Marriage of resistance and conduit arteries breeds critical limb ischemia

New Horizons in Peripheral Artery Disease

Peripheral artery disease (PAD) is the lower limb manifestation of systemic atherosclerotic disease. PAD may initially present with symptoms of intermittent claudication, whilst chronic limb-threatening ischaemia (CLTI), the end stage of PAD, presents with rest pain and/or tissue loss. PAD is an age-related condition present in over 10% of those aged ≥65 in high-income countries. Guidelines regarding definition, diagnosis and staging of PAD and CLTI have been updated to reflect the changing patterns and presentations of disease given the increasing prevalence of diabetes. Recent research has changed guidelines on optimal medical therapy, with low-dose anticoagulant plus aspirin recommended in some patients. Recently published randomised trials highlight where bypass-first or endovascular-first approaches may be optimal in infra-inguinal disease. New techniques in endovascular surgery have increased minimally invasive options for ever more complex disease. Increasing recognition has been given to the complexity of patients with CLTI where a high prevalence of both frailty and cognitive impairment are present and a significant burden of multi-morbidity and polypharmacy. Despite advances in minimally invasive revascularisation techniques and reduction in amputation incidence, survival remains poor for many with CLTI. Shared decision-making is essential, and conservative management is often appropriate for older patients. There is emerging evidence of the benefit of specialist geriatric team input in the perioperative management of older patients undergoing surgery for CLTI. Recent UK guidelines now recommend screening for frailty, cognitive impairment and delirium in older vascular surgery patients as well as recommending all vascular surgery services have support and input from specialist geriatrics teams.

Wharton's jelly mesenchymal stem cells transplantation for critical limb ischemia in patients with type 2 diabetes mellitus: a preliminary report of phase I clinical trial

Peripheral artery disease (PAD) affects more than 230 million people worldwide, with approximately 11% of patients presenting with advanced-stage PAD or critical limb ischemia (CLI). To avoid or delay amputation, particularly in no-option CLI patients with infeasible or ineffective revascularization, new treatment strategies such as regenerative therapies should be developed. Mesenchymal stem cells (MSCs) are the most popular cell source in regenerative therapies. They possess significant characteristics such as angiogenic, anti-inflammatory, and immunomodulatory activities, which encourage their application in different diseases. This phase I clinical trial reports the safety, feasibility, and probable efficacy of the intramuscular administration of allogeneic Wharton's jelly-derived MSCs (WJ-MSCs) in type 2 diabetes patients with CLI. Out of six screened patients with CLI, five patients were administered WJ-MSCs into the gastrocnemius, soleus, and the proximal part of the tibialis anterior muscles of the ischemic lower limb. The safety of WJ-MSCs injection was considered a primary outcome. Secondary endpoints included wound healing, the presence of pulse at the disease site, the absence of amputation, and improvement in visual analogue scale (VAS), pain-free walking time, and foot and ankle disability index (FADI). No patient experienced adverse events and foot or even toe amputation during the 6-month follow-up. Six months after the intervention, there were a significantly lower VAS score and significantly higher pain-free walking time and FADI score than the baseline, but no statistically significant difference was seen between other time points. In conclusion, allogeneic WJ-MSC transplantation in patients with CLI seems to be safe and effective.

Connexin 40-Mediated Regulation of Systemic Circulation and Arterial Blood Pressure

Vascular system is a complex network in which different cell types and vascular segments must work in concert to regulate blood flow distribution and arterial blood pressure. Although paracrine/autocrine signaling is involved in the regulation of vasomotor tone, direct intercellular communication via gap junctions plays a central role in the control and coordination of vascular function in the microvascular network. Gap junctions are made up by connexin (Cx) proteins, and among the four Cxs expressed in the cardiovascular system (Cx37, Cx40, Cx43, and Cx45), Cx40 has emerged as a critical signaling pathway in the vessel wall. This Cx is predominantly found in the endothelium, but it is involved in the development of the cardiovascular system and in the coordination of endothelial and smooth muscle cell function along the length of the vessels. In addition, Cx40 participates in the control of vasomotor tone through the transmission of electrical signals from the endothelium to the underlying smooth muscle and in the regulation of arterial blood pressure by renin-angiotensin system in afferent arterioles. In this review, we discuss the participation of Cx40-formed channels in the development of cardiovascular system, control and coordination of vascular function, and regulation of arterial blood pressure.

Development of a Non-Invasive Local Heating Load Test to Detect Severe Limb Ischemia Within 200 seconds

Purpose

To establish a non-invasive test method for the rapid detection of severe ischemia (SI) in the limbs in patients with peripheral arterial disease (PAD).

Methods

Between November 2019 and May 2021, 22 patients admitted for PAD to 2 hospitals agreed to participate in the study. All patients underwent a local heating load (LHL) test. SI was defined as at least 1 ankle-brachial index value of <.4 and/or transcutaneous oximetry value of <30 mmHg. The other cases were classified as mild-to-moderate ischemia (MMI). The LHL test was performed simultaneously with 15 minutes of heating and measurement by attaching a blood flow meter measuring probe combined with a warmer to the patient’s dorsal foot. Evaluation consisted of 200-s periods from the start of heating to 800 seconds. For each period, perfusion value (PV) was evaluated, and slope was calculated graphically based on linear regression as PV fluctuation per minute. Test accuracy was calculated using a receiver operating characteristic curve.

