Adverse Effects and Drug Interactions of Antithrombotic Agents Used in Prevention of Ischaemic Stroke

Polyphosphate as an antithrombotic target and hemostatic agent

Polyphosphate (PolyP) is a polymer comprised of linear phosphate units connected by phosphate anhydride bonds. PolyP exists in a diverse range of eukaryotes and prokaryotes with varied chain lengths ranging from six to thousands of phosphate units. Upon activation, human platelets and neutrophils release short-chain PolyP, along with other components, to initiate the coagulation pathway. Long-chain PolyP derived from cellular or bacterial organelles exhibits higher proinflammatory and procoagulant effects compared to short-chain PolyP. Notably, PolyP has been identified as a low-hemorrhagic antithrombotic target since neutralizing plasma PolyP suppresses the thrombotic process without impairing the hemostatic functions. As an inorganic polymer without uniform steric configuration, PolyP is typically targeted by cationic polymers or recombinant polyphosphatases rather than conventional antibodies, small-molecule compounds, or peptides. Additionally, because of its procoagulant property, PolyP has been incorporated in wound-dressing materials to facilitate blood hemostasis. This review summarizes current studies on PolyP as a low-hemorrhagic antithrombotic target and the development of hemostatic materials based on PolyP.

Post-treatment Antiplatelet Therapy Reduces Risk for Delayed Cerebral Ischemia due to Aneurysmal Subarachnoid Hemorrhage

BACKGROUND

Delayed cerebral ischemia (DCI) has a strong impact on outcome of patients with aneurysmal subarachnoid hemorrhage (SAH). Positive effect of antiplatelet therapy on DCI rates has been supposed upon smaller SAH series.

OBJECTIVE

To analyze the benefit/risk profile of antiplatelet use in SAH patients.

METHODS

This retrospective case-control study was based on institutional observational cohort with 994 SAH patients treated between January 2003 and June 2016. The individuals with postcoiling antiplatelet therapy (aspirin with/without clopidogrel) were compared to a control group without antiplatelet therapy. Occurrence of DCI, major/minor bleeding events in the follow-up computed tomography scans, and favorable outcome at 6 mo after SAH (modified Rankin scale < 3) were compared in both groups.

RESULTS

Of 580 patients in the final analysis, 329 patients received post-treatment antiplatelet medication. There were no significant differences between the compared groups with regard to basic outcome confounders. Aspirin use was independently associated with reduced DCI risk (P < .001, adjusted odds ratio = 0.41, 95% confidence interval 0.24-0.65) and favorable outcome (P = .02, adjusted odds ratio = 1.78, 95% confidence interval 1.06-2.98). Regarding bleeding complications, aspirin was associated only with minor bleeding events (P = .02 vs P = .51 for major bleeding events).

CONCLUSION

Regular administration of aspirin might have a positive impact on DCI risk and outcome of SAH patients, without increasing the risk for clinically relevant bleeding events. In our SAH cohort, dual antiplatelet therapy showed no additional benefit on DCI risk, but increased the likelihood of major bleeding events.

Role of PFO Closure in Ischemic Stroke Prevention

PURPOSE OF REVIEW

To highlight recent advancements in the management of acute ischemic stroke patients with patent foramen ovale (PFO).

RECENT FINDINGS

One significant recent development was publication of long-term follow-up data from the RESPECT trial demonstrating evidence in favor of PFO closure over medical management. This data subsequently led to FDA approval for AMPLATZER™ septal occluder in the treatment of patients aged 18 to 60 years with both PFO and no other determined etiology for ischemic stroke, otherwise referred to as embolic stroke of undetermined source. Several subsequent closure trial results have recently been published, which also demonstrated benefit of PFO closure over medical management for ischemic stroke risk reduction in select patients. Based on the results of the more recently published REDUCE trial, the FDA granted approval for the GORE™ septal occluder. There is current, well-established evidence that PFO closure for secondary stroke prevention is effective in select cases.

Liver disease and heart failure: Back and forth

In their clinical practice, physicians can face heart diseases (chronic or acute heart failure) affecting the liver and liver diseases affecting the heart. Systemic diseases can also affect both heart and liver. Therefore, it is crucial in clinical practice to identify complex interactions between heart and liver, in order to provide the best treatment for both. In this review, we sought to summarize principal evidence explaining the mechanisms and supporting the existence of this complicate cross-talk between heart and liver. Hepatic involvement after heart failure, its pathophysiology, clinical presentation (congestive and ischemic hepatopathy), laboratory and echocardiographic prognostic markers are discussed; likewise, hepatic diseases influencing cardiac function (cirrhotic cardiomyopathy). Several clinical conditions (congenital, metabolic and infectious causes) possibly affecting simultaneously liver and heart have been also discussed. Cardiovascular drug therapy may present important side effects on the liver and hepato-biliary drug therapy on heart and vessels; post-transplantation immunosuppressive drugs may show reciprocal cardio-hepatotoxicity. A heart-liver axis is drafted by inflammatory reactants from the heart and the liver, and liver acts a source of energy substrates for the heart.

