Infrapopliteal Angioplasty of One or More than One Artery for Critical Limb Ischaemia: A Randomised Clinical Trial

Popliteal-to-Distal Extreme Bypass in Endovascular Era

BACKGROUND

Chronic limb-threatening ischemia (CLTI) is characterized by rest pain and tissue loss, with an annual mortality rate of 20% and amputation rate of 40%, if not treated. Open bypass surgery is recommended in CLTI, depending on the availability of good quality venous material, outflow artery patency, and surgical expertise. The aim of the study is to analyze primary patency, limb salvage, and survival rate in patients undergoing popliteal-to-distal bypass.

METHODS

All consecutive patients who underwent popliteal-to-distal bypass surgery between January 2016 and December 2021 were enrolled in the study. Primary outcomes were primary patency, limb salvage, and overall survival. Secondary outcomes included amputation-free survival and secondary patency.

RESULTS

Forty-nine patients were included during the study. Technical success was achieved in 100% of cases. Target outflow artery was in 27% (n. 13) of cases the anterior tibial artery, in 27% (n. 13) the dorsalis pedis, in 2% (n. 1) the peroneal artery, in 30% (n. 15) the retromalleolar tibial artery, in 10% (n. 5) the medial plantar artery, and in 4% (n. 2) the tarsal artery. Two-year primary patency was 85% ± 5. Secondary patency rates were 86% ± 3 at 2 years. The overall survival was 81% ± 6 at 2 years, the amputation-free survival was 70% ± 9, and the limb salvage rate was 81% ± 6.

CONCLUSIONS

Popliteal-to-distal bypass requires high technical expertise to be performed. When a good autologous vein and adequate outflow artery are present, they can be feasible with good patency rates and overall survival.

Drug-Coated Balloon Angioplasty of Infrapopliteal Lesions in Chronic Limb-Threatening Ischemia: Six-month Outcomes of PRIME-WIFI

PURPOSE

To evaluate 6-month outcomes of drug-coated balloon (DCB) angioplasty of infrapopliteal lesions in patients with chronic limb-threatening ischemia (CLTI).

METHODS

We analyzed 6-month follow-up data from the 10-center PRIME-WIFI prospective registry on 300 consecutive patients (33.000% female) with CLTI who underwent DCB angioplasty for infrapopliteal arterial lesions. The primary outcome was freedom from major adverse event (MAE), a composite of major amputation, all-cause death, and clinically-driven target limb reintervention (CD-TLR). Secondary outcomes included amputation-free survival (AFS), freedom from each primary outcome component, primary sustained clinical improvement, and quality of life (QOL) score. Independent risk factors of MAE were determined using Cox proportional hazards regression analysis.

RESULTS

A total of 409 infrapopliteal lesions in 312 limbs were treated with DCB, with 54.167% of the limbs being treated for isolated infrapopliteal lesions. By Kaplan-Meier analysis, at 6 months post- procedure (follow-up rate, 85.000%), freedom from MAE was 86.353%; AFS was 90.318%; and freedom from major amputation, all-cause death, and CD-TLR were 96.429%, 93.480%, and 95.079%, respectively. At 6-month follow-up, 83.590% of patients showed primary sustained clinical improvement, and QOL score (4.902±1.388) improved compared with that before procedure (2.327±1.109; p<0.001). Chronic renal insufficiency, chronic obstructive pulmonary disease, Rutherford grade, and postoperative infrapopliteal runoff score were independent risk factors for MAE within 6 months.

CONCLUSION

In CLTI, DCB angioplasty of infrapopliteal lesions yields acceptable early efficacy and safety.

CLINICAL IMPACT

This study evaluated the 6-month outcomes of DCB angioplasty in infrapopliteal lesions in CLTI patients by analyzing multicenter prospective data, showing that infrapopliteal DCB angioplasty can be performed with acceptable freedom from MAE rate, amputation-free survival rate, freedom from major amputation rate, survival rate, and freedom from CD-TLR rate. No patient experienced DCB-related intraoperative distal embolism. Chronic renal insufficiency, chronic obstructive pulmonary disease, Rutherford grade and postoperative infrapopliteal runoff score were independent risk factors for MAE within 6 months. Comparative real-world studies are needed.

