A heart attack, or myocardial infarction, happens when blood flow to part of the heart muscle is suddenly blocked, most often by a clot that forms on a cracked cholesterol plaque in a coronary artery. Without oxygen, heart muscle cells start to die. The most common warning sign is pressure, squeezing or pain in the center or left side of the chest lasting more than a few minutes, often with shortness of breath, a cold sweat, nausea or pain spreading to the arm, jaw, neck or back.
A heart attack is an emergency: call 911 right away, even if you are not sure. About 805,000 Americans have a heart attack each year, according to the CDC. Doctors confirm it with an electrocardiogram (ECG) and a troponin blood test repeated over one to a few hours, then reopen the artery with a stent or clot-dissolving medicine. The faster the treatment, the more heart muscle is saved.
Key takeaways
- Chest discomfort is the most common symptom in both sexes, but women more often also have shortness of breath, nausea and pain between the shoulder blades.
- Call 911 at the first warning signs. Do not drive yourself, and never delay the call to take an aspirin.
- The diagnosis rests on a rise and/or fall of troponin above the 99th percentile of healthy people, plus signs of reduced blood flow.
- Treatment combines rapid reopening of the artery, two antiplatelet medicines, a high-intensity statin and cardiac rehabilitation.
- Recent trials show that beta-blockers help less than once thought when the heart pumps normally, and that colchicine did not reduce new events after a heart attack.
What is a heart attack (myocardial infarction)?
The heart muscle is fed by the coronary arteries. In most heart attacks, plaque made of fat, cholesterol and calcium has built up in the artery wall for years (atherosclerosis). The plaque breaks open, a clot forms on it and blocks the artery; if the blockage is not cleared quickly, the muscle it feeds begins to die (NHLBI). Myocardial infarction is simply the medical name for a heart attack. It differs from cardiac arrest, when the heart stops pumping, although a heart attack can trigger one.
Acute coronary syndrome: STEMI, NSTEMI and unstable angina
Acute coronary syndrome (ACS) is the umbrella term for sudden reduced blood flow to the heart:
- STEMI: the ECG shows ST-segment elevation, which usually means an artery is completely blocked. It must be reopened immediately.
- NSTEMI: troponin rises, so muscle is damaged, but without ST elevation. The artery is often partly blocked.
- Unstable angina: chest pain at rest or with minimal effort without muscle death, so troponin does not rise; for example rest pain lasting more than 20 minutes or new severe angina (ESC 2023).
Types of myocardial infarction
The Fourth Universal Definition of Myocardial Infarction (2018) describes five types. Type 1 is the classic heart attack from a ruptured or eroded plaque. Type 2 comes from a mismatch between oxygen supply and demand, for example severe anemia, very low blood pressure or a very fast rhythm. Types 3 to 5 concern sudden death and stent or bypass procedures. Some heart attacks occur without blocked arteries (MINOCA), more often in women and younger people (NHLBI). Broken heart syndrome can look identical; see broken heart syndrome vs heart attack.
Heart attack symptoms and warning signs
The CDC and NHLBI list the major symptoms:
- Chest pain, pressure, squeezing or fullness in the center or left side, lasting more than a few minutes or coming back.
- Discomfort in one or both arms or shoulders, the back, neck, jaw or upper belly.
- Shortness of breath, with or before the chest discomfort.
- Feeling weak, light-headed or faint, often with a cold sweat; nausea, unusual tiredness, a fast or irregular heartbeat.
The pain often lasts more than 20 minutes and can feel like indigestion (MedlinePlus). Angina usually eases with rest or medicine; heart attack pain does not. If you cannot tell the difference, call 911 (NHLBI). For other chest sensations, see tingling in the chest: causes and warning signs.
Heart attack symptoms in women
A meta-analysis of 27 studies found chest pain in 74% of women and 79% of men with ACS. Women had about twice the odds of pain between the shoulder blades and higher odds of nausea, vomiting and shortness of breath (van Oosterhout, Journal of the American Heart Association, 2020); the authors argue these symptoms should no longer be called "atypical". NHLBI adds unusual tiredness, sometimes for days, upset stomach and anxiety, and notes that women often downplay symptoms and reach the hospital later.
