Antithrombotic Therapy for Peripheral Artery Disease in 2018

Hyperbaric oxygen therapy attenuated limb ischemia in mice with high-fat diet by restoring Sirtuin 1 and mitochondrial function

Hyperbaric oxygen therapy (HBO) shows promise as a treatment for peripheral artery disease (PAD), particularly when complicated by metabolic syndrome and diabetes. However, its precise effects on endothelial function remain unclear. This study explored the impact of HBO on angiogenesis and apoptosis in high-fat diet (HFD)-fed mice with limb ischemia, focusing on the role of sirtuin 1 (SIRT1). After 8 weeks on a chow or HFD, mice underwent unilateral femoral artery ligation and received HBO (3 ATA, 1 h/day for 5 days). HBO improved blood flow, enhanced vascular density, and reduced apoptosis in ischemic calf muscles of HFD-fed mice. In vitro, human umbilical vein endothelial cells (HUVECs) were subjected to high-glucose and oxygen-glucose deprivation (OGD) conditions, with or without HBO. HBO restored cell proliferation, migration, and tube formation under these conditions, reduced mitochondrial dysfunction, and decreased reactive oxygen species (ROS) production. However, these benefits were reversed by treatment with sirtinol, a SIRT1 inhibitor. HBO also increased SIRT1 expression and shifted mitochondrial dynamics toward fusion. Additionally, HBO upregulated angiogenesis-related proteins (VEGF, VEGFR, and SIRT1) while downregulating apoptosis-associated proteins (Bax, caspase-3, and p53). Collectively, these findings suggest that HBO enhances angiogenesis and reduces apoptosis in both in vivo and in vitro ischemia models, primarily through SIRT1 activation.

Management and Pharmacological Treatment of Peripheral Arterial Disease

Background: Peripheral arterial disease (PAD) is a complex, heterogeneous condition that has become a leading health concern globally. Peripheral arterial disease often co-exists with other vascular disease states, including cerebrovascular and cardiovascular disease. Optimal therapy for managing symptoms and progression of disease employs non-pharmacological, pharmacological, and contemporary revascularisation techniques to improve clinical outcomes and quality of life. However, large well-designed randomised control trials (RCT) and corresponding evidence-based guidelines for management of PAD are lacking, with current practice standards often extrapolated from evidence in coronary artery disease. Purpose: This review article aims to discuss currently accepted best pharmacological practice for PAD. Method: Relevant articles were searched between May 2023 and January 2024 through PubMed, Cochrane Library, Google Scholar and international guidelines, focusing on pharmacological management for PAD. Results: This narrative review discusses holistic pharmacological treatments for PAD.

Midterm Results of Drug-Coated Balloon and Bare Metal Stent in the Treatment of TASCII C/D Femoropopliteal Artery Occlusive Disease: A Retrospective Multicenter Study

PURPOSE

This study aimed to compare midterm efficacy between drug-coated balloon (DCB) and bare metal stent (BMS) in the treatment of TASCII C/D femoropopliteal artery lesions.

METHODS

The clinical data of patients with TASCII C/D femoropopliteal artery disease admitted to 3 vascular surgery centers from January 2018 to January 2021 were retrospectively analyzed. Patients were divided into DCB group and BMS group. The DCB group was further subdivided into DCB alone subgroup and DCB+BMS subgroup. Study primary outcomes were freedom from clinical-driven target lesion reintervention (FCD-TLR) at 24 months postprocedure. Secondary outcomes included ankle brachial index (ABI), Rutherford classification, major amputation rate, and mortality.

RESULTS

A total of 410 consecutive patients were enrolled. At 24 months follow-up, in DCB group (114 patients) relative to BMS group (296 patients), FCD-TLR (86.00% vs 71.91%, p=0.039), and ABI (0.53±0.11 vs 0.47±0.19, p=0.007) were higher; mean Rutherford class was lower (1.57±0.68 vs 3.31±1.39, p=0.000); and major amputation rate (0.87% vs 4.05%, p>0.05) and all-cause mortality (8.92% vs 6.41%, p>0.05) were statistically similar. In DCB alone, subgroup relative to DCB+BMS subgroup, FCD-TLR (90.00% vs 85.00%, p>0.05), major amputation rate (0 vs 1.08%, p>0.05), and all-cause mortality rate (9.09% vs 8.69%, p>0.05) were statistically similar, while FCD-TLR was higher in the DCB+BMS subgroup (90.00% vs 71.91%, p=0.045).