Results

Twenty-four limbs of 18 patients were finally evaluated; 4 patients (2 with missing data, 1 with collagen disease, and 1 with embolism) were excluded, with 13 and 11 limbs in the SI and MMI groups, respectively. The SI group showed a significantly lower slope value in the first 200 seconds and lower PV at 200 seconds and thereafter. From the slope value, it was possible to detect SI with 85% sensitivity and 73% specificity at 200 seconds. PV could be determined with higher accuracy in periods after 200 seconds, with 85% sensitivity and 82% specificity at 800 seconds.

Conclusions

Our non-invasive LHL test could be used as a rapid screening test to detect SI in limbs within 200 seconds, as well as a more accurate test to detect ischemia within 800 seconds.

Macrophage Paired Immunoglobulin-Like Receptor B Deficiency Promotes Peripheral Atherosclerosis in Apolipoprotein E–Deficient Mice

Background: Peripheral atherosclerotic disease (PAD) is the narrowing or blockage of arteries that supply blood to the lower limbs. Given its complex nature, bioinformatics can help identify crucial genes involved in the progression of peripheral atherosclerosis.

Materials and Methods: Raw human gene expression data for 462 PAD arterial plaque and 23 normal arterial samples were obtained from the GEO database. The data was analyzed using an integrated, multi-layer approach involving differentially-expressed gene analysis, KEGG pathway analysis, GO term enrichment analysis, weighted gene correlation network analysis, and protein-protein interaction analysis. The monocyte/macrophage-expressed leukocyte immunoglobulin-like receptor B2 (LILRB2) was strongly associated with the human PAD phenotype. To explore the role of the murine LILRB2 homologue PirB in vivo, we created a myeloid-specific PirB-knockout Apoe^−/− murine model of PAD (PirB^MΦKO) to analyze femoral atherosclerotic burden, plaque features of vulnerability, and monocyte recruitment to femoral atherosclerotic lesions. The phenotypes of PirB^MΦKO macrophages under various stimuli were also investigated in vitro.

Results:PirB^MΦKO mice displayed increased femoral atherogenesis, a more vulnerable plaque phenotype, and enhanced monocyte recruitment into lesions. PirB^MΦKO macrophages showed enhanced pro-inflammatory responses and a shift toward M1 over M2 polarization under interferon-γ and oxidized LDL exposure. PirB^MΦKO macrophages also displayed enhanced efferocytosis and reduced lipid efflux under lipid exposure.

Conclusion: Macrophage PirB reduces peripheral atherosclerotic burden, stabilizes peripheral plaque composition, and suppresses macrophage accumulation in peripheral lesions. Macrophage PirB inhibits pro-inflammatory activation, inhibits efferocytosis, and promotes lipid efflux, characteristics critical to suppressing peripheral atherogenesis.

C-reactive Protein, Free Fatty Acid, and Uric Acid as Predictors of Adverse Events after Endovascular Revascularization of Arterial Femoropopliteal Occlusion Lesions

OBJECTIVES

This study aimed to investigate the relationship between pre-procedure high-sensitivity C-reactive protein (hsCRP), free fatty acid (FFA), and uric acid (UA) levels and post-procedure mortality and morbidity of endovascular revascularization of arterial femoropopliteal occlusion lesions.

METHODS

This was a retrospective review of clinical data retrieved from a prospectively held database in Peking Union Medical College Hospital. A total of 71 Patients who underwent endovascular treatment (EVT) for femoropopliteal occlusive disease between January 1, 2014 and November 1, 2017, were included in this study. Endpoints were defined as major adverse limb events (MALE; target vessel revascularization, amputation, or disease progression) and major adverse cardiovascular events (MACE; stroke, myocardial infarction, or all-cause death) during the entire follow-up period. Univariate and multivariate Cox proportional hazards regression models were used to evaluate the relationship of elevated biomarker levels (hsCRP, FFA and UA, measured by immunoturbidimetry assay, enzymatic assay and enzymatic assay, respectively) to MALE and MACE outcomes.

RESULTS

Seventy-one patients (72 limbs) with sufficient follow-up information were included in the analysis. The mean age was 69.7 ± 8.6 years; 21.1% were female. The Rutherford class of target limbs were ≥ 3. The median follow-up was 36 (range 18-59 months). Univariate analyses revealed that patients with elevated hsCRP levels had an increased risk of MALE (hazard ratio [HR], 2.682; 95% confidence interval [CI], 1.281-5.617, P = 0.009). High FFA levels were associated with an increased risk of MALE (HR, 2.658; 95% CI, 1.075-6.573; P = 0.034). Multivariate analyses demonstrated that elevated hsCRP values (HR, 4.015; 95% CI, 1.628-10.551; P = 0.003) and FFA value (HR, 3.034; 95% CI, 1.102-8.354; P = 0.032) were both significantly associated with increased MALE. Elevated UA levels predicted MACE in the presence of confounders (HR, 11.446; 95% CI, 1.367-95.801 P = 0.023).

CONCLUSION

Pre-procedure hsCRP and FFA levels could serve as predictors of adverse events after EVT in patients with arterial femoropopliteal occlusive disease. The role of UA in MACE may warrant further investigation, because the correlation is not as powerful as the other two in the study.