Chronic Limb-Threatening Ischemia in Patients with Type 2 Diabetes: Revascularization Index as a Predictor for Primary Endovascular Intervention Outcome

Purpose

Chronic limb-threatening ischemia in patients with diabetes is associated with a high risk of adverse outcomes. The associated co-morbidities, the heterogeneity of foot presentation and the distribution of atherosclerotic lesions led to the emergence of multiple revascularization strategies and scoring systems to improve management outcomes. This study aimed to introduce a new index, the revascularization index (RI), and to assess its predictive value for the outcomes of primary endovascular intervention in patients with type 2 diabetes presenting with chronic limb-threatening ischemia.

Patients and Methods

A retrospective electronic medical records review was conducted for patients with type 2 diabetes presenting with chronic limb-threatening ischemia managed at King Abdullah University Hospital by primary endovascular interventions between January 2014 and August 2019. The RI was analyzed for its predictive value for the treatment outcomes.

Results

A total of 187 patients were included in this study, with a major lower limb amputation rate of 19.3%. The performance of the RI was excellent in predicting secondary revascularization (AUC = 0.80, 95% CI: 0.73-0.86, p-value < 0.001), good to predict major amputation (AUC = 0.76, 95% CI: 0.67-0.85, p-value = 0.047), and poor in predicting death (AUC = 0.46, 95% CI: 0.40-0.55, p-value = 0.398). RI of <1.21 was significantly associated with a higher risk of major lower limb amputation (HR = 5.8, 95% CI: 1.25-26.97, p-value < 0.025), and RI of < 1.3 was associated with a higher risk for secondary revascularization.

Conclusion

The RI can be used to predict major adverse lower limb events (MALE). It might be used as a guide for the extent of endovascular interventions for diabetic chronic limb-threatening ischemia with multi-level outflow atherosclerotic disease.

Poor inter-observer agreement in anatomical classifications of infrapopliteal arterial disease due to mandatory selection of only one target artery

BACKGROUND

Established anatomical classifications of infrapopliteal arterial lesion severity are based on assessment of only one target artery, not including all infrapopliteal arteries although multivessel revascularization is common.

PURPOSE

To investigate the reproducibility of one of these classifications and a new aggregated score.

MATERIAL AND METHODS

A total of 68 patients undergoing endovascular infrapopliteal revascularization at Sahlgrenska University Hospital during 2008-2016 were included. Preoperative magnetic resonance angiographies (MRA) and digital subtraction angiographies (DSA) were evaluated by three blinded observers in random order, using the infrapopliteal TransAtlantic Inter-Society Consensus (TASC) II classification. An aggregated score, the Infrapopliteal Total Atherosclerotic Burden (I-TAB) score, including all infrapopliteal arteries, was constructed and used for comparison.

RESULTS

Inter-observer agreement on lesion severity for each evaluated artery was good; Krippendorff's α for MRA 0.64-0.79 and DSA 0.66-0.84. Inter-observer agreement on TASC II grade, based on the selected target artery as stipulated, was poor; Krippendorff's α 0.14 (95% confidence interval [CI]=-0.05 to 0.30) for MRA and 0.48 (95% CI=0.33-0.61) for DSA. Inter-observer agreement for the new I-TAB score was good; Krippendorff's α 0.76 (95% CI=0.70-0.81) for MRA and 0.79 (95% CI=0.74-0.84) for DSA.

CONCLUSION

Reproducible assessment of infrapopliteal lesion severity can be achieved for separate arteries with both MRA and DSA using the TASC II definitions. However, poor inter-observer agreement in selecting the target artery results in low reproducibility of the overall infrapopliteal TASC II grade. An aggregated score, such as I-TAB, results in less variability and may provide a more robust evaluation tool of atherosclerotic disease severity.

Wound healing: potential therapeutic options

This review highlights the range of therapeutic options available to clinicians treating difficult-to-heal wounds. While certain treatments are established in daily clinical practice, most therapeutic interventions lack robust and rigorous data regarding their efficacy, which would help to determine when, and for whom, they should be used. The purpose of this review is to give a broad overview of the available interventions, with a brief summary of the evidence base for each intervention.