CONCLUSION

At midterm follow-up of patients treated for TASCII C/D femoropopliteal artery disease, use of DCB or of DCB combined with rescue BMS appeared similarly efficacious, and yielded more favorable outcomes than use of BMS.

CLINICAL IMPACT

The efficacy of drug-coated balloons relative to that of bare metal stents for the treatment of complex femoropopliteal artery lesions, particularly TASCII grade D lesions, remains uncertain. There is a scarcity of multicenter comparative studies, and in this multicenter retrospective study with up to 24-month follow-up, use of drug-coated balloon alone or combined with rescue bare metal stent appeared similarly efficacious while yielding more favorable outcomes than use of bare metal stent alone in the treatment of TASCII grade C/D femoropopliteal artery lesions. Randomized studies are warranted.

Atherosclerotic Disease: Pathogenesis and Approaches to Management

Atherosclerotic disease, including stroke and myocardial infarction, is the leading cause of morbidity and mortality worldwide. Atherosclerotic plaque formation occurs in the setting of excess oxidative and hemodynamic stress and is perpetuated by smoking, poor diet, dyslipidemia, hypertension, and diabetes. Plaque may rupture, resulting in acute thrombotic events. Smoking cessation, lifestyle modification, risk factor optimization, and antithrombotic therapies are the mainstays of atherosclerotic disease management and are the cornerstones to reduce morbidity and mortality in this high-risk patient population. Novel therapeutics are in development and will add to the growing armamentarium available to physicians who manage atherosclerotic disease.

Dual Antiplatelet Therapy or Antiplatelet Plus Anticoagulant Therapy in Patients with Peripheral and Chronic Coronary Artery Disease: An Updated Review

Despite evidence-based therapies, patients presenting with atherosclerosis involving more than one vascular bed, such as those with peripheral artery disease (PAD) and concomitant coronary artery disease (CAD), constitute a particularly vulnerable group characterized by enhanced residual long-term risk for major adverse cardiac events (MACE), as well as major adverse limb events (MALE). The latter are progressively emerging as a difficult outcome to target, being correlated with increased mortality. Antithrombotic therapy is the mainstay of secondary prevention in both patients with PAD or CAD; however, the optimal intensity of such therapy is still a topic of debate, particularly in the post-acute and long-term setting. Recent well-powered randomized clinical trials (RCTs) have provided data in favor of a more intense antithrombotic therapy, such as prolonged dual antiplatelet therapy (DAPT) with aspirin and a P2Y12 inhibitor or a therapy with aspirin combined with an anticoagulant drug. Both approaches increase bleeding and selection of patients is a key issue. The aim of this review is, therefore, to discuss and summarize the most up-to-date available evidence for different strategies of anti-thrombotic therapies in patients with chronic PAD and CAD, particularly focusing on studies enrolling patients with both types of atherosclerotic disease and comparing a higher- versus a lower-intensity antithrombotic strategy. The final objective is to identify the optimal tailored approach in this setting, to achieve the greatest cardiovascular benefit and improve precision medicine.

Monitoring antiplatelet therapy: where are we now?

Single antiplatelet therapy represents the cornerstone of thrombosis prevention in atherosclerotic cardiovascular disease. Dual antiplatelet therapy (DAPT), consisting of aspirin plus a P2Y12 inhibitor, is the standard of care for patients with acute coronary syndrome or undergoing both coronary and peripheral percutaneous interventions. Recent data suggest the efficacy of DAPT also after minor stroke. In this setting, a large body of evidence has documented that genetic and acquired patients' characteristics may affect the magnitude of platelet inhibition induced by antiplatelet agents. The implementation of tools allowing the identification and prediction of platelet inhibition has recently been shown to improve outcomes, leading to an optimal balance between antithrombotic efficacy and bleeding risk. We are therefore clearly moving towards tailored antiplatelet therapy. The aim of this paper is to summarize the available evidence on the evaluation of platelet inhibition in patients with coronary, peripheral, or cerebrovascular atherosclerosis. We will here focus on antiplatelet therapy based on both aspirin and P2Y12 inhibitors. In addition, we provide practical insights into the clinical settings in which it appears reasonable to implement antiplatelet therapy monitoring.

