Specificities of primary and secondary prevention of lower extremity artery disease: introduction to a series of reviews

This article briefly discusses the risk factors for the development of lower extremity artery disease, namely smoking, diabetes mellitus, hyperlipidemia/dyslipidemia and hypertension. Each of these risk factors will be discussed in detail in forthcoming articles of the journal.

Characteristics of atherosclerosis in femoropopliteal artery and its clinical relevance

Atherosclerosis is a systemic disease with different faces. Despite identical or similar pathogenetic mechanisms, atherosclerotic lesions and their clinical manifestations vary in different parts of the vascular system. Peripheral arterial disease (PAD) represents one of the most frequent clinical manifestations of atherosclerosis with predominant location in the superficial femoral artery (SFA). Morphological characteristics of atherosclerotic plaques in peripheral arteries differ from lesions in the coronary and carotid arteries. Plaques in SFA have more fibrotic components, less lipids and inflammatory cells, which makes them more stable and less prone to rupture. Factors that determine the different structure of plaques in SFA compared to coronary arteries include hemodynamic forces, vasa vasorum and calcification. Low shear stress in SFA in the adductor canal is one of the factors which determines frequent atherosclerotic lesions in this region. Lower lipid content and fewer inflammatory cells explain higher stability of SFA plaques. The specific structure of SFA plaques may require preventive and therapeutic measures, which to some extent differ from prevention of coronary atherosclerosis and may include inhibition of fibrotic proliferation in SFA plaques and calcification. Revascularization of PAD differs from procedures used in coronary arteries and requires specific technical expertise and devices.

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.

A Review of Antithrombotic Treatment in Critical Limb Ischemia After Endovascular Intervention

Endovascular intervention is often used to treat critical limb ischemia (CLI). Post-intervention treatment with antiplatelet and/or anticoagulant therapy has reduced morbidity and mortality due to cardiovascular complications. The purpose of this review is to shed light on the various pharmacologic treatment protocols for treating CLI following endovascular procedures. We reviewed the literature comparing outcomes after antithrombotic treatment for patients with CLI. We characterized antithrombotic therapies into three categories: (1) mono-antiplatelet therapy (MAPT) vs. dual antiplatelet therapy (DAPT), (2) MAPT vs. antiplatelet (AP) + anticoagulant (AC) therapy, and (3) AC vs. AP + AC therapy. Relevant results and statistics were extracted to determine differences in the rates of the following outcomes: (1) re-stenosis, (2) occlusion, (3) target limb revascularization (TLR), (4) major amputation, (5) major adverse cardiac events, (6) all-cause death, and (7) bleeding. Studies suggest that DAPT reduces post-surgical restenosis, TLR, and amputation for diabetic patients, without increasing major bleeding incidences, compared to MAPT. Also, AP + AC therapy provides overall superior efficacy, with no difference in bleeding incidences, compared to antiplatelet alone. Additionally, the effects were significant for restenosis, limb salvage, survival rates, and cumulative rate of above ankle amputation or death. These results suggest that treatment with DAPT and AP + AC might provide better outcomes than MAPT following the endovascular intervention for CLI, and that the ideal treatment may be related to the condition of the individual patient. However, the studies were few and heterogenous with small patient populations. Therefore, further large controlled studies are warranted to confirm these outcomes.

Oral antiplatelet agents in cardiovascular disease

Antiplatelet agents significantly reduce mortality and morbidity in ischemic heart disease, cerebrovascular disease and peripheral artery disease (PAD), and are therefore part of guideline-driven daily medical treatment in these patients. Due to its beneficial effects in the secondary prevention of atherothrombotic events, aspirin remains the most frequently prescribed antiplatelet agent in cardiovascular disease. In patients with acute coronary syndromes (ACS) and in those undergoing angioplasty with stent implantation dual antiplatelet therapy with aspirin and an adenosine diphosphate (ADP) receptor antagonist is indicated. The development of the newer ADP P2Y₁₂ inhibitors prasugrel and ticagrelor has further improved prognosis in ACS patients compared to clopidogrel. Moreover, vorapaxar allows the inhibition of platelet activation by thrombin via protease-activated receptor-1 and has been approved for the use in patients with PAD and in those with a history of myocardial infarction. This review article summarizes the current evidence on oral antiplatelet agents in cardiovascular disease. Keywords: Aspirin, clopidogrel, prasugrel, ticagrelor, vorapaxar, cardiovascular disease.

