Critical Limb Ischemia: Current Trends and Future Directions

Pain Management in People with Diabetes-Related Chronic Limb-Threatening Ischemia

Management of neuropathic pain in people with diabetes has been widely investigated. However, little attention was paid to address ischemic-related pain in patients with diabetes mellitus who suffered from chronic limb-threatening ischemia (CLTI), the end stage of lower extremity arterial disease (LEAD). Pain management has a tremendous influence on patients' quality of life and prognosis. Poor management of this type of pain owing to the lack of full understanding undermines patients' physical and mental quality of life, which often results in a grim prognosis, such as depression, myocardial infarction, lower limb amputation, and even mortality. In the present article, we review the current strategy in the pain management of diabetes-related CLTI. The endovascular therapy, pharmacological therapies, and other optional methods could be selected following comprehensive assessments to mitigate ischemic-related pain, in line with our current clinical practice. It is very important for clinicians and patients to strengthen the understanding and build intervention strategy in ischemic pain management and possible adverse consequence.

Decellularized adipose tissue scaffolds guide hematopoietic differentiation and stimulate vascular regeneration in a hindlimb ischemia model

Cellular therapies to stimulate therapeutic angiogenesis in individuals with critical limb ischemia (CLI) remain under intense investigation. In this context, the efficacy of cell therapy is dependent on the survival, biodistribution, and pro-angiogenic paracrine signaling of the cells transplanted. Hematopoietic progenitor cells (HPC) purified from human umbilical cord blood using high aldehyde dehydrogenase-activity (ALDH^hi cells) and expanded ex vivo, represent a heterogeneous mixture of progenitor cells previously shown to support limb revascularization in mouse models of CLI. The objectives of this study were to investigate the utility of bioscaffolds derived from human decellularized adipose tissue (DAT) to guide the differentiation of seeded HPC in vitro and harness the pro-angiogenic capacity of HPC at the site of ischemia after implantation in vivo. Probing whether the DAT scaffolds altered HPC differentiation, label-free quantitative mass spectrometry and flow cytometric phenotype analyses indicated that culturing the HPC on the DAT scaffolds supported their differentiation towards the pro-angiogenic monocyte/macrophage lineage at the expense of megakaryopoiesis. Moreover, implantation of HPC in DAT scaffolds within a unilateral hindlimb ischemia model in NOD/SCID mice increased cell retention at the site of ischemia relative to intramuscular injection, and accelerated the recovery of limb perfusion, improved functional limb use and augmented CD31⁺ capillary density when compared to DAT implantation alone or saline-injected controls. Collectively, these data indicate that cell-instructive DAT scaffolds can direct therapeutic HPC differentiation towards the monocyte/macrophage lineage and represent a promising delivery platform for improving the efficacy of cell therapies for CLI.

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.

CD146+Mesenchymal stem cells treatment improves vascularization, muscle contraction and VEGF expression, and reduces apoptosis in rat ischemic hind limb

Peripheral arterial disease (PAD) is an increasingly common narrowing of the peripheral arteries that can lead to lower limb ischemia, muscle weakness and gangrene. Surgical vein or arterial grafts could improve PAD, but may not be suitable in elderly patients, prompting research into less invasive approaches. Mesenchymal stem cells (MSCs) have been proposed as potential therapy, but their effectiveness and underlying mechanisms in limb ischemia are unclear. We tested the hypothesis that treatment with naive MSCs (nMSCs) or MSCs expressing CD146 (^CD146+MSCs) could improve vascularity and muscle function in rat model of hind-limb ischemia. Sixteen month old Sprague-Dawley rats were randomly assigned to 4 groups: sham-operated control, ischemia, ischemia + nMSCs and ischemia+^CD146+MSCs. After 4 weeks of respective treatment, rat groups were assessed for ischemic clinical score, Tarlov score, muscle capillary density, TUNEL apoptosis assay, contractile force, and vascular endothelial growth factor (VEGF) mRNA expression. ^CD146+MSCs showed greater CD146 mRNA expression than nMSCs. Treatment with nMSCs or ^CD146+MSCs improved clinical and Tarlov scores, muscle capillary density, contractile force and VEGF mRNA expression in ischemic limbs as compared to non-treated ischemia group. The improvements in muscle vascularity and function were particularly greater in ischemia+^CD146+MSCs than ischemia + nMSCs group. TUNEL positive apoptotic cells were least abundant in ischemia+^CD146+MSCs compared with ischemia + nMSCs and non-treated ischemia groups. Thus, MSCs particularly those expressing CD146 improve vascularity, muscle function and VEGF expression and reduce apoptosis in rat ischemic limb, and could represent a promising approach to improve angiogenesis and muscle function in PAD.

Therapeutic Biomaterial Approaches to Alleviate Chronic Limb Threatening Ischemia

Chronic limb threatening ischemia (CLTI) is a severe condition defined by the blockage of arteries in the lower extremities that leads to the degeneration of blood vessels and is characterized by the formation of non-healing ulcers and necrosis. The gold standard therapies such as bypass and endovascular surgery aim at the removal of the blockage. These therapies are not suitable for the so-called "no option patients" which present multiple artery occlusions with a likelihood of significant limb amputation. Therefore, CLTI represents a significant clinical challenge, and the efforts of developing new treatments have been focused on stimulating angiogenesis in the ischemic muscle. The delivery of pro-angiogenic nucleic acid, protein, and stem cell-based interventions have limited efficacy due to their short survival. Engineered biomaterials have emerged as a promising method to improve the effectiveness of these latter strategies. Several synthetic and natural biomaterials are tested in different formulations aiming to incorporate nucleic acid, proteins, stem cells, macrophages, or endothelial cells in supportive matrices. In this review, an overview of the biomaterials used alone and in combination with growth factors, nucleic acid, and cells in preclinical models is provided and their potential to induce revascularization and regeneration for CLTI applications is discussed.

Cord Lining Mesenchymal Stem Cells Have a Modest Positive Effect on Angiogenesis in Hindlimb Ischemia

Purpose: We investigated the use of human Cord Lining Mesenchymal Stem Cells (CL-MSCs) (US Patent number 9,737,568), in a rabbit hindlimb ischemia model, and evaluated their potential in stimulating neovascularization. Allogenic human CL- MSCs could potentially be used to treat patients with lower limb ischemia and non-healing wounds. Methods: Twenty rabbits were divided into two separate groups. We created a hindlimb ischemia model surgically. At 21 and 49 days post-operatively, animals in the treatment group were injected with CL-MSCs (500,000 cells per 0.2 ml on each site) at 10 different sites (Quadriceps- 4 sites, Hamstrings- 4 sites and Calf--2 sites) in the hindlimb muscles. The control group received only saline injection to the corresponding sites at the same time point as the treatment group. We then evaluated the effects of treatment on neovascularization by angiography, laser doppler perfusion imaging, as well as by histology. We evaluated the tissue samples for any signs of local immune reaction to the cell implantation. We also observed the rabbit clinically for any adverse effects after treatment. Results: We found a higher number of CD31 positive cells in the treatment group, with a greater number of capillaries found in the treated muscles. The Rectus Femoris demonstrated a median vessel count/muscle fiber of 0.121 for the treatment group, compared to 0.076 in the control group (median difference 0.04; 95% CI 0.001-0.11; p = 0.041). The Gastrocnemius demonstrated a median vessel count/muscle fiber of 0.175 for the treatment group, compared to 0.089 in the control group (median difference 0.087; 95% CI -0.006 to 0.234; p = 0.07). Blood perfusion quantification through Laser Doppler Perfusion Imaging (LDPI) also demonstrated a non-statistically significant increase in perfusion in favor of the treatment group. CL-MSCs demonstrated no toxicity associated morbidity and minimal local immune reaction to implantation. Conclusion: CL-MSCs have a positive effect on angiogenesis in a rabbit hindlimb ischemia model. This preliminary data is encouraging and paves the way for future large animal studies or for clinical trials.

