Long-term oral anticoagulant therapy in patients with unstable angina or suspected non-Q-wave myocardial infarction: organization to assess strategies for ischemic syndromes (OASIS) pilot study results

Reduction in the need for hospitalization for recurrent ischemic events and bleeding with clopidogrel instead of aspirin. CAPRIE investigators

BACKGROUND

Repeat hospitalizations of patients with atherosclerosis represent a considerable burden on the health care system. We sought to determine whether clopidogrel compared with aspirin decreases the need for rehospitalization for ischemia and bleeding.

METHODS AND RESULTS

The Clopidogrel Versus Aspirin in Patients at Risk of Ischemic Events (CAPRIE) trial was a randomized, blinded, multicenter, trial of 19,185 patients with atherosclerotic disease manifested as recent ischemic stroke or myocardial infarction or symptomatic peripheral arterial disease. Without any double-counting of events, the number of rehospitalizations for ischemic events (defined as angina, transient ischemic attack, or limb ischemia) or bleeding events was determined for the entire cohort. There was a significant reduction in the total number of rehospitalizations for ischemic events or bleeding with clopidogrel use compared with aspirin (1502 vs 1673; P =.010) over an average of 1.6 years of treatment. This reduction in rehospitalization was consistent across individual outcomes of angina, transient ischemic attack, limb ischemia, and bleeding. Compared with aspirin, clopidogrel also resulted in a 7.9% relative risk reduction in a combined end point of vascular death, stroke, myocardial infarction, or rehospitalization for ischemic events or bleeding (15.1% to 13.7% at 1 year; P =.011). Adjusting for baseline prognostic variables, clopidogrel therapy was an independent predictor for reduction of vascular death, stroke, myocardial infarction, or rehospitalization for ischemic events or bleeding (P =.009).

CONCLUSIONS

Treatment with clopidogrel results in a significant decrease in the need for rehospitalization for ischemic events or bleeding compared with aspirin. This meaningful end point tracks well with other, more traditional measures of outcome and has incremental value beyond such end points.

Low molecular weight heparin in unstable coronary artery disease

Since the recognition that any thrombosis overlying a ruptured atherosclerotic plaque is a central component of the pathogenesis of unstable coronary artery disease (CAD), a number of antithrombotic treatment strategies have been investigated in randomised clinical trials. Aspirin reduces the occurrence of symptomatic and silent ischaemia, myocardial infarction (MI) and death in patients with unstable CAD, both in the acute phase and during continued long-term treatment and is now considered routine therapy. The addition of unfractionated heparin infusion further reduces cardiac events during the treatment period, but is not associated with any sustained benefits during long-term follow-up. Low molecular weight heparins (LMWHs) are completely absorbed by the sc. route. A predictable anticoagulant effect is maintained by sc. injections every 12 - 24 h without laboratory monitoring. The FRISC trial demonstrated that, in conjunction with aspirin, the LMWH dalteparin reduced death and MI by more than 50% in the acute phase. Four similar trials have directly compared LMWH with unfractionated heparin and demonstrated at least the same efficacy in the acute phase, treated between three and eight days. The LMWH enoxaparin was more effective at reducing death or MI than unfractionated heparin infusion during the three days of treatment, an effect which lasted up to 12 months. Prolonged out-patient treatment beyond the acute phase has been evaluated in four trials. It was demonstrated, in two of these trials, that continuing twice-daily injections of dalteparin further reduced the risk of death, MI and need for revascularisation at least during the initial six weeks of treatment. This effect was confined, however, to patients with signs of myocardial damage, i.e., elevation of troponin, at admission. During prolonged out-patient treatment, there is an increased risk of severe bleeding due to the combination of LMWH with aspirin. Based on successful results, the LMWHs, having the convenience of treatment and the option for continuation in an out-patient setting, should replace unfractionated heparin as the routine treatment in unstable CAD. If an early invasive procedure is considered, the LMWH therapy should be continued until the intervention as a 'bridge-to-revascularisation'. New antiplatelet agents are also emerging as additional useful tools for treating these patients, thus it is urgent to evaluate the comibination of these new therapies with the LMWHs.

Changes in levels of factor VII and protein S after acute myocardial infarction: effects of low-dose warfarin

Persistent coagulation activity after an acute myocardial infarction may increase the risk of reinfarction. We prospectively investigated the effects on plasma coagulation of a low, fixed dose of warfarin in combination with aspirin after myocardial infarction. We also evaluated the influence of coagulation activity on clinical outcome. Plasma samples from 97 patients, randomised to 1.25 mg of warfarin daily in combination with 75 mg of aspirin or aspirin alone were drawn 4 days, 1 month, and 6 months after myocardial infarction. Patients receiving warfarin had a greater reduction in factor VII coagulation activity (FVII:C) after 6 months: 0.18 vs. 0.06 U/mL,(95% CI, 0.02-0.22), whereas no differences were seen in levels of protein C, protein S, or prothrombin fragment 1+2. In the acute phase, the level of free protein S was lower than after 6 months in both groups: 25.6 vs. 28.8% (95% CI, 4.19--2.35). Cardiovascular mortality, reinfarction, and stroke were evaluated after 4 years (median). In a survival analysis, every 0.1 U/mL increase in the level of FVII:C1 month after myocardial infarction was associated with an 15% increase in risk of cardiovascular events (95% C1, 1.01-1.30). Warfarin at 1.25 mg daily reduces FVII:C but not systemic thrombin generation measured as prothrombin fragment 1 +2. Low levels of the anticoagulant protein S may contribute to a procoagulant state.

