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    Interventional procedure overview of intravascular lithotripsy for calcified arteries in peripheral arterial disease

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    Outcome measures

    The main efficacy outcomes include technical or procedural success, reduction in stenosis, residual stenosis after the procedure, stent placement, target lesion revascularisation and ankle brachial index (ABI). The main safety outcomes are dissection, perforation, embolisation and amputation. The measures used are detailed in the following paragraphs.

    The Rutherford classification system is widely used to categorise chronic limb ischaemia:

    • 0: asymptomatic

    • 1: mild claudication

    • 2: moderate claudication

    • 3: severe claudication

    • 4: ischaemic rest pain

    • 5: minor tissue loss

    • 6: ulceration or gangrene

    PAD can be diagnosed using the ABI, which is the systolic pressure at the ankle divided by the systolic pressure at the arm. Normal ABI ranges from 1.0 to 1.4. A value below 0.9 is considered diagnostic of PAD and values less than 0.5 suggest severe PAD.

    The presence and grading of lesion calcification can be assessed using the peripheral artery calcification scoring system (PACSS), which has the following criteria:

    • Grade 0: no visible calcium at the target lesion site

    • Grade 1: unilateral calcification less than 5 cm

    • Grade 2: unilateral calcification 5 cm or more

    • Grade 3: bilateral calcification less than 5 cm

    • Grade 4: bilateral calcification 5 cm or more

    The Peripheral Academic Research Consortium (PARC), together with the US Food and Drug Administration and the Japanese Pharmaceuticals and Medical Devices Agency, has developed a series of pragmatic consensus definitions for people having treatment for PAD that affects the lower extremities. It includes the following definitions for peripheral artery stenosis:

    • Mild: less than 50%

    • Moderate: 50% to 69%

    • Severe: 70% to 99%

    • Occluded: 100%

    The following definitions are used for the degree of calcification:

    • Focal: less than 180° (1 side of vessel) and less than one-half of the total lesion length

    • Mild: less than 180° and greater than one-half of the total lesion length

    • Moderate: 180° or more (both sides of vessel at same location) and less than one-half of the total lesion length

    • Severe: more than 180° (both sides of the vessel at the same location) and greater than one-half of the total lesion length