A Study of Below The Knee Arteries' Stenosis or Occlusion Treated With LEGFLOW OTW

To evaluate the safety and efficacy of the Paclitaxel Releasing Peripheral Balloon Dilatation Catheter (LEGFLOW) compared to the PTA catheter (AMPHIRION DEEP) in treatment of stenosis or occlusion in below the knee artery.

To evaluate the safety and efficacy of the Paclitaxel Releasing Peripheral Balloon Dilatation Catheter (LEGFLOW) compared to the PTA catheter (AMPHIRION DEEP) in treatment of stenosis or occlusion inbelow the knee artery.

This is a prospective, multi-center, randomized, control, opening, superiority designed clinical study. Plan to enroll 172 eligible subjects in 15 centers in China, all these subjects will be randomized 1:1 to the study group (LEGFLOW OTW group, n=86) and control group (AMPHIRION DEEP group, n=86), and accept the treatment of LEGFLOW OTW and AMPHIRION DEEP respectively.

Eligibility Criteria:
Inclusion Criteria:

* age from 18 to 85 years (include 18 and 85 year);
* critical limb ischemia subjects (Rutherford classification from 3 to 6)
* expective survival more than 1 year;
* can understand the study objective, self willing enrolls and sign the informed consent, and accept scheduled followed up at the specific time.

Angiographic inclusive criteria:

* reference vessel diameter 2.0-3.5mm;
* stenosis or occlusion in arterial vasculature below the knee shall have distal outflow;
* target lesion stenosis ≥70% or occlusion, length ≤270mm;
* if subject has ipsilateral / contralateral iliac lesions, the iliac lesion shall meet all the following criteria:

  * iliac lesion or occlusion length ≤100mm and
  * shall be treated earlier than the target lesion and
  * shall be treated successfully. the successful treatment standard: 1) residual stenosis \<30%; 2) without flow limiting dissection 3) without thrombosis, embolism or any other serious adverse events

Exclusion Criteria:

* subjects currently participate in other drugs or medical devices clinical study and have not reach the primary endpoint;
* childbearing aged women whose pregnancy test before intervention operation is not negative, and lactating mothers;
* subjects with renal function insufficiency (serum creatinine\> 2.5mg / dL or in renal dialysis);
* subjects have known be allergy or contraindication to the contrast agent, paclitaxel, heparin, antiplatelet, anticoagulant or thrombolytic agents;
* subjects plan to a major amputation (over metatarsal level);
* stroke subjects within 3 months or stroke subjects with severe hemiplegia and aphasia associated sequelaes over 3 months before the intervention operation;
* subjects with acute myocardial infarction, thrombolytic therapy or angina within 30 days before the intervention operation;
* subjects whose target lesion limb have gangrene (the gangrene range over the metatarsophalangeal joint);
* target lesion is a stenosis or occlusion that have prior been treated by scaffold implantation, DEB, ordinary balloon catheter or bypass graft;
* lesions and /or occlusion locate or extend to popliteal artery or below ankle joint;
* subjects requiring be intervention in bilateral lower limb;
* the stenosis lesion of ipsilateral femoral artery or ipsilateral popliteal artery have a diameter stenosis ≥50% untreated before the intervention operation;
* ipsilateral femoral artery or ipsilateral popliteal artery has single or adjacent lesion length ≥15cm, or ipsilateral femoral artery or ipsilateral popliteal artery has multiple lesion and one of these multiple lesion length ≥10cm or occlusion;
* - adjacent lesion: 1) interval no more than 30 mm, 2) can be treated as a single lesion;
* - multiple lesion: 1) interval no more than 30 mm, 2) need to be treated as multiple lesion;
* the residual stenosis still ≥30%, even when the length \<15cm and stenosis ≥50% single or adjacent lesion in ipsilateral femoral artery or ipsilateral popliteal artery has been treated, or when each lesion length \<10cm and stenosis ≥50% multiple lesion in ipsilateral femoral artery or ipsilateral popliteal artery has been treated;
* DES and /or DEB has been used in the inflow vessel of lesions treatment;
* subject has no patency vessel below the ankle artery before the intervention operation;
* target vessel aneurysm;
* acute or subacute thrombosis in target vessel;
* angiography shows severe calcification in the target lesion (before contrast injection or digital subtraction angiography, intensive annular calcifications that make target lesion not expansion and / or a calcification within the target lesion and locate on either sides of the vessel wall whose continuous length over than 5cm);
* lesions that the guild wire cannot pass through;
* subjects need be treated by thrombus endarterectomy, percutaneous transluminal plaque circumcision or laser treatment device indicate by intraoperative angiography;