Contemporary Management of Critical Limb Ischemia

Deletion of endothelial IGFBP5 protects against ischaemic hindlimb injury by promoting angiogenesis

BACKGROUND

Angiogenesis is critical for forming new blood vessels from antedating vascular vessels. The endothelium is essential for angiogenesis, vascular remodelling and minimisation of functional deficits following ischaemia. The insulin-like growth factor (IGF) family is crucial for angiogenesis. Insulin-like growth factor-binding protein 5 (IGFBP5), a binding protein of the IGF family, may have places in angiogenesis, but the mechanisms are not yet completely understood. We sought to probe whether IGFBP5 is involved in pathological angiogenesis and uncover the molecular mechanisms behind it.

METHODS AND RESULTS

IGFBP5 expression was elevated in the vascular endothelium of gastrocnemius muscle from critical limb ischaemia patients and hindlimb ischaemic (HLI) mice and hypoxic human umbilical vein endothelial cells (HUVECs). In vivo, loss of endothelial IGFBP5 (IGFBP5EKO) facilitated the recovery of blood vessel function and limb necrosis in HLI mice. Moreover, skin damage healing and aortic ring sprouting were faster in IGFBP5EKO mice than in control mice. In vitro, the genetic inhibition of IGFBP5 in HUVECs significantly promoted tube formation, cell proliferation and migration by mediating the phosphorylation of IGF1R, Erk1/2 and Akt. Intriguingly, pharmacological treatment of HUVECs with recombinant human IGFBP5 ensued a contrasting effect on angiogenesis by inhibiting the IGF1 or IGF2 function. Genetic inhibition of IGFBP5 promoted cellular oxygen consumption and extracellular acidification rates via IGF1R-mediated glycolytic adenosine triphosphate (ATP) metabolism. Mechanistically, IGFBP5 exerted its role via E3 ubiquitin ligase Von Hippel-Lindau (VHL)-regulated HIF1α stability. Furthermore, the knockdown of the endothelial IGF1R partially abolished the reformative effect of IGFBP5EKO mice post-HLI.

CONCLUSION

Our findings demonstrate that IGFBP5 ablation enhances angiogenesis by promoting ATP metabolism and stabilising HIF1α, implying IGFBP5 is a novel therapeutic target for treating abnormal angiogenesis-related conditions.

Important Role of Concomitant Lymphangiogenesis for Reparative Angiogenesis in Hindlimb Ischemia

[Figure: see text].

Below-the-Ankle Arrival Time as a Novel Limb Tissue Perfusion Index: Two-dimensional Perfusion Angiography Evaluation

Purpose: To identify lower limb 2-dimensional (2D) perfusion angiographic parameters that are related to skin perfusion pressure (SPP), a predictor of wound healing in patients with chronic limb-threatening ischemia (CLTI) undergoing below-the-knee (BTK) endovascular treatment (EVT). Materials and Methods: Thirty-three consecutive patients (mean age 74.5 years; 18 men) with 47 isolated BTK lesions in 33 limbs (Rutherford category 3–5) underwent EVT. Dorsal and plantar SPPs were measured before EVT and the day after. The indexed blood flow below the ankle was measured using 2D perfusion angiography before and after EVT to determine changes in perfusion parameters [arrival time (AT), time to peak, wash-in rate, mean transit time, and width and area under the time-density curve] at rest vs during hyperemia induced with a 20-mg intra-arterial papaverine infusion. Correlations between the 2D perfusion parameters and SPPs were assessed using the Pearson coefficient. The cutoff points to predict mean SPPs >40 mm Hg were analyzed using a receiver operating characteristic curve; outcomes are reported as the area under the curve (AUC) with 95% confidence interval (CI). Results: After EVT at rest and during hyperemia, only AT was significantly changed, although hyperemia produced significant changes in all the pre-/post-EVT 2D perfusion parameters except the wash-in rate. Dorsal and plantar SPPs after EVT were significantly increased and correlated with hyperemic AT and the AT ratio (hyperemia/at rest values) below the ankle. Hyperemic ATs <6.3 seconds and AT ratios <0.78 were predictive factors for a mean SPP >40 mm Hg, with AUCs of 0.83 (95% CI 0.67 to 0.99) and 0.78 (95% CI 0.61 to 0.95), respectively. Conclusion: Hyperemic ATs <6.3 seconds or AT ratios <0.78 below the ankle may be essential to obtain sufficient SPPs for limb salvage in BTK lesions. Thus, the use of 2D perfusion angiography enabled the monitoring of lower limb tissue perfusion throughout EVT and may thereby optimize treatment of CLTI.

Evaluation of machine learning methodology for the prediction of healthcare resource utilization and healthcare costs in patients with critical limb ischemia-is preventive and personalized approach on the horizon?

Background

Critical limb ischemia (CLI) is a severe stage of peripheral arterial disease and has a substantial disease and economic burden not only to patients and families, but also to the society and healthcare systems. We aim to develop a personalized prediction model that utilizes baseline patient characteristics prior to CLI diagnosis to predict subsequent 1-year all-cause hospitalizations and total annual healthcare cost, using a novel Bayesian machine learning platform, Reverse Engineering Forward Simulation™ (REFS™), to support a paradigm shift from reactive healthcare to Predictive Preventive and Personalized Medicine (PPPM)-driven healthcare.

