Antiplatelet therapy in peripheral artery disease

Protective effects of fisetin against myocardial ischemia/reperfusion injury

The underlying mechanism of the myocardial protective effect of fisetin was studied in a rat ischemia/reperfusion injury model. Sprague-Dawley rats were randomly assigned to seven groups and pretreated with different solutions by gavage administration. A rat model of cardiac ischemia/reperfusion injury was established. Plasma levels of Von Willebrand factor (vWF) were determined by ELISA, flow cytometry was used to determine the level of cardiomyocyte apoptosis and 2,3,5-triphenyltetrazolium staining was used to determine the size of myocardial infarcts. Hematoxylin and eosin-stained sections of myocardial tissues were examined for pathological changes. Expressions of nuclear factor (NF)-κB and matrix metallopeptidase 9 (MMP-9) were measured by immunohistochemistry. Compared with the model group, rats pretreated with fisetin, quercetin and aspirin showed significant prolongation of clotting time, prothrombin time, thrombin time and activated partial thromboplastin time. Fisetin treatment better maintained the integrity of myocardial fibers and nuclear integrity, reduced the percentage of apoptotic myocardial cells, inhibited expression of NF-κB, decreased the loss of MMP-9 and reduced nuclear translocation of NF-kB. Rats pretreated with fisetin also demonstrated a significant decrease in plasma levels of vWF. In addition, the protective effect of fisetin on myocardial cells was found to be dose dependent.

Platelets Are at the Nexus of Vascular Diseases

Platelets are important actors of cardiovascular diseases (CVD). Current antiplatelet drugs that inhibit platelet aggregation have been shown to be effective in CVD treatment. However, the management of bleeding complications is still an issue in vascular diseases. While platelets can act individually, they interact with vascular cells and leukocytes at sites of vascular injury and inflammation. The main goal remains to better understand platelet mechanisms in thrombo-inflammatory diseases and provide new lines of safe treatments. Beyond their role in hemostasis and thrombosis, recent studies have reported the role of several aspects of platelet functions in CVD progression. In this review, we will provide a comprehensive overview of platelet mechanisms involved in several vascular diseases.

Exposure to polycyclic aromatic hydrocarbons and risk of disability among an elderly population

Polycyclic aromatic hydrocarbons (PAHs) are environmental pollutants. Exposure to PAHs is associated with several adverse health outcomes. However, no previous study has examined the relationship between PAH exposure and functional dependence in an elderly population. Our aim was to examine whether PAH exposure was associated with functional dependence including total disability, activities of daily living (ADL), instrumental activities of daily living (IADL), leisure and social activities (LSA), lower extremity mobility (LEM), and general physical activities (GPA) in an elderly population. A total of 5816 elderly adults from the National Health and Nutrition Examination Survey (NHANES) from 2001 to 2006 were examined. PAH exposure was measured by urinary biomarkers. Functional dependence was assessed by 19 structured questions. The association between PAH exposures with functional dependence was performed by using a multivariable linear regression model. After adjusting for pertinent variables, positive associations were observed between the total number of disabilities and 2-naphthalene and 1-pyrene quartiles (all P_trend < 0.05). There was a dose-dependent relationship between 1-pyrene quartiles and all functional dependence domains, and the higher quartile of 1-pyrene was more closely associated with functional impairment (all P_trend < 0.05). PAH exposure is associated with functional dependence in American elderly adults. Future research is needed to bring to light the pathophysiological underlying mechanisms related to these findings.

Combination Therapy with Dipyridamole and Clopidogrel for Secondary Stroke Prevention in Aspirin-Intolerant Patients After Myocardial Infarction: Results of a Nationwide Case-Control Study

BACKGROUND AND PURPOSE

Combination therapy with dipyridamole and clopidogrel in stroke prevention and long-term outcomes in aspirin-intolerant patients with acute myocardial infarction (AMI) and previous stroke are unknown. This nationwide study analyzed the impact of dipyridamole and clopidogrel on secondary stroke prevention and long-term outcomes in aspirin-intolerant stroke patients after AMI.

METHODS

This was a nationwide, case-control study involving 186,112 first AMI patients, 78,607 of whom had a previous history of stroke. In the final analysis, we included 4637 patients taking clopidogrel alone and 208 patients using a combination of clopidogrel and dipyridamole.

RESULTS

The 12-year survival rate was not different between clopidogrel and clopidogrel-dipyridamole groups (log-rank p = 0.6247). Furthermore, there were no differences in event-free survival after stroke (log-rank p = 0.6842), gastrointestinal (GI) bleeding (log-rank p = 0.9539), or intracerebral hemorrhage (ICH; log-rank p = 0.6191) between the two groups. Dipyridamole did not contribute significantly to AMI survival (hazard ratio 0.98, 95% confidence interval 0.84-1.15), and did not show benefits in any of the subgroups regardless of sex, age (younger or older than 75 years), comorbidities, percutaneous coronary intervention, or medications.

CONCLUSION

No differences were observed in the 12-year survival rate between clopidogrel and clopidogrel-dipyridamole groups. The two groups had balanced event-free survival in recurrent stroke, ICH, GI bleeding, and myocardial infarction.