A novel model of chronic limb ischemia to therapeutically evaluate the angiogenic effects of drug candidates

Critical limb ischemia (CLI) is a severe state of peripheral artery disease with high unmet clinical needs. Further, there are no effective treatment options for patients with CLI. Based on preclinical study results, predicting the clinical efficacy of CLI treatments is typically difficult because conventional hindlimb ischemia (HLI) rodent models display spontaneous recovery from ischemia, which is not observed in patients with CLI. Therefore, we aimed to develop a novel chronic and severe HLI model to properly evaluate the therapeutic effects of drug candidates for CLI. Severe HLI mice (Type-N) were generated by increasing the excised area of blood vessels in a hindlimb of NOG mice. Immunohistochemistry and gene expression analysis at 9 wk after the Type-N operation revealed that the ischemic limb was in a steady state with impaired angiogenesis, like that observed in patients with CLI. We did selection of chronic Type-N mice based on the number of necrotic nails and blood flow rate at 2 wk after surgery because some Type-N mice showed mild symptoms. Therapeutic treatment with cilostazol, which is used for intermittent claudication, did not restore blood flow in chronic Type-N mice. In contrast, therapeutic transplantation of pericytes and vascular endothelial cells, which can form new blood vessels in vivo, significantly improved blood flow in a subset of Type-N mice. These findings suggest that this novel chronic and severe HLI model may be a valuable standard animal model for therapeutic evaluation of the angiogenic effects of CLI drug candidates.NEW & NOTEWORTHY We developed a chronic and severe hindlimb ischemia (HLI) mouse model for preclinical research on critical limb ischemia (CLI). This model partially reflects human CLI pathology in that it does not show spontaneous restoration of blood flow or expression of angiogenic genes in the ischemic limb. This novel model may be valuable for therapeutic evaluation of the angiogenic effects of CLI drug candidates.

Current Status of Angiogenic Cell Therapy and Related Strategies Applied in Critical Limb Ischemia

Critical limb ischemia (CLI) constitutes the most severe form of peripheral arterial disease (PAD), it is characterized by progressive blockade of arterial vessels, commonly correlated to atherosclerosis. Currently, revascularization strategies (bypass grafting, angioplasty) remain the first option for CLI patients, although less than 45% of them are eligible for surgical intervention mainly due to associated comorbidities. Moreover, patients usually require amputation in the short-term. Angiogenic cell therapy has arisen as a promising alternative for these "no-option" patients, with many studies demonstrating the potential of stem cells to enhance revascularization by promoting vessel formation and blood flow recovery in ischemic tissues. Herein, we provide an overview of studies focused on the use of angiogenic cell therapies in CLI in the last years, from approaches testing different cell types in animal/pre-clinical models of CLI, to the clinical trials currently under evaluation. Furthermore, recent alternatives related to stem cell therapies such as the use of secretomes, exosomes, or even microRNA, will be also described.

The role of prognostic nutritional index in predicting amputation in patients with lower extremity peripheral artery disease

Introduction: Lower-extremity peripheral artery disease (PAD) can lead to a wide spectrum of symptoms that can progress from claudication to amputation. The prognostic nutritional index (PNI), which is calculated using the levels of albumin and lymphocyte, is an accepted indicator of immunological and nutritional status. In this study, the association between nutritional status determined using the PNI, and extremity amputation in patients with lower-extremity PAD was investigated.

Methods: Lower-extremity PAD patients who had been admitted to the cardiology clinic of the Dışkapı Yıldırım Beyazıt Training & Research Hospital with stage 2b or higher claudication, and who were technically unsuitable for revascularization or underwent unsuccessful revascularization procedure were enrolled in this retrospective study. Patients were grouped according to whether or not limb amputation had been performed previously. Potential factors were tested to detect independent predictors for amputation with logistic regression analysis.

Results: A study group was formed with 266 peripheral artery patients. The amputated group (39 patients) had a higher number of hypertensive (76.9% vs 57.7%; P = 0.032) and diabetic (92.3% vs 54.2%; P <0.001) patients than those in the non-amputated group (227 patients). The median PNI value of the amputated group was lower than that of the non-amputated group (31.8 vs 39.4; P <0.001). Multivariate logistic regression showed that the PNI (OR: 0.905, 95% CI: 0.859 – 0.954; P <0.001) was independently related with amputation.

Conclusion: Immune-nutritional status based on PNI was independently associated with limb amputation in patients with lower-extremity PAD.

Critical limb ischemia patients clinically improving with medical treatment have lower neutrophil-to-lymphocyte and platelet-to-lymphocyte ratios

OBJECTIVES

Inflammation is a component in the pathogenesis of critical limb ischemia. We aimed to assess how inflammation affects response to treatment in patients treated for critical limb ischemia using neutrophil-to-lymphocyte (NLR) and platelet-to-lymphocytes ratios (PLR) as markers of inflammation.

METHODS

Patients in a single tertiary cardiovascular center with critical limb ischemia unsuitable for surgical or interventional revascularization were retrospectively identified. Data were collected on medical history for risk factors, previous surgical or endovascular revascularization, and outcome. A standard regimen of low molecular weight heparin, aspirin, statins, iloprost infusions, and a standard pain medication protocol were applied to each patient per hospital protocol. Patients with improvement in ischemic pain and healed ulcers made up the responders group and cases with no worsening pain or ulcer size or progression to minor or major amputations made up the non-responders group. Responders and Non-responders were compared for risk factors including pretreatment NLR and PLR.

RESULTS

268 included patients who were not candidates for surgical or endovascular revascularization were identified. Responders had significantly lower pretreatment NLR (4.48 vs 8.47, p < 0.001) and PLR (162.19 vs 225.43, p = 0.001) values. After controlling for associated risk factors NLR ≥ 4.63 (p < 0.001) and PLR ≥ 151.24 (p = 0.016) were independently associated with no response to treatment.

CONCLUSIONS

Neutrophil-to-lymphocyte ratio and platelet-to-lymphocytes ratio are markers of inflammation that are reduced in patients improving with medical treatment suggesting a decreased state of inflammation before treatment in responding patients.

