Table 5

Short- and Long-Term Surrogate Endpoints for Procedural Success Using Imaging and Physiologic Measures

Time Point of Evaluation
Measurement TechniqueSubacute
(72 h to 30 days)
3 Months6 Months12 MonthsRef. #
Intermittent Claudication
ABI (or TBI) at restIncrease in resting ABI or TBI ≥0.10 from pre-procedure valueResting ABI or TBI ≥0.10 from pre-procedure valueResting ABI or TBI ≥0.10 from pre-procedure valueResting ABI or TBI ≥0.10 from pre-procedure value(7,29)
Failure in follow up defined as reduction in ABI or TBI by 0.10 or return to pre-procedure value(29)
Duplex ultrasound≤50% diameter stenosis as defined by peak systolic velocity index (ratio of intrastenotic peak systolic velocity to pre-stenotic velocity) <2.4≤50% diameter stenosis as defined by peak systolic velocity index (ratio of intrastenotic peak systolic velocity to pre-stenotic velocity) <2.4≤50% diameter stenosis as defined by peak systolic velocity index (ratio of intrastenotic peak systolic velocity to pre-stenotic velocity) <2.4≤50% diameter stenosis as defined by peak systolic velocity index (ratio of intrastenotic peak systolic velocity to pre-stenotic velocity) <2.4(7)
CT/CMR/invasive angiography≤50% diameter stenosis or ≤70% area stenosis≤50% diameter stenosis or ≤70% area stenosis≤50% diameter stenosis or ≤70% area stenosis≤50% diameter stenosis or ≤70% area stenosis(1,7)
Critical Limb Ischemia
Ankle (or toe) pressure§>70 mm Hg (Rutherford 4)
>50 mm Hg (Rutherford 5–6)
>70 mm Hg (Rutherford 4)
>50 mm Hg (Rutherford 5–6)
>70 mm Hg (Rutherford 4)
>50 mm Hg (Rutherford 5–6)
>70 mm Hg (Rutherford 4)
>50 mm Hg (Rutherford 5–6)
(7,24)
Duplex ultrasound≤50% diameter stenosis as defined by peak systolic velocity index (ratio of intrastenotic peak systolic velocity to pre-stenotic velocity) <2.4≤50% diameter stenosis as defined by peak systolic velocity index (ratio of intrastenotic peak systolic velocity to pre-stenotic velocity) <2.4≤50% diameter stenosis as defined by peak systolic velocity index (ratio of intrastenotic peak systolic velocity to pre-stenotic velocity) <2.4≤50% diameter stenosis as defined by peak systolic velocity index (ratio of intrastenotic peak systolic velocity to pre-stenotic velocity) <2.4(7)
CT/MRI/invasive angiography≤50% diameter stenosis or ≤70% area stenosis≤50% diameter stenosis or ≤70% area stenosis≤50% diameter stenosis or ≤70% area stenosis≤50% diameter stenosis or ≤70% area stenosis(1,7)

ABI = ankle brachial index; CT = computed tomography; CMR = cardiac magnetic resonance; TBI = toe-brachial index; other abbreviations as in Table 2.

  • Patients with ABI ≥1.4 are considered noncompressible and should not be included in analyses of improvements in ABI.

  • The PARC group felt that the Duplex ultrasound is difficult to reliably obtain in infrageniculate vessels, and patients with CLI may benefit from evaluation of presence or absence of total occlusion of below knee vessels.

  • Toe pressure and toe-brachial index should be used only in the event of noncompressible vessels.

  • § Ankle (or toe) pressure used instead of ratio for CLI patients as a guide for a threshold level to maintain adequate perfusion, applies to patients treated with either endovascular and surgical therapy.

  • The PARC group did not define hemodynamic failure in follow-up, as the shorter-term goals of wound healing may have been achieved. The PARC group suggests these time points for evaluation but recommend that analyses and reports include the entire pre-specified reporting window to ensure all possible data and relevant findings are captured.