Aspirin plus either dipyridamole or ticlopidine is effective in preventing recurrent myocardial infarction. Secondary Prevention Group

Adenosine-diphosphate (ADP) receptor antagonists for the prevention of cardiovascular disease in type 2 diabetes mellitus

BACKGROUND

Cardiovascular disease (CVD) is the most prevalent complication of type 2 diabetes with an estimated 65% of people with type 2 diabetes dying from a cause related to atherosclerosis. Adenosine-diphosphate (ADP) receptor antagonists like clopidogrel, ticlopidine, prasugrel and ticagrelor impair platelet aggregation and fibrinogen-mediated platelet cross-linking and may be effective in preventing CVD.

OBJECTIVES

To assess the effects of adenosine-diphosphate (ADP) receptor antagonists for the prevention of cardiovascular disease in type 2 diabetes mellitus.

SEARCH METHODS

We searched the Cochrane Central Register of Controlled Trials (CENTRAL) in The Cochrane Library (issue 2, 2011), MEDLINE (until April 2011) and EMBASE (until May 2011). We also performed a manual search, checking references of original articles and pertinent reviews to identify additional studies.

SELECTION CRITERIA

Randomised controlled trials comparing an ADP receptor antagonist with another antiplatelet agent or placebo for a minimum of 12 months in patients with diabetes. In particular, we looked for trials assessing clinical cardiovascular outcomes.

DATA COLLECTION AND ANALYSIS

Two review authors extracted data for studies which fulfilled the inclusion criteria, using standard data extraction templates. We sought additional unpublished information and data from the principal investigators of all included studies.

MAIN RESULTS

Eight studies with a total of 21,379 patients with diabetes were included. Three included studies investigated ticlopidine compared to aspirin or placebo. Five included studies investigated clopidogrel compared to aspirin or a combination of aspirin and dipyridamole, or compared clopidogrel in combination with aspirin to aspirin alone. All trials included patients with previous CVD except the CHARISMA trial which included patients with multiple risk factors for coronary artery disease. Overall the risk of bias of the trials was low. The mean duration of follow-up ranged from 365 days to 913 days.Data for diabetes patients on all-cause mortality, vascular mortality and myocardial infarction were only available for one trial (355 patients). This trial compared ticlopidine to placebo and did not demonstrate any statistically significant differences for all-cause mortality, vascular mortality or myocardial infarction. Diabetes outcome data for stroke were available in three trials (31% of total diabetes participants). Overall pooling of two (statistically heterogeneous) studies showed no statistically significant reduction in the combination of fatal and non-fatal stroke (359/3194 (11.2%) versus 356/3146 (11.3%), random effects odds ratio (OR) 0.81; 95% confidence interval (CI) 0.44 to 1.49) for ADP receptor antagonists versus other antiplatelet drugs. There were no data available from any of the trials on peripheral vascular disease, health-related quality of life, adverse events specifically for patients with diabetes, or costs.

AUTHORS' CONCLUSIONS

The available evidence for ADP receptor antagonists in patients with diabetes mellitus is limited and most trials do not report outcomes for patients with diabetes separately. Therefore, recommendations for the use of ADP receptor antagonists for the prevention of CVD in patients with diabetes are based on available evidence from trials including patients with and without diabetes. Trials with diabetes patients and subgroup analyses of patients with diabetes in trials with combined populations are needed to provide a more robust evidence base to guide clinical management in patients with diabetes.

Antiplatelet and Antithrombin Therapy for Early Management of Acute Coronary Syndromes

Acute coronary syndromes (ACS) are defined as either unstable angina (UA), non-ST-segment elevation myocardial infarction (NSTEMI), or ST-segment elevation myocardial infarction (STEMI). Their management is continuously evolving in terms of pharmacologic therapy. The usual cause of ACS is the disruption of an atherosclerotic plaque leading to formation of a thrombus within a coronary artery. Initial antiplatelet and antithrombin therapy for patients with ST-segment elevation (STE) ACS includes aspirin and unfractionated heparin (UFH). Patients presenting to the hospital early may undergo percutaneous intervention (PCI) with administration of additional medications such as clopidogrel and abciximab or may receive a fibrinolytic agent. Patients with non-ST-segment elevation (NSTE) ACS receive aspirin, clopidogrel, either a low-molecular-weight heparin or UFH, and, in selected patients, a glycoprotein (GP) IIb/IIIa receptor blocker. All of these agents have shown benefit when administered to patients with ACS, but results vary depending on the type of syndrome, timing of administration, and patient’s overall risk. Their mechanism of action, role in ACS, clinical practice recommendations, adverse effects, and monitoring are reviewed. Some inherent limitations to agents such as aspirin and UFH require the need for newer treatment approaches. Therefore, newer classes of drugs such as the direct thrombin inhibitor bivalirudin and the selective factor Xa inhibitor fondaparinux are being explored as alternatives to heparins for ACS management.