Elastin-like hydrogel stimulates angiogenesis in a severe model of critical limb ischemia (CLI): An insight into the glyco-host response

Critical limb ischemia (CLI) is characterized by the impairment of microcirculation, necrosis and inflammation of the muscular tissue. Although the role of glycans in mediating inflammation has been reported, changes in the glycosylation following muscle ischemia remains poorly understood. Here, a murine CLI model was used to show the increase of high mannose, α-(2, 6)-sialic acid and the decrease of hybrid and bisected N-glycans as glycosylation associated with the ischemic environment. Using this model, the efficacy of an elastin-like recombinamers (ELR) hydrogel was assessed. The hydrogel modulates key angiogenic signaling pathways, resulting in capillary formation, and ECM remodeling. Arterioles formation, reduction of fibrosis and anti-inflammatory macrophage polarization wa also induced by the hydrogel administration. Modulation of glycosylation was observed, suggesting, in particular, a role for mannosylation and sialylation in the mediation of tissue repair. Our study elucidates the angiogenic potential of the ELR hydrogel for CLI applications and identifies glycosylation alterations as potential new therapeutic targets.

Hmox1 (Heme Oxygenase-1) Protects Against Ischemia-Mediated Injury via Stabilization of HIF-1α (Hypoxia-Inducible Factor-1α)

OBJECTIVE

Hmox1 (heme oxygenase-1) is a stress-induced enzyme that catalyzes the degradation of heme to carbon monoxide, iron, and biliverdin. Induction of Hmox1 and its products protect against cardiovascular disease, including ischemic injury. Hmox1 is also a downstream target of the transcription factor HIF-1α (hypoxia-inducible factor-1α), a key regulator of the body's response to hypoxia. However, the mechanisms by which Hmox1 confers protection against ischemia-mediated injury remain to be fully understood. Approach and Results: Hmox1 deficient (Hmox1-/-) mice had impaired blood flow recovery with severe tissue necrosis and autoamputation following unilateral hindlimb ischemia. Autoamputation preceded the return of blood flow, and bone marrow transfer from littermate wild-type mice failed to prevent tissue injury and autoamputation. In wild-type mice, ischemia-induced expression of Hmox1 in skeletal muscle occurred before stabilization of HIF-1α. Moreover, HIF-1α stabilization and glucose utilization were impaired in Hmox1-/- mice compared with wild-type mice. Experiments exposing dermal fibroblasts to hypoxia (1% O2) recapitulated these key findings. Metabolomics analyses indicated a failure of Hmox1-/- mice to adapt cellular energy reprogramming in response to ischemia. Prolyl-4-hydroxylase inhibition stabilized HIF-1α in Hmox1-/- fibroblasts and ischemic skeletal muscle, decreased tissue necrosis and autoamputation, and restored cellular metabolism to that of wild-type mice. Mechanistic studies showed that carbon monoxide stabilized HIF-1α in Hmox1-/- fibroblasts in response to hypoxia.

CONCLUSIONS

Our findings suggest that Hmox1 acts both downstream and upstream of HIF-1α, and that stabilization of HIF-1α contributes to Hmox1's protection against ischemic injury independent of neovascularization.

Two-year Outcome of Quality of Life and Health Status for the Elderly with Chronic Limb-threatening Ischemia

Purpose

In elderly patients with chronic limb-threatening ischemia (CLTI), there is little scientific understanding of the long-term changes of quality of life (QoL) and health status (HS) after treatment. The primary goal of this study was to provide long-term QoL and HS results for elderly CLTI patients after therapy. Treatments consisted of endovascular revascularization, surgical revascularization, or conservative treatment. Furthermore, the aim of this study was to identify the distinctive trajectories of QoL and HS.

Patients and Methods

CLTI patients aged ≥70 years were included in a prospective observational cohort study with a two-year follow-up. The WHOQOL-BREF was used to asses QoL. The 12-Item Short Form Health Survey was used to measure HS. The QoL and HS scores were compared to the scores in the general elderly Dutch population. Latent class trajectory analysis was used.

Results

A total of 195 patients were included in this study. After two years, in all treatment groups patients showed significantly higher physical QoL score compared to baseline and there was no significant difference with the corresponding values in the elderly Dutch population. In the latent class trajectory analysis, there were no overlapping risk factors for poorer QoL or HS.

Conclusion

This study shows that QoL levels in surviving elderly CLTI patients in the long-term do not differ from the corresponding values for elderly in the general population. There were no disparities in sociodemographic, clinical and treatment characteristics associated with poorer QoL and HS. This study was carried out to encourage further analysis of the influence of biopsychosocial characteristics on QoL and HS in elderly CLTI patients.

Prognostic Value of Radiotracer-Based Perfusion Imaging in Critical Limb Ischemia Patients Undergoing Lower Extremity Revascularization

OBJECTIVES

The purpose of this study was to evaluate the prognostic value of single-photon emission computed tomography (SPECT)/computed tomography (CT) imaging of angiosome foot perfusion for predicting amputation outcomes in patients with critical limb ischemia (CLI) and diabetes mellitus (DM).

BACKGROUND

Radiotracer imaging can assess microvascular foot perfusion and identify regional perfusion abnormalities in patients with critical limb ischemia CLI and DM, but the relationship between perfusion response to revascularization and subsequent clinical outcomes has not been evaluated.

METHODS

Patients with CLI, DM, and nonhealing foot ulcers (n = 25) were prospectively enrolled for SPECT/CT perfusion imaging of the feet before and after revascularization. CT images were used to segment angiosomes (i.e., 3-dimensional vascular territories) of the foot. Relative changes in radiotracer uptake after revascularization were evaluated within the ulcerated angiosome. Incidence of amputation was assessed at 3 and 12 months after revascularization.

RESULTS

SPECT/CT detected a significantly lower microvascular perfusion response for patients who underwent amputation compared with those who remained amputation free at 3 (p = 0.01) and 12 (p = 0.01) months after revascularization. The cutoff percent change in perfusion for predicting amputation at 3 months was 7.55%, and 11.56% at 12 months. The area under the curve based on the amputation outcome was 0.799 at 3 months and 0.833 at 12 months. The probability of amputation-free survival was significantly higher at 3 (p = 0.002) and 12 months (p = 0.03) for high-perfusion responders than low-perfusion responders to revascularization.

CONCLUSIONS

SPECT/CT imaging detects regional perfusion responses to lower extremity revascularization and provides prognostic value in patients with CLI (Radiotracer-Based Perfusion Imaging of Patients With Peripheral Arterial Disease; NCT03622359).

Outcomes of open and endovascular interventions in patients with chronic limb threatening ischemia

OBJECTIVES

Widespread adoption of endovascular therapy for the treatment of chronic limb-threatening ischemia has transformed the field of vascular surgery. In this modern era, we aimed to define where open surgical interventions are of greatest benefit for limb salvage.

METHODS

Patients who underwent interventions for chronic limb-threatening ischemia were identified in the vascular-targeted lower extremity National Surgical Quality Improvement Program database for open surgical interventions (OPEN) and endovascular surgical interventions (ENDO) from 2011 to 2017. Patients were further stratified based on the criteria of chronic limb-threatening ischemia (rest pain or tissue loss), and the location of the diseased arteries (femoropopliteal or tibioperoneal). The main outcomes measured included 30-day mortality, amputation, and major adverse cardiovascular events.