Hydrogel-based therapeutic angiogenesis: An alternative treatment strategy for critical limb ischemia

Critical limb ischemia (CLI) is the most severe clinical manifestation of peripheral arterial disease (PAD), resulting in the total or partial loss of limb function. Although the conventional treatment strategy of CLI (e.g., medical treatment and surgery) can improve blood perfusion and restore limb function, many patients are unsuitable for these strategies and they still face the threats of amputation or death. Therapeutic angiogenesis, as a potential solution for these problems, attempts to manipulate blood vessel growth in vivo for augment perfusion without the help of extra pharmaceutics and surgery. With the rise of interdisciplinary research, regenerative medicine strategies provide new possibilities for treating many clinical diseases. Hydrogel, as an excellent biocompatibility material, is an ideal candidate for delivering bioactive molecules and cells for therapeutic angiogenesis. Besides, hydrogel could precisely deliver, control release, and keep the bioactivity of cargos, making hydrogel-based therapeutic angiogenesis a new strategy for CLI therapy. In this review, we comprehensively discuss the approaches of hydrogel-based strategy for CLI treatment as well as their challenges, and future directions.

Microvascular Dysfunction in Peripheral Artery Disease: Is Heat Therapy a Viable Treatment?

Peripheral artery disease (PAD) is characterized by the development of atherosclerotic plaques in the lower-body conduit arteries. PAD is commonly accompanied by microvascular disease, which may result in poor wound healing, plantar ulcer development, and subsequent limb amputation. Understanding the mechanisms underlying the development of plantar ulcers is a critical step in the development of adequate treatment options for patients with PAD. Skin is classified into two major components: glabrous and non-glabrous. These skin types have unique microcirculation characteristics, making it important to differentiate between the two when investigating mechanisms for plantar ulcer development in PAD. There is evidence for a microcirculation compensatory mechanism in PAD. This is evident by the maintenance of basal microcirculation perfusion and capillary filling pressure despite a reduced pressure differential beyond an occlusion in non-critical limb ischemia PAD. The major mechanism for this compensatory system seems to be progressive vasodilation of the arterial network below an occlusion. Recently, heat therapies have emerged as novel treatment options for attenuating the progression of PAD. Heat therapies are capable of stimulating the cardiovascular system, which may lead to beneficial adaptations that may ultimately reduce fatigue during walking in PAD. Early work in this area has shown that full-body heating is capable of generating an acute cardiovascular response, similar to exercise, which has been suggested as the most efficient treatment modality and may generate adaptations with chronic exposure. Heat therapies may emerge as a conservative treatment option capable of attenuating the progression of PAD and ultimately impeding the development of plantar ulcers.

Strategies to Overcome the Barrier of Ischemic Microenvironment in Cell Therapy of Cardiovascular Disease

The transplantation of various immune cell types are promising approaches for the treatment of ischemic cardiovascular disease including myocardial infarction (MI) and peripheral arterial disease (PAD). Major limitation of these so-called Advanced Therapy Medicinal Products (ATMPs) is the ischemic microenvironment affecting cell homeostasis and limiting the demanded effect of the transplanted cell products. Accordingly, different clinical and experimental strategies have been evolved to overcome these obstacles. Here, we give a short review of the different experimental and clinical strategies to solve these issues due to ischemic cardiovascular disease.

Involvement of microcirculation in critical ischemia: how to identify it?

Critical limb ischemia represents the most severe pattern of peripheral arterial disease (PAD) associated with the high risk of major amputation, cardiovascular events and death. The diagnosis and management of critical limb ischemia (CLI) is often challenging. Systolic ankle and toe pressure measurements are considered to be the basic techniques for the identification of PAD. However, they provide rough insight into the dependent local tissue perfusion. Furthermore, those techniques do not enable investigation of microcirculation which has crucial role in the pathogenesis of CLI. Some patients with mild deterioration of macrocirculation develop CLI if microcirculation is affected. Investigation of perfusion on macro- and local microcirculatory level enables more effective treatment: revascularization of the angiosome-related artery. The technologies capable of assessing limb tissue oxygenation or perfusion on microcirculatory level enable direct assessment of distant tissue oxygenation. Transcutaneous oxygen tension (TcPO2) measurement which was introduced in clinical practice represents one of the objective criteria for the diagnosis of CLI. Main weakness of this technique as well as laser Doppler flow measurement is low penetrance from the skin surface. Measurement of tissue blood flow on microcirculatory level can be performed with indocyanine green fluorescent imaging (ICG), contrast-enhanced magnetic resonance and vital microscopy. ICG is promising method which provides excellent informative image of tissue perfusion. However, it offers little quantitative information. Investigation of microcirculation in patients with CLI is of outmost importance because it enables insight in local tissue perfusion and oxygenation, which represents the basis of identification of most ischemic regions and provide more successful angiosome related revascularization of an affected artery.

