ST-segment-elevation myocardial infarction (STEMI) occurs when a coronary artery becomes blocked by a blood clot, causing the heart muscle supplied by the artery to die. It belongs to a group of heart conditions known as acute coronary syndromes.
The incidence of STEMI has been declining over the past 20 years. It varies between regions and averages around 500 hospitalised episodes per million people each year in the UK. The London Ambulance Service attended 9657 cardiac arrests in 2011–12 for a population of around 8.2 million people (1177 per million people). Most of these will have been attributed to acute coronary syndromes, so the overall population prevalence of STEMI is likely to be in the region of 750–1250 per million people. Over the past 30 years, in-hospital mortality after acute coronary syndromes has fallen from around 20% to nearer 5%. This has been attributed to various factors, including improved drug therapy and speed of access to effective treatments.
Nearly half of potentially salvageable myocardium is lost within 1 hour of the coronary artery being occluded, and two-thirds are lost within 3 hours. Apart from resuscitation from any cardiac arrest, the highest priority in managing STEMI is to restore an adequate coronary blood flow as quickly as possible. In the 1980s and 1990s, the best way to restore flow was to administer a fibrinolytic drug.
The UK introduced a comprehensive system for delivering fibrinolysis after publication of the Department of Health's National Service Framework for Coronary Heart Disease. However, fibrinolysis was not suitable for use in some people because of bleeding complications. In around 20–30% of people, fibrinolysis failed to result in coronary reperfusion, and in a few (1.0%) it caused haemorrhagic stroke. To improve outcomes, attention turned to mechanical techniques to restore coronary flow (for example, coronary angioplasty, thrombus extraction catheters and stenting), which are grouped under the overarching term primary percutaneous coronary intervention (primary PCI).
The National Infarct Angioplasty Project concluded that primary PCI is both feasible and cost effective, and that it should become the treatment of choice for STEMI, provided it could be delivered 'in a timely fashion'.
Primary PCI 'timeliness' is a key part of this guideline. This is addressed in detail, so commissioners and professionals delivering services for people with STEMI can plan their configuration in such a way that outcomes are optimal. This guideline also covers procedural primary PCI issues, the use of antiplatelet and antithrombin agents, and improving outcomes for the minority of people still receiving fibrinolysis.
The recommendations in this guideline relate only to people with a diagnosis of STEMI. Chest pain of recent onset (NICE clinical guideline 95) covers the diagnosis of STEMI and should be read in conjunction with this guideline. The guideline will assume that prescribers will use a drug's summary of product characteristics to inform decisions made with individual patients.