RESULTS

A total of 17,193 patients were revascularized for chronic limb-threatening ischemia: 10,532 were OPEN and 6661 were ENDO. OPEN had higher 30-day mortality, major adverse cardiovascular events, pulmonary, renal dysfunction, and wound complications. However, OPEN resulted in significantly lower 30-day major amputation (3.8% vs. 5.0%, odds ratio (OR): 0.83 [0.72-0.97], P = .018). Subgroup analysis revealed a higher mortality rate in OPEN was observed only in tibioperoneal intervention for tissue loss. Major adverse cardiovascular event was higher in OPEN for most subgroups. OPEN for patients with tissue loss had significantly lower amputation rate than ENDO in both femoropopliteal and tibioperoneal subgroups (3.7% vs. 5.1%, OR: 0.76 [0.59-0.98], P = .036, and 4.7% vs. 6.6%, OR: 0.74 [0.57-0.96], P = .024, respectively). The benefit of open surgery in reducing the amputation rate was not seen in patients with rest pain.

CONCLUSIONS

Open surgical intervention is associated with significantly better limb salvage than endovascular intervention in patients with tissue loss. Surgical options should be given more emphasis as the first-line option in this cohort of patients unless the cardiopulmonary risk is prohibitive.

Relationship between cell number and clinical outcomes of autologous bone-marrow mononuclear cell implantation in critical limb ischemia

Cell therapy using intramuscular injections of autologous bone-marrow mononuclear cells (BM-MNCs) improves clinical symptoms and can prevent limb amputation in atherosclerotic peripheral arterial disease (PAD) patients with critical limb ischemia (CLI). The purpose of this study was to evaluate the effects of the number of implanted BM-MNCs on clinical outcomes in atherosclerotic PAD patients with CLI who underwent cell therapy. This study was a retrospective observational study with median follow-up period of 13.5 years (range, 6.8–15.5 years) from BM-MNC implantation procedure. The mean number of implanted cells was 1.2 ± 0.7 × 10⁹ per limb. There was no significant difference in number of BM-MNCs implanted between the no major amputation group and major amputation group (1.1 ± 0.7 × 10⁹ vs. 1.5 ± 0.8 × 10⁹ per limb, P = 0.138). There was also no significant difference in number of BM-MNCs implanted between the no death group and death group (1.5 ± 0.9 × 10⁹ vs. 1.8 ± 0.8 × 10⁹ per patient, P = 0.404). Differences in the number of BM-MNCs (mean number, 1.2 ± 0.7 × 10⁹ per limb) for cell therapy did not alter the major amputation-free survival rate or mortality rate in atherosclerotic PAD patients with CLI. A large number of BM-MNCs will not improve limb salvage outcome or mortality.

Temporal trends and outcomes of critical limb ischemia among patients with chronic kidney disease

There is a paucity of data on the outcomes and revascularization strategies for critical limb ischemia (CLI) among patients with chronic kidney disease (CKD). Hence, we conducted a nationwide analysis to evaluate the trends and outcomes of hospitalizations for CLI with CKD. The National Inpatient Sample database (2002-2015) was queried for hospitalizations for CLI. The trends of hospitalizations for CLI with CKD were reported, and endovascular versus surgical revascularization strategies for CLI with CKD were compared. The main study outcome was in-hospital mortality. The analysis included 2,139,640 hospitalizations for CLI, of which 484,224 (22.6%) had CKD. There was an increase in hospitalizations for CLI with CKD (P_trend = 0.01), but a reduction in hospitalizations for CLI without CKD (P_trend = 0.01). Patients with CLI and CKD were less likely to undergo revascularization compared with patients without CKD. CLI with CKD had higher rates of in-hospital mortality (4.8% vs 2.5%, adjusted odds ratio (OR) 2.01; 95% CI 1.93-2.11) and major amputation compared with no CKD. Revascularization for CLI with CKD was associated with lower rates of mortality (3.7% vs 5.3%, adjusted-OR 0.78; 95% CI 0.72-0.84) and major amputation compared with no revascularization. Compared with endovascular revascularization, surgical revascularization for CLI with CKD was associated with higher rates of in-hospital mortality (4.7% vs 2.7%, adjusted-OR 1.67; 95% CI 1.43-1.94). In conclusion, this contemporary observational analysis showed an increase in hospitalizations for CLI among patients with CKD. CLI with CKD was associated with higher in-hospital mortality compared with no CKD. Compared with endovascular therapy, surgical revascularization for CLI with CKD was associated with higher in-hospital mortality.

Impact of the Timing of Foot Tissue Resection on Outcomes in Patients Undergoing Revascularization for Chronic Limb-Threatening Ischemia

The objective of this study is to describe utilization of revascularization and tissue resection in patients with chronic limb-threatening ischemia (CLTI) and determine whether the timing of resection impacts outcomes. Revascularizations for CLTI were queried (ACS-NSQIP 2011-2015). Outcomes included 30-day major adverse limb events (MALE), major adverse cardiac events (MACE), length of stay (LOS), operative time, 30-day readmissions, and wound infections. Groups included revascularization alone, revascularization/tissue resection during the same procedure (concurrent), or revascularization/delayed tissue resection (delayed). Resections were debridement or transmetatarsal amputations. Multivariate logistic regression determined risk-adjusted effects of tissue resection on outcomes. There was no difference in overall 30-day MACE or MALE between groups (P = .70 and P = .35, respectively). Length of stay (6.1 days revascularization alone vs 7.8 days concurrent vs 8.7 days delayed, P < .0001) was longer in patients who underwent any tissue resection. Highest 30-day readmission and operative time was the concurrent group (P = .02 and P < .0001, respectively). Wound infection was highest in the delayed group (1.4% revascularization alone vs 1.3% concurrent vs 6.2% delayed, P < .0001). After risk adjustment, timing of resection did not impact LOS for concurrent and delayed groups compared to revascularization alone (both P < .0001). Debridement and minor amputations can be done concurrently in patients undergoing revascularization for CLTI.

Administration of Slow-Release Synthetic Prostacyclin Agonist Promoted Angiogenesis and Skeletal Muscle Regeneration for Limb Ischemia

Gene or cell therapy is currently not fully efficacious for arteriosclerosis obliterans (ASO). In this study, we determined whether YS-1402, a slow-release synthetic prostacyclin agonist, promoted neovascularization and skeletal muscle regeneration in a mouse model of critical limb ischemia (CLI). We ligated the femoral artery and its branches to obtain the CLI mouse model, administered saline (S group) or YS-1402 (YS group) to the thigh adductor 1 week after femoral artery occlusion, and evaluated tissue blood flow after surgery. After treatment, the leg muscle was obtained for histological, gene expression, and protein analyses to assess angiogenesis and skeletal muscle regeneration. Tissue blood flow improved in the YS group compared with that in the S group, and the number of CD31⁺/α-smooth muscle actin (αSMA)⁺ arterioles increased in the YS group. Prostacyclin receptor (IPR), stromal cell-derived factor-1, hepatocyte growth factor, and neural cell adhesion molecule expression levels were higher in the YS than in the S group. Skeletal muscle regeneration was detected based on PAX7- and Ki-67-positive satellite cells in the YS group. Myogenin and MyoD expression was higher in the YS than in the S group. Therefore, YS-1402 promoted functional angiogenesis and skeletal muscle regeneration in the CLI mouse model, suggesting a new therapy for ASO.