Fluorescence angiography compared to toe blood pressure in the evaluation of severe limb ischemia

Background: Severity of limb ischemia in peripheral arterial disease (PAD) patients is usually evaluated by clinical assessment and toe blood pressure (TBP) or transcutaneous oxygen pressures (TcPO 2). Indocyanin green angiography (IGA) is a promising tool generating a foot cartography of skin microvascular perfusion. However, there is no consensus about the fluorescence parameters that should be used to evaluate ischemia. The purpose of this cross-sectional evaluation and 3-month clinical follow-up was to determine the best fluorescence parameter for the evaluation of severe PAD, using TBP as reference. Patients and methods: IGA was realized in patients with clinical suspicion of CLI in addition to TBP and TcPO 2. Parameters from the time intensity fluorescence curve measured on the foot were compared with TBP (primary reference), and with TcPO2. Clinical outcomes (amputation, revascularization, death) were recorded at 3 months follow-up. Results: Thirty-four patients were included and IGA could be analysed in 29 of them. When all limbs were studied, no significant correlation was found between any of the measured fluorescence parameters (saturation time, ingress slope, amplitude, delay) and TBP pressure neither TCPO2. In the limbs with CLI, a significant correlation between the TBP and amplitude on the forefoot was found. According to the outcome, none of the fluorescence parameters showed a significant prognostic value in contrast to the significant results for TBP and TcPO2. Conclusions: In this study, quantitative analysis of IGA parameters did not show any prognostic value, nor was there any significant statistical association with well-established prognostic parameters such as TBP and TcPO 2 in patients with suspected CLI. A correlation was found between amplitude and TBP in patients with CLI. Topographical information such as perfusion heterogeneity was not evaluated and remains a valuable target to be investigated.

Current review with evolving management strategies in critical limb ischemia

Critical limb ischemia represents the end stage of peripheral artery disease, which is associated with impaired quality of life and considerable morbidity and mortality. Economical impact of the disease is huge with a substantial burden on patients, healthcare providers, and resources. Varied therapeutic strategies have been employed in the management of these patients. These patients usually have complex multilevel occlusive arteriopathy with significant comorbidities, rendering surgical interventions undesirable in many cases. Recent therapeutic advances with evolving endovascular techniques and gene or cell-based therapies have the potential to dramatically change the therapeutic outlook in these patients.

Cost-Effective, Safe, and Personalized Cell Therapy for Critical Limb Ischemia in Type 2 Diabetes Mellitus

Cell therapy is a progressively growing field that is rapidly moving from preclinical model development to clinical application. Outcomes obtained from clinical trials reveal the therapeutic potential of stem cell-based therapy to deal with unmet medical treatment needs for several disorders with no therapeutic options. Among adult stem cells, mesenchymal stem cells (MSCs) are the leading cell type used in advanced therapies for the treatment of autoimmune, inflammatory and vascular diseases. To date, the safety and feasibility of autologous MSC-based therapy has been established; however, their indiscriminate use has resulted in mixed outcomes in preclinical and clinical studies. While MSCs derived from diverse tissues share common properties depending on the type of clinical application, they markedly differ within clinical trials in terms of efficacy, resulting in many unanswered questions regarding the application of MSCs. Additionally, our experience in clinical trials related to critical limb ischemia pathology (CLI) shows that the therapeutic efficacy of these cells in different animal models has only been partially reproduced in humans through clinical trials. Therefore, it is crucial to develop new research to identify pitfalls, to optimize procedures and to clarify the repair mechanisms used by these cells, as well as to be able to offer a next generation of stem cell that can be routinely used in a cost-effective and safe manner in stem cell-based therapies targeting CLI.

Review of the Current Basic Science Strategies to Treat Critical Limb Ischemia

Critical limb ischemia (CLI) is a highly morbid disease with many patients considered poor surgical candidates. The lack of treatment options for CLI has driven interest in developing molecular therapies within recent years. Through these translational medicine studies in CLI, much has been learned about the pathophysiology of the disease. Here, we present an overview of the macrovascular and microvascular changes that lead to the development of CLI, including impairment of angiogenesis, vasculogenesis, and arteriogenesis. We summarize the randomized clinical controlled trials that have used molecular therapies in CLI, and discuss the novel imaging modalities being developed to assess the efficacy of these therapies.

Enhancement of Functionality and Therapeutic Efficacy of Cell-Based Therapy Using Mesenchymal Stem Cells for Cardiovascular Disease

Cardiovascular disease usually triggers coronary heart disease, stroke, and ischemic diseases, thus promoting the development of functional failure. Mesenchymal stem cells (MSCs) are cells that can be isolated from various human tissues, with multipotent and immunomodulatory characteristics to help damaged tissue repair and avoidance of immune responses. Much research has proved the feasibility, safety, and efficiency of MSC-based therapy for cardiovascular disease. Despite the fact that the precise mechanism of MSCs remains unclear, their therapeutic capability to treat ischemic diseases has been tested in phase I/II clinical trials. MSCs have the potential to become an effective therapeutic strategy for the treatment of ischemic and non-ischemic cardiovascular disorders. The molecular mechanism underlying the efficacy of MSCs in promoting engraftment and accelerating the functional recovery of injury sites is still unclear. It is hypothesized that the mechanisms of paracrine effects for the cardiac repair, optimization of the niche for cell survival, and cardiac remodeling by inflammatory control are involved in the interaction between MSCs and the damaged myocardial environment. This review focuses on recent experimental and clinical findings related to cardiovascular disease. We focus on MSCs, highlighting their roles in cardiovascular disease repair, differentiation, and MSC niche, and discuss their therapeutic efficacy and the current status of MSC-based cardiovascular disease therapies.