Costs and outcomes of noncardioembolic ischemic stroke in a managed care population

PURPOSE

To evaluate the clinical outcomes and incremental health care costs of ischemic stroke in a US managed care population.

PATIENTS AND METHODS

A retrospective cohort analysis was done on patients (aged 18+ years) hospitalized with noncardioembolic ischemic stroke from January 1, 2002, through December 31, 2003, identified from commercial health plan administrative claims. New or recurrent stroke was based on history in the previous 12 months, with index date defined as first date of indication of stroke. A control group without stroke or transient ischemic attack (TIA) was matched (1:3) on age, sex, and geographic region, with an index date defined as the first medical claim during the patient identification period. Patients with atrial fibrillation or mitral value abnormalities were excluded. Ischemic stroke and control cohorts were compared on 4-year clinical outcomes and 1-year costs.

RESULTS

Of 2180 ischemic stroke patients, 1808 (82.9%) had new stroke and 372 (17.1%) had a recurrent stroke. Stroke patients had higher unadjusted rates of additional stroke, TIA, and fatal outcomes compared with the 6540 matched controls. Recurrent stroke patients had higher rates of adverse clinical outcomes compared with new stroke patients; costs attributed to recurrent stroke were also higher. Stroke patients were 2.4 times more likely to be hospitalized in follow-up compared with controls (hazard ratio [HR] 2.4, 95% confidence interval [CI]: 2.2, 2.6). Occurrence of stroke following discharge was 21 times more likely among patients with index stroke compared with controls (HR 21.0, 95% CI: 16.1, 27.3). Stroke was also predictive of death (HR 1.8, 95% CI: 1.3, 2.5). Controlling for covariates, stroke patients had significantly higher costs compared with control patients in the year following the index event.

CONCLUSION

Noncardioembolic ischemic stroke patients had significantly poorer outcomes and higher costs compared with controls. Recurrent stroke appears to contribute substantially to these higher rates of adverse outcomes and costs.

Potential economic impact of increasing low dose aspirin usage on CVD in the US

BACKGROUND

Cardiovascular disease (CVD) is a leading cause of death in the US and Western Europe, but regular use of preventive low-dose aspirin has proven effective in preventing CVD events. The purpose of this study was to explore the potential economic impact in the US if preventive aspirin usage were to be increased in line with clinical guidelines for primary and secondary prevention.

METHODS

The risk profile of the US population was characterized using NHANES data, and Framingham cardiovascular risk equations were applied to calculate risk for myocardial infarction, angina and ischemic stroke according to age and gender. Primary and secondary patients were considered separately. Using publicly available unit costs, a budget impact model calculated the annual impact of increased preventive aspirin usage considering gastrointestinal bleeding and hemorrhagic stroke adverse events and diminishing aspirin adherence over a 10-year time horizon.

RESULTS

In a base population of 1,000,000 patients, full implementation of clinical guidelines would potentially prevent an additional 1273 myocardial infarctions, 2184 angina episodes and 565 ischemic strokes in primary prevention patients and an additional 578 myocardial infarctions, and 607 ischemic strokes in secondary prevention patients. This represents a total savings of $79.6 million for primary prevention and $32.2 million for secondary and additional out-of-pocket expense to patients of $29.0 million for primary prevention and $2.6 million for secondary prevention for the cost of aspirin.

CONCLUSIONS

This budgetary model suggests that there is a strong economic case, both for payers and society, to encourage aspirin use for patients at appropriate risk and per clinical guidelines. It also provides an example of how minimizing costs do not necessarily have to imply a rationing of care. Limitations include the exclusion of other CVD interventions in the analysis.

Protective effects of triflusal on secondary thrombus growth and vascular cyclooxygenase-2

BACKGROUND

Carotid residual mural thrombus predisposes to recurrent thrombosis and/or distal embolization (i.e. cerebrovascular ischemia).

