Cardiology: Aspirin Resistance in Patients with Stable Coronary Artery Disease with and without a History of Myocardial Infarction

Closing the sex gap in cardiovascular mortality by achieving both horizontal and vertical equity

Addressing sex differences and disparities in coronary heart disease (CHD) involves achieving both horizontal and vertical equity in healthcare. Horizontal equity in the context of CHD means that both men and women with comparable health statuses should have equal access to diagnosis, treatment, and management of CHD. To achieve this, it is crucial to promote awareness among the general public about the signs and symptoms of CHD in both sexes, so that both women and men may seek timely medical attention. Women often face inequity in the treatment of cardiovascular disease. Current guidelines do not differ based on sex, but their applications based on gender do differ. Vertical equity means tailoring healthcare to allow equitable care for all. Steps towards achieving this include developing treatment protocols and guidelines that consider the unique aspects of CHD in women. It also requires implementing guidelines equally, when there is not sex difference rather than inequities in application of guideline directed care.

A Supramolecular Nitric Oxide Nanodelivery System for Prevention of Tumor Metastasis by Inhibiting Platelet Activation and Aggregation

Tumor cell-induced platelet aggregation (TCIPA) is known as a critical step in hematogenous tumor metastasis. The endogenous nitric oxide (NO) plays an important role in anticoagulation, which might have great potential to inhibit TCIPA. Herein, a glutathione-sensitive supramolecular nanocarrier is prepared via host-guest interaction for effective delivery of NO and chemotherapeutic agent gemcitabine (GEM). NO could be effectively released in tumor cells and inhibits platelet activation and aggregation. The inhibition of TCIPA by NO could effectively attenuate the migration and invasion of tumor cells in vitro. Furthermore, the in vivo experiments demonstrate that the NO and GEM co-delivered supramolecular nanocarriers can suppress the growth of primary tumor. More importantly, although NO-containing nanocarriers cannot inhibit the growth of primary tumors effectively, they can significantly inhibit tumor metastasis. This NO-based nano-delivery system not only provides new inspiration for multifunctional applications of NO in cancer therapy but also shows great potential in clinical antimetastatic applications.

Increased platelet aggregation and serum thromboxane levels in aspirin-treated patients with prior myocardial infarction

The antiplatelet effect of aspirin displays considerable inter-individual variability. We investigated the antiplatelet effect of aspirin in patients with coronary artery disease on aspirin mono-therapy with and without prior myocardial infarction (MI). Further, we investigated whether the effect of aspirin differed between patients with and without aspirin use at the time of MI onset. We performed a study on 231 patients, including 171 with prior MI. Among patients with only one prior MI (116 patients), 59 patients were on aspirin at the time of MI onset. All patients received 75 mg aspirin as mono-therapy. Platelet aggregation was assessed by multiple electrode aggregometry (Multiplate®) and Verify -Now®, and platelet activation was evaluated by soluble P-selectin. Furthermore, we measured serum thromboxane B2. MI patients had higher median platelet aggregation levels than patients without prior MI when evaluated by Multiplate® (parachidonic acid<0.0001, pcollagen=0.20). This was not supported by VerifyNow®. Furthermore, MI patients had higher median serum thromboxane B2 levels than patients without prior MI (p=0.01). Patients on aspirin before MI onset had significantly higher median aggregation levels compared with MI patients not on aspirin when evaluated by Multiplate® (pcollagen=0.02) and VerifyNow® (p<0.0001). In conclusion, patients with prior MI had higher platelet aggregation levels than patients without prior MI when evaluated by Multiplate®, despite same aspirin dose and optimal compliance. Serum thromboxane B2 levels were higher in MI patients than in patients without prior MI. Finally, patients on aspirin before MI onset had higher aggregation levels compared with patients not on aspirin.