Assessment of the Severity of Ischaemia and the Outcomes of Revascularisation in Peripheral Arterial Disease Patients Based on the Skin Microcirculatory Response to a Thermal Load Test

Objective

This study investigated the skin microcirculatory response to a thermal load test using a laser Doppler flowmetry device to evaluate the severity of limb ischaemia and the outcomes of revascularisation in patients with peripheral arterial disease (PAD).

Methods

A total of 34 PAD patients (39 limbs) including 17 critical limb ischaemia (CLI) patients (21 limbs) who underwent revascularisation were enrolled. The skin microcirculation of the dorsal side of the affected foot was investigated for 15 minutes after local heating. The tests were performed both before and after revascularisation, and several parameters gleaned from the microcirculatory fluctuations were analysed and compared with the ankle brachial pressure index and the transcutaneous oxygen tension (tcPO₂) values.

Results

Among the parameters, significant differences were observed between the CLI patients and patients with claudication with regard to the increasing phase time (T_inc), the difference in the perfusion values at the onset and the peak of the transient increase in blood perfusion (PΔ), the slope of the transient increase in blood perfusion (S_in), and the slope of the decrease in blood perfusion after the peak (S_de). In CLI patients, the PΔ, S_in, and S_de values increased significantly after revascularisation. In the patients with claudication, the changes in the parameters after revascularisation were not statistically significant. The S_de showed the most statistically significant correlation with the tcPO₂ value (ρ .759, p < .001).

Conclusions

Thermal load testing can be used to evaluate the severity of limb ischaemia in patients with PAD.

•

New thermal load testing for evaluation of the severity of limb ischaemia is presented.

•

Skin blood flow response to thermal load was investigated by laser Doppler flowmetry.

•

Thermal load testing can be used to evaluate the severity of limb ischaemia.

Pathophysiology of chronic limb ischemia

Chronic ischemia of the lower extremities is an everyday problem in vascular surgery clinics. In Germany, approximately 3% of all hospitalizations are due to peripheral artery disease (PAD), with critical limb ischemia (CLI) in particular showing a rapid increase. The consequences of chronic undersupply range from reduced walking distance to loss of limbs. At the beginning there are stress factors, such as hyperlipidemia (LDL), free radicals, arterial hypertension, infections or subclinical inflammation that interfere with endothelial homeostasis and cause endothelial dysfunction with increased permeability. Cells of the immune system are attracted and migrate into the vascular wall, where they lead to the degradation of matrix components and destabilization of the plaque. By changing the phenotype of smooth muscle cells and macrophages towards osteoclast-like cells, bone-like hardening of the vessel wall takes place. Above a vessel wall thickness of approximately 100 µm, hypoxia-induced factor (HIF-1α) is intensified by the lack of oxygen, which leads to an increase in growth factors, such as vascular endothelial growth factor (VEGF). This promotes angiogenesis, but it is not sufficient to compensate for a stenosed artery. Arteriogenesis refers to the growth of existing collateral vessels. The driving forces are the pressure gradient before and after the stenosis and the shear forces acting on the vessel walls. In the case of progressive stenosis, the compensatory capacities can be overtaxed and a manifest hypoxia in the tissue with regression of the obtained vascular structures and tissue atrophy occurs.

In Patients with Severe Peripheral Arterial Disease, Revascularization-Induced Improvement in Lower Extremity Ischemia Can Be Detected by Laser Speckle Contrast Imaging of the Fluctuation in Blood Perfusion after Local Heating

BACKGROUND

We previously reported the utility of the perfusion value (PV) fluctuation slope for detecting severe ischemia in the lower limb. Our approach was based on a thermal load test mimicking the well-known physiological reaction termed "cold-induced vasodilation," which is known to occur as a 3-phase phenomenon. The slope parameter quantifies the decrease in PVs accompanying the relative cooling (third phase) following the transient increase in blood flow (second phase) induced by the applied thermal load. This phenomenon of "relative" cold-induced vasodilation (rCIVD) can be monitored using laser speckle contrast imaging (LSCI) after applying the thermal load (LTL test). Here, we aimed to determine whether the slope parameter obtained via the LTL test also reflects the improvement in hemodynamics after revascularization.

METHODS

The study enrolled 16 patients (18 limbs), who underwent revascularization for peripheral arterial disease (PAD). The measurements were performed at 2 sites in each limb (in total, 34 sites; 2 sites in one patient were excluded because of significant movement during the measurement). For each site, we recorded the slope describing the behavior of PVs (decrease or plateau) in the third phase of rCIVD, following the initial, heating-induced increase in perfusion (second phase of rCIVD). The plateau group (group P), which included patients with an abnormal rCIVD, and the decrease group (group D), which included patients with a normal rCIVD, were defined based on perfusion slope values of <0.20 and ≥ 0.20 perfusion units/min, respectively. We also quantified the transient increase in perfusion (from baseline to peak) as a descriptor of perfusion behavior during the second phase of rCIVD.