OBJECTIVES

Our aims were (i) to analyze and compare the efficacy of aspirin, triflusal, and its main metabolite 2-hydroxy-4-trifluorometylbenzoic acid (HTB) on secondary thrombus growth; and (ii) evaluate to what extent the three Cox-1 inhibitors influenced vascular Cox-1/Cox-2 expression and endothelial prostacyclin synthesis.

METHODS

In a rabbit model of ex vivo thrombosis, a fresh mural thrombus was formed on damaged vessels at flow conditions typical of mild and severe carotid stenoses. The effects of Cox-1 inhibitors administered both intravenously (i.v.) (aspirin 5 mg kg(-1), triflusal 10 mg kg(-1), and HTB 10 mg kg(-1)) and orally (p.o.) (8 days; aspirin 30 mg kg(-1) day(-1), and triflusal 40 mg kg(-1) day(-1)) on secondary thrombus growth were assessed by In-(111)deposited platelets and compared with a placebo control. Arterial Cox-1/Cox-2 expression after 8-day treatment was evaluated at mRNA and protein levels. Additionally, a drug-related dose-dependent in vitro assay was performed for endothelial PGI(2) release measurement (Cox-2 activity).

RESULTS

All Cox inhibitors similarly and significantly (P < 0.05) reduced secondary thrombus formation after i.v. and p.o. administration versus placebo control. Treatments exerted no effect on vascular Cox-1 mRNA whereas Cox-2 mRNA was moderately reduced by aspirin and triflusal (placebo 100% +/- 9%, aspirin 70% +/- 2% and triflusal 70% +/- 2%; P < 0.05). Cox-2 protein levels were slightly higher in the triflusal versus aspirin group (placebo 100% +/- 6%, aspirin 35% +/- 10% and triflusal 61% +/- 9%; P < 0.005 versus placebo). Interestingly, in vitro, HTB solely maintained endothelial PGI(2) synthesis levels similar to the control.

CONCLUSIONS

At a similar level of efficacy in inhibiting secondary thrombosis, triflusal seems to better preserve Cox-2 expression than aspirin and its metabolite HTB was able to protect endothelial prostacyclin production.

Simultaneous determination of dipyridamole and salicylic acid in human plasma by high performance liquid chromatography-mass spectrometry

A sensitive, rapid and simple high-performance liquid chromatography-electrospray ionization-mass spectrometry (HPLC-ESI-MS) method for simultaneous determination of dipyridamole and salicylic acid in human plasma has been developed and validated. After the addition of diazepam and rosiglitazone as internal standard (IS), plasma samples were prepared by liquid-liquid extraction followed by an isocratic elution with methanol:2 mM ammonium acetate buffer (pH 4.25; 70/30, v/v) on a Shimadzu VP-ODS C(18) column (5 microm, 150 x 2.0 mm I.D.). Detection was performed on a quadrupole mass spectrometer with ESI interface operating in the positive-ion mode for dipyridamole and negative-ion mode for salicylic acid. Calibration curves were linear (r(2) > 0.99) over the concentration range 10-2500 ng/mL for dipyridamole and 30-4000 ng/mL for salicylic acid with acceptable accuracy and precision, respectively. The intra- and inter-batch precisions were less than 15% of the relative standard deviation. The limits of detection of dipyridamole and salicylic acid were 1 and 15 ng/mL, respectively. The validated HPLC-ESI-MS method was successfully applied to a preliminary pharmacokinetic study of fixed-dose combination of sustained-release dipyridamole/aspirin in Chinese healthy male volunteers.

Antiplatelet therapy for aneurysmal subarachnoid haemorrhage

BACKGROUND

Secondary ischaemia is a frequent cause of poor outcome in patients with aneurysmal subarachnoid haemorrhage (SAH). Besides vasospasm, platelet aggregation seems to play a role in the pathogenesis of secondary ischaemia. Experimental studies have suggested that antiplatelet agents can prevent secondary ischaemia.

OBJECTIVES

To determine whether antiplatelet agents change outcome in patients with aneurysmal SAH.

SEARCH STRATEGY

We searched the Cochrane Stroke Group Trials Register (last searched August 2006), MEDLINE (1966 to August 2006) and EMBASE databases (1980 to August 2006). We also searched reference lists of identified trials.

SELECTION CRITERIA

All randomised controlled trials (RCTs) comparing any antiplatelet agent with control in patients with aneurysmal SAH.