Gender Differences in Non-Persistence with Angiotensin-Converting Enzyme Inhibitors and Angiotensin Receptor Blockers among Older Hypertensive Patients with Peripheral Arterial Disease

The beneficial effects of angiotensin-converting enzyme inhibitors (ACEIs) and angiotensin receptor blockers (ARBs) in hypertensive patients with peripheral arterial disease (PAD) depends on long-term persistence. The aims of our study were to analyse gender differences in non-persistence with ACEIs/ARBs, and to identify the characteristics associated with the likelihood of non-persistence. Our study cohort included 7080 hypertensive patients (4005 women and 3075 men) aged ≥65 years, treated with ACEIs/ARBs, in whom PAD was diagnosed between 1 January and 31 December 2012. Non-persistence was identified according to a treatment gap of 6 months without ACEI/ARB prescriptions. The characteristics associated with non-persistence were identified using the Cox regression model. At the end of the 5-year follow-up, 23.2% of the whole study cohort, 22.3% of men, and 23.9% of women were non-persistent with ACEIs/ARBs, with no significant gender differences in persistence. While a number of characteristics were associated with non-persistence, only three characteristics had consistent, statistically significant associations in both genders: being a new ACEI/ARB user increased the likelihood of non-persistence, and general practitioner as index prescriber and increasing the overall number of medications decreased the likelihood of non-persistence. Information on the differences in characteristics that are associated with non-persistence between genders may help to better identify patients for whom special attention should be paid to improve their persistence.

Towards personalized antithrombotic management with drugs and devices across the cardiovascular spectrum

Intravascular thrombus formation and embolization are among the most frequent events leading to a number of cardiovascular conditions with high morbidity and mortality. The underlying causes are stasis of the circulating blood, genetic and acquired coagulation disorders, and reduced antithrombotic or prothrombotic properties of the vascular wall (Virchow's triad). In the venous system, intravascular thrombi can cause venous thrombosis and pulmonary and even peripheral embolism including ischaemic stroke [through a patent foramen ovale (PFO)]. Thrombi in the left atrium and its appendage or ventricle form in the context of atrial fibrillation and infarction, respectively. Furthermore, thrombi can form on native or prosthetic aortic valves, within the aorta (in particular at sites of ulcers, aortic dissection, and abdominal aneurysms), and in cerebral and peripheral arteries causing stroke and critical limb ischaemia, respectively. Finally, thrombotic occlusion may occur in arteries supplying vital organs such the heart, brain, kidney, and extremities. Thrombus formation and embolization can be managed with anticoagulants and devices depending on where they form and embolize and on patient characteristics. Vitamin K antagonists are preferred in patients with mechanical valves, while novel oral anticoagulants are first choice in most other cardiovascular conditions, in particular venous thromboembolism and atrial fibrillation. As anticoagulants are associated with a risk of bleeding, devices such as occluders of a PFO or the left atrial appendage are preferred in patients with an increased bleeding risk. Platelet inhibitors such as aspirin and/or P2Y12 antagonists are preferred in the secondary prevention of coronary artery disease, stroke, and peripheral artery disease either alone or in combination depending on the clinical condition. A differential and personalized use of anticoagulants, platelet inhibitors, and devices is recommended and reviewed in this article.

No benefit of vorapaxar on walking performance in patients with intermittent claudication

Background: The effect of pharmacologic agents in improving walking and quality of life measures in patients with intermittent claudication (IC) is variable. The objective of this study was to investigate the effect of the novel antithrombotic vorapaxar on symptom status in patients with IC. Methods: The study was a multicenter, randomized, placebo-controlled trial wherein patients with IC were treated with either vorapaxar or placebo in addition to a home exercise program for 6 months. Walking performance and quality of life were assessed by graded treadmill test (GTT) and 12-Item Short-Form Survey (SF-12), respectively, at baseline and at 6 months. A total of 102 subjects were randomized across 12 centers. Results: Of the subjects randomized, 66 completed all study assessments and comprised the dataset that was analyzed. After 6 months, there was no significant difference between the vorapaxar and placebo groups in walking performance, as reflected by the GTT, or in quality of life, as reflected by the SF-12. There were no severe bleeding events in either group. Conclusion: This study found no benefit of vorapaxar in patients with IC and reiterates the need for future drug therapy studies that expand the benefits of supervised exercise therapy in patients with IC. ClinicalTrials.gov Identifier: NCT02660866.