The Role of Lower Extremity Amputation in Chronic Limb-Threatening Ischemia

Chronic limb-threatening ischemia (CLTI) is a severe form of peripheral artery disease associated with high rates of limb loss. The primary goal of treatment in CLTI is limb salvage via revascularization. Multidisciplinary teams provide improved care for those with CLTI and lead to improved limb salvage rates. Not all patients are candidates for revascularization, and a subset will require major amputation. This article highlights the role of amputations in the management of CLTI, and describes the patients who should be offered primary amputation.

2D perfusion DSA with an open-source, semi-automated, color-coded software for the quantification of foot perfusion following infrapopliteal angioplasty: a feasibility study

BACKGROUND

Foot perfusion has been recently implemented as a new tool for optimizing outcomes of peripheral endovascular procedures. A custom-made, two-dimensional perfusion digital subtraction angiography (PDSA) algorithm has been implemented to quantify outcomes of endovascular treatment of critical limb ischemia (CLI), assist intra-procedural decision-making, and enhance clinical outcomes.

METHODS

The study was approved by the Hospital's Ethics Committee. This prospective, single-center study included seven consecutive patients scheduled to undergo infrapopliteal endovascular treatment of CLI. Perfusion blood volume (PBV), mean transit time (MTT), and perfusion blood flow (PBF) maps were extracted by analyzing time-intensity curves and signal intensity on the perfused vessel mask. Mean values calculated from user-specified regions of interest (ROIs) on perfusion maps were employed to evaluate pre- and post-endovascular treatment condition. Measurements were performed immediately after final PDSA.

RESULTS

In total, five patients (aged 54 ± 16 years, mean ± standard deviation) were analyzed, as two patients were excluded due to significant motion artifacts. Post-procedural MTT presented a mean decrease of 19.1% for all patients and increased only in 1 of 5 patients, demonstrating in 4/5 patients an increase in tissue perfusion after revascularization. Overall mean PBF and PBV values were also analogously increased following revascularization (446% and 69.5% mean, respectively) and in the majority of selected ROIs (13/15 and 12/15 ROIs, respectively).

CONCLUSIONS

Quantification of infrapopliteal angioplasty outcomes using this newly proposed, custom-made, intra-procedural PDSA algorithm was performed using PBV, MTT, and PBF maps. Further studies are required to determine its role in peripheral endovascular procedures ( ClinicalTrials.gov Identifier: NCT04356092).

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.

Outcomes after Open Lower Extremity Revascularization in Patients with Critical Limb Ischemia

BACKGROUND

For decades, open intervention was the treatment of choice in patients requiring lower extremity revascularization. In the endovascular era, however, open and endovascular revascularization are options. The implications of prior revascularization on the outcomes for subsequent revascularization are not known. In the present study, we evaluated 30-day outcomes after open lower extremity revascularization for critical limb ischemia (CLI) in those who had previous interventions.

METHODS

The 2012-2017 open lower extremity bypass Participant User Data Files from the National Surgical Quality Improvement Program were used to identify a cohort of patients with CLI. Patients whose operation was considered emergent were excluded from the analysis. Patients were stratified on whether they had a previous open or endovascular intervention or undergoing a primary revascularization. The primary outcome measure was 30-day major adverse limb events (MALEs). Secondary outcomes included major adverse cardiac events (MACEs) and wound complications.

RESULTS

A total of 12,668 patients met study criteria with 59.6% (n = 7,549) undergoing a primary open revascularization, 22.4% (n = 2,839) having a prior endovascular intervention, and 18.0% (n = 2,280) having a prior open revascularization. There were notable differences in the baseline characteristics between the 3 groups. In addition, there were differences in the reason for intervention (rest pain versus tissue loss), type of revascularization, and type of conduit used between the 3 groups. After adjustment, a prior open revascularization was significantly associated with 30-day MALE when compared with a primary revascularization (adjusted odds ratio, 1.69; 95% confidence interval, 1.47-1.94; P < 0.001) and prior endovascular intervention (adjusted odds ratio, 1.76; 95% confidence interval, 1.46-2.12; P < 0.001). There were no differences in outcomes between primary revascularization and prior endovascular patients. There were no differences between MACEs or wound complications between the 3 groups.

CONCLUSIONS

A prior endovascular intervention does not seem to accrue any additional short-term risk when compared with primary revascularization, suggesting an endovascular-first approach may be a safe strategy in patients with CLI. However, a prior open intervention is significantly associated with 30-day MALE in patients undergoing redo open revascularization, which may be related to the rapid decline in patients once they have exhausted their best open revascularization option.

The Triple Wire Technique for Delivery of Endovascular Components in Difficult Anatomy

We describe a novel endovascular technique in which three 0.014″ guidewires are placed in parallel through a 0.035″ lumen catheter, in order to create a stiff platform to allow for delivery of 0.035″ profile devices through challenging anatomy. Three illustrative cases are presented: a difficult aortic bifurcation during lower extremity intervention, a tortuous internal iliac artery during placement of an iliac branch device, and salvage of a renal artery after inadvertent coverage during proximal cuff deployment for type 1a endoleak. We also quantify the relative stiffness of the triple 0.014″ wire configuration, using several well-known 0.035″ wires for comparison. The "triple wire technique" is an effective method for tracking endovascular devices through difficult tortuous anatomy, and can be used in a variety of clinical settings. The technique is especially useful when a traditional, stiff 0.035″ wire will not track without "kicking out." Each 0.014″ wire is reasonably soft and traverses the tortuous vessel easily, but when the 3 wires are used together as a rail it provides a stiff enough platform for delivery.

A Single-Center Experience of Paclitaxel in the Treatment of Femoropopliteal Disease-No Evidence for an Association With Mortality

PURPOSE

Paclitaxel-coated devices have been increasingly used in endovascular treatment of femoropopliteal disease as they limit recurrence of lesions and improve patient outcomes. However, a recent meta-analysis reported that these devices increase mortality risk at 2 years post-intervention but did not account for confounding variables. Therefore, our goal was to evaluate mortality after paclitaxel treatment of femoropopliteal disease using patient-level data.

METHODS

We performed a retrospective review of all patients who received endovascular treatment for femoropopliteal lesions at our center between December 2009 and July 2017. There were 388 patients in the paclitaxel group and 314 control patients.

RESULTS

Survival analysis with hazard ratios showed no difference between mortality in the paclitaxel and control groups. Age, renal insufficiency, and chronic limb-threatening ischemia were significant predictors of mortality. We also used logistic regression to evaluate mortality at 1, 2, and 5 years post-intervention and found no difference between the paclitaxel and control groups at any time point, while age, renal insufficiency, and chronic limb-threatening ischemia at the time of intervention were all associated with the risk of death. Finally, we tallied the causes of death in our cohort and found no difference in the distribution of causes between groups.

CONCLUSION

Our single-center, retrospective study provides no evidence of increased risk of death with paclitaxel treatment in femoropopliteal disease. Contrastingly, age, renal insufficiency, and chronic limb-threatening ischemia were the most important factors contributing to mortality and therefore should be included as potential confounders in future studies assessing mortality in femoropopliteal disease.