DATA COLLECTION AND ANALYSIS

Two review authors independently extracted the data and assessed trial quality. Relative risks (RR) were calculated with regard to poor outcome, case fatality, secondary ischaemia, haemorrhagic intracranial complications and aneurysmal rebleeding according to the intention-to-treat principle. In case of a statistically significant primary analysis, a worst case analysis was performed.

MAIN RESULTS

Seven RCTs were included in the review, totalling 1385 patients. Four of these trials met the criteria for good quality studies. For any antiplatelet agent there were reductions of a poor outcome (RR 0.79, 95% confidence interval (CI) 0.62 to 1.01) and secondary brain ischaemia (RR 0.79, 95% CI 0.56 to 1.22) and more intracranial haemorrhagic complications (RR 1.36, 95% CI 0.59 to 3.12), but none of these differences were statistically significant. There was no effect on case fatality (RR 1.01, 95% CI 0.74 to 1.37) or aneurysmal rebleeding (RR 0.98, 95% CI 0.78 to 1.38). For individual antiplatelet agents, only ticlopidine was associated with statistically significant fewer occurrences of a poor outcome (RR 0.37, 95% CI 95% CI 0.14 to 0.98) but this estimate was based on only one small RCT.

AUTHORS' CONCLUSIONS

This review shows a trend towards better outcome in patients treated with antiplatelet agents, possibly due to a reduction in secondary ischaemia. However, results were not statistically significant, thus no definite conclusions can be drawn. Also, antiplatelet agents could increase the risk of haemorrhagic complications. On the basis of the current evidence treatment with antiplatelet agents in order to prevent secondary ischaemia or poor outcome cannot be recommended.

Impact of Prior Antiplatelet Therapy on Risk of Embolism in Infective Endocarditis

BACKGROUND

Embolism is a dreaded complication of infective endocarditis (IE). Currently, antimicrobial therapy is the only medical intervention proven to decrease the risk of embolism associated with IE. We hypothesized that, because platelet aggregation is operative in the pathogenesis of vegetation formation, embolism associated with IE should occur less frequently among patients who have received prior, continuous daily antiplatelet therapy for noninfectious reasons.

METHODS

We studied a retrospective cohort of adult patients with a diagnosis of IE who presented to the Mayo Clinic (Rochester, MN) during 1980-1998. The cohort was divided into 2 groups on the basis of whether they had received continuous daily antiplatelet therapy for at least 6 months prior to the time of hospitalization for IE. Antiplatelet therapy included aspirin, dipyridamole, clopidogrel, ticlopidine, or any of combination of these agents. The primary end point was a symptomatic embolic event that occurred prior to or during hospitalization. Multivariable logistic regression was used to assess the impact of continuous daily antiplatelet therapy on risk of symptomatic emboli associated with IE.

RESULTS

One hundred forty-seven (24.5%) of 600 patients experienced a symptomatic embolic event; the most common embolic manifestation was stroke (in 48.2% of patients). Embolic events occurred significantly less often among those who had received prior, continuous daily antiplatelet therapy (12.0% of patients who had received therapy vs. 27.8% patients who had not receive therapy; P<.001). After adjustment for several covariates known to influence both risk of embolism and propensity for antiplatelet use, the adjusted odds ratio for a symptomatic embolic event was 0.36 (95% confidence interval, 0.19-0.68; P=.002) for patients receiving continuous daily antiplatelet therapy.

CONCLUSIONS

The risk of symptomatic emboli associated with IE was reduced in patients who received continuous daily antiplatelet therapy before onset of IE.

Stroke prevention in diabetes and obesity

Stroke is an important cause of morbidity and mortality, and is an economic burden. Diabetes and obesity are two important modifiable risk factors for stroke. Patients with diabetes have a higher incidence of stroke and a poorer prognosis after stroke. Risk-factor modification is the most important aspect of prevention of stroke in diabetes and obesity. This includes lifestyle modifications and different therapeutic modalities to control conditions, such as diabetes, hypertension, dyslipidemia and arrhythmia. Recent landmark studies have shown the beneficial effects of statins in diabetic patients even with close to normal or normal low-density lipoprotein cholesterol. Obesity, which is a risk factor for diabetes, hypertension and hyperlipidemia has been shown to be an independent risk factor for stroke. Increased leptin, dysregulation of adipocyte proteins, increased insulin resistance and C-reactive protein may be factors involved in the increased incidence of cardiovascular morbidity and mortality directly related to obesity. Visceral fat is a much bigger health risk than subcutaneous fat. Lifestyle interventions and pharmacotherapeutic agents have been used to manage obesity. In morbidly obese patients, surgical intervention seems to be the best method of treatment with a long-lasting favorable metabolic outcome. In the 21st Century, with the advanced medical knowledge and the therapeutic modalities available, it should be possible to reduce the incidence of stroke associated with diabetes and obesity.

