Pedal Acceleration Time (PAT): A Novel Predictor of Limb Salvage

  • Author Footnotes
    a Presented at the 44th Annual Winter Meeting. January 30-February 2, 2020. Vascular and Endovascular Surgery Society. Steamboat Springs, Colorado.
    Desarom Teso
    Correspondence
    Correspondence to: Desarom Teso, MD, PeaceHealth Southwest Medical Center, 505 NE 87th Avenue. Bld B, Suite 301, Vancouver, WA, 98664.
    Footnotes
    a Presented at the 44th Annual Winter Meeting. January 30-February 2, 2020. Vascular and Endovascular Surgery Society. Steamboat Springs, Colorado.
    Affiliations
    PeaceHealth Southwest Medical Center, Vancouver, WA

    Elson S. Floyd College of Medicine, Washington State University, Pullman, WA
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  • Jill Sommerset
    Affiliations
    PeaceHealth Southwest Medical Center, Vancouver, WA

    Elson S. Floyd College of Medicine, Washington State University, Pullman, WA
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  • Matthew Dally
    Affiliations
    Oregon Health and Sciences University, Portland, OR
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  • Beejay Feliciano
    Affiliations
    PeaceHealth Southwest Medical Center, Vancouver, WA

    Elson S. Floyd College of Medicine, Washington State University, Pullman, WA
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  • Yolanda Vea
    Affiliations
    PeaceHealth Southwest Medical Center, Vancouver, WA

    Elson S. Floyd College of Medicine, Washington State University, Pullman, WA
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  • Riyad Karmy Jones
    Affiliations
    PeaceHealth Southwest Medical Center, Vancouver, WA

    Elson S. Floyd College of Medicine, Washington State University, Pullman, WA
    Search for articles by this author
  • Author Footnotes
    a Presented at the 44th Annual Winter Meeting. January 30-February 2, 2020. Vascular and Endovascular Surgery Society. Steamboat Springs, Colorado.
Open AccessPublished:April 02, 2021DOI:https://doi.org/10.1016/j.avsg.2021.02.038

      Background

      In the setting of Peripheral Arterial Disease (PAD), pedal arch interrogation by ultrasound has not been well described. Patients with noncompressible vessels and/or open wounds of the foot may preclude the use of ankle-brachial indices, toe pressure measurements, or TcPO2, respectively. We propose that pedal artery interrogations with Pedal Acceleration Time (PAT) can be a predictor for limb salvage in patients with Chronic Limb-Threatening Ischemia (CLTI).

      Methods

      A retrospective review of a prospectively kept database was performed from 2018 to 2019. Patients with pending amputation due to severe infection (WIFI infection class 2 and 3) were excluded from the study. We identified 73 limbs with CLTI that fit the inclusion criteria. Data included WIFI classification, age, gender, cardiovascular risk factors, PAT, ABI, and TBI when reliable, were collected. PAT measurements were categorized into 4 classifications; 1 (40–120 msec), 2 (121–180 msec), 3 (181–224 msec), and 4 (Greater than 225 msec). Statistical analyses were performed.

      Results

      Seventy-three limbs with CLTI were included in our study. All patients underwent arterial revascularization with either percutaneous technique or arterial bypass. Limb salvage was achieved in 59 (81%) of the 73 limbs. All 59 limbs had a 2-classification improvement in their PAT following interventions. A total of 14 (19%) limbs without improvement in their PAT underwent above ankle level amputations. An improvement in PAT classes to class 1 or 2 is associated with limb salvage.

      Conclusions

      Patients with noncompressible ankle pressures or nonobtainable toe pressures poses a challenge in the complete assessment of WIFI classification. Our group has shown that PAT can be used in the scoring system for severity of ischemia in conjunction with current WIFI classification. Our data suggests that limb salvage correlates with post procedure PAT in category 1 and 2. Therefore we propose that PAT be added as part of the WIFI classification.