Silent heart attacks
About 1 in 5 heart attacks are silent (CDC). They are more common in older adults and people with diabetes or high blood sugar (NHLBI), and make up 9% to 37% of nonfatal heart attacks in studies that repeated ECGs over time (universal definition).
Causes and risk factors
Coronary artery disease is the main cause. Less common causes include a coronary artery spasm (smoking, extreme cold, stress, cocaine), a clot traveling into a coronary artery (atrial fibrillation, pregnancy) and spontaneous coronary artery dissection (SCAD), a tear more common in women under 50 and during pregnancy (NHLBI).
Risk factors you can change: high LDL cholesterol (see our guide to high cholesterol), high blood pressure, smoking, diabetes, high triglycerides, overweight, inactivity and a diet rich in saturated fat and sodium. About half of Americans have at least one of three key risk factors: high blood pressure, high cholesterol or smoking (CDC).
Risk factors you cannot change: age (men after 45, women after 55 or menopause) and early heart disease in a father or brother before 55 or a mother or sister before 65 (NHLBI). An inherited high lipoprotein(a) also raises risk.
How a heart attack is diagnosed: ECG and high-sensitivity troponin
An ECG is the first test, within minutes of arrival (NHLBI). Under the universal definition, ST elevation means a new rise of at least 1 mm in two neighboring leads; in leads V2 and V3 the threshold depends on age and sex. ST elevation sends the patient straight to the catheterization lab, but a normal ECG does not rule out a heart attack.
Troponin is a protein inside heart muscle cells that leaks into the blood when they are damaged. In healthy people the level is so low that only the most sensitive tests can measure it (MedlinePlus). High-sensitivity troponin (hs-cTn) tests report tiny amounts in nanograms per liter (ng/L). For a deep dive on the marker, see our troponin blood test guide.
The 99th percentile and why the change matters
Troponin above the 99th percentile upper reference limit (URL) of healthy people is called myocardial injury. It becomes a myocardial infarction only when troponin rises and/or falls and there is evidence of reduced blood flow: symptoms, new ECG changes, new loss of muscle on imaging or a clot seen on angiography. The 99th percentile is specific to each test brand, and sex-specific cutoffs are recommended because women have lower values.
0/1-hour and 0/2-hour algorithms
With the European 0h/1h and 0h/2h algorithms, troponin is measured on arrival and 1 or 2 hours later. A very low value or tiny change means "rule-out", a high value or clear rise "rule-in", and patients in between get a third test at 3 hours (ESC 2023). A meta-analysis of 11 studies and 19,213 patients found that the 0/1-hour algorithm detected 99% of heart attacks, with a 30-day death rate of 0.11% in the rule-out group (Burgos, 2020); another found a sensitivity of 98% to 99% depending on the test brand (Chiang, Heart, 2020). A single early sample should not be used to rule out a heart attack if you arrive less than 2 hours after the pain started. Faster bedside tests are coming; see the new rapid troponin test in the ER.
Imaging and angiography
Coronary angiography uses dye and X-rays to show the blockage, which can usually be treated during the same procedure. An echocardiogram shows how well the heart pumps (the ejection fraction); stress tests, CT and MRI help in unclear cases (MedlinePlus).
Other blood tests after a heart attack
Our overview of cardiac markers: troponin, BNP and CK compares the main heart tests. The hospital usually also checks:
- CK-MB: an older heart enzyme, less sensitive and less specific than troponin (universal definition). Read why troponin replaced CK-MB.
- BNP or NT-proBNP: high values point to heart strain or heart failure. See the BNP blood test.
- Lipid panel: LDL, HDL, non-HDL cholesterol and triglycerides, to set the statin dose. See our lipid panel guide.
- HbA1c and glucose: a heart attack often reveals diabetes or prediabetes. See the HbA1c test.
- Kidney function and potassium: needed before contrast dye and to dose medicines. See the kidney function panel and the potassium blood test.
- Complete blood count: anemia can cause a type 2 heart attack and changes the bleeding risk of antiplatelet drugs. See the complete blood count.