Technical Success and Mid-Term Outcomes of Endovascular Revascularization of Tibio-Peroneal Trunk Lesions

Tibio-peroneal trunk (TPT) lesions are usually categorized as ‘complex’ in anatomical classifications, which leads to the perception that endovascular therapy (EVT) will be challenging and the outcome most likely poor. This multicenter, retrospective cohort study investigates the efficacy of the EVT of TPT lesions in patients with chronic limb threatening ischemia (CLTI) or an infrapopliteal bypass at risk. The primary endpoint was limb-salvage. The secondary outcomes were technical success, freedom from clinically driven target lesion revascularization (CD-TLR), overall survival, and amputation-free survival. A total of 107 TPT lesions were treated in 101 patients. At 3 years, the limb-salvage rate was 76.4% (95% CI 66.0–86.8%). Technical success was achieved in 96.3% of cases. The freedom from CD-TLR, amputation-free survival, and overall survival at 3 years were 53.0% (95% CI 38.1–67.9%), 33.6% (95% CI 23.0–44.2%), and 47.7% (95% CI 36.1–59.3%), respectively. Reintervention significantly increased the hazard ratio for amputation by 7.65 (95% CI 2.50–23.44, p < 0.001). Our results show that the EVT of both isolated and complex TPT lesions is associated with high technical success and acceptable limb-salvage rates, with reintervention being a major risk factor for amputation. Moreover, mid-term mortality rate was relatively high. In future revisions of the anatomical grading scales, the classification of TPT lesions as highly complex should be reconsidered.

Endovascular Treatment for Critical Limb Ischemia in Type II Diabetes Mellitus Involving Femoropopliteal and Infrapopliteal Segments: Revascularization Strategy

Purpose

To determine if further endovascular infrapopliteal angioplasty in combination with femoropopliteal revascularization improves the clinical outcomes regarding major amputation rate, rate of secondary interventions, and mortality in diabetic type-II patients presented with critical lower limb ischemia (CLI).

Patients and Methods

This is a retrospective study in which all type-II diabetic patients with CLI at King Abdullah University Hospital between October 2015 and September 2019 were identified. Patients with concomitant femoropopliteal and infrapopliteal vessels atherosclerotic lesions (total occlusion or more than 50% stenosis) who received successful endovascular treatment were included. Patients were divided into 2 groups. Group-I included patients treated for femoropopliteal segment alone, while Group-II included patients treated for both femoropopliteal and infrapopliteal segments. The outcomes of the two groups were compared regarding major amputation rate, rate of secondary interventions, and mortality. In addition, demographic data, atherosclerotic lesions distributions and cardiovascular risk factors were also collected and analyzed.

Results

In all, 90 patients (65 males and 25 females) with a mean age of 67.5±12 years were included. In Group-I; 44 patients (48.9%) were included (36 males and 8 females) with a mean age of 67±12 years. In group-II; 46 patients (51.1%) were included (29 males and 17 females) with a mean age of 68±13 years. The major amputation rate was higher and statistically significant in Group-I (38.6% vs 17.4%, p-value = 0.034). However, the secondary interventions and the mortality rates showed no statistically significant differences (56.8% vs 39.1%, p-value = 0.139) and (22.7% vs 28.3%, p-value = 0.632), respectively.

Conclusion

Endovascular infrapopliteal angioplasty in combination with femoropopliteal revascularization in diabetic type-II patients with CLI improves the clinical outcome regarding major amputation rate. However, there were no significant differences regarding the rate of secondary interventions and the mortality rate.

A novel technique of percutaneous intraluminal cracking using a puncture needle for severe calcified lesions of below-the-knee and below-the-ankle arteries

PURPOSE

Endovascular therapy has recently become acceptable for the reconstruction of below-the-knee (BTK) and below-the-ankle (BTA) arterial lesions. However, we have sometimes experienced BTK or BTA lesions with calcifications that are too severe for balloon catheters to cross or expand despite successful guidewire passage. In this study, we assessed the feasibility and safety of the novel inner PIERCE technique for breaking down the calcium burden of BTK and BTA arterial lesions.

METHODS

We retrospectively reviewed the records of patients who had undergone endovascular therapy between August 2018 and December 2019. The inner PIERCE technique was performed in those cases where low-profile balloon catheters were unable to pass through the target lesions or balloon indentation did not disappear beyond the rated burst pressure. An externalized guidewire system was established in 8 cases via bidirectional approaches, and a 20-gauge needle was directly inserted through the guidewires from the distal puncture site. In 10 cases of successful antegrade wiring, the tibial or pedal arteries distal to the lesion site were punctured for a retrograde guidewire approach to the lesion. The needle was slowly rotated and advanced across the lesion.

