--- title: Myocardial infarction description: What myocardial infarction (heart attack) is, what types there are, how it shows itself, how it is confirmed, how blood flow is restored, why it is dangerous, life after it and when to call an ambulance. type: disease preset: stemi aliases: - heart attack - MI - acute myocardial infarction - STEMI - NSTEMI - MINOCA sources: - tier: guideline org: minzdrav-rf title: Острый инфаркт миокарда с подъемом сегмента ST электрокардиограммы year: 2024 doi: 10.15829/1560-4071-2025-6306 url: https://cr.minzdrav.gov.ru/view-cr/157_5 - tier: guideline org: minzdrav-rf title: Острый коронарный синдром без подъема сегмента ST электрокардиограммы year: 2024 doi: 10.15829/1560-4071-2025-6319 url: https://cr.minzdrav.gov.ru/view-cr/154_4 - tier: guideline org: esc title: 2023 ESC Guidelines for the management of acute coronary syndromes year: 2023 doi: 10.1093/eurheartj/ehad191 url: https://doi.org/10.1093/eurheartj/ehad191 - tier: review title: Fifth Universal Definition of Myocardial Infarction (2026) year: 2026 doi: 10.1093/eurheartj/ehag101 url: https://doi.org/10.1093/eurheartj/ehag101 - tier: reference org: msd-manuals title: Acute Myocardial Infarction (MI) year: 2026 url: https://www.msdmanuals.com/professional/cardiovascular-disorders/coronary-artery-disease/acute-myocardial-infarction-mi - tier: reference org: msd-manuals title: Acute Coronary Syndromes (Unstable Angina and Heart Attack [Myocardial Infarction]) year: 2026 url: https://www.msdmanuals.com/home/heart-and-blood-vessel-disorders/coronary-artery-disease/acute-coronary-syndromes-unstable-angina-and-heart-attack-myocardial-infarction - tier: reference org: msd-manuals title: Complications of an Acute Coronary Syndrome year: 2026 url: https://www.msdmanuals.com/home/heart-and-blood-vessel-disorders/coronary-artery-disease/complications-of-an-acute-coronary-syndrome sources_checked: 2026-10-13 review: null --- Myocardial infarction is the death of an area of heart muscle because it does not get enough blood and oxygen. If the blood supply to an area is greatly reduced or cut off for more than a few minutes, the muscle starts to die. Myocardial infarction, together with unstable angina, is classed as an acute coronary syndrome. What coronary heart disease and acute coronary syndrome are, why plaques form in the arteries and what raises the risk are covered in the article on [coronary heart disease](../coronary-heart-disease/). This article is about the infarction itself: its types, how it is recognised and treated, and life after it.

The diagram shows the left ventricle in longitudinal section and the artery that runs along its inferior wall. The heart muscle needs a constant supply of oxygen-rich blood, and the coronary arteries bring it.

Most often, a heart attack happens when a large coronary artery is blocked by a clot on a ruptured atherosclerotic plaque. In ST-elevation myocardial infarction, the blockage of a large artery is almost always complete and persistent, and the area beyond it is damaged through the whole thickness of the wall. An inferoposterior infarction is usually caused by blockage of the right coronary artery or a dominant left circumflex artery.

