Myocardial Infarction (Heart Attack)
Recognition, emergency management and long-term secondary prevention of heart attack
Myocardial infarction (MI) occurs when a coronary artery becomes completely blocked, causing death of heart muscle tissue due to prolonged ischaemia. It is one of the most common causes of death and disability in the UK. MI is classified as STEMI (ST-elevation MI) or NSTEMI (non-ST-elevation MI) based on ECG findings and troponin levels — each requires a different but equally urgent management pathway. Early recognition, rapid treatment, and long-term secondary prevention are the cornerstones of improving outcomes.
What Happens During a Heart Attack?
A heart attack occurs when a coronary artery is suddenly blocked, usually by a blood clot forming on top of a ruptured atherosclerotic plaque. The resulting lack of blood flow causes cardiac muscle cells to become ischaemic and, if blood supply is not restored quickly, to die. The extent of damage depends on which artery is blocked, how completely it is occluded, and how long the blockage persists before treatment. The sooner blood flow is restored, the more heart muscle is saved — hence the phrase 'time is muscle'.
Recognising the Symptoms
The classic symptom of MI is central or left-sided chest pain — typically described as heavy, crushing, or tight — radiating to the left arm, jaw, or back. Associated symptoms include sweating, nausea, vomiting, breathlessness, and a sense of impending doom. In some patients — particularly women, older adults, and people with diabetes — symptoms may be atypical: breathlessness alone, epigastric pain, or simply extreme fatigue. Silent MI (with no chest pain at all) occurs in up to 25% of cases. Any sudden cardiac symptoms should be treated as a potential emergency until proven otherwise.
Emergency Treatment
MI is a medical emergency. Call 999 immediately. While waiting for the ambulance: aspirin 300 mg chewed (if not allergic and not already taken). GTN spray 0.4 mg sublingually for chest pain — may be repeated after 5 minutes. Do not give GTN if systolic BP is below 90 mmHg. Oxygen is given only if SpO2 is below 94% — routine high-flow oxygen is no longer recommended as it may worsen outcomes. For STEMI: primary percutaneous coronary intervention (PPCI) is the treatment of choice — aim 'door-to-balloon' time under 90 minutes. For NSTEMI: risk-stratified management; high-risk patients proceed to early invasive angiography within 24–72 hours. Thrombolysis is now rarely used — reserved for when PPCI is unavailable within 120 minutes.
Medications Used in MI
During and after MI, a range of medicines are used to reduce further clot formation, limit ischaemic damage, and prevent future events. Dual antiplatelet therapy (DAPT) — aspirin plus a P2Y12 inhibitor (ticagrelor 90 mg BD or prasugrel 10 mg OD) — is started at presentation and continued for 12 months following PPCI. Anticoagulation (fondaparinux for NSTEMI; unfractionated heparin during PPCI) prevents further thrombus formation. Beta-blockers (bisoprolol or metoprolol) reduce heart rate and oxygen demand. ACE inhibitors (ramipril or lisinopril) improve left ventricular remodelling and reduce mortality — particularly important when ejection fraction is reduced. High-intensity statin (atorvastatin 80 mg) for LDL reduction and plaque stabilisation. Aldosterone antagonist (eplerenone) in patients with LVEF under 40% following MI. All information in this article has been prepared following careful evaluation of NICE NG185, NG167, and NICE TA420 guidance.
Recovery and Secondary Prevention
After a heart attack, lifelong secondary prevention is essential to reduce the risk of a further event. All patients should receive: aspirin 75 mg OD (lifelong), P2Y12 inhibitor for 12 months, atorvastatin 80 mg (lifelong), ACE inhibitor, and beta-blocker. Cardiac rehabilitation — a structured programme of exercise, education and psychological support — is offered to all patients and significantly reduces mortality and hospital readmissions. Lifestyle changes are equally important: stopping smoking (single most important intervention), Mediterranean-style diet, regular physical activity, and weight management. Patients should know the warning signs of a further MI and act immediately by calling 999.