2.1 Acute coronary syndromes refers to a group of symptoms associated with acute myocardial ischaemia with or without infarction. It encompasses a spectrum of disorders or syndromes including acute myocardial infarction and unstable angina pectoris. Acute coronary syndromes are usually the result of an acute or sub-acute primary reduction of myocardial oxygen supply provoked by disruption of an atherosclerotic plaque (build-up of material in a heart vessel) associated with inflammation, thrombosis, vasoconstriction and microembolisation.
2.2 The presence of ST-segment-elevation on an electrocardiogram usually indicates total occlusion of the affected artery, resulting in necrosis of the tissue supplied by that artery or ST-segment-elevation myocardial infarction (STEMI). This condition is treated immediately with reperfusion therapy (thrombolysis or percutaneous coronary intervention). Acute coronary syndrome without STEMI is classified as either unstable angina or non-ST-segment-elevation myocardial infarction (NSTEMI). NSTEMI differs from unstable angina primarily in the severity of myocardial ischaemia. In NSTEMI, the ischaemia is severe enough to result in the release of biochemical markers of myocardial injury into the blood. Immediate treatment for these conditions aims to prevent progression to total occlusion of the artery and, for people at high risk of myocardial infarction, may include coronary revascularisation, either by means of percutaneous coronary intervention or coronary artery bypass graft.
2.3 Acute coronary syndromes become more prevalent with increasing age and incidence is higher in men than women. There were around 32,000 hospital admissions for unstable angina in England in 2012–13, and it is estimated that there are about 82,000 myocardial infarctions in the country every year. Of the 80,974 hospital admissions with a final diagnosis of myocardial infarction recorded between April 2012 and March 2013 in the Myocardial Ischaemia National Audit Project (MINAP), 40% were STEMIs and 60% were NSTEMIs. The average age of people with STEMI and NSTEMI was 65 years and 72 years respectively. Twice as many men had myocardial infarctions as women.
2.4 Long‑term management of acute coronary syndromes includes the use of aspirin in combination with a thienopyridine (clopidogrel, prasugrel) or acyclopentyl‑triazolo‑pyrimidine (ticagrelor). NICE has produced clinical guidelines on Myocardial infarction with ST-segment-elevation: The acute management of myocardial infarction with ST-segment-elevation (NICE clinical guideline 167) and on Unstable angina and NSTEMI: the early management of unstable angina and non-ST-segment-elevation myocardial infarction (NICE clinical guideline 94). NICE's myocardial infarction with ST-segment-elevation guideline recommends that after STEMI, patients treated with clopidogrel in combination with low‑dose aspirin during the first 24 hours after the myocardial infarction should continue with treatment for at least 4 weeks. Thereafter, standard treatment, including low‑dose aspirin, should be given unless there are other indications to continue clopidogrel in combination with aspirin. In its unstable angina and NSTEMI guideline, NICE recommends that clopidogrel in combination with low-dose aspirin should be continued for 12 months after the most recent acute episode of NSTEMI. Thereafter, standard care, including treatment with low‑dose aspirin alone, is recommended unless there are other indications to continue clopidogrel in combination with aspirin.
2.5 NICE recommends prasugrel in combination with aspirin as an option for preventing atherothrombotic events in people with acute coronary syndromes having percutaneous coronary intervention, only when: immediate primary percutaneous intervention for STEMI is necessary; stent thrombosis has occurred during clopidogrel treatment; or the person has diabetes (NICE technology appraisal guidance 182). NICE also recommends ticagrelor in combination with low-dose aspirin for up to 12 months as an option for people with STEMI who are to be treated with percutaneous coronary intervention, NSTEMI or unstable angina (NICE technology appraisal guidance 236).
2.6 Since the publication of the original appraisal of prasugrel (NICE technology appraisal guidance 182) in October 2009, generic formulations of clopidogrel have become available and NICE has published its appraisal of ticagrelor (2011; NICE technology appraisal guidance 236).