## Why it happens Most often, a heart attack happens when a large coronary artery is suddenly blocked by a clot, which usually forms on the surface of a ruptured atherosclerotic plaque. The blockage often develops where the plaque had previously narrowed the artery only slightly. Less often, the cause is a spasm of a coronary artery (for example, from cocaine), a tear in its wall, or a clot that formed in the heart itself, broke away and lodged in a coronary artery. Sometimes the problem is not in the artery itself: a lack of oxygen in the heart muscle can be caused or made worse by other illnesses, such as anaemia, low oxygen in the blood, an infection with fever or too much thyroid hormone. In the 2026 classification, an infarction caused by another acute condition is called secondary if certain signs of heart damage are confirmed. The Fifth Universal Definition of MI (2026) replaced the numbered types with a clinical classification: primary, secondary and procedure-related MI. Primary MI includes all acute coronary pathologies: atherothrombosis, spontaneous coronary artery dissection, coronary embolism, vasospasm, and restenosis, stent thrombosis or graft failure more than 30 days after the procedure. Secondary MI is a myocardial oxygen supply–demand imbalance due to an alternative acute condition, together with obstructive coronary artery disease without acute coronary pathology and/or a new regional wall motion abnormality or absence of viable myocardium. Procedure-related MI is a coronary complication within 30 days of a percutaneous intervention or heart surgery. The term "type 3 MI" has been removed. The 2024 Russian Ministry of Health guideline and the MSD Manual still use the earlier classification into types 1–5. According to the Russian Ministry of Health guideline, type 1 is atherothrombosis (plaque rupture or erosion with intracoronary thrombus); type 2 is ischaemia from causes not related to thrombotic complications of coronary atherosclerosis (increased myocardial oxygen demand and/or reduced supply); type 3 is death with symptoms of ischaemia before blood samples are taken or before biomarkers rise; types 4a, 4b and 4c are MI related to PCI, stent thrombosis and restenosis; type 5 is MI related to coronary artery bypass grafting. MI with persistent (more than 20 minutes) ST-segment elevation in at least two contiguous leads is called STEMI (the same diagnosis is made with new-onset left bundle branch block); MI without such elevation and without new-onset left bundle branch block is called NSTEMI. The distinction matters because treatment strategies and timing differ. By depth of damage, MI is classed as subendocardial or transmural. Anterior infarcts tend to be larger and carry a worse prognosis than inferoposterior ones; they are usually caused by occlusion of the left coronary artery, especially the left anterior descending artery. Myocardial infarction with non-obstructive coronary arteries (MINOCA) is found in about 5–6% of patients with acute MI who undergo coronary angiography; these patients tend to be younger, female and without dyslipidaemia. Causes of MINOCA are plaque disruption without significant stenosis, vasospasm, coronary thrombosis or embolism, and spontaneous coronary artery dissection. ## Symptoms The main sign is pain, squeezing, pressure or heaviness behind the breastbone; sometimes people describe it simply as discomfort. The sensations may spread to the neck, lower jaw, left arm, below the left shoulder blade or to the upper abdomen. The pain is like an angina attack but stronger and longer: it may come in waves and last from 20 minutes to several hours, usually starts at rest and does not go away with rest. Do not wait for those 20 minutes to pass: if a heart attack is suspected, help is needed straight away. There may also be heavy sweating, nausea, breathlessness, a pounding heartbeat, dizziness or fainting, anxiety and a sense of impending doom. A heart attack can also start in an unusual way. In some people, breathlessness, pain in the upper abdomen, nausea, dizziness or weakness come to the fore. Abdominal pain is easily mistaken for indigestion, and some people, especially those with diabetes, have no chest pain at all. According to the ESC, about 80% of both women and men with acute coronary syndrome have chest pain or pressure, but women may more often have dizziness or fainting, nausea and vomiting, jaw or neck pain, breathlessness, pain between the shoulder blades, palpitations and tiredness. There is also the "silent" heart attack: with no symptoms, or with sensations so mild that the person does not feel ill; sometimes it is found only later, on an ECG. A few days or weeks before a heart attack, warning signs may appear: angina attacks become more frequent or stronger, and breathlessness and tiredness appear. The symptoms of STEMI and NSTEMI are the same. For atypical presentations, the Russian Ministry of Health guideline describes asthmatic, abdominal, arrhythmic and cerebrovascular variants and a low-symptom (painless) form. The clinical picture may be dominated by symptoms of complications: acute heart failure (pulmonary oedema, cardiogenic shock), marked bradycardia or tachycardia; sometimes the only manifestation of MI is cardiac arrest. According to MSD, about 20% of acute