RESULTS

We found that all lesions were severely calcified and 83.3% had chronic total occlusion. The inner PIERCE procedure allowed successful passage of the needle and subsequent low-profile balloon catheters in all cases. Optimal balloon dilatation was achieved in 94.4% of the cases using this technique. No procedure-related adverse events were observed.

CONCLUSION

The novel inner PIERCE technique is a safe and feasible method for disrupting calcified BTK and BTA lesions.

Repeat BTK revascularization: when, how and what are the results?

INTRODUCTION

Owing to the ageing of the population and rising rates of diabetes, more patients suffering from chronic limb threatening ischemia (CLTI) need revascularization for often complex, multilevel peripheral arterial occlusive disease. Below the knee (BTK) lesions are common in CLTI and short-term outcomes of BTK endovascular revascularizations have improved substantially over the last decade as a consequence of improved techniques and dedicated low profile devices.

EVIDENCE ACQUISITION

The manuscript summarized the information identified through a limited literature review conducted on key resources including MEDLINE and EMBASE databases as well as conference proceedings. The keywords were "angioplasty," "endovascular intervention," "infrapopliteal," "tibial arteries" and "below the knee." The search was limited to contemporary English-language documents published between 2000 and 2020.

EVIDENCE SYNTHESIS

Rates of re-stenosis and re-occlusion are high after infrapopliteal interventions limiting long-term success and necessitating frequent repeat procedures.

CONCLUSIONS

In this article we aimed to summarize current knowledge regarding the need, options and outcome of repeat BTK interventions through a limited literature review and presentation of own data.

Outcomes of open and hybrid treatments in below the knee pathology for critical limb threatening ischemia

INTRODUCTION

The optimal management of below the knee pathology remains one of the most challenging areas for revascularization in patients presenting with critical limb threatening ischemia. Patients commonly have multilevel lesions and have a high amputation rate and associated mortality. This review aimed to assess the outcomes of below the knee revascularization strategies.

EVIDENCE ACQUISITION

An online literature search of medical databases for original articles or review articles was conducted using mesh terms.

EVIDENCE SYNTHESIS

Bypass surgery remains the gold standard for revascularization with good long-term outcomes with regards to patency, limb salvage, and quality of life but is associated with a higher morbidity than the endovascular approach. Given the increasing frailty of our patients, endovascular treatments have become the preferred strategy with results that are now equal to bypass. Hybrid surgery is an increasingly popular option as it combines the benefits of both endovascular and open surgery and although the evidence base is small the outcomes are encouraging.

CONCLUSIONS

Hybrid surgery offers promising results and could be considered in the treatment of multi-level lower limb arterial disease especially in high-risk patients or those who are not suitable for either open or endovascular techniques as a sole treatment modality.

Comparison of Magnetic Resonance Angiography and Digital Subtraction Angiography for the Assessment of Infrapopliteal Arterial Occlusive Lesions, Based on the TASC II Classification Criteria

This paper aimed to study the agreement and repeatability, both intra- and interobserver, of infrapopliteal lesion assessment with magnetic resonance angiography (MRA), using the TransAtlantic Inter-Society Consensus (TASC) II criteria, with perioperative digital subtraction angiography (DSA) as a reference. Sixty-eight patients with an MRA preceding an endovascular infrapopliteal revascularization were included. Preoperative MRAs and perioperative DSAs were evaluated in random order by three independent observers using the TASC II classification. The results were analyzed using visual grading characteristics (VGC) analysis and Krippendorff’s α. No systematic difference was found between modalities: area under the VGC curve (AUC_VGC) = 0.48 (p = 0.58) or intraobserver; AUC_VGC for Observer 1 and 2 respectively, 0.49 (p = 0.85) and 0.53 (p = 0.52) for MRA compared with 0.54 (p = 0.30) and 0.49 (p = 0.81) for DSA. Interobserver differences were seen: AUC_VGC of 0.63 (p < 0.01) for DSA and 0.80 (p < 0.01) for MRA. These results were confirmed using Krippendorff’s α for the three observers showing 0.13 (95% confidence interval (CI) −0.07–0.31) for MRA and 0.39 (95% CI 0.23–0.53) for DSA. Poor interobserver agreement was also found in the choice of a target vessel on preoperative MRA: Krippendorff’s α = 0.19 (95% CI 0.01‒0.36). In conclusion, infrapopliteal lesions can be reliably determined on preoperative MRA, but interobserver variability regarding the choice of a target vessel is a major concern that appears to affect the overall TASC II grade.