      Introduction

      Noninvasive arterial studies are a mainstay of any vascular practice for patients with chronic limb-threatening ischemia (CLTI). However, current noninvasive arterial testing such as ankle-brachial indices (ABI), absolute toe pressures (TSP), and TCPO2 may not be reliable in patients with calcific tibial disease and/or extensive tissue loss.
      • Tehan PE
      • Santos D
      • Chuter V.
      A systematic review of the sensitivity and specificity of the toe-brachial index for detecting peripheral artery disease.
      ,
      • Tehan PE
      • Bray A
      • Chuter VH.
      Non-invasive vascular assessment in the foot with diabetes: sensitivity and specificity of the ankle-brachial index, toe brachial index and continuous wave Doppler for detecting peripheral arterial disease.
      Acceleration time has been utilized extensively in the evaluation of arterial occlusive disease.
      • Burdick L
      • Airoldi F
      • Marana I
      • et al.
      Superiority of acceleration and acceleration time over pulsatility and resistance indices as screening tests for renal artery stenosis.
      Recent in-vitro study revealed that systolic acceleration is superior in predicting diameter reduction and flow compared to use of velocity alone.
      • Brouwers J
      • van Doorn LP
      • van Wissen RC
      • et al.
      Using maximum systolic acceleration to diagnose and assess the severity of peripheral artery disease in a flow model study.
      Pedal Acceleration Time (PAT) has been correlated to ankle-brachial indices in symptomatic and nonsymptomatic patients with compressible tibial vessels.
      • Sommerset J
      • Karmy-Jones R
      • Dally M
      • et al.
      Plantar acceleration time: a novel technique to evaluate arterial flow to the foot.
      PAT is direct duplex imaging of the pedal vessels which can provides real time physiologic information on pedal flow hemodynamics.
      • Sommerset J
      • Teso D
      • Karmy-Jones R
      • et al.
      Pedal flow hemodynamics in patients with chronic limb-threatening ischemia.
      This technique can be performed using standard arterial duplex imaging available in most vascular laboratories. While the absolute value of PAT is important, PAT can be categorized into four classes: Class 1 (20–120ms), Class 2 (121–180 ms), Class 3 (181–224 ms), and Class4 (Greater than 225 ms). In addition, the specific angiosomic distribution of the entire foot can be elucidated
      • Sommerset J
      • Karmy-Jones R
      • Dally M
      • et al.
      Plantar acceleration time: a novel technique to evaluate arterial flow to the foot.
      • Sommerset J
      • Teso D
      • Karmy-Jones R
      • et al.
      Pedal flow hemodynamics in patients with chronic limb-threatening ischemia.
      We propose that PAT in diabetic patients with Chronic Limb-Threatening Ischemia (CLTI) are comparable to other physiologic testing and are a good predictor of limb salvage.

      Methods

      We performed a retrospective review of a prospectively kept database in a single institution between January 1, 2018 and 31 December, 2019. Patient selection criteria include those with only infra-inguinal disease, who underwent arterial intervention, and who has had a PAT performed pre- and postprocedure. All patients had noncompressible ankle brachial indices. Patients with significant infection (WiFi class 2 and 3) were excluded due to urgent need for source control.
      We use the Global Vascular Guidelines on the Management of Chronic limb-threatening ischemia to define CLTI as “…. the presence of peripheral arterial occlusive disease in combination with rest pain, gangrene, or a lower limb ulceration of greater than 2 weeks duration”.
      • Conte MS
      • Bradbury AW
      • Kolh P
      • et al.
      Global vascular guidelines on the management of chronic limb-threatening ischemia.
      Comorbid conditions were identified. Coronary artery disease (CAD) was defined as patients with a history of coronary intervention. Congestive heart failure (CHF) was defined as patients who historically had been managed for heart failure. Hypertension (HTN) was defined as patients being managed with anti-hypertensive medication. End-stage renal disease (ESRD) was defined as patients on dialysis. Diabetes was defined as patients with type 1 or 2 diabetes, on medication. Infection grade 0 and 1 were included as defined by WIFI classification.
      • sr Mills JL
      • MS Conte
      • Armstrong DG
      • et al.
      The Society for Vascular Surgery lower extremity threatening limb classification system: risk stratification based on wound, ischemia, and foot infection (WIFI).
      Pedal Acceleration Time measurement was previously described.
      • Sommerset J
      • Karmy-Jones R
      • Dally M
      • et al.
      Plantar acceleration time: a novel technique to evaluate arterial flow to the foot.
      Briefly, Duplex imaging of the Pedal Arteries was performed using a Philips Epic 5 duplex ultrasound system (Philips Healthcare, Andover, MA). A linear array transducer with pulsed-doppler frequencies between 3 and 12 MHz was used to measure Pedal Acceleration Time.
      • Sommerset J
      • Karmy-Jones R
      • Dally M
      • et al.
      Plantar acceleration time: a novel technique to evaluate arterial flow to the foot.
      The anterior circulation was evaluated using the Arcuate Artery and First Dorsal Metatarsal Artery whereas the Posterior Circulation was evaluated using the Medial, Lateral, and Deep Plantar Arteries. Special attention was paid to evaluate visualized vessels leading to the wound bed. The Acceleration Time was measured in time over slope from the onset of systole to the peak of systole (Fig. 1, Table I).
      Fig. 1
      Fig. 1Measuring technique of normal pedal acceleration time.
      Table IPedal acceleration time criteria
      No ischemia Class 1Mild ischemia Class 2Moderate ischemia Class 3Severe ischemia Class 4
      Clinical symptomsAsymptomaticGreater than 2 block claudicationLess than 2 block claudicationCLTI Tissue Loss; Rest Pain
      PAT20 – 120 msec121 – 180 msec181 – 224 msecGreater than 225 msec
      ABI1.3 – 0.900.89 – 0.690.68 – 0.500.49 – 0.00
      Post-PAT was measured 1-week post intervention. Primary outcome measured was limb loss higher than the ankle. Each limb was considered individually.
      The study was approved by the Institutional Review Board. Statistical analyses were performed using linear regression and ANOVA testing using Microsoft Excel database (version 2016; Microsoft Corp, Redmond, Washington). Univariate analysis and Multivariate regression analysis were performed using SPSS statistical software (version 2020. Armonk, New York). Interventions included surgical bypass and catheter-based interventions.

