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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.
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.
Pedal Acceleration Time (PAT) has been correlated to ankle-brachial indices in symptomatic and nonsymptomatic patients with compressible tibial vessels.
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
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”.
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.
The Society for Vascular Surgery lower extremity threatening limb classification system: risk stratification based on wound, ischemia, and foot infection (WIFI).
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.
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. 1Measuring technique of normal pedal acceleration time.
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 ± 7.8
75.3 ± 8.9
0.352
Male
26 (44%)
3(21%)
0.12
Smoker
27 (48%)
9 (64%)
0.213
HTN
53 (90%)
14 (100%)
0.213
CAD
32 (54%)
10 (71%)
0.242
CHF
6 (10%)
0
0.213
ESRD
14 (24%)
12 (86%)
P = 0.001
Diabetes
56 (95%)
14 (100%)
0.389
Infection
6 (10%)
9 (64%)
P = 0.001
Direct revascularization
37
9
ns
Indirect revascularization
22
5
ns
Smoker, active smoker; NTN, hypertension; CAD, coronary artery disease; CHF, congestive heart failure; ESRD, on dialysis.
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.
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.
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.
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.
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.
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.
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.
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.
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. 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.
Reference
Tehan PE
Santos D
Chuter V.
A systematic review of the sensitivity and specificity of the toe-brachial index for detecting peripheral artery disease.
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.
The Society for Vascular Surgery lower extremity threatening limb classification system: risk stratification based on wound, ischemia, and foot infection (WIFI).
Editor's Choice-Comparison of Outcomes after open surgical and endovascular lower extremity revascularization among end stage renal disease patients on dialysis.
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