Reference values and thresholds
Cutoffs vary between laboratories and test brands: compare with your own report. Troponin examples come from published studies; lipid and glucose ranges from MedlinePlus (SI values rounded).
| Test | Threshold or range (US / SI) | Meaning |
|---|---|---|
| hs-troponin I (Abbott) | 99th percentile: 16 ng/L women, 34 ng/L men | Above = myocardial injury; rise or fall plus ischemia = heart attack |
| hs-troponin I (Siemens Atellica) | 99th percentile: 34 ng/L women, 53 ng/L men | Each test has its own cutoff |
| hs-troponin T, ESC 0/1 h | Rule-out in the lowest range (about 5 to 12 ng/L, small change); rule-in from 52 ng/L | Read with a second sample 1 hour later |
| LDL cholesterol | Below 100 mg/dL (2.6 mmol/L); after ACS, add-on drug if above 70 mg/dL (1.8 mmol/L) on a maximal statin | Main modifiable cause of plaque |
| Total / non-HDL cholesterol | Below 200 mg/dL (5.2 mmol/L) / below 130 mg/dL (3.4 mmol/L) | Higher = more plaque-forming particles |
| HDL cholesterol | Best 60 mg/dL (1.55 mmol/L) or more; low below 40 mg/dL (1.04) men, 50 mg/dL (1.29) women | Low HDL is part of metabolic syndrome |
| Triglycerides (fasting) | High above 150 mg/dL (1.69 mmol/L) | Often high with diabetes and excess weight |
| Fasting glucose | 100 to 125 mg/dL (5.6 to 7.0 mmol/L) = impaired | Prediabetes or metabolic syndrome |
| HbA1c | Normal below 5.7% (39 mmol/mol); prediabetes 5.7% to 6.4%; diabetes 6.5% (48 mmol/mol) or more | Diabetes changes treatment and follow-up |
Table sources: Gunsolus (2018), Christenson (2020), van der Hagen (2019), Restrepo and Rao (2026), MedlinePlus.
How to read your results
- One high troponin is not a diagnosis: doctors look at the change between samples, your symptoms and the ECG.
- Troponin can be high without a heart attack: heart failure, a fast rhythm, myocarditis, pulmonary embolism, sepsis, severe COVID-19, chest injury, a marathon or chronic kidney disease (MedlinePlus). With severely reduced kidney function, the Abbott test's specificity fell to 57% to 61%, versus 93% to 95% with normal kidneys, while rule-out stayed reliable (Gunsolus, 2018).
- A normal troponin 12 hours after symptoms began suggests you probably did not have a heart attack (MedlinePlus). It does not exclude stable coronary disease, which a coronary calcium score can assess.
- After discharge, track your LDL cholesterol, blood pressure, HbA1c and kidney function.
Treatment of a heart attack
Reopening the artery
Percutaneous coronary intervention (PCI) opens the artery with a balloon and usually a stent, ideally within 90 minutes of arrival and usually no later than 12 hours after the heart attack. When PCI cannot be done in time, clot-dissolving drugs (thrombolytics) are given, ideally within 30 minutes of arrival (MedlinePlus); the European guideline uses them when PCI within 120 minutes is not feasible, followed by angiography 2 to 24 hours later. Some people need bypass surgery (CABG). Nitroglycerin and sometimes morphine relieve pain.
Aspirin and a P2Y12 inhibitor
Aspirin blocks the cyclooxygenase enzyme in platelets (ChEMBL). The European guideline uses a 150 to 300 mg loading dose, then 75 to 100 mg a day; 81 mg a day is usual after PCI (MedlinePlus). A second drug blocks the platelet P2Y12 receptor: ticagrelor, prasugrel or clopidogrel. The 2025 ACC/AHA guideline prefers ticagrelor or prasugrel over clopidogrel after PCI; this dual antiplatelet therapy (DAPT) generally lasts 12 months, and people at high bleeding risk may stop aspirin after one month and keep the P2Y12 inhibitor alone (Restrepo and Rao, 2026). Never stop these medicines on your own: stopping certain heart medicines can be deadly (MedlinePlus).
Statins and other cholesterol drugs
Statins such as atorvastatin block HMG-CoA reductase, the liver enzyme that makes cholesterol (ChEMBL). A high-intensity statin starts in the hospital, and the 2025 guideline adds a nonstatin drug when LDL stays above 70 mg/dL on the maximal dose. For muscle aches on statins, see statin muscle pain and the CK test.