Long Term Outcomes of Endovascular Therapy for Failing Distal Bypass Vein Grafts

OBJECTIVE

Although distal bypass using vein has been established with acceptable outcomes for chronic limb threatening ischaemia (CLTI), the major issue affecting long term outcomes is vein graft disease. This study aimed to analyse the peri-procedural results and long term outcomes of endovascular therapy (EVT) for failing vein grafts after distal bypass.

METHODS

A retrospective analysis of 113 failing vein grafts (94 patients, 113 limbs) after distal bypass between 2009 and 2019 at the study hospital.

RESULTS

The mean age was 74 ± 9 years and 72% of the patients were men. Of the 113 grafts, 54 grafts (48%) were detected in asymptomatic patients, 41 grafts (36%) in patients with recurrent ulcer or gangrene, and 18 grafts (16%) in patients with rest pain. The failing grafts were treated by low pressure long inflation balloon angioplasty with a mean balloon size of 3.0 ± 0.8 mm. The mean procedural time was 60 ± 29 min and procedural success was 98% (111 grafts). During the mean follow up period of 34 months, EVT was performed a median frequency of two times (range 1-11 times). The primary and assisted primary patency of the EVT revised grafts were 41% and 80% at one year, 34% and 68% at three years, 31% and 58% at five years, respectively. Of 41 limbs with recurrent ulcer or gangrene, the wound healed in 34 limbs (85%). The complete healing rate was 71% at three months and 84% at 12 months. Eight patients required major amputation, and the freedom from major amputation rate was 96% at one year and 80% at five years.

CONCLUSION

Long term outcomes including patency, wound healing rate, and amputation free survival after EVT for failing vein grafts were acceptable. EVT could be a viable alternative to surgical revascularisation in patients with a failing distal bypass graft for CLTI.

Foot Angiosomes: Instructions for Use

In the last 15 years an abundance of literature has demonstrated that angiosome-targeted revascularization, either endovascular or open, can lead to better clinical results in patients with chronic limb-threatening ischemia. According to this literature, the angiosome concept should guide our treatment strategy in every chronic limb-threatening ischemia patient. However, in our daily practice, its application is often difficult or impossible. Most foot wounds spread over multiple angiosomes and, moreover, the value of an angiosome-guided revascularization approach can vary according to vascular anatomy, collateral vessel network, type of revascularization, and wound. The aim of this article is to explore values and limits of the angiosome concept, and to propose some “instructions for use” regarding its application in our daily practice.

Kissing Balloon Technique for Infrapopliteal Angioplasty in Patients with Critical Limb Ischemia

BACKGROUND

This study aimed to analyze the technical aspects and follow-up findings regarding patients with critical limb ischemia who underwent the kissing balloon technique (KBT).

METHODS

Thirty patients (34 bifurcations) were enrolled in this retrospective analysis between September 2010 and February 2017. All patients were submitted to infrapopliteal intervention for critical limb ischemia. The KBT is the primary treatment in 3 situations: for cases with >70% stenosis of the main artery located less than 1 cm of the bifurcation, occlusion of one branch with greater than 50% stenosis of the contralateral branch, or greater than 50% bilateral stenosis. Stents were considered in cases of recoil greater than 30% or flow-limiting recoil and were used in 7 of the 34 bifurcations (20.5%).

RESULTS

Primary patency at 30 days, 1 year, and 2 years was 100%, 68.1%, and 68.1, respectively. Limb salvage rates at 30 days, 1 year, and 2 years were 100%, 86.6%, and 65.0%, respectively. Wound healing rates at 30 days, 6 months, 1 year, and 2 years were 7.1%, 34.4%, 44.5%, and 68.7%, respectively. The bifurcations of the V-shape and T-shape groups were compared in terms of wound healing, primary patency, and limb salvage. No differences were observed in wound healing (P = 0.268), primary patency (P = 0.394), and limb salvage (P = 0.755).