Methods

Patients ≥ 50 years with CLI plus clinical activity for a 6-month pre-index and a 12-month post-index period or death during the post-index period were included in this retrospective cohort of the linked Optum-Humedica databases. REFS™ built an ensemble of 256 predictive models to identify predictors of all-cause hospitalizations and total annual all-cause healthcare costs during the 12-month post-index interval.

Results

The mean age of 3189 eligible patients was 71.9 years. The most common CLI-related comorbidities were hypertension (79.5%), dyslipidemia (61.4%), coronary atherosclerosis and other heart disease (42.3%), and type 2 diabetes (39.2%). Post-index CLI-related healthcare utilization included inpatient services (14.6%) and ≥ 1 outpatient visits (32.1%). Median annual all-cause and CLI-related costs per patient were $30,514 and $2196, respectively. REFS™ identified diagnosis of skin and subcutaneous tissue infections, cellulitis and abscess, use of nonselective beta-blockers, other aftercare, and osteoarthritis as high confidence predictors of all-cause hospitalizations. The leading predictors for total all-cause costs included region of residence and comorbid health conditions including other diseases of kidney and ureters, blindness of vision defects, chronic ulcer of skin, and chronic ulcer of leg or foot.

Conclusions

REFS™ identified baseline predictors of subsequent healthcare resource utilization and costs in CLI patients. Machine learning and model-based, data-driven medicine may complement physicians' evidence-based medical services. These findings also support the PPPM framework that a paradigm shift from post-diagnosis disease care to early management of comorbidities and targeted prevention is warranted to deliver a cost-effective medical services and desirable healthcare economy.

Switch to Ticagrelor in critical limb ischemia antiplatelet study (STT-CLIPS)

OBJECTIVE

To investigate platelet reactivity in patients with critical limb ischemia (CLI) after switching from clopidogrel to ticagrelor.

BACKGROUND

High on-treatment platelet reactivity (HPR) is highly prevalent in patients with CLI treated with clopidogrel. The effect of ticagrelor in patients with CLI is not known, however.

METHODS

We performed P2Y12 platelet receptor inhibition studies (VASP and VerifyNow) in 50 patients with CLI. Tests were performed before and 6±1h after daily 75mg clopidogrel dose. Patients were then switched to ticagrelor 90mg twice daily for two weeks and platelet assays repeated. Patients were divided based on VerifyNow P2Y12 reaction units (PRU). Group 1: HPR defined as PRU ≥208 and Group 2: Appropriate platelet inhibition (API), PRU <208.

RESULTS

After two weeks of uninterrupted antiplatelet therapy, mean PRU results were 173 PRU and 71 PRU at baseline (p<0.0001) and 140 PRU and 63 PRU after 6h (p<0.0001) for clopidogrel and ticagrelor, respectively. Before daily clopidogrel dose, 36% of patients (n=18) demonstrated HPR and after 6h, 30% (n=15). One patient (2%) had HPR on ticagrelor. Ninety-four percent of patients with HPR on clopidogrel demonstrated appropriate platelet inhibition after switching to ticagrelor and all patients with API on clopidogrel remained with API after switching to ticagrelor. Six hours after daily dosing, VASP-PRI >50% was found in 42% of clopidogrel and 2% of ticagrelor treated patients.

CONCLUSIONS

Among patients with CLI, ticagrelor achieved greater platelet inhibition than clopidogrel during maintenance treatment and at 6h after daily dosing. High on-treatment platelet reactivity to clopidogrel in patients with CLI can be overcome by switching to ticagrelor.

Midterm Outcomes After Infrapopliteal Interventions in Patients With Critical Limb Ischemia Based on the TASC II Classification of Below-the-Knee Arteries

Purpose: To analyze the relationship between the new TransAtlantic Inter-Society Consensus (TASC II) infrapopliteal classification and limb outcomes among patients with critical limb ischemia (CLI). Methods: A single-center retrospective study was performed on 166 consecutive CLI patients (mean age 71 years; 113 men) undergoing endovascular treatment of 244 infrapopliteal lesions from 2006 to 2013. Patient, procedural, angiographic, and limb outcomes were compared for the new TASC A/B vs C/D classification for infrapopliteal lesions. Binary restenosis was determined by a peak systolic velocity ratio >2.0 by duplex ultrasound on follow-up at 1, 3, 6, and 12 months. Results: Seventy-two (43.4%) patients had TASC A/B lesions, while 94 (56.6%) had TASC C/D patterns of infrapopliteal disease. Baseline demographics and tissue loss (93% vs 94%, p=0.59) were similar between the groups. TASC A/B lesions were shorter (53±35 vs 170±83 mm, p<0.001), less severely stenosed (77%±24% vs 93%±14%, p<0.001), had a larger target vessel diameter (2.9±0.5 vs 2.6±0.5 mm, p<0.001), and were less frequently chronic total occlusions (24% vs 64%, p<0.001) compared with the TASC C/D group. Three-year freedom from both amputation (85% vs 67%, p=0.02) and major adverse limb events (79% vs 61%, p=0.02) were significantly higher in the TASC A/B group. Technical success rates (95% vs 80%, p<0.001) and 1-year primary patency (58% vs 51%, p=0.04) were higher in the A/B group. Overall 3-year survival was similar between the groups (96% A/B vs 88% C/D, p=0.2). Conclusion: TASC C/D infrapopliteal lesions are associated with higher amputation and major adverse limb events rates and lower primary patency compared with TASC A/B infrapopliteal lesions. Further studies are needed to assess the association between TASC C/D infrapopliteal lesions and clinical outcomes in patients with CLI.