Lower Extremity Peripheral Artery Disease Without Chronic Limb-Threatening Ischemia: A Review

IMPORTANCE

Lower extremity peripheral artery disease (PAD) affects approximately 8.5 million people in the US and approximately 230 million worldwide.

OBSERVATIONS

Peripheral artery disease is uncommon before aged 50 years but affects up to 20% of people aged 80 years and older. It can be noninvasively diagnosed with the ankle-brachial index (ABI), a ratio of Doppler-recorded pressures in the dorsalis pedis and/or posterior tibial artery in each leg to brachial artery pressures. An ABI value less than 0.90 is 57% to 79% sensitive and 83% to 99% specific for arterial stenosis of at least 50%. Intermittent claudication, consisting of exertional calf pain that does not begin at rest and that resolves within 10 minutes of rest, is considered the classic symptom of PAD. However, 70% to 90% of people with an ABI value less than 0.90 either report no exertional leg symptoms (ie, asymptomatic) or report leg symptoms with walking that are not consistent with classic claudication. Over time, people with PAD restrict walking activity or slow walking speed to avoid leg symptoms. Thus, although approximately 75% of people with PAD report no change in leg symptoms over time, those with PAD have significantly greater annual declines in 6-minute walk performance compared with those without it. Approximately 11% of people with PAD develop chronic limb-threatening ischemia, the most severe form of PAD. Compared with people without PAD, those with the disease have approximately twice the rate of all-cause mortality, cardiovascular mortality, and major coronary events at 10-year follow-up. High-dose statins and antiplatelet therapy with or without antithrombotic therapy reduced rates of coronary events and stroke in people with PAD. Supervised treadmill exercise improved 6-minute walk distance by 30 to 35 m, consistent with a clinically meaningful change, whereas effective home-based walking exercise interventions improved 6-minute walk by 42 to 53 m. Effective home-based exercise programs require behavioral methods, including monitoring by a coach.

CONCLUSIONS AND RELEVANCE

Peripheral artery disease affects approximately 230 million people worldwide and is associated with increased rates of cardiovascular events, lower extremity events, and functional decline compared with that of people without PAD. People with PAD should be treated with the highest dose of statin tolerated, antithrombotic and/or antiplatelet therapy, and exercise.

Do we have a unified consensus on antithrombotic management of PAD?

Peripheral artery disease (PAD) is one of the most frequent manifestations of atherosclerosis with high rates of morbidity and mortality. Platelets and coagulation are involved in the progression of atherosclerosis and thromboembolic complications. PAD patients have increased prothrombotic potential, which includes platelet hyperaggregability and increased pro-coagulant state. Therefore, antithrombotic treatment is of utmost importance for the prevention of cardiovascular events in this group of patients. Aspirin is the basic antiplatelet drug, but with limited efficacy in PAD. In contrast to coronary artery disease, its effect on the prevention of cardiovascular events in PAD has been limited proven. Particularly in asymptomatic PAD, there is no evidence for risk reduction with aspirin. Clopidogrel and ticagrelor are more effective than aspirin. Clopidogrel is thus an effective alternative to aspirin for prevention of cardiovascular events in symptomatic PAD. In patients who are non-responders to clopidogrel, ticagrelor is indicated. Dual antiplatelet treatment (DAPT) with aspirin and ticagrelor in patients with coronary artery disease and concomitant PAD significantly decreased the rate of major adverse cardiovascular events, including adverse limb events. However, in the CHARISMA Trial, aspirin and clopidogrel were not more effective than aspirin alone and increased bleeding complications. Therefore, DAPT seems effective only in PAD accompanied by coronary artery disease. Anticoagulant treatment for symptomatic PAD with vitamin K antagonists alone or in combination with aspirin is not more effective than single antiplatelet treatment but increases the rate of major bleeding. Low dose rivaroxaban combined with aspirin in PAD patients significantly reduces cardiovascular events, including limb-threatening ischemia and limb amputations. Anticoagulation and antiplatelet treatment after percutaneous or surgical revascularization of PAD improve the patency of treated vessels. Aspirin with or without dipyridamole improved patency of infra-inguinal by-pass grafts at one year. The combination of clopidogrel with aspirin was more effective than aspirin alone in the prevention of prosthetic graft occlusions in patients undergoing below-knee by-pass-grafting. Oral vitamin K antagonists were not more effective than aspirin in the prevention of infra-inguinal by-pass occlusion. The combination of low dose rivaroxaban and aspirin was effective in preventing major adverse cardiovascular events and adverse limb events after infrainguinal endovascular or surgical revascularization in patients with intermittent claudication. However, the data on antithrombotic treatment after revascularization for limb-threatening ischemia is scanty and inconclusive. In conclusion: Antithrombotic treatment of PAD is a cornerstone for the management of these patients. Antiplatelet drugs prevent the initiation and progression of atherosclerosis and are effective also in the prevention of thromboembolic events. Simultaneous use of antiplatelet and anticoagulation drugs is accompanied by an increased risk of bleeding. However, combined treatment with aspirin and low-dose rivaroxaban is more effective than single antithrombotic treatment and safer than full-dose combined treatment.