MIs in the general population are silent, and up to 30% in patients with diabetes; a silent MI is one that is asymptomatic or causes vague symptoms the patient does not recognise as illness. Nausea and vomiting are particularly typical of inferior MI. ## How it is diagnosed An ECG is recorded where the person is first seen by medical staff, within 10 minutes. It shows which type of acute coronary syndrome it is. If the ECG shows ST-segment elevation, the decision to restore blood flow is not delayed until a blood test result is available. The ECG model further down the page shows this elevation in one lead; for the diagnosis, it has to be present in at least two neighbouring leads. In infarction without ST elevation, there is no such elevation, and the ECG may show ST-segment depression or an inverted T wave. A blood test measures troponin, a heart muscle protein that enters the blood when heart muscle cells are damaged or die. The test is repeated after 1–2 hours: the change in troponin level confirms or rules out a heart attack. Raised troponin points to heart muscle damage, but not always to a heart attack: it is also seen, for example, in [myocarditis](../myocarditis/) and [pulmonary embolism](../pulmonary-embolism/). Coronary angiography, an X-ray of the heart's arteries taken through a catheter, shows which arteries are blocked; blood flow is often restored during the same procedure. An ultrasound of the heart (echocardiography) may show that part of the left ventricular wall moves less well, but it should not delay angiography. If angiography shows no significant narrowing of the large arteries and the cause is unclear, the ESC recommends a cardiac MRI scan. Russian Ministry of Health guideline criteria: a rise and/or fall in cardiac troponin with at least one value above the 99th percentile upper reference limit, together with at least one criterion of acute ischaemia: ischaemic ECG changes, pathological Q waves, new loss of viable myocardium or new regional wall motion abnormality on imaging, or intracoronary thrombus at angiography or autopsy. The Fifth Universal Definition defines acute myocardial injury as a rise and/or fall in troponin I or T with at least one value above the sex-specific 99th percentile. Primary MI is likely with acute injury and at least one feature: ischaemic symptoms, new ischaemic ECG changes or pathological Q waves; the diagnosis is confirmed by imaging evidence of acute coronary pathology, or of a new regional wall motion abnormality or non-viable myocardium. Acute myocardial injury also occurs without MI: in myocarditis, pulmonary embolism, takotsubo syndrome, sepsis and other conditions. ST elevation: at the J point in at least two contiguous leads, ≥0.1 mV, and in V2–V3 ≥0.2 mV in men aged 40 and over, ≥0.25 mV in men under 40 and ≥0.15 mV in women. The ESC recommends 0 h/1 h or 0 h/2 h algorithms with high-sensitivity troponin. ## How it is treated The main aim is to restore blood flow in the blocked artery as quickly as possible: opening the artery quickly saves a substantial part of the heart muscle and lowers the risk of fatal complications. Many deaths from a heart attack happen in the first 3–4 hours after symptoms start. In ST-elevation infarction, restoring blood flow is recommended for everyone whose symptoms have lasted no more than 12 hours. The preferred method is primary percutaneous coronary intervention (PCI): during angiography, the artery is opened from the inside and a stent, a metal scaffold, is placed in it. It is chosen if PCI can be done within 120 minutes of the diagnosis. If that is not possible, a clot-dissolving medicine is given (thrombolysis) within 10 minutes of the diagnosis, sometimes even before hospital; the person is then transferred to a hospital that performs PCI. This is why an ambulance takes a person with a suspected infarction of this kind straight to a hospital that performs PCI. In infarction without ST elevation, thrombolysis is not used. The doctor assesses the risk and decides whether angiography is needed urgently, within the first 24 hours, or after assessing the response to initial treatment and further tests. Blood flow is restored with PCI or coronary artery bypass surgery. Medicines that stop clots from forming and other medicines are also started straight away; the doctor decides which are needed. An acute heart attack is treated in specialised hospital units, because the risk of dangerous complications is high in the first days. After fibrinolysis, the ESC recommends immediate transfer of all patients to a PCI-capable centre; after successful fibrinolysis, angiography and PCI of the infarct-related artery (if indicated) between 2 and 24 h; and after failed fibrinolysis (ST-segment resolution of less than 50% at 60–90 minutes), rescue PCI. With ongoing ischaemia, cardiogenic shock or life-threatening arrhythmias, PCI is recommended regardless of the time since STEMI onset. NSTE-ACS: the ESC recommends an immediate invasive strategy (angiography as soon as possible) with at least one very-high-risk criterion: haemodynamic instability or cardiogenic shock, recurrent or refractory pain, life-threatening arrhythmias, mechanical complications of MI, or acute heart failure due to ongoing ischaemia; an early strategy (within 24 h) should be considered