Antithrombotic treatment in peripheral artery disease

Abstract. This review treats antithrombotic use for peripheral arterial disease (PAD). In asymptomatic patients, there are no scientific data to support single antiplatelet therapy (SAPT) for primary prophylaxis. In symptomatic PAD, SAPT with aspirin or clopidogrel is indicated. The efficacy of aspirin is controversial. Clopidogrel may be preferred over aspirin. Ticagrelor is not superior to clopidogrel in reducing major adverse cardiovascular events and major adverse limb events, but lowers the risk of ischaemic stroke. In symptomatic PAD, dual antiplatelet therapy (DAPT) with clopidogrel and aspirin does not provide benefit over SAPT with aspirin alone and is associated with increased risk of major bleeding. DAPT with ticagrelor 60 mg b. i. d. and aspirin provides a significant major adverse cardiovascular events reduction in symptomatic PAD patients and may be considered in PAD patients with prior myocardial infarction. The use of a new thrombin receptor antagonist, vorapaxar, on top of SAPT or DAPT with aspirin and/or clopidogrel, reduces the risk of acute limb ischaemia and peripheral artery revascularization in patients with symptomatic PAD, at the cost of an increased risk for bleeding. Rivaroxaban (2.5 mg b. i. d.) plus aspirin (100 mg daily) is the first antithrombotic association that proved significant benefit for PAD patients, in terms of strong endpoints – total mortality and cardiovascular mortality. Therefore, this association shows the strongest evidence for secondary prevention of symptomatic PAD patients. In PAD patients undergoing percutaneous peripheral interventions, at least four weeks of DAPT with aspirin and clopidogrel is recommended after infrainguinal stent implantation. Stenting below-the-knee arteries is often followed by a longer period of DAPT, but no specific evidence is available. Anticoagulation is mandatory to prevent arterial occlusion during radial or brachial invasive procedures. The strategy includes use of unfractioned heparin, bivalirudin or enoxaparin. Vitamin K antagonists may be considered after autologous vein infrainguinal bypass.

Antithrombotic therapy in peripheral artery disease

Antiplatelet agents are recommended for the reduction of major adverse cardiovascular events among all patients with symptomatic peripheral artery disease. However, the optimal antiplatelet regimen and duration of therapy in peripheral artery disease (PAD) remains unclear, largely due to limited and conflicting data in this patient population. This article reviews current data on antithrombotic therapy in PAD and discusses the implications of this data for current practice and future research.

Potential role of aspirin in the prevention of aneurysmal subarachnoid hemorrhage

BACKGROUND

Inflammation is a key element behind the pathophysiology of cerebral aneurysm formation and rupture. Aspirin is a potent inhibitor of cyclooxygenase-2 (COX), which plays a critical role in the expression of immune modulators known to contribute to cerebral aneurysm formation and rupture. Currently, there are no pharmacological therapies for patients with cerebral aneurysms. Both endovascular and microsurgical interventions may be associated with significant morbidity and mortality. Potentially, a medical alternative that prevents aneurysm progression and rupture may be a beneficial therapy for a significant number of patients.