      Results

      A total of 72 patients formed the study group, with follow up 12.8 ± 3.6 months. One patient underwent staged bilateral interventions resulting in 73 limbs for analysis. By univariate analysis, the Limb Salvage group had significantly lower incidence of infection, lower incidence of ESRD and significantly better postprocedure PAT (Tables II and III).
      Table IIDemographics.
      Limb salvage (N = 59)Limb loss (N = 14)P-value
      Age (years)73.1 ± 7.875.3 ± 8.90.352
      Male26 (44%)3(21%)0.12
      Smoker27 (48%)9 (64%)0.213
      HTN53 (90%)14 (100%)0.213
      CAD32 (54%)10 (71%)0.242
      CHF6 (10%)00.213
      ESRD14 (24%)12 (86%)P = 0.001
      Diabetes56 (95%)14 (100%)0.389
      Infection6 (10%)9 (64%)P = 0.001
      Direct revascularization379ns
      Indirect revascularization225ns
      Smoker, active smoker; NTN, hypertension; CAD, coronary artery disease; CHF, congestive heart failure; ESRD, on dialysis.
      Table IIIPre- and post-PAT
      (mSec)Overall 73Limb salvage 59Amputation 14P-value
      PAT preprocedure224 +/- 25240 +/- 23244 +/- 300.54
      PAT Postprocedure144 +/- 49122 +/- 30213 +/- 47< 0.00001
      PAT change103 +/- 25117 +/- 3430 +/- 30< 0.00001
      P = 0.P = 0.P = 0.Table IIIdata on table III not included in this final version) All patients underwent revascularization with 80% underwent an endovascular intervention. 20% underwent open revascularization. There were no statically significant major amputations between the 2 groups.
      Revascularization with antegrade flow to the wound bed was consider direct, while retrograde flow in the angiosomic wound bed was considered indirect revascularization.
      • Sommerset J
      • Teso D
      • Karmy-Jones R
      • et al.
      Pedal flow hemodynamics in patients with chronic limb-threatening ischemia.
      Of the 14 patients who underwent amputation, 5 had indirect revascularization and 9 had direct revascularization. This was not statically significant.