with high-risk criteria. In the Russian Ministry of Health guideline, an immediate invasive strategy means angiography within 2 hours of admission, an early one within 24 hours, and a selective one only if ischaemia appears or recurs. ## Complications In the first days after a heart attack, the risk of life-threatening complications is high: cardiac arrest, rupture of the heart and acute heart failure. Areas of muscle with poor blood flow can cause dangerous heart rhythm disorders, [ventricular tachycardia](../ventricular-tachycardia/) and ventricular fibrillation, in which the heart may stop. Rarely, the heart muscle ruptures; this usually happens in the first 1–10 days: the wall between the ventricles, the outer wall of the heart or the muscles that open and close the mitral valve may tear. Over time, the dead muscle is replaced by a scar that does not contract. If a large area has died, the heart pumps blood less well and [heart failure](../heart-failure/) may develop. The ventricular wall may thin and bulge (an aneurysm), and clots may form in the heart chamber over the dead muscle; pieces of them can travel in the bloodstream to the arteries of the brain and cause a stroke. In the first day or two, [pericarditis](../pericarditis/), inflammation of the lining around the heart, may develop, and 10 days to 2 months later a special form of it, Dressler syndrome, rarely develops. Anxiety and depression are common after a heart attack. The amount of dead myocardium is almost linearly related to the risk of cardiac arrest from asystole or fatal ventricular arrhythmias, above all ventricular fibrillation; the area and depth of necrosis determine the risk of myocardial rupture. Cardiogenic shock is the largest cause of in-hospital mortality in patients with STEMI undergoing PCI. Left ventricular remodelling leads to heart failure; its most unfavourable form is a left ventricular aneurysm, sometimes with thrombus in its cavity and a risk of embolism. According to Russian Ministry of Health monitoring data, 10.9% of patients with acute MI died in hospital in Russia in 2022 (17.7% in 2018); according to European national registries cited in the same guideline, in-hospital mortality ranges from 4 to 12%. According to observational studies cited by the Russian Ministry of Health guideline, major cardiovascular events after MI (cardiac death, recurrent MI, ischaemic stroke) occur in about 20% of patients. ## Life after a heart attack A heart attack is usually a manifestation of atherosclerosis, which develops in all the arteries, so after discharge there is still a risk of another heart attack and of vascular emergencies in other organs. Treatment started in hospital must not be stopped: stopping medicines too early raises the risk of another heart attack, heart failure and death. Do not stop taking your medicines without talking to your doctor. Cardiac rehabilitation is recommended for everyone who has had a heart attack: a programme with supervised exercise training, education, work on risk factors and psychological support. According to the Russian Ministry of Health guideline, it has three stages and lasts at least 24 weeks. It is worth asking your doctor about your rehabilitation programme, medicines and lifestyle changes. It is important to stop smoking, eat a healthy diet, limit alcohol, be physically active and keep a healthy weight. Following your doctor's advice, keep cholesterol low, blood pressure normal and, with diabetes, blood sugar normal. The Russian Ministry of Health guideline recommends a yearly flu vaccination. For the first 12 months after a heart attack, the person is followed up by a cardiologist, and then for life by a general practitioner. After the cardiac rehabilitation programmes end, the Russian Ministry of Health guideline recommends keeping up moderate-intensity physical activity for at least 150 minutes a week or vigorous-intensity activity for at least 75 minutes a week. The ESC suggests considering an assessment of mental well-being with a validated tool and onward referral when appropriate. ## When to call an ambulance A heart attack is a medical emergency. At the first signs of one, call an ambulance straight away: call your local emergency number (112 in the EU, 911 in the US and Canada, 999 in the UK). Do not wait to see whether the pain passes, and do not put off the call: many deaths from a heart attack happen in the first 3 or 4 hours after symptoms begin, and the most dangerous time is before the person reaches hospital. Call an ambulance if: - pressing pain or discomfort behind the breastbone does not go away at rest; - these sensations spread to the neck, lower jaw, left arm, below the left shoulder blade or to the upper abdomen; - they come with heavy sweating, nausea, breathlessness, dizziness or fainting; - chest pain or discomfort is new, has become more frequent or stronger, comes on at rest or with little exertion, or lasts a long time. A heart attack can also start without chest pain, with breathlessness, pain in the upper abdomen, nausea or weakness. In people with diabetes it often happens without chest pain, and older people may complain more of breathlessness than of pain. Do not waste time calling your own doctor, relatives or friends: getting to hospital quickly by ambulance can save a life.