treatment of longer lesions in the SFA.

In regard to the future treatment of femoropopliteal arteries, for TASC A and B lesions, Bosier stated that endovascular treatment should be the first treatment choice, and for TASC C and D, surgery should be the first treatment choice. However, better design, platform improvements and new active coatings could see the future treatment of the SFA rely solely on endovascular therapy.