      Discussion

      It has been recognized that patients with noncompressible ankle pressures or nonobtainable TCPO2 and toe pressures cannot provide accurate information on the severity of ischemia in the WIFI scoring system.
      • Hoyer C
      • Sandermann J
      • Petersen LJ.
      The toe-brachial index in the diagnosis of peripheral arterial disease.
      Ankle-brachial indices and toe-brachial indices have low specificity in predicting arterial occlusive disease in diabetic patients.
      • Tehan PE
      • Santos D
      • Chuter V.
      A systematic review of the sensitivity and specificity of the toe-brachial index for detecting peripheral artery disease.
      This can be attributed to medial wall calcifications and arterial stiffness. TCPO2 has been suggested as the next best test to predict wound healing. However, in patients with extensive foot wound and/or edema, direct measurement of TCPO2 can be difficult to obtain and provide false readings.
      • Tehan PE
      • Bray A
      • Chuter VH.
      Non-invasive vascular assessment in the foot with diabetes: sensitivity and specificity of the ankle-brachial index, toe brachial index and continuous wave Doppler for detecting peripheral arterial disease.
      Indocyanine green angiography (ICGA) is also being used to help determine perfusion, but is invasive, results can be subjective, and costly and not readily portable.
      • Igari K
      • Kudo T
      • Uchiyama H
      • et al.
      Indocyanine green angiography for the diagnosis of peripheral arterial disease with isolated infrapopliteal lesions.
      Our previous study revealed that PAT is highly correlative with ankle-brachial indices in evaluating patients with compressible vessels. PAT can be performed in the office setting, operative theater, angiographic suits, and in-patient wards. Pedal artery duplex imaging can be easily performed with appropriate additional training and technique validation. Based on our experience, the learning curve for training is roughly 20 studies.
      • Sommerset J
      • Karmy-Jones R
      • Dally M
      • et al.
      Plantar acceleration time: a novel technique to evaluate arterial flow to the foot.
      Based on our data, a change in PAT from class 4 to class 2 is an independent predictor for limb salvage. As with previous studies, patients with end-stage-renal disease and infection are also at high risk for amputation.
      • Meyer A
      • Lang W
      • Borowski M
      • et al.
      In-hospital outcomes in patient with critical limb ischemia and end-stage renal disease after revascularization.
      Our study showed that there were no significant differences in limb salvage when comparing open versus endovascular revascularization in the early postoperative period. This is contrary to recent data suggesting that endovascular interventions in the infrageniculate vascular bed are associated with worst outcome.
      • Yuo TH
      • Wallace JR
      • Fish L
      • et al.
      Editor's Choice-Comparison of Outcomes after open surgical and endovascular lower extremity revascularization among end stage renal disease patients on dialysis.
      We believe that this short-term success is due to direct interrogation of the wound bed in question with Pedal Acceleration Time so allow for adequate monitoring of wound healing process.Table III.. We elected not to include WIFI infection class 3 and 4, secondary to immediate need for source control.
      Further evaluation of those patients that underwent higher level amputations following revascularization can be attributed to 3 bypass thromboses 12–18 months following the procedure, 11 catheter base interventions underwent higher level amputations 9–12 months following index procedure. Our limb salvage rate is similar to other published reports.
      • Ricco JB
      • Gargiulo M
      • Stella A
      • et al.
      Impact of angiosome-and non-angiosome-targeted peroneal bypass on limb salvage and healing in patients with chronic limb-threatening ischemia.
      The failure to achieve limb salvage was attributed to poor runoff, incomplete pedal arch, and/or severe pedal vessel occlusive disease.
      Although acceleration time in the evaluation of lower extremity arterial occlusive disease is not widely used, our institution has been performing Pedal Acceleration Time on all patients with arterial occlusive disease and found it to be an important additional predictor of limb salvage. As an example, Fig. 2, Fig. 3, Fig. 4 illustrates the utility of Pedal Acceleration Time in the evaluation and treatment of a complex wound patient.
      Fig. 2
      Fig. 2Non healing amputation with abnormal retrograde pedal acceleration time. Confirmatory angiogram.
      Fig. 3
      Fig. 3Angiographic findings of 2 vessel runoff with normal retrograde Pedal Acceleration Time indicative of indirect revascularization.
      Fig. 4
      Fig. 4Complete wound healing with Class 1 pedal acceleration time. Indirect revascularization via retrograde flow in the arcuate artery and antegrade flow in the dorsal metatarsal artery.
      The weaknesses of this study included data obtained retrospectively from a single institution. There may be selection bias given study was performed only on patients with infrainguinal arterial occlusive diseases.

      Conclusion

      Pedal acceleration time can be added to a vascular practice for evaluation and treatment of patients with chronic limb threatening ischemia. Our study showed that limb salvage is associated with a pedal acceleration time of less than 180 milliseconds regardless of direct or indirect flow to the wound bed. As such, we recommend that PAT be added to the WIFI classification in the evaluation of ischemic limbs.

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