Comparing medications in a therapeutic area using an NNT model

OBJECTIVES

Clinicians are told to use the number needed to treat (NNT) to compare the benefits of therapeutic strategies, and researchers are asked to report results this way, generally without considering differences among the studies from which these were derived.

METHODS

The crude NNT currently advocated is compared to the NNT standardized for a common outcome, follow-up time, study population and comparator. An NNT model for cardiovascular disease is described as an example that addresses differences among studies of secondary prevention of cardiovascular disease. Crude NNTs are compared to those obtained from the model.

RESULTS

Follow-up in the 18 trials identified varied from 1.0 to 6.2 years; rates of cardiovascular events in the untreated subgroups ranged from 4.8% to 45.9%. The crude NNTs were more variable (9.1-163.7) than those obtained from the model (9.1-75.2). The effect of standardization was substantial in some cases, with proportional changes ranging from a 91% decrease to a 223% increase.

CONCLUSION

Using an NNT model to account for differences in study design allows for more meaningful comparisons.

Beta-Blockers Prevent Cardiac Events in Japanese Patients With Myocardial Infarction

BACKGROUND

Although the favorable effects of beta-blockers in the treatment of myocardial infarction (MI) have been repeatedly demonstrated in Western countries, administration of this drug has been limited in Japan.

METHODS AND RESULTS

The study group of 1,896 patients with MI was retrospectively divided into 1,029 patients treated by beta-blockers and 867 not treated by beta-blockers, and the incidences of cardiac events, consisting of recurrent MI, death because of worsening heart failure, and sudden death, and cardiovascular events, comprising cardiac events and stroke, were compared in both groups. There were 45 cardiac events (4.4%, 30.1 patients/1,000 patients. year) among the beta-blocker group, which was significantly less than the 56 cardiac events (6.5%, 52.3 patients/1,000 patients. year) among the no-beta-blocker group (p<0.05). The total mortality was 92 (8.9%, 61.6 patients/1,000 patients. year) and 124 (14.3%, 115.8 patients/1,000 patients. year), respectively, and cardiac death occurred in 42 (4.1%, 28.1 patients/1,000 patients. year) and 53 (6.1%, 49.5 patients/1,000 patients. year), respectively, indicating that both these events occurred significantly less in the beta-blocker group (p<0.01 and p<0.05).

CONCLUSIONS

Beta-blockers prevent cardiac events in Japanese patients with MI. However, a placebo-controlled, double-blind, multicenter, clinical trial conducted on a large scale in Japan would further contribute more precise information of the useful effects of beta-blockers.

Modification of treatment strategies over a period of 14 years has markedly reduced cardiac events among post-myocardial infarction patients

Recent trends in the treatment of post-myocardial infarction (MI) patients and the factors accounting for the improvement in outcome are presented. A total of 6,602 post-MI patients (5,320 males, 1,282 females; 58.9 +/- 10.4 years of age) enrolled between 1986 and 1999 were followed up for an average of 12.6 +/- 16.3 months. The incidence of cardiac events, which included fatal and nonfatal recurrent MIs, sudden death and death by congestive heart failure, was highest (44.9 events/1,000 person year) in 1986-1987, but decreased steadily to 22.5 events/1,000 person year by 1997-1999 (Trend p<0.0001). This trend accompanied the increased use of coronary thrombolysis, percutaneous transluminal coronary angioplasty and coronary artery bypass graft surgery, increased prescription of antiplatelet agents (51.5%-83.4%), lipid-lowering agents (29.8%-52.6%) and angiotensin-converting enzyme inhibitors (5.3%-->41.0%), and reduced prescription of calcium antagonists (68.5%-41.0%) and nitrates (60.7%-->45.7%). These changes in treatment have led to a decreased incidence of angina pectoris, wall motion abnormalities and abnormal Q waves on electrocardiograms. The decline in the incidence of cardiac events among post-MI patients in the 14 years between 1986 and 1999 reflects implementation of new therapeutic modalities proven to be effective in clinical trials and in daily practice.

