Heparins reduce the number of heart attacks but caused more minor bleeding after acute coronary syndromes compared to placebo

Magee K, Campbell SG, Moher D, Rowe BH

Published Online:

September 8, 2010

Blood clots in the arteries leading to the heart can cause acute coronary syndromes: unstable angina (a feeling of tightness in the chest) or a type of heart attack (non-ST segment myocardial infarction - NSTEMI). Drugs that prevent clots from forming (such as aspirin) or thin the blood (such as heparin) can relieve the problem. Unfractionated heparin (UFH) and low molecular weight heparin (LMWH) are two types of heparin. This review of trials found that UFH and LMWH when given to patients with high-risk unstable angina or NSTEMI in the acute phase of treatment in addition to standard therapy with aspirin, prevent more heart attacks than placebo but do not reduce mortality, the need for revascularization procedures or recurrent angina. Although there was limited reporting of side effects, heparins caused more cases of minor bleeding.

Abstract (click to read)

Background:

Acute coronary syndromes (ACS) represent a spectrum of disease including unstable angina (UA) and non-ST segment myocardial infarction (NSTEMI). Despite treatment with aspirin, beta-blockers and nitroglycerin, UA/NSTEMI is still associated with significant morbidity and mortality. Although emerging evidence suggests that low molecular weight heparin (LMWH) is more efficacious compared to unfractionated heparin (UFH), there is limited data to support the role of heparins as a drug class in the treatment of ACS.

Objectives:

To determine the effect of heparins (UFH and LMWH) compared with placebo for the treatment of patients with ACS.

Search strategy:

We searched the Cochrane Central Register of Controlled Trials on The Cochrane Library (issue 4, 2002), MEDLINE (1966 to May 2002), EMBASE (1980 to May 2002) and CINAHL (1982 to May 2002). Authors of included studies and pharmaceutical industry representatives were contacted to determine if unpublished studies which met the inclusion criteria were available.

Selection criteria:

Randomized controlled trials of parenteral UFH or LMWH versus placebo in people with ACS (UA or NSTEMI).

Data collection and analysis:

Two reviewers independently assessed quality of studies. Data were extracted independently by two reviewers. Study authors were contacted to verify and clarify missing data.

Main results:

Eight studies (3118 participants) were included in this review. We found no evidence for difference in overall mortality between the groups treated with heparin and placebo (RR = 0.84, 95% CI 0.36 to 1.98). Heparins reduced the occurrence of MI (RR = 0.40, 95% CI 0.25 to 0.63, NNT = 33). An increase in the incidence of minor bleeds (RR = 6.80, 95% CI 1.23 to 37.49, NNH = 17).

Authors' conclusions:

Compared to placebo, patients treated with heparins had similar risk of mortality, revascularization, recurrent angina, major bleeding and thrombocytopenia. However, those treated with heparins had decreased risk of MI and a higher incidence of minor bleeding.

This record should be cited as:

Magee K, Campbell SG, Moher D, Rowe BH. Heparin versus placebo for acute coronary syndromes. Cochrane Database of Systematic Reviews 2008, Issue 2. Art. No.: CD003462. DOI: 10.1002/14651858.CD003462.pub2

Assessed as up to date:

January 28, 2008

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Primary Review Group:

Heart Group

PEARLS - Practical Evidence About Real Life Situations (click to read)

Clinical question:

How effective are heparins in the treatment of patients with acute coronary syndromes (ACS)?

Bottom line:

Compared to placebo, heparins reduce the number of heart attacks (NNT* 33) but cause more minor bleeding (NNH* 17) after ACS. The risks of mortality, revascularisation, recurrent angina, major bleeding and thrombocytopenia were similar in both groups. *NNT = number needed to treat to benefit one individual. *NNH = number needed to treat to cause harm in one individual.

Caveat:

Parenteral unfractionated heparin (UFH) or low molecular weight heparin (LMWH) was given in addition to standard therapy with aspirin.

Context:

Acute coronary syndromes include unstable angina and non-ST segment myocardial infarction. The use of UFH and LMWH heparin were evaluated in these trials, and were given within 24 to 72 hours of the onset of symptoms for a 2 to 8 day period.

Cochrane Systematic Review:

Magee KD et al. Heparin versus placebo for acute coronary syndromes. Cochrane Reviews 2008, Issue 1. Art. No.: CD003462. DOI:10.1002/14651858.CD003462.pub2. This review contains 8 studies involving 3,118 participants.

Authored by:

Brian R McAvoy

Cochrane Primary Health Care Field

Health topics:

Heart & circulation > Myocardial ischemia/coronary disease > Acute coronary syndrome: anticoagulants

Cochrane Summaries^beta

Independent high-quality evidence for health care decision making

Heparins reduce the number of heart attacks but caused more minor bleeding after acute coronary syndromes compared to placebo

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