Aspirin as a Potential Geroprotector: Experimental Data and Clinical Evidence

Aging is a biological process with effects at the molecular, cellular, tissue, organ, system, and organismal levels and is characterized by decline in physical function and higher risks of age-related diseases. The use of anti-aging drugs for disease prevention has become a high priority for science and is a new biomedicine trend. Geroprotectors are compounds which slow aging and increase lifespan of the organism in question. The common painkiller aspirin, a member of the non-steroidal anti-inflammatory drug (NSAID) family, is one of the potential geroprotective agents. Aspirin is often used in treatment of mild to moderate pain. It has anti-inflammatory and anti-pyretic properties and acts as an inhibitor of cyclooxygenase which results in inhibition of prostaglandin. Acetylsalicylic acid as an active compound of aspirin also inhibits platelet aggregation and is used in the prevention of arterial and venous thrombosis. Aspirin has shown life-extending effects in numerous model organisms. This chapter reviews the evidence for clinical efficacy of aspirin including cardiovascular disease prevention, anti-cancer effects, and improvement of cognitive function. However, there are some limitations of these therapies, including the risk of excessive bleeding. We have also summarized numerous experimental and analytical data that support health and longevity benefits of aspirin treatment by affecting pro-longevity pathways.

[Ways of limbs salvage in postoperative period of treatment of complications of diabetic foot syndrome]

The article deals with the use of a genetically engineered drug for stimulation of angiogenesis as a component of combined treatment of complications of ischaemic form of diabetic foot syndrome, showing comparative results of using therapeutic angiogenesis in patients in whom it was impossible to perform operative revascularization of the affected extremity, also providing a detailed description of the methodology of combined treatment of pyonecrotic complications of diabetic foot syndrome. The study included a total of 62 patients with pyonecrotic complications of Wagner grade III-IV diabetic foot syndrome. The patients were divided into two groups. Group One patients after minor amputation on the foot were assigned to receive conventional basic therapy and topical treatment of the foot wound with antiseptics and modern dressings. Group Two patients, besides basic therapy, additionally received combined treatment which was carried out in two stages and included urokinase, sulodexide, and a venotonic agent. Local treatment of the foot wound was performed with the help of two-stage vacuum therapy. Both groups were further subdivided into subgroups A and B. The patients in subgroups B of both groups in order to prevent progression of limb ischaemia were additionally given Neovasculgen, a genetically engineered drug for stimulation of angiogenesis. The patients of subgroups A of both groups did not receive this drug. The immediate results were assessed on the 1st, 7th and 14th days of treatment by the dynamics of changes in subjective symptoms, cytograms of the wound surface, level of partial pressure of oxygen in capillary blood of foot tissues, and the necessity to perform repeated necrectomy. The remote results were evaluated by the dynamics of changes in the pain-free walking distance, maximum distance walked, ankle-brachial index, linear velocity of blood flow through tibial arteries and partial pressure of oxygen in capillary blood of the affected limb at the 6th, 12th and 36th months after the performed treatment, as well as by the limb salvage and patients' survival during 3 years.