Aggrenox: an aspirin and extended-release dipyridamole combination

Stroke is one of the leading causes of death in the United States. The risk of experiencing a recurrent stroke remains elevated for several years after an initial stroke or a transient ischemic attack (TIA), therefore secondary prevention is crucial in reducing the risk of stroke and the complications and costs associated with stroke. Aggrenox, a combination of low-dose aspirin and extended-release dipyridamole, is a new agent that is effective in the secondary prevention of stroke and transient ischemia of the brain. The clinical effect of its two antiplatelet agents are additive and significantly better than either aspirin or dipyridamole alone, although it has not been shown to be more effective than aspirin alone in preventing death. Aggrenox is much more expensive than aspirin alone but has been shown to be more cost-effective. At this point, much of the pharmacologic information concerning this combination agent is based on previous data about aspirin and immediate-release dipyridamole. This combination of aspirin and extended-release dipyridamole may play a significant role in secondary stroke and TIA prevention.

Value of antiplatelet therapy in preventing thrombotic events in generalized vascular disease

Atherothrombosis is the major underlying cause of acute coronary syndromes, ischemic stroke, and peripheral artery disease, and thus is the leading cause of death and disability in Western countries. Platelet inhibitors play a major role in preventing these ischemic complications. There is strong evidence from the Antiplatelet Trialists' Collaboration meta-analysis that aspirin reduces the combined risk of stroke, myocardial infarction (MI), or vascular death in atherosclerotic patients. The Ticlopidine Aspirin Stroke Study (TASS) compared aspirin and ticlopidine in the secondary prevention of high-risk patients after ischemic stroke and demonstrated a significant advantage for ticlopidine over aspirin. In peripheral arterial disease, the Swedish Ticlopidine Multicentre Study (STIMS) showed that ticlopidine was very effective against placebo. Intravenous antiplatelet agents, such as abciximab, tirofiban, and eptifibitide were also proven effective in acute coronary syndromes and unstable angina. In the Clopidogrel versus Aspirin in Patients at Risk of Ischaemic Events (CAPRIE) trial, clopidogrel was compared with aspirin in patients with symptomatic atherothrombosis regardless of the initial localization of the ischemic event (coronary, cerebral, or peripheral). The efficacy of clopidogrel based on the first occurrence of ischemic stroke, MI, or vascular death showed a relative risk reduction of 8.7% over and above the 25% reduction currently accepted with aspirin (p < 0.05). The greatest benefit of clopidogrel was in the reduction of fatal and nonfatal MI in the most severe groups of patients, providing a 19% relative risk reduction (p = 0.008). The recent disappointing results obtained with oral glycoprotein IIb/IIIa receptor blocking agents may emphasize the need for other antiplatelet combination therapy, such as aspirin-clopidogrel, in coronary disease, stents, stroke, and possibly atherothrombosis in high-risk patients.

Inconsistencies in the classification of preventive interventions

BACKGROUND AND OBJECTIVE

Preventive measures are commonly classified into primary (prevention of a disease from occurring), secondary (screening of asymptomatic persons with a view of early detection and treatment of disease), and tertiary (treatment of patients with a view of palliation, cure, rehabilitation, prevention of relapse, or prevention of complications). The objective of the present survey was to assess the adherence to this classification in a sample of abstracts of scientific publications.

METHOD

We searched the literature (key terms prevention and primary, secondary, or tertiary) and identified 317 abstracts describing various preventive interventions. We tabulated the level of prevention as defined in the abstract, by what was done, to whom, and why.

MAIN FINDINGS

There was a considerable variability in the way the various levels of prevention were defined in the reviewed abstracts.

CONCLUSIONS

The definitions of the levels of prevention are not specific enough to be appropriately used by all. We suggest, therefore, to define clinical interventions by their objective, target population, and type ("reduction of mortality of patients with symptomatic ventricular ectopy by beta-blockers"), rather than in terms of level of prevention ("tertiary prevention of ventricular ectopy").

Antiplatelet therapy in the prevention of ischemic vascular events: literature review and evidence-based guidelines for drug selection

BACKGROUND

New antiplatelet drugs are being developed and many clinical trials evaluating the benefits of antiplatelet drugs for the secondary prevention of ischemic events in patients with atherosclerotic vascular disease have been performed.