RESULTS

In group P, the change in median values (25-75%) of the slope, transcutaneous oxygen tension, and ankle-brachial index (ABI) from before to after operation was (-0.02 [-0.04 to 0.02]; 4 [1-11]; and 0.08 [0-0.27]) to (0.39 [0.32-0.59]; 46 [37-54]; and 0.81 [0.72-0.90]). Conversely, in group D, the change in the median values of the slope, transcutaneous oxygen tension, and ABI between before and after operation was (0.38 [0.32-0.49]; 40.5 [35-45]; and0.58 [0.57-0.65]) to (0.44 [0.30-0.64]; 52 [43-56]; and 0.92 [0.81-0.99]). Sites exhibiting perfusion pattern of group D in the third phase of rCIVD showed no significant change in slope after revascularization (P = 0.21), whereas the slope in group P increased significantly after revascularization, becoming similar to the postoperative slopes in group D (P = 0.81). The amount of transient increase in perfusion, which quantified the behavior in the second phase of rCIVD, showed a similar behavior. Preoperatively, all patients in group P had rest pain and/or ulcer of the foot, whereas only few patients in group D had such symptoms.

CONCLUSIONS

Normal rCIVD response in the LTL test indicates less-than-severe ischemia, while abnormal rCIVD response measured via the LTL test indicates severe ischemic symptoms, such as critical limb ischemia. Notably, patients with an abnormal rCIVD response can develop a normal rCIVD response following revascularization, thereby reflecting an improvement in blood flow. The LTL test assessing rCIVD response can be useful for detecting severe limb ischemia, such as critical limb ischemia (CLI), and determining the departure from severe limb ischemia by revascularization.

The Use of the Profunda Femoral Artery as the Sole Target Vessel to Bypass Aortoiliac Disease in Patients with Critical Limb Ischemia and Concomitant Unreconstructable Infrainguinal Disease

BACKGROUND

Critical limb ischemia (CLI) often results from multilevel occlusive disease. There are occasions where a patent profunda femoral artery (PFA) is the only target artery that can be used as outflow during reconstruction to bypass aortoiliac disease (AOID), with no further option for infrainguinal revascularization. We aim to report results of the use of PFA as the sole target vessel for the treatment of these patients.

METHODS

This is a retrospective, single-center study including CLI patients treated during 36 months. All procedures were included regardless of inflow site. The outcomes examined were hemodynamic improvement, clinical status change, amputation-free and overall survival, and patency of the prosthesis. Univariate analysis was performed to identify possible predictors of adverse outcomes.

RESULTS

Twenty-three patients and 27 limbs were included (2 female, mean age 70.6). Sixteen limbs presented rest pain and 11 tissue loss. Inflow was obtained from the axillary (n = 9), contralateral femoral (n = 8), abdominal aorta (n = 2), thoracic aorta (n = 1), ipsilateral external iliac (n = 2), and contralateral external iliac artery (n = 1). Immediately postoperatively ankle-brachial index significantly increased from 0.15 (0-0.5) to 0.50 (0.25-0.9), (P-value < 0.001). Twenty-four limbs presented clinical improvement (3 minimally, 18 moderately, and 3 markedly improved) and 3 presented no change. During a mean follow-up of 15.8 (2-36) months, we recorded 4 deaths and 4 major amputations. Mean predicted overall survival and amputation-free survival were 29.8 (95% confidence interval [CI] 24.5-35.1) and 26.5 months (95% CI 21.1-31.8), respectively. Predicted primary patency was 76% at 3 years. Univariate analysis revealed significant associations only between bypass patency and limp loss (P-value = 0.021).

CONCLUSIONS

In the presence of CLI due to AOID and unreconstructable infrainguinal disease, the use of PFA as the sole target vessel during bypass is associated with significant rates of clinical improvement and limb salvage.

Novel assessment tool based on laser speckle contrast imaging to diagnose severe ischemia in the lower limb for patients with peripheral arterial disease

Objective

We propose a new assessment tool to diagnose severe ischemia of the lower limb in peripheral arterial disease, using laser speckle contrast imaging to evaluate heating‐induced microcirculatory fluctuations in the proximal and distal sites of the dorsal foot.

Study Design

A cross‐sectional study.

Methods

We recorded the slope describing the behavior of perfusion values (decrease or plateau) following the initial, heating‐induced increase in perfusion in 63 feet of patients with clinical signs of peripheral arterial disease.

Results

The plateau and decrease groups were defined as having perfusion slopes of <0.20 and ≥0.20 PU/min, respectively. Transcutaneous oxygen tension was significantly lower (P < 0.001) in the plateau than in the decrease group (8 vs. 45 mmHg), indicating more severe ischemia. The laser speckle contrast imaging thermal load test discriminated transcutaneous oxygen tension <30 mmHg with good sensitivity (78.7%) and specificity (96.2%), and an area under the curve of 0.908.

Conclusions

Both transcutaneous oxygen tension and the laser speckle contrast imaging thermal load test are useful in diagnosing severe ischemia in the foot. Lasers Surg. Med. 49:645–651, 2017. © 2017. The Authors. Lasers in Surgery and Medicine Published by Wiley Periodicals, Inc.