Gender related issues in thrombosis and hemostasis

INTRODUCTION

Many aspects of hemostasis, both primary and secondary, as well as fibrinolysis display sex differences. From a clinical viewpoint, certain differential phenotypic presentations clearly arise within various disorders of thrombosis and hemostasis. Areas covered: The present mini-review summarizes selected clinical entities where sex differences are reflected in both frequency and clinical presentation of hemostasis disorders. Sex differences are discussed within the settings of cardiovascular disease, including coronary artery disease and ischemic stroke, venous thromboembolism and inherited bleeding disorders. Moreover, pregnancy and labor present particular challenges in terms of increased thromboembolic and bleeding risk, and this is also summarized. Expert commentary: Available knowledge on sex differences in risk factors and clinical presentation of disorders within thrombosis and hemostasis is increasing. However, more evidence is needed to further clarify different risk factors and treatment effect in men and women, both as regards to cardiovascular disease and venous thromboembolism. This should facilitate improved gender guided risk stratification, and prevention and treatment of these diseases. Finally, risk assessment during pregnancy remains a challenge; this applies both to thromboembolic risk assessment during normal pregnancy and special care of women with inherited bleeding disorders during labor.

Aspirin for primary prevention of cardiovascular disease events

Aspirin has been used for the prevention and treatment of cardiovascular disease (CVD) for several decades. The efficacy of aspirin for secondary prevention of cardiovascular disease is well established, but the clinical benefit of aspirin for primary prevention of CVD is less clear. The primary literature suggests that aspirin may provide a reduction in CVD events, but the absolute benefit is small and accompanied by an increase in bleeding. For aspirin to be beneficial for an individual patient, the risk of a future CVD event must be large enough to outweigh the risk of bleeding. The estimation of CVD risk is multifaceted and can involve numerous risk scores and assessments of concomitant comorbidities that confer additional CVD risk. Numerous guidelines provide recommendations for the use of aspirin for primary prevention, but they often contradict one another despite being based on the same clinical trials. Additional literature suggests that the presence of comorbidities that increase CVD risk, such as diabetes mellitus, asymptomatic peripheral arterial disease, or chronic kidney disease, does not ensure that aspirin therapy will be beneficial. Ongoing clinical trials may provide additional insight, but until more data are available, an individualized assessment of CVD risk with careful evaluation of risk and benefit should be performed before recommending aspirin therapy for primary prevention of CVD.

Aspirin's effect on platelet inhibition in migraineurs

OBJECTIVE

To assess the effect of aspirin on platelet reactivity in migraineurs.

BACKGROUND

Migraineurs, particularly women with aura and high monthly migraine frequency, are at risk for ischemic stroke and myocardial infarction (MI). High on-aspirin platelet reactivity (HAPR), or aspirin resistance, has been reported in females and patients with coronary artery disease, and is associated with adverse outcomes.

METHODS

Using a single group, pretest/posttest design, 50 migraineurs without prior history of stroke or MI were prospectively treated for 14 to 21 consecutive days with 325 mg generic enteric-coated aspirin, after undergoing a 14-day aspirin washout. Platelet reactivity was measured after aspirin washout and following aspirin treatment. Subjects were screened for HAPR using the VerifyNow™ Aspirin Assay (Accumetrics, San Diego, CA, USA). HAPR was defined as ≥ 460 Aspirin Reaction Units (ARU; primary endpoint).

RESULTS

Fifty subjects, 44 (88%) female, aged (mean ± standard deviation) 43 ± 12 years were enrolled. Twelve (24%; 95% CI 12-36%) subjects, all female, had HAPR and were classified as aspirin resistant. Subjects with HAPR had lower baseline hemoglobin levels than those without HAPR (P = .03). Baseline hemoglobin was significantly correlated with final ARU (r = -0.39, P = .005).

CONCLUSIONS

Findings of this exploratory study suggest that migraineurs have a higher prevalence of HAPR than healthy volunteers or patients with coronary artery disease taking aspirin 325 mg. The clinical implications of HAPR in migraine warrant further exploration due to the risk of stroke and MI and the potential need for antiplatelet therapy in this population.