Current opinions about the definition of critical limb ischemia: A debate still open after three decades

Critical limb ischemia (CLI) is the most advanced stage of peripheral arterial disease. It is clinically defined as rest pain with or without skin ulcer or gangrene and carries a very poor prognosis with a high rates of limb amputation and cardiovascular mortality. Despite the first definition of CLI has been published more than 30 years ago, the debate about what it really is, is still open. Over the years the hemodynamic parameters utilised to define the critical level of limb perfusion have changed. This has raised some question about the apparent confusion about the definition of CLI. Moreover, a new term such as "limb threatening ischemia" has replaced the definition of CLI in recent guideline. Therefore, it becomes necessary to understand the evolution of the concept and the definition of CLI, to interpret the future trend.Hence, this work analysing the guideline documents on peripheral arterial disease that have defined the CLI to date, aims to clarify the path that has brought to the current conceptual changes of the definition of CLI.

Applicability of Transcutaneous Oxygen Tension Measurement in the Assessment of Chronic Limb-Threatening Ischemia

Transcutaneous oxygen tension measurement (TcPO2) is widely applied for the evaluation of chronic limb-threatening ischemia (CLTI). Nevertheless, studies that focused on the clinical value of TcPO2 have shown varying results. We identified factors that potentially play a role in TcPO2 measurement variation such as probe placement, probe temperature, and the use of a reference probe. In this review of the current literature, we assessed the application of these factors. A systematic search was conducted. Parameters that were assessed were probe placement, probe temperature, and mentioning and/or use of a reference probe. In total, 36 articles were eligible for analysis. In 24 (67%) studies, probes were placed on specific anatomical locations. Seven (19%) studies placed probes, regardless of the location of the ulcer, adjacent to an ischemic lesion or ulcer (perilesion). Selected temperature setting of the probe differed; in 18 (50%), a default probe temperature of 44°C was selected, and in 13 (36%), a different temperature was selected. In 31 (84%) studies, the use of a reference probe was not reported. Transcutaneous oxygen tension measurement is applied diversely in patients with CLTI. Homogeneity in TcPO2 protocols is warranted for reliable clinical application and to compare future TcPO2 research.

Mortality After Paclitaxel-Coated Device Use in Patients With Chronic Limb-Threatening Ischemia: A Systematic Review and Meta-Analysis of Randomized Controlled Trials

Purpose:

To report the risk of all-cause mortality after treatment with paclitaxel-coated devices vs uncoated controls in patients with chronic limb-threatening ischemia (CLTI).

Materials and Methods:

A search of the PubMed, Embase, Cochrane, CINAHL, DARE, and PROSPERO databases was made on 5 November 2019 to identify randomized controlled trials (RCT) using intention-to-treat analysis to compare a paclitaxel-coated device to an uncoated device in PAD patients having clinical follow-up of at least 6 months. Half of the study population had to have CLTI or extractable data on the CLTI subgroup if <50%. The search identified 11 trials having 1450 patients randomized to a paclitaxel-coated device (n=866) or an uncoated control (n=584). There were 1367 (94.3%) patients with CLTI (range 10–429). The single endpoint was all-cause mortality, which was analyzed by pooling the mortality data in a DerSimonian and Laird random effects model. Summary statistics are expressed as relative risk ratios (RR) with a 95% confidence interval (CI).

Results:

The mean follow-up was 25.6 months (range 6–60); 10 of 11 studies reported a minimum 12-month follow-up. There were 161 (18.6%) deaths among 866 subjects in the paclitaxel device group and 116 deaths among 584 (19.9%) subjects in the non-coated control group (RR 0.93, 95% CI 0.78 to 1.12, p=0.45).

Conclusion:

There was no observed difference in short- to midterm mortality among a pooled patient population of predominately CLTI patients treated with paclitaxel-coated balloons or stents compared with uncoated controls.

Rates and timing of subsequent amputation after initial minor amputation

OBJECTIVE

Studies evaluating major amputation after initial minor amputation are few with rates of subsequent major amputation ranging from 14% to 35% with limited understanding of associated comorbidities and time to limb loss. The aim of this study is to determine the major amputation rates for patients who had already undergone an initial minor amputation and determine which factors are associated with the need for subsequent major amputation.

METHODS

Using statewide data between 2005 and 2013, patients with peripheral artery disease (PAD), diabetes mellitus (DM), and combined PAD/DM who had a lower extremity ulcer and who had also undergone a minor amputation were identified. These patients were evaluated for the rate of subsequent major amputation and competing risk Cox proportional hazards modeling was used to study which factors were associated with the risk of subsequent limb loss.

RESULTS

The cohort consisted of 11,597 patients (DM, n = 4254; PAD, n = 2142; PAD/DM, n = 5201) with lower extremity ulcers who underwent an initial minor amputation. The rate of any subsequent amputation was highest in patients with PAD/DM (23% vs DM = 17%, PAD = 17%; P = not statistically significant). The rate of subsequent minor amputation was 16% in the PAD/DM versus 15.2% in PAD and 12.2% in patients with DM (P < .001). Patients with PAD/DM had the highest rate of subsequent major amputation (6.3% vs DM = 5.2%, PAD = 2.1%; P < .001). There was no statistically significant difference in the median time to major amputation among the three groups (PAD/DM, 13 months; DM, 14 months; PAD, 8.6 months; P = NS). Patients who were revascularized before a repeat minor amputation had a decreased risk of a major amputation compared with those who were intervened on after a repeat minor amputation (hazard ratio, 0.002; 95% confidence interval, 0-0.22). Patients treated completely in the outpatient setting were also less likely to undergo subsequent major amputation (hazard ratio, 0.7; 95% confidence interval, 0.5-0.98) compared with those who required hospitalization or presented to the emergency room.

CONCLUSIONS

Patients with ulcers and combined PAD and DM have a higher risk for secondary major and minor amputation than patients with either disease alone with half of the limb loss occurring at approximately 1 year after the initial minor amputation. Additionally, early diagnosis and appropriate referral may result in decreased limb loss for these patients.

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.

Cost-Effectiveness of Drug-Eluting Stents for Infrapopliteal Lesions in Patients with Critical Limb Ischemia: The PADI Trial

PURPOSE

Drug-eluting stents (DES) improve clinical and morphological long-term results compared to percutaneous transluminal angioplasty (PTA) with bailout bare metal stenting (BMS) in patients with critical limb ischemia (CLI) and infrapopliteal lesions (PADI trial). We performed a cost-effectiveness analysis of DES compared to PTA ± BMS in cooperation with Dutch health insurance company VGZ, using data from the PADI trial.

MATERIALS AND METHODS

In the PADI trial, adults with CLI (Rutherford category ≥ 4) and infrapopliteal lesions were randomized to receive DES with paclitaxel or PTA ± BMS. Seventy-four limbs (73 patients) were treated with DES and 66 limbs (64 patients) with PTA ± BMS. The costs were calculated by using the mean costs per stent multiplied by the mean number of stents used per patient (€750 × 1.8 for DES vs €250 × 0.3 for PTA ± BMS). These costs were compared with the costs of major amputation (€16.000) and rehabilitation (first year €15.750, second year €7.375 and third year €3.600).

RESULTS

The 5-year major amputation rate was lower in the DES group (19.3% vs 34.0% for PTA ± BMS; p = 0.091). In addition, the 5-year amputation-free survival and event-free survival were significantly higher in the DES group (31.8% vs 20.4%, p=0.043; and 26.2% vs 15.3%, p=0.041, respectively). After 1 year, the cost difference per patient between DES and PTA ± BMS is €1.679 in favor of DES and €2.694 after 3 years.