Role of Heme Oxygenases in Cardiovascular Syndromes and Co-morbidities

Cardiovascular Diseases (CVD), are the leading cause of human mortality worldwide and the focus of the intensive investigation is to characterize their pathogenesis. This review examines contribution to CVD of heme oxygenases (HOs), heat shock protein enzymes, comprising 3 isoforms: HO-1 (inducible), HO-2 (constitutively expressed) and HO-3 (function presently undefined), which constitute a primary endogenous countermeasure to oxidative tissue damage. Their role as CVD countermeasures is considered in the context of atherosclerosis, consequences of which are the leading cause of CVD deaths and from which 5 major syndromes may develop, namely: coronary artery disease and stroke, peripheral artery disease, kidney disease, cardiopulmonary disease and cerebrovascular disease. Over 75% of CVD deaths result from Coronary artery disease and stroke, with the severity of these conditions correlating with a systemic increase of the endogenous antioxidant bilirubin, produced by HO degradation of heme. Peripheral artery disease, (PAD) resulting from constricted arteries of the extremities is a painful and disabling condition, the severity of which correlates with elevated serum HO. Whether this represents an adaptive response or the enzyme is a contributor to PAD, remains to be determined. CVD symptoms, particularly hypertension, damage the vasculature and filtering structures of the kidneys and may be ameliorated by HO inducers. Interestingly, constitutive renal expression of HO-2 indicates that the enzyme is vital for healthy kidney function. Right ventricular hypertrophy and increased vascular resistance in blood vessels of the lungs exhibit mutually reinforcing positive feedback to result in cardiopulmonary heart disease, with morbidity and mortality resulting from associated inflammation and may be decreased with HO-1 inducers. Cerebrovascular disease, a major CVD complication affecting brain vasculature, with resulting susceptibility to stroke, maybe potently ameliorated by HO-1 inducers. Conclusion: Each of the six major categories of CVD exhibit features of pathogenesis that hold potential as future therapeutic targets, for modulated heme oxygenase activity.

Geographic variation and risk factors for systemic and limb ischemic events in patients with symptomatic peripheral artery disease: Insights from the REACH Registry

Background

Patients with symptomatic peripheral artery disease (PAD) are at high risk of ischemic events. However, data about predictors of this risk are limited.

Hypothesis

We analyzed baseline characteristics and 4‐year follow‐up of patients enrolled in the international REduction of Atherothrombosis for Continued Health (REACH) Registry with symptomatic PAD and no history of stroke/transient ischemic attack to describe annual rates of recurrent ischemic events globally and geographically.

Methods

The primary outcome was systemic ischemic events (composite of cardiovascular death, myocardial infarction, or stroke) at 4 years. The secondary outcome was limb ischemic events (composite of lower limb amputation, peripheral bypass graft, and percutaneous intervention for PAD) at 2 years. Multivariate analysis identified risk factors associated with recurrent ischemic events.

Results

The primary endpoint rate reached 4.7% during the first year and increased continuously (by 4%–5% each year) to 17.6% by year 4, driven mainly by cardiovascular mortality (11.1% at year 4). Japan experienced lower adjusted ischemic rates (P < 0.01) vs North America. Renal impairment (P < 0.01), congestive heart failure (P < 0.01), history of diabetes (P < 0.01), history of myocardial infarction (P = 0.01), vascular disease (single or poly, P < 0.01), and older age (P < 0.01) were associated with increased risk of systemic ischemic events, whereas statin use was associated with lower risk (P = 0.03). The limb ischemic event rate was 5.7% at 2 years.

Conclusions

Four‐year systemic ischemic risk in patients with PAD and no history of stroke or transient ischemic attack remains high, and was mainly driven by cardiovascular mortality.

Place of non-vitamin K antagonist oral anticoagulants in anticoagulant-antiplatelet combinations in peripheral artery disease

Non-vitamin K antagonist oral anticoagulants are becoming increasingly important in the prophylaxis and treatment of thrombosis in atrial fibrillation and venous thromboembolism. Antiplatelets are widely prescribed in the primary and secondary prevention of cardiac and vascular diseases. There are potentially numerous situations where anticoagulants and antiplatelets may be combined; these combinations have been explored in coronary artery disease, and some have been included in updated recommendations. Is it legitimate to transpose these recommendations to the management of peripheral artery disease? The specific characteristics of the treated vessels, the stents used, the respective frequencies of stent thrombosis and its effect on the target organ are probably different, and explain why opinions differ. However, because of a lack of evidence, empirical behaviours are being established without scientific validation. This review of the literature details the situations in which combinations of an anticoagulant and an antiplatelet have been explored in peripheral artery disease. We discuss the issue of antithrombotic combinations in stable peripheral artery disease and for vascular or endovascular surgery.