Functional testing methods for the antiplatelet effects of aspirin

At antiplatelet doses of 75–325 mg/day, aspirin irreversibly inhibits the platelet cyclooxygenase (COX)-1-dependent thromboxane A2 (TXA2) formation. This is the pharmacological mode of action of aspirin, and it can be predicted that if aspirin does not inhibit COX-1 sufficiently, patients will not benefit from its antiplatelet effects. A pharmacodynamic failure of aspirin occurs in 1–2% of patients. The vast majority of atherothrombotic events in patients treated with aspirin result from mechanisms that are dependent on residual (non-COX-1-dependent) platelet reactivity. Global tests of platelet activation in vitro may identify patients with high residual platelet reactivity but are not sufficiently specific to test the pharmacological effect of aspirin. A further problem is the absence of standardized normal ranges for many assays and the fact that different equipment measures different signals, which are also influenced by the agonist and the anticoagulant used. Similar considerations apply for the determination of platelet-derived biomarkers such as circulating P-selectin, soluble CD40 ligand and others. The direct measurement of inhibition of thromboxane-forming capacity is the most specific pharmacological assay for aspirin. However, there is no linear correlation between inhibition of TXA2 formation and inhibition of platelet function. Measurement of urinary levels of the TXB2 metabolite, 11-dehydro-thromboxane B2, represents an index of TXA2 biosynthesis in vivo, but is also sensitive to other cellular sources of TXA2. One general problem of all assays is the relationship with clinical outcome, which is still unclear. Monitoring aspirin treatment by testing platelet function or measuring biomarkers in clinical practice should not be recommended until a clear relationship for the predictive value of these assays for clinical outcome has been established.

Aspirin and antiplatelet agent resistance: implications for prevention of secondary stroke

Oral antiplatelet drugs, including aspirin, clopidogrel and extended-release dipyridamole, are widely prescribed for the secondary prevention of vascular events, including stroke. Despite the benefits of antiplatelet therapy, 10−20% of patients experience a recurrent vascular event while taking antiplatelet medication. This article discusses the concept of antiplatelet resistance in general, focusing on aspirin resistance in particular, as a poorly defined cause of recurrent vascular events. Factors such as the lack of a standardized method to diagnose aspirin resistance and a poor clinical correlation with laboratory assays make the treatment of aspirin nonresponders difficult. In addition, there are confounding conditions such as diabetes mellitus that can affect aspirin resistance and determine a different course of treatment for these patients. Other antiplatelet options may also have resistant subpopulations; thus, alternative strategies for the secondary stroke patient must be explored.

Aspirin resistance and compliance with therapy

INTRODUCTION

Aspirin resistance is associated with increased cardiovascular risk in aspirin-treated patients. Poor compliance may explain many cases of "resistance," yet few clinical studies have used objective measurement of therapy compliance. We did so in a case-controlled study.

METHODS

We enrolled patients within 24 h of ischemic stroke and a group of controls taking aspirin who had never suffered a vascular event on therapy. All claimed to be compliant. We assessed platelet function using platelet function analyser (PFA)-100 and rapid platelet function analyser (RPFA) devices, applying standard definitions of resistance. We used high-performance liquid chromatography for levels of aspirin metabolites in the urine to confirm compliance with therapy. We compared rates of resistance in stroke patients and controls, and performed subgroup analysis restricted to patients with objective confirmation of recent aspirin ingestion.

RESULTS

We recruited 90 cases and 90 controls. Complete platelet function tests were available in 177. Resistance rates seen in cases and controls, respectively, were: resistance on one or more test, 30 (34%) versus 21 (25%), P= 0.19; on PFA-100 testing only, 28 (32%) versus 15 (18%), P= 0.031; on RPFA testing only, 16 (18%) versus 12 (14%), P= 0.54; resistance on both tests, 12 (14%) versus 5 (6%), P= 0.037. When only patients with objective evidence of recent aspirin ingestion were considered (n = 71), rates were similar regardless of definition of resistance used.

CONCLUSION

Aspirin resistance is common but poor compliance accounted for nearly half of cases of apparent aspirin "failure." Objective measures to assess compliance are essential in studies of aspirin resistance.

Aspirin resistance: disparities and clinical implications

Abstract Aspirin is one of the most widely prescribed drugs for the prevention of thrombosis in patients with vascular disease. Yet, aspirin is unable to prevent thrombosis in all patients. The term "aspirin resistance" has been used to broadly define the failure of aspirin to prevent a thrombotic event. Whether this is directly related to aspirin itself through biochemical aspirin resistance or treatment failure, or if it is because of aspirin's inability to overcome the thrombogenic aspects of the disease process itself, has not been elucidated. This can have dramatic clinical implications for a variety of vascular disease subsets and is cause for concern, considering the high prevalence of aspirin use for both primary and secondary prevention. Disparities exist in the rates of aspirin resistance among certain patient populations, such as women, patients with diabetes mellitus, and those with heart failure, and across clinical conditions, such as cardiovascular and cerebrovascular disease. Clinical trial data from studies observing resistance have revealed that regardless of study size, dose of aspirin, control for drug interactions and adherence, or assay used to measure platelet function, aspirin resistance is associated with an increased risk for adverse events. Although the evidence is mounting, there has yet to be a consensus on the appropriate clinical response to aspirin resistance.