HYPOTHESIS

An updated systematic review and evidence-based guidelines for the appropriate selection of antiplatelet drugs may be beneficial to physicians and healthcare organizations attempting to create or update current clinical practice guidelines or clinical pathways aimed at caring for these patients.

METHODS

(1) A systematic review of the recent literature on the relative efficacy and safety of aspirin, ticlopidine, and clopidogrel was undertaken; (2) an evidence-based, expert panel approach using a modified Delphi technique to create explicit guidelines for prescribing antiplatelet therapy was instituted; and (3) the recommendations of an expert panel were summarized.

RESULTS

Consensus guidelines were developed for the utilization of aspirin, ticlopidine, or clopidogrel for the prevention of ischemic events in patients with manifestations of atherosclerotic vascular disease (prior myocardial infarction, prior ischemic stroke, or established peripheral arterial disease) who are at increased risk for recurrent ischemic events. Based on efficacy and safety, clopidogrel was recommended as the drug of choice for patients with established peripheral arterial disease; aspirin or clopidogrel should be considered in patients with prior myocardial infarction (with clopidogrel favored for patients who have had a recurrent event while on aspirin or in whom aspirin is contraindicated); aspirin or clopidogrel should be considered as first-line treatment in patients with prior ischemic (nonhemorrhagic) stroke--however, clopidogrel is the favored drug in patients in whom other antiplatelet drugs are either contraindicated or who have had recurrent events while on therapy.

CONCLUSIONS

Myocardial infarction, ischemic stroke, and peripheral arterial disease are all clinical manifestations of the same underlying disease process (atherosclerosis), with thrombus formation on the disrupted atherosclerotic plaque (atherothrombosis) being a common precipitating factor of ischemic events in patients suffering from these disorders. An evidence-based approach was used to develop a practice guideline, based on available published evidence, for the appropriate utilization of antiplatelet agents (aspirin, ticlopidine, or clopidogrel). These guidelines may be of use to multidisciplinary teams wishing to create or update clinical guidelines or clinical pathways which address the care of patients with atherosclerotic vascular disease. New antiplatelet agents such as clopidogrel may be more effective and associated with lower risk of selected adverse effects (such as gastrointestinal distress, gastrointestinal hemorrhage, and neutropenia) than those previously used to prevent thrombus formation in the setting of atherosclerotic arterial disease. Combination antiplatelet therapy is being evaluated as an option for those patients who experience recurrent events on a single antiplatelet agent.

Effects of aspirin and trapidil on cardiovascular events after acute myocardial infarction. Japanese Antiplatelets Myocardial Infarction Study (JAMIS) Investigators

Aspirin therapy confers conclusive net benefits in the acute phase of evolving myocardial infarction, but no clear evidence of benefit from the long-term use of aspirin after acute myocardial infarction (AMI) has been shown in any single study. This multicenter study, the Japanese Antiplatelets Myocardial Infarction Study, was performed to find out whether aspirin or trapidil would improve clinical outcome compared with no antiplatelets in postinfarction patients. The study was a multicenter, open-label, randomized controlled trial of aspirin 81 mg/day, trapidil 300 mg/day, and no antiplatelets in patients with AMI admitted within 1 month from the onset of symptoms. Seven hundred twenty-three patients were enrolled at 70 hospitals in 18 prefectures of Japan; 250 were randomly assigned to treatment with 81 mg aspirin (aspirin group), 243 to that with trapidil (trapidil group), and 230 were not given antiplatelet agents. The mean follow-up period was 475 days. This study demonstrated that long-term use of aspirin at the dose of 81 mg/day reduced the incidence of recurrent AMI compared with the group receiving no antiplatelets after AMI (p = 0.0045) and that trapidil also reduced the occurrence of reinfarction compared with the group receiving no antiplatelets, but the difference was not significant (p = 0.0810). The incidence of cardiovascular events including cardiovascular death, reinfarction, uncontrolled unstable angina requiring admission to hospital, and nonfatal ischemic stroke was reduced in the group receiving 300 mg trapidil daily compared with the group receiving no antiplatelets (p = 0.0039). The use of aspirin 81 mg/day provided almost no benefit over no antiplatelets therapy in the incidence of cardiovascular events. In conclusion, low-dose aspirin (81 mg) effectively prevented recurrent AMI in postinfarction patients after thrombolysis or coronary angioplasty when used over a long term. Furthermore, the long-term use of trapidil resulted in a significant reduction in the incidence of cardiovascular events.