Antithrombotic strategies for patients with coronary and lower extremity peripheral artery diseases: a narrative review

INTRODUCTION

Patients with coexisting coronary artery disease (CAD) and peripheral artery disease (PAD) present a very high rate of cardiovascular (CV) morbidity and mortality. Several studies have demonstrated that different regimens of antithrombotic therapies may reduce adverse CV events in patients with CAD or PAD. However, data on optimal antithrombotic combination to use in these very high-risk patients are scarce and conflicting.

AREAS COVERED

This paper reviews current data on antithrombotic therapies tested in CAD patients with concomitant lower extremity PAD.

EXPERT OPINION

The antithrombotic response in lower extremity PAD patients varies based on the atherosclerotic burden. For patients with isolated stable PAD may be sufficient a less potent P2Y12 inhibitor as clopidogrel, whereas patients with lower extremity PAD and documented CAD benefit from a more intense and prolonged antithrombotic treatment.

Clopidogrel preventive effect based on cytochrome P450 2C19 genotype in ischaemic stroke: protocol for multicentre observational study

INTRODUCTION

Clopidogrel is an antiplatelet agent that is widely used for the secondary prevention of cardiovascular and cerebrovascular events. The genotype of cytochrome P450 2C19 (CYP2C19) differentially affects the liver's metabolism of clopidogrel, which may influence the drug's response and efficacy for cardiovascular event prevention. In contrast to prior studies of patients with coronary artery diseases, little is known about whether the CYP2C19 genotype influences the preventive efficacy of clopidogrel in patients who had a stroke. We hypothesise that, among patients who had an acute ischaemic stroke who are prescribed clopidogrel, the patients with a loss-of-function CYP2C19 genotype (poor and intermediate metabolisers) may be at a higher risk of composite cardiovascular events than those who are non-carriers (extensive metabolisers).

METHODS AND ANALYSIS

This prospective observational multicentre study was designed to determine whether composite cardiovascular events would differ among patients who had an ischaemic stroke prescribed clopidogrel according to CYP2C19 genotype (poor or intermediate vs extensive metabolisers). Inclusion criteria were patients who had an acute ischaemic stroke who underwent CYP2C19 genotype evaluation and received clopidogrel within 72 hours of stroke onset. The primary outcome is composite cardiovascular events (stroke, myocardial infarction, or cardiovascular death) within 6 months after acute ischaemic stroke between patients categorised as poor or intermediate metabolisers and those categorised as extensive metabolisers according to their CYP2C19 genotype.

ETHICS AND DISSEMINATION

The Institutional Review Board of Severance Hospital, Yonsei University College of Medicine approved this study (3-2019-0195). We received study approval from the institutional review board of each participating hospital. We plan to disseminate our findings at relevant conferences and meetings and through peer-reviewed journals.

TRIAL REGISTRATION NUMBER

NCT04072705.

Rivaroxaban in patients with ischaemic chronic cardiomyopathy and obstructive peripheral arterial disease: rationale for treatment and results

Patients with overt clinical atherosclerosis (ATS) or with previous peripheral vascular events have a high risk of ischaemic complications. A careful control of cardiovascular (CV) risk factors has been shown to improve prognosis, likely driven by a decrease progression of ATS. Prevention of occlusive complications is, on the other hand, based on antithrombotic therapy. So far, this therapeutic goal has been pursued through antiplatelet therapy with aspirin and P2Y12 receptor inhibitors. Anticoagulant therapy with full-dose vitamin K inhibitors, although effective in some arterial conditions, is burdened by high bleeding risk, and by low long-term compliance. In the COMPASS study, the association of aspirin with the factor Xa inhibitor, rivaroxaban, in a dose of one-fourth of the dose used in atrial fibrillation, decreased by more than 20% the incidence of CV events in patients with multi-district ATS. The positive effect was also observed as far as major peripheral complications, the like of critical limb ischaemia or limb amputations. This positive preventive effect was in addition to the effect of other preventive measures, such as the use of statins, ACE inhibitors, and aspirin itself. As compared to the aspirin-only treatment, the association with low-dose rivaroxaban had a significantly higher bleeding risk, which should be carefully considered when evaluating the individual risk/benefit ratio of the combined treatment.