Ghrelin, MicroRNAs, and Critical Limb Ischemia: Hungering for a Novel Treatment Option

Critical limb ischemia (CLI) is the most severe manifestation of peripheral artery disease. It is characterized by chronic pain at rest, skin ulcerations, and gangrene tissue loss. CLI is a highly morbid condition, resulting in a severely diminished quality of life and a significant risk of mortality. The primary goal of therapy for CLI is to restore blood flow to the affected limb, which is only possible by surgery, but is inadvisable in up to 50% of patients. This subset of patients who are not candidates for revascularisation are referred to as "no-option" patients and are the focus of investigation for novel therapeutic strategies. Angiogenesis, arteriogenesis and vasculogenesis are the processes whereby new blood vessel networks form from the pre-existing vasculature and primordial cells, respectively. In therapeutic angiogenesis, exogenous stimulants are administered to promote angiogenesis and augment limb perfusion, offering a potential treatment option for "no option" patients. However, to date, very few clinical trials of therapeutic angiogenesis in patients with CLI have reported clinically significant results, and it remains a major challenge. Ghrelin, a 28-amino acid peptide, is emerging as a potential novel therapeutic for CLI. In pre-clinical models, exogenous ghrelin has been shown to induce therapeutic angiogenesis, promote muscle regeneration, and reduce oxidative stress via the modulation of microRNAs (miRs). miRs are endogenous, small, non-coding ribonucleic acids of ~20-22 nucleotides which regulate gene expression at the post-transcriptional level by either translational inhibition or by messenger ribonucleic acid cleavage. This review focuses on the mounting evidence for the use of ghrelin as a novel therapeutic for CLI, and highlights the miRs which orchestrate these physiological events.

A review of the pathophysiology and potential biomarkers for peripheral artery disease

Peripheral artery disease (PAD) is due to the blockage of the arteries supplying blood to the lower limbs usually secondary to atherosclerosis. The most severe clinical manifestation of PAD is critical limb ischemia (CLI), which is associated with a risk of limb loss and mortality due to cardiovascular events. Currently CLI is mainly treated by surgical or endovascular revascularization, with few other treatments in routine clinical practice. There are a number of problems with current PAD management strategies, such as the difficulty in selecting the appropriate treatments for individual patients. Many patients undergo repeated attempts at revascularization surgery, but ultimately require an amputation. There is great interest in developing new methods to identify patients who are unlikely to benefit from revascularization and to improve management of patients unsuitable for surgery. Circulating biomarkers that predict the progression of PAD and the response to therapies could assist in the management of patients. This review provides an overview of the pathophysiology of PAD and examines the association between circulating biomarkers and PAD presence, severity and prognosis. While some currently identified circulating markers show promise, further larger studies focused on the clinical value of the biomarkers over existing risk predictors are needed.

Critical and acute limb ischemia: an overview

Some patients with peripheral arterial disease may present with critical limb ischemia, a condition associated with high rates of morbidity and mortality. Early diagnosis and effective medical therapy and revascularization are indicated to avoid amputation and reduce mortality. Ideally, a multidisciplinary approach with collaboration between endovascular interventionist, vascular surgeons, podiatrist, infectious disease, and wound care specialist is recommended for these patients.

Critical limb ischemia

Critical limb ischemia (CLI) continues to be a significantly morbid disease process for the aging population. Rigid guidelines for the management of patients with CLI are inappropriate due to the complexities that are involved in optimally treating these patients. A thin line exists in the decision process between medical management vs surgical management by revascularization or amputation, and the perception of "success" in this patient population is evolving. This review explores these issues and examines the challenges the treating physician will face when managing the care of patients with CLI. The epidemiology and natural history of CLI is discussed, along with the pathophysiology of the disease process. A review of the literature in regards to the different treatment modalities is presented to help the physician optimize therapy for patients with CLI. New scoring systems to help predict outcomes in patients with CLI undergoing revascularization or amputation are discussed, and an overview of the current status of patient-oriented outcomes is provided. Finally, we briefly examine emerging therapies for the treatment of CLI and provide an algorithm to help guide the practicing physician on how to approach the critically ischemic limb with regard to the complicated issues surrounding these patients.

Suppressed hindlimb perfusion in Rac2-/- and Nox2-/- mice does not result from impaired collateral growth

While tissue perfusion and angiogenesis subsequent to acute femoral artery occlusion are suppressed in NADPH oxidase 2 (Nox2)-null (Nox2(-/-)) mice, studies have not established the role of Nox2 in collateral artery enlargement. Rac2 is a small GTPase that binds Nox2 and activates Nox2-based NAD(P)H oxidase but, unlike Nox2, is primarily restricted to bone marrow-derived cells. In this study, we used Rac2-null (Rac2(-/-)) and Nox2(-/-) mice with a novel method of identifying primary hindlimb collaterals to investigate the hypothesis that collateral growth requires these molecules. When initial experiments performed with femoral ligation demonstrated similar perfusion and collateral growth in Rac2(-/-) and wild-type C57BL/6J (BL6) mice, subsequent experiments were performed with a more severe ischemia model, femoral artery excision. After femoral excision, tissue perfusion was suppressed in Rac2(-/-) mice relative to BL6 mice. Histological assessment of ischemic injury including necrotic and regenerated muscle fibers and lipid and collagen deposition demonstrated greater injury in Rac2(-/-) mice. The diameters of primary collaterals identified during Microfil injection with intravital microscopy were enlarged to a similar extent in BL6 and Rac2(-/-) mice. Intimal cells in collateral cross sections were increased in number in both strains and were CD31 positive and CD45 negative. Circulating leukocytes and CD11b(+) cells were increased more in Rac2(-/-) than BL6 animals. Experiments performed in Nox2(-/-) mice to verify that the unexpected results related to collateral growth were not unique to Rac2(-/-) mice gave equivalent results. The data demonstrate that, subsequent to acute femoral artery excision, perfusion recovery is impaired in Rac2(-/-) and Nox2(-/-) mice but that collateral luminal expansion and intimal cell recruitment/proliferation are normal. These novel results indicate that collateral luminal expansion and intimal cell recruitment/proliferation are not mediated by Rac2 and Nox2.

