The six-month results of the TOBA BTK (Tack optimised balloon angioplasty below the knee) study show that the Tack endovascular system (Intact Vascular) demonstrated high levels of primary patency, freedom from target lesion revascularisation and total freedom from amputation.
Marianne Brodmann, Medical University, Graz, Austria, told Leipzig Interventional Course 2016 (LINC; 26–29 January, Leipzig, Germany) attendees that Tack optimised balloon angioplasty—a new method for treating critical limb ischaemia with post-angioplasty dissections—may represent “a new paradigm for managing dissections with minimal metal, minimal outward force and minimal injury to vessels.”
Brodmann and colleagues are investigating use of the Tack system because they believe that existing below-the-knee treatment options, such as plain angioplasty, stents, atherectomy and bypass surgery, are poor. Brodmann told the audience that angioplasty—the “standard” treatment—has poor outcomes and is associated with dissections. This is also the case, she said, for treating dissections; both bare metal and drug-eluting stents require multiple implants per lesion and are susceptible to stent fractures, while drug-eluting stents also require patients to be on long-term anticoagulation regimes.
The treatments that are available lead to high technical and procedural success, but also high complication rates. Angioplasty complication rates range from 3.4–51%, drug-eluting balloon complication rates are around 30% and bare metal stenting can be as high at 41.7–63.3%, Brodmann told delegates. This leads to varied one-year outcomes between these different treatment options, for primary patency (range 37.9–94.7%), target lesion revascularisation (range 5.3–47%) and amputation rates (range 0–20%).
The 4F Tack system is specifically for below-the-knee use and is designed to achieve better healing of dissections. Its short open cell design reduces the amount of metal in the device, its flat force curve gives it a low radial force and it is a focal treatment as it is used only where needed. Brodmann explained that this “gives physicians more control over where they treat while maintaining normal vessel biomechanics and preserving future treatment options.”
Brodmann told Vascular News that “The completion of previous trials has led to growing clinical experience with the Tack system. The first in man study was both above- and below-the-knee, and showed feasibility and safety from the superficial femoral to tibial artery with 83.3% 12-month patency. The TOBA study was an above-the-knee study which showed 89.5% freedom from clinically-driven target lesion revascularisation, 76.4% patency rate and 98.5% technical success rate.”
The TOBA BTK study is a first-in-man study collecting data to support existing conclusions on the Tack system’s use. The prospective, single-arm, multicentre study enrolled 35 patients in Europe and New Zealand. All patients had critical limb ischaemia with Rutherford classification 4 and 5 and angiographic evidence of a post-angioplasty dissection. All had de novo lesions ≥70% stenosed/occluded with reference vessel diameter 1.5–4.5mm and lesions located between the knee joint and ankle.
Primary safety endpoint was a composite of major adverse limb events and periprocedural death assessed at one month. Device success was defined as successful delivery and deployment of the device at the intended target site and successful withdrawal of the delivery catheter. Procedural success was defined as the ability of Tack to demonstrate vessel patency as reported by the physician without the occurrence of major adverse limb events or perioperative death on the day of the procedure.
The patient characteristics were challenging, with 87.5% of patients in the device performance arm (n=32) classified as Rutherford category 5. Brodmann also noted that the mean age of 76.1 years made this “a very old patient population”.
The safety sample population exhibited complex lesions. There was a broad anatomical distribution and >60% of patients had moderate or severe calcification. One fifth of patients had total occlusions, lesion lengths ranged up to 8cm and approximately 80% of dissections were grade B+.
The device exhibited “excellent safety and performance” said Brodmann. Device success was 91.4% and procedure success was 97.1% in the safety sample and 96.9% in the performance sample. There were no amputations or deaths at 30 days. There were two reinterventions, one in the safety sample and one in the performance sample.
Six-month primary patency by vessel was 86.5% and primary patency by subject was 87.1%, while six-month primary assisted patency by vessel was 94.6% and by subject was 93.5%. Brodmann told the audience that compared with six-month outcomes of alternative bare metal stent scaffolding options, these data were comparable or superior.
Twelve-month follow-up data are expected later in 2016, while 24-month results are expected in 2017. Furthermore, the TOBA II BTK pivotal study is now in development.