An in vitro Model System for Evaluating Remote Magnetic Nanoparticle Movement and Fibrinolysis

Background

Thrombotic events continue to be a major cause of morbidity and mortality worldwide. Tissue plasminogen activator (tPA) is used for the treatment of acute ischemic stroke and other thrombotic disorders. Use of tPA is limited by its narrow therapeutic time window, hemorrhagic complications, and insufficient delivery to the location of the thrombus. Magnetic nanoparticles (MNPs) have been proposed for targeting tPA delivery. It would be advantageous to develop an improved in vitro model of clot formation, to screen thrombolytic therapies that could be enhanced by addition of MNPs, and to test magnetic drug targeting at human-sized distances.

Methods

We utilized commercially available blood and endothelial cells to construct 1/8th inch (and larger) biomimetic vascular channels in acrylic trays. MNP clusters were moved at a distance by a rotating permanent magnet and moved along the channels by surface walking. The effect of different transport media on MNP velocity was studied using video photography. MNPs with and without tPA were analyzed to determine their velocities in the channels, and their fibrinolytic effect in wells and the trays. 

Results

MNP clusters could be moved through fluids including blood, at human-sized distances, down straight or branched channels, using the rotating permanent magnet. The greatest MNP velocity was closest to the magnet: 0.76 ± 0.03 cm/sec. In serum, the average MNP velocity was 0.10 ± 0.02 cm/sec. MNPs were found to enhance tPA delivery, and cause fibrinolysis in both static and dynamic studies. Fibrinolysis was observed to occur in 85% of the dynamic MNP + tPA experiments.

Conclusion

MNPs hold great promise for use in augmenting delivery of tPA for the treatment of stroke and other thrombotic conditions. This model system facilitates side by side comparisons of MNP-facilitated drug delivery, at a human scale.

Tackling Elevated Risk in PAD: Focus on Antithrombotic and Lipid Therapy for PAD

The PAD population is at increased risk of major adverse cardiovascular events (MACE) and major adverse limb events (MALE). Risk factor modification, symptom control, antithrombotic, and lipid therapies are the mainstays of PAD medical therapy. Recent data has challenged prior recommendations regarding the optimal secondary prevention strategies in PAD. PURPOSE OF REVIEW: To review clinical evidence from large randomized controlled trials showing the benefit of antithrombotic and lipid therapy in the PAD population. RECENT FINDINGS: The COMPASS trial challenged prior recommendations regarding anticoagulation in PAD. Among the PAD subgroup, rivaroxaban 2.5 mg plus aspirin reduced MACE (HR 0.72, 95% CI 0.57-0.90, p = 0.0047), MALE (HR 0.54, 95% CI 0.35-0.82, p = 0.0037), and major amputation (HR 0.30, 95% CI 0.11-0.80, p = 0.011) compared with aspirin monotherapy. The THEMIS trial showed a 55% risk reduction for MALE with ticagrelor DAPT compared with aspirin monotherapy (HR 0.45, 95% CI 0.23-0.86). The FOURIER trial revealed that lowering LDL cholesterol below current targets with a PCSK9 inhibitor reduced MACE (HR 0.73, 95% CI 0.59-0.91, p = 0.0040) and MALE (HR 0.43, 95% CI 0.19-0.99, p = 0.042) in subjects with symptomatic PAD. Recent high-quality evidence shows the benefit of antiplatelet therapy, anticoagulation therapy, and lipid therapy in reducing MACE and MALE in PAD. Despite these findings, implementation remains a challenge and focus should now shift towards adopting evidence-based recommendations in clinical practice.

Potential of mesenchymal stem cells for bioengineered blood vessels in comparison with other eligible cell sources

Application of stem cells in tissue engineering has proved to be effective in many cases due to great proliferation and differentiation potentials as well as possible paracrine effects of these cells. Human mesenchymal stem cells (MSCs) are recognized as a valuable source for vascular tissue engineering, which requires endothelial and perivascular cells. The goal of this review is to survey the potential of MSCs for engineering functional blood vessels in comparison with other cell types including bone marrow mononuclear cells, endothelial precursor cells, differentiated adult autologous smooth muscle cells, autologous endothelial cells, embryonic stem cells, and induced pluripotent stem cells. In conclusion, MSCs represent a preference in making autologous tissue-engineered vascular grafts (TEVGs) as well as off-the-shelf TEVGs for emergency vascular surgery cases.