SUMMARY

In animal models, treatment with aspirin and genetic inactivation of COX-2 decreases aneurysm formation and rupture. Selective inhibition of COX-1 did not decrease aneurysm rupture, suggesting that selection inhibition of COX-2 may be critical in thwarting aneurysm progression. Walls of ruptured human intracranial aneurysms have higher levels of COX-2 and microsomal prostaglandin E2 synthase 1 (mPGES-1), both of which are known to be inhibited by aspirin. In a pilot study, patients undergoing microsurgical clipping had attenuated expression of COX-2, mPGES-1, and macrophages in aneurysm walls after 3 months of aspirin therapy versus those that did not receive aspirin. Additionally, in patients undergoing endovascular therapy, local circulating expression of chemokines and COX-2 were increased in blood samples taken from within aneurysm domes as compared to peripheral blood sample controls. Treatment with aspirin also resulted in decreased expression of COX-2 within leukocytes within aneurysms as compared to peripheral blood samples. Novel molecular imaging with ferumoxytol-enhanced MRI may help in the identification of patients at increased risk for aneurysm rupture and assessment of a response to aspirin therapy. Key Messages: Aspirin has been found to be a safe in patients harboring cerebral aneurysms and clinical studies provide evidence that it may decrease the overall rate of rupture. Furthermore, aspirin is an accessible and inexpensive medicine for patients who may not have access to endovascular or microsurgical treatment or for patients who are deemed low risk of aneurysm rupture, high risk for intervention, or both. Future clinical trials are indicated to determine the overall effect of aspirin on aneurysm progression and rupture. This review provides an update on the potential mechanisms and benefits of aspirin in the treatment of cerebral aneurysms.

The efficacy and safety of cilostazol in ischemic stroke patients with peripheral arterial disease (SPAD): protocol of a randomized, double-blind, placebo-controlled multicenter trial

RATIONALE

It is not uncommon for patients with ischemic stroke to have peripheral arterial disease (PAD). Patients with polyvascular diseases carry greater burden of atherosclerosis and higher risks of developing vascular events and death. More effective regimens, such as dual antiplatelet agents, may be more effective for controlling progression of atherosclerosis in secondary prevention.

AIM

This study aims to evaluate whether cilostazol plus aspirin is more efficacious than aspirin alone for preventing progression of atherosclerosis in patients with ischemic stroke or transient ischemic attack (TIA) who also have peripheral arterial disease.

DESIGN

The Safety and Efficacy of Cilostazol in Ischemic Stroke Patients with Peripheral Arterial Disease (SPAD) study is a randomized double-blinded placebo-controlled trial. Patients with previous ischemic stroke or TIA who had been taking aspirin (100 mg per day), aged 50 years or older, with PAD in the lower limbs based on ankle-brachial index (ABI) <1·0 will be randomized into the treatment group with cilostazol (200 mg/day) or the placebo group on 1:1 basis.

STUDY OUTCOMES

Patients will be evaluated at 1, 3, 6, 9 and 12 months after randomization. The primary endpoint is difference in change in ABI between groups. The secondary and tertiary endpoints are the difference between groups in change in carotid intima-media thickness (IMT) and incidence rate of major cardiovascular events, including recurrent stroke, myocardial infarction, unstable angina, other vascular events, and death; and the safety measures, including major bleeding events, hemorrhagic stroke and death of any cause.

CONCLUSION

The SPAD trial is the first study to evaluate the safety and efficacy of dual antiplatelet agents, aspirin plus cilostazol, in comparison with aspirin alone in patients with both ischemic stroke or TIA and PAD. Results from this trial will provide important information on the merit of adding cilostazol to aspirin for slowing down progression of atherosclerosis in patients with ischemic stroke and PAD.

Antiplatelet Therapy for Peripheral Arterial Disease and Critical Limb Ischemia

Antiplatelet therapy is invariably prescribed for patients with peripheral arterial disease and critical limb ischemia, and numerous major society guidelines espouse their use, but high-quality data in this high-risk and challenging patient population are often lacking. This article summarizes the major guidelines for antiplatelet therapy, reviews the major studies of antiplatelet therapy in peripheral arterial disease (including data for aspirin, clopidogrel, dipyridamole, cilostazol, and prostanoids), and offers perspective on the potential benefits of ticagrelor, vorapaxar, and rivaroxaban. The review concludes with a discussion of the relative lack of efficacy that antiplatelet therapy has shown in regard to peripheral vascular outcomes.