Endovascular therapy for critical limb ischemia

Abstract

Chronic critical limb ischemia (CLI) occurs when arterial perfusion is reduced below a threshold level that results in rest pain and/or tissue breakdown in the lower extremities. Importantly, it is associated with high cardiovascular morbidity and mortality. Without prompt revascularization, CLI may result in loss of a limb (i.e. amputation) and/or life. The goal of endovascular therapy is the re-establishment of pulsatile, straight-line flow to the distal extremity. Percutaneous transluminal angioplasty (PTA) has been shown to be effective and safe in the setting of CLI, with limb salvage rates that compare favorably with surgical procedures. Stents are indicated for failed PTA, while adjunctive therapies such as lasers, thermal angioplasty and atherectomy devices lack data demonstrating improved efficacy compared with conventional lower extremity interventions. In addition to successful revascularization, the institution of lifestyle changes, atherosclerotic risk factor modification, and pharmacologic therapies are indicated to reduce cardiovascular morbidity and mortality.

Therapeutic potential of atrial natriuretic peptide administration on peripheral arterial diseases

Peripheral arterial diseases are caused by arterial sclerosis and impaired collateral vessel formation, which are exacerbated by diabetes, often leading to leg amputation. We have reported that an activation of the natriuretic peptides/cGMP/cGMP-dependent protein kinase pathway accelerated vascular regeneration and blood flow recovery in murine legs, for which ischemia had been induced by a femoral arterial ligation as a model for peripheral arterial diseases. In this study, ip injection of carperitide, a human recombinant atrial natriuretic peptide, accelerated blood flow recovery with increasing capillary density in ischemic legs not only in nondiabetic mice but also in mice kept upon streptozotocin-induced hyperglycemia for 16 wk, which significantly impaired the blood flow recovery compared with nondiabetic mice. Based on these findings, we tried to apply the administration of carperitide to the treatment of peripheral arterial diseases. The study group comprised a continuous series of 13 patients with peripheral arterial diseases (Fontaine's classification I, one; II, five; III, two; and IV, five), for whom conventional therapies had not accomplished appreciable results. Carperitide was administrated continuously and intravenously for 2 wk to Fontaine's class I-III patients and for 4 weeks to class IV patients. The dose was gradually increased to the maximum, with the patient's systolic blood pressure being kept above 100 mm Hg. Carperitide administration improved the ankle-brachial pressure index, intermittent claudication, rest pain, and ulcers. In conclusion, this study showed a therapeutic potential of carperitide to treat peripheral arterial diseases refractory to conventional therapies.

Effect of phosphodiesterase 5 inhibitor on alteration in vascular smooth muscle sensitivity and renal function in rats with liver cirrhosis

Previous studies suggested that increased activity of phosphodiesterase (PDE)5 in the kidneys of cirrhotic rats contributes to sodium retention. This study examined the role of PDE5 in the changes in vascular reactivity, hemodynamics, and sodium excretion in rats with liver cirrhosis. Four weeks after bile duct ligation (BDL) or sham operation (SO), in vitro reactivity of aortic rings to various agents and in vivo effects of a PDE5-selective inhibitor [1,3-dimethyl-6-(2-propoxy-5-methanesulfonylamidophenyl)pyrazolo[3,4d]-pyrimidin-4-(5H)-one, DMPPO] were studied. The vasodilator responses to nitroglycerin and S-nitroso-N-acetyl-penicillamine (SNAP) in phenylephrine-precontracted rings without endothelium were attenuated in BDL compared with SO rats. Pretreatment with DMPPO (0.1 microM) enhanced these responses and eliminated the differences between the two groups. Vasodilation to DMPPO itself was also less in BDL rats. The responses to phenylephrine were attenuated in endothelium-rich aorta from BDL relative to SO rats, but they were similar in endothelium-denuded aorta and remained similar despite preincubation with SNAP (0.1 microM) alone or with SNAP and DMPPO. In vivo, BDL rats were vasodilated relative to SO rats; DMPPO (5 mg/kg i.v.) decreased arterial pressure and vascular resistance in both groups equally and caused significant increase in sodium excretion in BDL rats only. In conclusion, the results are in accordance with a possible increase in PDE5 activity in aorta and kidney of cirrhotic rats that results in reduced responses to NO donors and contributes to the increase in sodium retention. PDE5 inhibitors may ameliorate sodium retention in cirrhosis but may worsen vasodilation. Examining the effect of PDE5 inhibitors after chronic administration will be more revealing.