The Role of Aspirin in Cardiovascular Disease Prevention in Women

Cardiovascular disease is the nation's number one killer of women. Through its actions on platelet inhibition, aspirin is an effective agent for primary and secondary cardiovascular disease prevention and for use with cardiac interventions. However, the evidence for aspirin's effectiveness in women differs by age and indication compared to men. As primary prevention, low dose aspirin is recommended for women over age 65 to reduce the risk of myocardial infarction and stroke while younger women at high risk for stroke may benefit from aspirin. Aspirin has benefits in other selected patient groups, including diabetics and patients presenting with ST segment elevation myocardial infarction (STEMI), non-ST segment elevation myocardial infarction acute coronary syndrome (NSTEMI/ACS), peripheral arterial disease, stroke, coronary artery bypass graft (CABG), and percutaneous coronary intervention (PCI). Alternative platelet therapy using dipyridamole or clopidogrel, alone or with aspirin, provides some improved efficacy for reduction in recurrent events for NSTEMI, ASC and PCI, although bleeding risks may be greater. However, dual antiplatelet therapy is not currently recommended for primary prevention in even high risk subjects. Despite the evidence base and guidelines, the use of aspirin in women remains suboptimal and warrants improved provider and patient awareness.

Comparison of laboratory detection methods of aspirin resistance in coronary artery disease patients

Aspirin reduces the prevalence of nonfatal myocardial infarction, stroke, and death by 25.0% in high risk group of patients with cardiovascular disease. Previous studies have estimated that about 5.5-56.8% of the population are aspirin resistant. The mechanisms of aspirin resistance (AR) have not been fully understood. We compared the detection methods for AR using traditional platelet aggregometry and VerifyNow system. One hundred and seventy-two coronary artery disease patients who had taken aspirin only or combinations with aspirin and clopidogrel for over 7 days were included. Of the 55 patients with aspirin only, aggregometer detected six AR (10.9%) and VerifyNow identified 10 AR (18.2%) cases. Among 117 patients with combined therapy, none (0.0%) and 10 (8.5%) of AR were detected by aggregometer and VerifyNow, respectively. There were six (3.4%) patients of AR defined by both methods and they all received aspirin monotherapy. Although the correlation between the aggregometry and VerifyNow was low, with defined criteria both methods gave 91.9% agreement to find AR. VerifyNow showed a higher sensitivity to detect AR. Further studies are required to biologically define AR and to alter therapy based on platelet function tests.

Review: Prevention of coronary heart disease in women

Objective Coronary heart disease (CHD) mortality is higher in women than in men and misdiagnosis of CHD in women is one of the reasons for this, with differences in the presentation of CHD between men and women being a cause for the misdiagnosis. This review discusses the need for evidence-based guidelines to diagnose and treat CHD in women.

Methods Reviews, randomized controlled trials, and other studies pertinent to the topic were obtained using electronic search strategies, such as MEDLINE and Cochran Library, as well as manual selection. Sources selected were limited to those that discussed CHD, with specific emphasis placed on sources that focused on CHD in women. Selected studies were then assessed for quality of data and relevance via analysis of the study's methodology, results, and data. Results of selected studies were then stratified using a rating system devised to determine the quality of results using the scientific evidence provided for them. The references of the selected studies were then used to obtain and analyze additional studies in the same manner.

Results Control of lifestyle factors such as smoking, physical activity, diet, and weight are all necessary in women to control CHD, as is the maintenance of healthy lipid levels and blood pressure. Angiotensin-converting enzyme inhibitors and antiplatelets can help aid lifestyle changes in CHD management for women while hormone therapy and vitamin E have no proven benefits in CHD management.

Conclusions New gender- and evidence-based guidelines for the prevention of CHD in women need to be developed and adopted by physicians so that prevention, diagnosis, and treatment of CHD is made more effective.