CONCLUSIONS

The KBT is a feasible bifurcation approach for infrapopliteal angioplasties to maintain the patency of both branches after ballooning. The comparison between the anterior tibial artery and tibioperoneal trunk bifurcation and the peroneal artery and posterior tibial artery bifurcation revealed no difference in wound healing, primary patency, and limb salvage.

Editor's Choice - Impact of Endovascular Pedal Artery Revascularisation on Wound Healing in Patients With Critical Limb Ischaemia

OBJECTIVE

The present study investigated the impact of endovascular pedal artery revascularisation (PAR) on the clinical outcomes of patients with critical limb ischaemia (CLI).

METHODS

This retrospective analysis of a single centre cohort included 239 patients who underwent endovascular revascularisation of infrapopliteal arteries for a chronic ischaemic wound. PAR was attempted in 141 patients during the procedure. After propensity score matching, there were 87 pairs of patients with and without PAR.

RESULTS

After the matching, the two groups showed balanced baseline clinical and lesion characteristics. PAR was achieved in 60.9% of the PAR group. Direct angiosome flow was more frequently obtained in the PAR group than in the non-PAR group (81.6% vs. 34.5%; p < .001). Subintimal angioplasty (47.1% vs. 29.9%; p = .019) and pedal-plantar loop technique (18.4% vs. 0%; p < .001) were more frequent in the PAR group. At the one year follow up, the PAR group showed greater freedom from major amputation (96.3% vs. 84.2%; p = .009). The wound healing rate, overall survival, major adverse limb event, and freedom from re-intervention did not differ significantly between the two groups. However, the patient subgroup with successful PAR showed a higher wound healing rate than the non-PAR group (76.0% vs. 67.0%; p = .031). In a multivariable Cox proportional hazards regression model, successful PAR (hazard ratio [HR] 1.564, 95% confidence interval [CI] 1.068-2.290; p = .022) was identified as an independent factor associated with improved wound healing, whereas gangrene (HR 0.659, 95% confidence interval [CI] 0.471-0.923; p = .015), C reactive protein >3 mg/dL (HR 0.591, 95% CI 0.386-0.904; p = .015), and pre-procedural absence of pedal arch (HR 0.628, 95% CI 0.431-0.916; p = .016) were associated with impaired wound healing.

CONCLUSION

Successful PAR significantly improved wound healing in patients with CLI. Thus, efforts should be made to revascularise the pedal arteries, especially when the pedal arch is completely absent.

Is Angiosome-Guided Endovascular Therapy Worthwhile?

Endovascular therapy (EVT) plays a major role in the treatment of critical limb ischemia (CLI). The latest guidelines state that the angiosome concept should be considered when performing revascularization of infrapopliteal lesions in patients with CLI. There have been several reports both of favorable and unfavorable results of angiosome-guided EVT. Based on previous reports, angiosome-guided EVT tends to improve wound healing (WH) rather than amputation-free survival and overall survival. In addition, indirect revascularization based on the angiosome concept with a good collateral flow may achieve good WH comparable to that achieved by direct revascularization. In the future, rather than just debating the effectiveness/ineffectiveness of the angiosome concept, it will be desirable to investigate the patient and lesion characteristics that may have significant influences on WH after angiosome-guided EVT and to apply the results to clinical practice.

Angiosome Specific Revascularisation: Does the Evidence Support It?

OBJECTIVE

To explain the angiosome concept and explore the practical application of the angiosome literature to a clinical scenario, in this case a tibial angioplasty for critical ischaemia.

METHODS

Clinical vignette with explanation of the decisions made and subsequent clinical results based on the theory of the angiosome concept and the literature on angiosomal revascularisation; in this case the results of our group's recent update to a systematic review and meta-analysis.

RESULTS

Endovascular combined or direct angiosomal revascularisation if superior to indirect revascularisation. This was borne out in the clinical scenario, where an indirect peroneal reperfusion of the AT angiosome resulted in major amputation. Open surgery is less dependent on the angiosome concept. The presence of adequate collateralisation into a foot arch seems to be the most important factor predicting success of indirect revascularisation. The evidence for both suffers from selection bias and many of the findings in the literature are wholly due to selection bias.

CONCLUSION

The angiosome concept is useful during both open and endovascular tibial revascularisation. However, the runoff in the foot is critical to success and may not follow the 'classic' angiosome model in diabetes.