To assess the continued safety, effectiveness, and optimal clinical use of the Shockwave Medical Peripheral IVL System for the treatment of calcified, stenotic BTK arteries.

Post-market, prospective , multi-center, single-arm study.

Inclusion Criteria:

- General Inclusion Criteria

1. Age of subject is ≥ 18.

2. Subject is able and willing to comply with all assessments in the study.

3. Subject or subject's legal representative has been informed of the nature of the study, agrees to participate, and has signed the approved consent form.

4. Critical limb ischemia (CLI) in the target limb from the distal segment (P3) of the popliteal artery to the ankle joint prior to the study procedure with Rutherford Category 4-5; or Rutherford 3 in the target limb from the distal segment (P3) of the popliteal artery to the ankle joint prior to the study procedure.

5. Estimated life expectancy >1 year.

   • Angiographic Inclusion Criteria

6. Up to 2 below-the-knee target lesion(s) in native vessels in one or both limbs.

7. Target lesion reference vessel diameter (RVD) between 2.0 mm and 4.0 mm by investigator visual estimate.

8. Target lesion with ≥70% stenosis by investigator visual estimate.

9. Target lesion length is ≤200 mm by investigator visual estimate. Target lesion can be all or part of the 200 mm treated zone.

10. Distal reconstitution of at least one pedal vessel (<50% stenosis) (desert foot excluded).

11. Evidence of at least moderate calcification at the target lesion site by angiography/IVUS OR non-dilatable lesion indicating presence of calcium. Must meet one of the following:

    1. Angiography requires fluoroscopic evidence of calcification on parallel sides of the vessel and extending > 50% the length of the lesion.
    2. IVUS requires presence of ≥270 degrees of calcium over the course of at least 10mm.
    3. Non-dilatable lesion requires attempted treatment with PTA during the index procedure with residual stenosis > 50% and no serious angiographic complications.

Exclusion Criteria:

- General Exclusion Criteria

1. Rutherford Category 0, 1, 2 or 6 (target limb).

2. Osteomyelitis or deep soft tissue infection extending proximal from the metatarsals that cannot be treated with an individual toe ray amputation or transmetatarsal amputation (TMA) .

3. History of endovascular or surgical procedure on the target limb within the last 30 days, or planned within 30 days of the index procedure.

4. Subject in whom antiplatelet or anticoagulant therapy is contraindicated.

5. Subject has known allergy to contrast agents or medications used to perform endovascular intervention that cannot be adequately pre-treated.

6. Subject has known allergy to urethane, nylon, or silicone.

7. Myocardial infarction within 30 days prior to enrollment.

8. History of stroke within 60 days prior to enrollment.

9. Subject has acute or chronic renal disease with eGFR <30 ml/min/1.73 m2 (using CKD-EPI formula), unless on renal replacement therapy.

10. Subject is pregnant or nursing.

11. Subject is participating in another research study involving an investigational agent (pharmaceutical, biologic, or medical device) that has not reached the primary endpoint.

12. Subject has other medical, social or psychological problems that, in the opinion of the investigator, preclude them from receiving this treatment, and the procedures and evaluations pre- and post-treatment.

13. Covid-19 diagnosis within 90 days.

14. The planned use of cutting/scoring balloons, re-entry or atherectomy devices in target lesions during the index procedure.

15. Planned major amputation (of either leg).

16. Acute limb ischemia.

17. Occlusion of all the inframalleolar outflow arteries/vessels (i.e., desert foot).

18. Subject has an anticipated life span of less than one (1) year.

19. Subject already enrolled into this study.

    • Angiographic Exclusion Criteria

20. Failure to treat clinically significant inflow lesions in the ipsilateral iliac, femoral, or popliteal arteries with ≤30% residual stenosis, and no serious angiographic complications (e.g., embolism).

21. Failure to successfully treat significant non-target infra-popliteal lesions prior to treatment of target lesion(s). Successful treatment is defined as obtaining ≤50% residual stenosis with no serious angiographic complications (e.g., embolism ).

22. Failed PTA in target lesion during index procedure with angiographic evidence of serious angiographic complications .

23. Target lesion includes in-stent restenosis.

24. Evidence of aneurysm or thrombus in target vessel.

25. No calcium or mild calcium in the target lesion.

26. Target lesion within native or synthetic vessel grafts.

27. Failure to successfully cross the guidewire across the target lesion; successful crossing defined as tip of the guidewire distal to the target lesion in the absence of flow limiting dissections or perforations.