Adjunctive pharmacologic use in carotid endarterectomy: a review

Although carotid endarterectomy (CEA) is now widely accepted as the surgical therapy for carotid stenosis, the role of and indications and evidence for many pharmacologic agents that are used adjunctively in the perioperative setting have not been conclusively established. Aspirin (acetylsalicylic acid) is the pharmaceutical agent that has been studied most extensively in conjunction with CEA; other than aspirin and dextran, the use of many agents before, during, and after CEA has not been standardized. Prospective randomized trials are still needed to demonstrate efficacy, predict outcome, and determine the optimal use of these medications in their adjunctive use during CEA to improve patient care and obtain optimal surgical outcomes.

Sub-Tenon's anesthesia with aspirin, warfarin, and clopidogrel

PURPOSE

To review the frequency of hemorrhagic complications with sub-Tenon's anesthesia in patients on aspirin, warfarin or clopidogrel.

SETTING

St. James's University Hospital, Leeds, United Kingdom.

METHODS

Data were collected prospectively for patients having elective phacoemulsification under sub-Tenon's anesthesia. Seventy-five patients were on aspirin, 65 were on warfarin, and 40 were on clopidogrel. Seventy-five patients on no anticoagulants were used as the control group. No changes in the anticoagulant regimen were made prior to surgery.

RESULTS

No sight-threatening hemorrhagic complications were noted, and no surgery was postponed or cancelled due to an anesthesic complication. Subconjunctival hemorrhage occurred in 19% in the control group, 40% in the clopidogrel group, 35% in the warfarin group, and 21% in the aspirin group. The warfarin and clopidogrel groups had the highest incidence of subconjunctival hemorrhage (P<.05). The incidence of hemorrhages involving more than 1 quadrant was highest in these 3 groups; however, this did not achieve statistical significance (P = .37, Fisher exact test).

CONCLUSION

Data from this study support the continued use of anticoagulant agents among routine users during cataract surgery using a sub-Tenon's block.

Triflusal: An Antiplatelet Drug with a Neuroprotective Effect?

Triflusal is a derivative of salicylic acid with a well-established platelet aggregation inhibitory profile. Its pharmacokinetic and pharmacodynamic properties differ, however, somewhat from those of acetylsalicylic acid. A number of recent experimental and clinical studies have shown that triflusal is a potentially useful choice in the treatment and prophylaxis of brain ischemia because of its antithrombogenic as well as neuroprotective effects. Its antithrombogenic effect has been demonstrated at the clinical as well as at the experimental level, while its neuroprotective effect has been shown only in experimental models. The drug interferes with thrombogenesis by inhibiting thromboxane synthesis and increasing the levels of cAMP and nitric oxide. Its neuroprotective action is the result of its antioxidant and antiinflammatory effects in brain tissue. From a clinical standpoint triflusal is similar in efficacy to acetylsalicylic acid in preventing stroke, but has less adverse effects, especially it is less likely to cause bleeding. Because of its pharmacodynamic properties and lower rate of adverse reactions, triflusal may be a useful alternative to acetylsalicylic acid in the prevention of stroke.

Mechanisms of target organ damage caused by hypertension: therapeutic potential

Hypertension is a major risk factor for cardiovascular mortality and morbidity through its effects on target organs like the brain, heart, and kidney. Structural alterations in the microcirculation form a major link between hypertension and target organ damage. In this review, we describe damages related to hypertension in these target organs and the mechanisms involved in the pathogenesis of hypertension-induced cardiovascular diseases such as dementia, cardiac ischemia and remodeling, or nephropathy. We also focus on the therapeutical potential on the basis of such mechanisms. Several antihypertensive agents like diuretics, angiotensin converting enzyme (ACE) inhibitors, angiotensin II (Ang II) receptor antagonists, beta-blockers, or calcium channel blockers (CCBs) have been shown to reduce effectively hypertension associated cardiovascular events and to improve end organ damage. More recently, aldosterone antagonism has also shown beneficial effects. Part of the favorable effects of these agents is due to blood pressure lowering as such. Other mechanisms such as oxidative stress, inflammation, or endothelial dysfunction have appeared to play a key role in the pathogenesis of target organ damage and therefore represent another important pathway for therapy. In this review, we discuss the different therapeutic approaches aiming at reducing cardiovascular events and damages induced by hypertension.