The Organization to Assess Strategies for Ischemic Syndromes (OASIS) Pilot Study: evaluation of acute and long-term therapies for patients with acute coronary syndromes without ST elevation

The objectives of the Organization to Assess Strategies for Ischemic Syndromes (OASIS) Pilot Study (phase 2) were (1) to compare the efficacy, safety, and feasibility of recombinant hirudin versus unfractionated heparin as short-term therapy in patients with acute coronary syndromes without ST elevation and (2) to compare the efficacy and safety of long-term therapy with warfarin and aspirin versus standard therapy with aspirin alone in the same patient population. Investigators at 31 Canadian centers randomized 909 patients to receive either medium-dose hirudin, low-dose hirudin, or unfractionated heparin. The incidence of the 7-day primary composite outcome of cardiovascular death, new myocardial infarction (MI), or refractory angina was significantly lower among patients who received hirudin than among those assigned to unfractionated heparin. A subset of these patients was subsequently randomized to long-term, low-intensity (international normalized ratio [INR] < 1.5) or moderate-intensity (INR 2-2.5) anticoagulant treatment with warfarin or to standard therapy. In this substudy, promising results were observed in favor of moderate-intensity warfarin. These findings provided the rationale for the design and conduct of the large-scale, phase III OASIS-2 trial.

Haemostatic function, arterial disease and the prevention of arterial thrombosis

Recent years have seen the expansion of information linking raised plasma levels of individual clotting factors and evidence of disturbances of fibrinolytic activity with the risk of thrombotic manifestations of arterial disease, both in community-based, apparently healthy populations and in patients with known atherosclerosis. Some of these prothrombotic changes in the haemostatic system may result partly from underlying chronic inflammation or acute infection and may, in turn, contribute substantially to the thrombotic risk which accompanies these underlying processes. The importance of the coagulation system in the pathogenesis of arterial thrombosis is further illustrated by the benefit in the Thrombosis Prevention Trial of low-intensity, dose-adjusted warfarin in the primary prevention of ischaemic heart disease. Clinical trials of bezafibrate, which is being used for its fibrinogen-lowering as well as lipid-modifying properties, are in progress.

Evidence supporting secondary prevention strategies

Currently 14 million individuals in the United States have coronary disease. Within the next 2 decades, this number is expected to increase to 21 million persons. To minimize the excessive risk of recurrent cardiac events in these people, evidence-based, cost-effective prevention strategies must be developed. This review highlights the evidence supporting commonly used means of secondary prevention and is divided into two major sections: lifestyle modifications and pharmacologic interventions. Lifestyle changes discussed include smoking cessation, especially newer pharmacologic adjuncts; the efficacy of dietary interventions; and current inroads into the treatment of depression in recurrent events. Pharmacologic innovations include reexamination of a role for warfarin; continued advances in the treatment of hyper- and dyslipidemias, new roles for beta-blockade in congestive heart failure, and finally a view of future measures, risk and targets of risk intervention.

The health care burden of unstable angina

Worldwide, UA represents a significant allocation of resources. UA represents a syndrome where not only do many therapies exist, but considerable clinical trial evidence has accumulated. Universal application of effective practice patterns is warranted if we are to successfully reduce the burden of UA. Economic analyses cannot resolve many of the underlying societal issues that affect decision making. Often, the acceptability of an economic burden is dependent on the willingness of both individuals and society to pay. In an interesting study, Chestnut et al evaluated the willingness of 50 patients to pay for avoiding a worsening of their angina symptoms. On average, the patients were willing to pay between $210 and $499 to avoid four to eight additional angina episodes each month. The "rule of rescue" suggests that society is often willing to pay large sums of money to save those in extreme need, such as the 55-year-old man rushed to the emergency department clutching his chest. Only recently has attention been paid to how much this disease entity costs us. Whereas the 1980s and 1990s saw a focus on costs, the next century will increasingly focus on value--obtaining the best health outcome for the dollars spent. Debate has shifted, at least in part, from purely financial costs to medical effectiveness and outcomes management. Continuing assessments of value of interventions and application of evidence based-management strategies permit rational selection of therapy and allow us best to bear the burden of UA.