CHALLENGES IN FEMORO-POPLITEAL STENTING

Transcription

1 CHALLENGES IN FEMORO-POPLITEAL STENTING Karathanos C MD, MSc, PhD, Athanasoulas A, Rousas N, Spanos K, Giannoukas A Department of Vascular Surgery, University Hospital of Larissa, Faculty of Medicine, School of Health Sciences, University of Thessaly, Larissa, Greece

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3 Peripheral Artery Disease (PAD) INCIDENCE Superficial Femoral Artery (SFA)- 50% Popliteal Artery (PA)

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8 A B Usually PTA PTA preferred Endo or Medical Endo or Medical Treatment Consideration: Anatomic status C D Surgery preferred Usually surgery Endo or Medical or Open Open or Endo or Medical

9 Metalic stents-nitinol stents- e-ptfe covered stents- Drug eluting stents- Bioabsornable stents

10 The name comes from the components of the alloy (Ni and Ti) and initial laboratory Naval Ordnance Laboratory The starting alloy containing 55% Ni and 45% Ti, (01/01 ratio of atoms of the two components.)

11 They are superelastic (crush recoverable) Full elastic recovery after yet and greater than 10% deformation

12 PLASTIC DEFORMATION If the force applied is greater than a limit (yield point), then some bonds between atoms are broken, people are moved and new links are created. The end result is a permanent change of shape.

13 ELASTIC DEFORMATION The metal atoms are moved slightly together, but after removal of the force revert to the previous position. Thus, the wire (STENT) changes shape as the force effect, but then resumes its original shape.

14 S T R E S S STRAIN

15 Superelastic NiTi: Superelastic NiTi wires have a flat response in the elastic region. That is, the force exerted by a superelastic wire is the same in large deformation range A superelastic spring continuously exerts the same force and a common spring will exercise great power in the beginning, which will decrease as the artery open

16 Flat unloading curve over a wide deflection (strain) range Importance Exercise constant force in the artery regardless of their level of deployment Exert a gentle chronic outward force Continuing external pressure in the artery until they acquire their diameter. If the artery is stretched will follow further opening of the stent

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18 Nitinol Properties Kink Resistance

19 Remembering shape The Ni-Ti wires have the property of returning to a former shape when heated above a certain temperature. The temperature depends on the manufacturing conditions and the proportion of cobalt. Usually the Co is 1.6%

20 Temperature - dependent stiffness Nitinol stents with a transition temperature of 30 C Weak when squeezed at low temperature. Much stiffer when squeezed at T above 30

21 Presently Most self-expanding Nitinol stents are produced by laser cutting of Nitinol tubing.

22 Laser-cut Nitinol tubular stents. Top: Memotherm (Bard Angiomed) bottom: SMART (Cordis) Laser-cut Nitinol tubular stents. Top: Jostent SelfX (Jomed) bottom: DynaLink (Guidant)

23 Mechanical stent fatigue or/and fracture is emerging as one of the critical issues for the stenting procedure success Reported incidence and clinical relevance of femoropopliteal stent fractures vary across studies Stent fracture may lead to repeat revascularization due to in-stent restenosis.

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27 Multiple lesions are the most critical condition since the strain values are higher Highest deformation are concentrated between two stenoses were the stiffness of the vessel is lower Suggests the use of multiple stents to cover a double peak plaque, instead of a single long stent, that might be subjected to high deformation between the two stenoses Longer stents are more prone to fracture Stent is more prone to fracture under axial compression than bending, especially for distal SFAproximal Pop A

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31 OBJECTIVES: To evaluate longer-term safety and efficacy of a single self-expanding stent up to 20 cm in length in patients with atherosclerotic disease of the superficial femoral (SFA) and proximal popliteal arteries. METHODS: 287 patients (mean age 68 years, 66% male) were treated with the EverFlex Self-Expanding Peripheral Stent System. Patients were followed through 3 years with yearly core lab adjudicated duplex ultrasonography for patency, radiographic assessment of stent fractures, and resting ankle brachial indices. RESULTS: Overall freedom from loss of primary patency at 3 years was 60.0%. Patency was significantly higher for lesions 8 cm compared with lesions >8 cm (71.0 vs. 50.5%, P < ). There was no significant difference in patency between single-stent and multistent recipients (60.4 vs. 52.4%, P = 0.343). The three-year freedom from clinically driven target lesion revascularization was 70.0%. At 3 years, the overall stent fracture rate was 0.9%. CONCLUSIONS: DURABILITY II is the first investigational device exemption trial to report 3- year duplex Doppler defined stent patency and CD-TLR outcomes in long SFA and proximal popliteal lesions and demonstrated acceptable stent patency and freedom from CD-TLR with a low fracture rate. These data suggest that use of a single long stent provides reasonable long-term outcomes when intervention is required for symptomatic SFA and proximal popliteal arterial disease

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37 6 closed-end interwoven nitinol wires

38 The Supera Vascular Mimetic Implant: Mimics the natural structure and movement of the anatomy Maintains a visibly round, open lumen for normal, healthy blood flow in challenging anatomy

39 Provides the highest levels of both strength and flexibility for a durable solution Provides the strength needed to treat highly calcified lesions with the lowest chronic outward force 4x the compression resistance 86% primary patency at 1 year in the SUPERB trial

40 METHODS AND RESULTS: 527 limbs in 470 patients with femoropopliteal arterial disease were treated with SUPERA stents. The primary patency (PP) rates were 83.3% after 12 months and 72.8% at two years. The secondary patency rates were 98.1% after 12 months and 92.0% at two years. Patency rates did not differ between superficial femoral artery (SFA) and popliteal lesions. Between baseline and a mean of 21 months of follow-up, mean ABI increased from 0.53 to 0.91, and mean RBC decreased from 3.0 to 1.9 (p<0.001 for both comparisons). Radiographs performed on 229 patients at a mean of 16.6 months confirmed the absence of stent fractures in all patients. CONCLUSIONS: Over a two-year surveillance period, the patency rate and fracture resistance of SUPERA stents implanted for complex femoropopliteal artery disease were high.

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43 Ansel GM. J Endovasc Ther. 2009;16(Suppl II):II82 II97

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45 Sirolimus-eluting stents (SMART stents) Paclitaxel-eluting non polymer-based stent (Zilver PTX) Self-expanding polymerbased everolimus-eluting stent (Dynalink-E)

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