Accelerated Blood Clearance Phenomenon Reduces the Passive Targeting of PEGylated Nanoparticles in Peripheral Arterial Disease

Peripheral arterial disease (PAD) is a leading global health concern. Due to limited imaging and therapeutic options, PAD and other ischemia-related diseases may benefit from the use of long circulating nanoparticles as imaging probes and/or drug delivery vehicles. Polyethylene glycol (PEG)-conjugated nanoparticles have shown shortened circulation half-lives in vivo when injected multiple times into a single subject. This phenomenon has become known as the accelerated blood clearance (ABC) effect. The phenomenon is of concern for clinical translation of nanomaterials as it limits the passive accumulation of nanoparticles in many diseases, yet it has not been evaluated using inorganic or organic-inorganic hybrid nanoparticles. Herein, we found that the ABC phenomenon was induced by reinjection of PEGylated long circulating organic-inorganic hybrid nanoparticles, which significantly reduced the passive targeting of (64)Cu-labeled PEGylated reduced graphene oxide-iron oxide nanoparticles ((64)Cu-RGO-IONP-PEG) in a murine model of PAD. Positron emission tomography (PET) imaging was performed at 3, 10, and 17 days postsurgical induction of hindlimb ischemia. At day 3 postsurgery, the nanoparticles displayed a long circulation half-life with enhanced accumulation in the ischemic hindlimb. At days 10 and 17 postsurgery, reinjected mice displayed a short circulation half-life and lower accumulation of the nanoparticles in the ischemic hindlimb, in comparison to the naïve group. Also, reinjected mice showed significantly higher liver uptake than the naïve group, indicating that the nanoparticles experienced higher sequestration by the liver in the reinjected group. Furthermore, photoacoustic (PA) imaging and Prussian blue staining confirmed the enhanced accumulation of the nanoparticles in the liver tissue of reinjected mice. These findings validate the ABC phenomenon using long circulating organic-inorganic hybrid nanoparticles upon multiple administrations to the same animal, which may provide valuable insight into the future clinical applications of nanoparticles for imaging and treatment of PAD.

Baseline Platelet Activation and Reactivity in Patients with Critical Limb Ischemia

Background

Patients with critical limb ischemia (CLI) have a high risk to develop cardiovascular events (CVE). We hypothesized that in CLI patients platelets would display increased baseline activation and reactivity.

Objectives

We investigated baseline platelet activation and platelet reactivity in patients with CLI.

Patients/Methods

In this study baseline platelet activation and platelet reactivity in response to stimulation of all major platelet activation pathways were determined in 20 CLI patients (11 using aspirin and 9 using vitamin K-antagonists) included in the Juventas-trial (clinicaltrials.gov NCT00371371) and in 17 healthy controls. Platelet activation was quantified with flow cytometric measurement of platelet P-selectin expression and fibrinogen binding.

Results

CLI patients not using aspirin showed higher baseline platelet activation compared to healthy controls. Maximal reactivity to stimulation of the collagen and thrombin activation pathway was decreased in CLI patients compared to healthy controls. In line, attenuated platelet reactivity to stimulation of multiple activation pathways was associated with several traditional risk factors for cardiovascular disease.

Conclusions

Baseline platelet activation was increased in CLI patients, whereas the reactivity of circulating platelets to several stimulatory agents is decreased. Reactivity of platelets was inversely correlated with cardiovascular risk factors.

Comparison of dual-antiplatelet therapy durations after endovascular revascularization of infrainguinal arteries

BACKGROUND

The optimal dual-antiplatelet therapy (DAPT) duration after endovascular revascularization of infrainguinal arteries is uncertain.

METHODS

This study examines DAPT prescription trends and 12-month major adverse limb events (MALEs; a composite of repeat endovascular or surgical revascularization, acute vessel thrombosis, or amputation of the target limb), major adverse cardiovascular events (MACEs; all-cause mortality, nonfatal myocardial infarction [MI], stroke, or coronary revascularization), fatal bleeding events, and those requiring interruption or discontinuation of DAPT (hemorrhagic complications) for patients enrolled into the Excellence in Peripheral Artery Disease (XLPAD) registry.

RESULTS

Data on 368 patients prescribed antiplatelet therapy were analyzed; 8.2% were prescribed antiplatelet monotherapy, 48.6% DAPT for ≤3 months, and 43.2% for >3 months. Patients in the >3 DAPT prescribed group were older, had preexisting coronary artery disease (CAD), and prior MI (all P < 0.001). Overall MALE in the ≤3 and >3-month DAPT prescribed groups were 22.3% and 23.9%, respectively (P = 0.541). Survival analysis showed significantly higher rates of MACE in patients prescribed >3-month DAPT (17.6% vs. 9.5%; P = 0.019). An "as-treated" analysis excluded 10 patients who were prescribed DAPT for >3 months and revealed similar rates of MALE (24.9% vs. 20.8%; P = 0.386) and MACE (12.2% vs. 14.8%; P = 0.443) in patients receiving ≤3 and >3 DAPT. Hemorrhagic complications were similar across all prescribed and "as-treated" DAPT groups.

CONCLUSIONS

After infrainguinal endovascular procedures, patients with underlying CAD were prescribed longer (>3 months) duration of DAPT and experienced more cardiovascular events compared with those prescribed ≤3 months of DAPT. Adverse limb events were similar in both groups.