CONCLUSION

In our analysis, DES are cost-effective due to the higher hospital costs of amputation and rehabilitation in the PTA ± BMS group.

LEVEL OF EVIDENCE

Level 1b, analysis based on clinically sensible costs and randomized controlled trial.

Validation of randomized controlled trial-derived models for the prediction of postintervention outcomes in chronic limb-threatening ischemia

BACKGROUND

Chronic limb-threatening ischemia (CLTI) represents the most severe form of peripheral artery disease and has a large impact on quality of life, morbidity, and mortality. Interventions are aimed at improving tissue perfusion and averting amputation and secondary cardiovascular complications with an optimal risk-benefit ratio. Several prediction models regarding postprocedural outcomes in CLTI patients have been developed on the basis of randomized controlled trials to improve clinical decision-making. We aimed to determine model performance in predicting clinical outcomes in selected CLTI cohorts.

METHODS

This study validated the Bypass versus Angioplasty in Severe Ischaemia of the Leg (BASIL), Finland National Vascular registry (FINNVASC), and Prevention of Infrainguinal Vein Graft Failure (PREVENT III) models in data sets from a peripheral artery disease registry study (Athero-Express) and two randomized controlled trials of CLTI in The Netherlands, Rejuvenating Endothelial Progenitor Cells via Transcutaneous Intra-arterial Supplementation (JUVENTAS) and Percutaneous Transluminal Angioplasty and Drug-eluting Stents for Infrapopliteal Lesions in Critical Limb Ischemia (PADI). Receiver operating characteristic (ROC) curve analysis was used to calculate their predictive capacity. The primary outcome was amputation-free survival (AFS); secondary outcomes were all-cause mortality and amputation at 12 months after intervention.

RESULTS

The BASIL and PREVENT III models showed predictive values regarding postintervention mortality in the JUVENTAS cohort with an area under the ROC curve (AUC) of 81% and 70%, respectively. Prediction of AFS was poor to fair (AUC, 0.60-0.71) for all models in each population, with the highest predictive value of 71% for the BASIL model in the JUVENTAS population. The FINNVASC model showed the highest predictive value regarding amputation risk in the PADI population with AUC of 78% at 12 months.

CONCLUSIONS

In general, all models performed poor to fair in predicting mortality and amputation. Because the BASIL model performed best in predicting AFS, we propose use of the BASIL model to aid in the clinical decision-making process in CLTI. However, improvements in performance have to be made for any of these models to be of real additional value in clinical practice.

Perfusion Assessment in Critical Limb Ischemia: Principles for Understanding and the Development of Evidence and Evaluation of Devices: A Scientific Statement From the American Heart Association

There are >12 million patients with peripheral artery disease in the United States. The most severe form of peripheral artery disease is critical limb ischemia (CLI). The diagnosis and management of CLI is often challenging. Ethnic differences in comorbidities and presentation of CLI exist. Compared with white patients, black and Hispanic patients have higher prevalence rates of diabetes mellitus and chronic renal disease and are more likely to present with gangrene, whereas white patients are more likely to present with ulcers and rest pain. A thorough evaluation of limb perfusion is important in the diagnosis of CLI because it can not only enable timely diagnosis but also reduce unnecessary invasive procedures in patients with adequate blood flow or among those with other causes for ulcers, including venous, neuropathic, or pressure changes. This scientific statement discusses the current tests and technologies for noninvasive assessment of limb perfusion, including the ankle-brachial index, toe-brachial index, and other perfusion technologies. In addition, limitations of the current technologies along with opportunities for improvement, research, and reducing disparities in health care for patients with CLI are discussed.

Trends in statin utilization among adults with severe peripheral artery disease including critical limb ischemia in an integrated healthcare delivery system

Evidence suggests that statin therapy in patients with peripheral artery disease (PAD) is beneficial yet use remains suboptimal. We examined trends in statin use, intensity, and discontinuation among adults aged ⩾ 40 years with incident severe PAD and a subset with critical limb ischemia (CLI) between 2002 and 2015 within an integrated healthcare delivery system. Discontinuation of statin therapy was defined as the first 90-day gap in treatment within 1 year following PAD diagnosis. We identified 11,059 patients with incident severe PAD: 31.1% (n = 3442) with CLI and 68.9% (n = 7617) without CLI. Mean (SD) age was 68.6 (11.3) years, 60.5% were male, 54.2% white, 23.2% Hispanic, and 16.2% black. Statin use in the year before diagnosis increased from 50.4% in 2002 to 66.0% in 2015 (CLI: 43.7% to 68.0%; without CLI: 53.1% to 64.2%, respectively). The proportion of patients on high-intensity statins increased from 7.3% in 2002 to 41.9% in 2015 (CLI: 7.2% to 39.4%; without CLI: 7.4% to 44.2%, respectively). Of the 40.5% (n = 4481) who were not on a statin in the year before diagnosis, 13.5% (n = 607) newly initiated therapy within 1 month (CLI: 10.1% (n = 150); without CLI: 15.3% (n = 457)). Following diagnosis, 12.5% (n = 660) discontinued statin therapy within 1 year (CLI: 15.5% (n = 202); without CLI: 11.5% (n = 458)). Although use of statins increased from 2002 to 2015, a substantial proportion of the overall PAD and CLI subpopulation remained untreated with statins, representing a significant treatment gap in a population at high risk for cardiovascular events and adverse limb outcomes.

Safety and Efficacy of Placenta-Derived Mesenchymal Stem Cell Treatment for Diabetic Patients with Critical Limb Ischemia: A Pilot Study

AIM

Diabetic foot has become the main cause of non-traumatic amputation. Stem cell therapy, especially mesenchymal stem cells (MSCs), holds a great promise as a therapy for diabetic foot with ischemia limb arterial disease. The aim of this pilot study is to evaluate the safety and efficacy of placenta-derived MSCs (P-MSCs) treatment for diabetic patients with critical limb ischemia (CLI).

METHODS

Four eligible diabetic patients with CLI were consecutively enrolled in this pilot study. On the base of the standard-of-care treatment, these patients accepted P-MSCs treatment by intramuscular injection for successive 3 times at an interval of 4 weeks, and the safety and efficacy of placenta-derived MSCs (P-MSCs) treatment were evaluated.

RESULTS

There were no serious adverse events during the period of P-MSCs injection and the 24-weeks follow-up period. The clinical ischemic features of patients were improved 24 weeks after P-MSCs treatment. The scores of resting pain and limb coldness significantly decreased, and pain-free walking distance significantly increased from baseline to 24 weeks after P-MSCs therapy. The resting ankle brachial index increased, but no statistically significant difference was found. The findings of magnetic resonance angiography showed the increase of collateral vessel formation in one patient, but there were no significant changes observed in the other patients.

CONCLUSIONS

The data in this pilot study indicated that multiple intramuscular P-MSCs injections may be a safe and effective alternative therapy for diabetic patients with CLI, and larger, placebo-controlled, perspective studies are needed to prove these results.

Rational and design of the INtentional COronary revascularization versus conservative therapy in patients undergOing successful peripheRAl arTEry revascularization due to critical limb ischemia trial (INCORPORATE trial)

Critical limb ischemia is associated with excessively high risk for cardiovascular events, including myocardial infarction and death. Additionally, in this patient population non-invasive evaluation of coronary artery disease is limited due to (1) inability of exercise testing, (2) frequent occurrence of balanced ischemia and (3) frequent occurrence of diffuse coronary calcification. Intentional Coronary Revascularization Versus Conservative Therapy in Patients Undergoing Peripheral Artery Revascularization Due to Critical Limb Ischemia trial (INCORPORATE trial) is a multicentric international randomized open label clinical trial. Trial will recruit patients, who underwent successful peripheral artery revascularization due to critical limb ischemia and randomize 1:1 to conservative medical therapy versus an immediate invasive strategy to investigate and treat coronary artery disease. The objective is to evaluate whether intentional invasive strategy with ischemia targeted reasonably complete coronary revascularization is superior as compared to conventional primarily conservative approach in terms of spontaneous myocardial infarction and overall survival at 12 months follow-up. The trial is registered at clinicaltrials.gov (NCT03712644).

Evaluation of Risk Factors for Major Amputation in Patients With Diabetes and Peripheral Artery Disease Receiving Antiplatelet Therapy - Post Hoc Analysis of a Prospective Observational Multicenter Cohort Study (SEASON)

BACKGROUND

Guidelines for peripheral arterial disease (PAD) recommend long-term antiplatelet therapy in symptomatic patients to reduce cardiovascular morbidity and mortality risk. Although diabetes is a known risk factor for PAD, PAD has been undertreated in these patients. This study aimed to evaluate risk factors for major amputation in patients with diabetes undergoing antiplatelet therapy for PAD.Methods and Results:This retrospective analysis of a 2-year observational cohort study (1,745 clinics in Japan, September 2009-2013) evaluated predictors of amputation in patients with diabetes undergoing antiplatelet therapy for PAD. Among 4,016 eligible patients, 52 had an amputation during follow-up. Amputation risk (Cox regression analysis) was predicted at baseline by history of lower extremity revascularization/amputation (hazard ratio [HR]: 2.92; 95% confidence interval [CI]: 1.39, 6.14), chronic kidney disease (HR: 4.19; 95% CI: 1.95, 8.97), and comorbid cerebrovascular and heart disease (HR: 3.32; 95% CI: 1.19, 9.30), and was unaffected by choice of oral antiplatelet therapy. In patients with PAD and diabetes, amputation event rate was highest for those with ankle-brachial pressure index (ABI) <0.40 and progressively decreased at higher ABI cut-offs.

CONCLUSIONS

These findings inform real-world understanding of PAD in diabetic patients receiving antiplatelet therapy in Japan, and showed that ABI <0.4 was the strongest risk factor for amputation.

Applications of Ultrasound to Stimulate Therapeutic Revascularization

Many pathological conditions are characterized or caused by the presence of an insufficient or aberrant local vasculature. Thus, therapeutic approaches aimed at modulating the caliber and/or density of the vasculature by controlling angiogenesis and arteriogenesis have been under development for many years. As our understanding of the underlying cellular and molecular mechanisms of these vascular growth processes continues to grow, so too do the available targets for therapeutic intervention. Nonetheless, the tools needed to implement such therapies have often had inherent weaknesses (i.e., invasiveness, expense, poor targeting, and control) that preclude successful outcomes. Approximately 20 years ago, the potential for using ultrasound as a new tool for therapeutically manipulating angiogenesis and arteriogenesis began to emerge. Indeed, the ability of ultrasound, especially when used in combination with contrast agent microbubbles, to mechanically manipulate the microvasculature has opened several doors for exploration. In turn, multiple studies on the influence of ultrasound-mediated bioeffects on vascular growth and the use of ultrasound for the targeted stimulation of blood vessel growth via drug and gene delivery have been performed and published over the years. In this review article, we first discuss the basic principles of therapeutic ultrasound for stimulating angiogenesis and arteriogenesis. We then follow this with a comprehensive cataloging of studies that have used ultrasound for stimulating revascularization to date. Finally, we offer a brief perspective on the future of such approaches, in the context of both further research development and possible clinical translation.

The Role of Delirium and Other Risk Factors on Mortality in Elderly Patients with Critical Limb Ischemia Undergoing Major Lower Limb Amputation

BACKGROUND

Delirium in patients with critical limb ischemia (CLI) is associated with increased mortality. The main goal of this study was to investigate the association between delirium and mortality in patients undergoing major lower limb amputation for CLI. In addition, other risk factors associated with mortality were analyzed.

METHODS

An observational cohort study was conducted including all patients aged ≥70 years with CLI undergoing a major lower limb amputation between January 2014 and July 2017. Delirium was scored using the Delirium Observation Screening Score in combination with the Diagnostic and Statistical Manual of Mental Disorders, Fifth Edition. Risk factors for mortality were analyzed by calculating hazard ratios using a Cox proportional hazards model.

RESULTS

In total, 95 patients were included; of which, 29 (31%) patients developed a delirium during admission. Delirium was not associated with an increased risk of mortality (hazard ratio [HR] = 0.84; 95 % confidence interval [CI]: 0.51-1.73; P = 0.84). Variables independently associated with an increased risk of mortality were age (HR 1.1; 95% CI 1.0-1.1), cardiac history (HR 3.3; 95% CI 1.8-6.1), current smoking (HR 2.9; 95% CI 1.6-5.5), preoperative anemia (HR 2.8; 95% CI 1.1-7.2), and living in a nursing home (HR 2.2; 95% CI 1.1-4.4).

CONCLUSION

Delirium was not associated with an increased mortality risk in elderly patients with CLI undergoing a major lower limb amputation. Factors related to an increased mortality risk were age, cardiac history, current smoking, preoperative anemia, and living in a nursing home.

Long-Term Outcomes of BMMSC Compared with BMMNC for Treatment of Critical Limb Ischemia and Foot Ulcer in Patients with Diabetes

We first compared long-term clinical outcomes in treating critical limb ischemia (CLI) and foot ulcer in patients with diabetes between autologous bone marrow mesenchymal stem cell (BMMSC) and bone-marrow-derived mononuclear cell (BMMNC) transplants. Forty-one patients were enrolled and followed up for 3 years. They received an 18-day standard treatment before stem cell transplantation. Patients with bilateral CLI and foot ulcer were injected intramuscularly or basally with BMMSC, BMMNC, or normal saline (NS). Cox model analysis showed significant differences in the hazard ratio (HR) for amputation with treatment by BMMSC (HR 0.21 [95% CI (0.05, 0.95)], P = 0.043), infection of foot (HR 5.30 [95% CI (1.89, 14.92)], P = 0.002), and age ≥64 (HR 3.01 [95% CI (1.11, 8.15)], P = 0.030), but no significant differences by BMMNC at 9 months after transplantation. Regarding ulcer healing and recurrence rate, the BMMSC group demonstrated a significant difference from the NS group during the 3-6 months after transplantation or healing, but the BMMNC group did not. This trial suggests that, compared with BMMNC treatment, BMMSC treatment leads to a longer time of limb salvage and blood flow improvement, and, when compared with conventional therapy, it can promote limb blood flow and ulcerative healing, and reduce ulcer recurrence and amputation within 9 months.