Beta-blockers, ACE inhibitors and complications
Beta-blockers such as metoprolol slow the heart and treat rhythm problems; ACE inhibitors lower blood pressure and help the heart pump (NHLBI). Both remain standard when the ejection fraction is reduced or heart failure develops. A heart attack can also cause dangerous rhythms, cardiac arrest, cardiogenic shock and inflammation of the heart, which is why the first days are spent under monitoring (NHLBI).
Recovery and cardiac rehabilitation
Most people survive a heart attack and go on to live active, full lives (NHLBI). Many can walk right away and return to normal activities within a few weeks; depending on state law, driving may be possible within a week if you have no symptoms. Cardiac rehabilitation combines supervised exercise, education and counseling; Medicare and most insurers cover 36 sessions over 12 weeks. It improves quality of life and reduces returns to the hospital (NHLBI). Sadness and anxiety are common and usually ease within 2 to 3 weeks; tell your care team if they last longer (MedlinePlus).
Preventing a heart attack, or a second one
- Do not smoke, and treat your LDL cholesterol, blood pressure and blood sugar. With diabetes, see our guide to diabetes symptoms and treatment.
- Eat less saturated fat and sodium, and aim for 150 minutes a week of moderate exercise such as walking (MedlinePlus).
- Take your medicines every day, even when you feel well, and finish cardiac rehab.
- Daily aspirin is not for everyone: it helps people with known coronary disease but is not advised for healthy people at low risk, because it raises the risk of stomach bleeding (MedlinePlus).
Women, older adults and people with diabetes
Women tend to have heart attacks at older ages. Smoking, high blood pressure, high cholesterol, high blood sugar, obesity and stress raise their risk more than in men, and causes other than blocked arteries, such as SCAD, are more frequent, which can delay diagnosis (NHLBI). Sex-specific troponin cutoffs help avoid missed diagnoses.
In older adults, shortness of breath or weakness may be the main symptom, and silent heart attacks are more common (NHLBI). Age alone is no reason to withhold modern treatment, as the FIRE trial shows (below).
People with diabetes may have little or no chest pain, with shortness of breath, fatigue or weakness instead (MedlinePlus). Controlling HbA1c, blood pressure and LDL lowers the risk of another event.
When to see a doctor
Call 911 immediately for chest pain or pressure lasting more than a few minutes or coming back, pain spreading to the arm, back, neck or jaw, or shortness of breath, cold sweat, nausea or light-headedness. A second heart attack may not feel like the first (NHLBI). Do not drive yourself: paramedics can start treatment on the way. Never delay calling 911 to take aspirin; chew one only if the 911 dispatcher or your doctor tells you to. If the person collapses and is not breathing normally, start CPR. See your doctor soon if chest discomfort comes only with exertion and goes away with rest.
Latest scientific advances in myocardial infarction
The 2025 ACC/AHA guideline for acute coronary syndromes
Published in February 2025 with emergency physicians and EMS doctors, it covers STEMI, NSTEMI and unstable angina in one document, the first major update since 2013-2015. It recommends treating the other narrowed arteries in stable STEMI patients with multivessel disease, prefers ticagrelor or prasugrel after PCI, allows single antiplatelet therapy at one month for high bleeding risk and sets stricter LDL goals (Rao, Circulation, 2025; Restrepo and Rao, 2026).
Beta-blockers when the heart pumps normally
REDUCE-AMI (5,020 patients, ejection fraction at least 50%) found no difference in death or new heart attack, 7.9% vs 8.3% over 3.5 years (NEJM, 2024). REBOOT (8,438 patients, ejection fraction above 40%) found no benefit either (NEJM, 2025). BETAMI-DANBLOCK (5,574 patients) found fewer events with beta-blockers, 14.2% vs 16.3% (NEJM, 2025). In patients with a mildly reduced ejection fraction of 40% to 49%, pooled data showed a 25% lower risk (Rossello, Lancet, 2025), but across 19,245 patients the absolute benefit was only 0.9% (Zuin, 2026). Your cardiologist may now discuss whether you need a beta-blocker long term; do not stop it without asking.
Colchicine did not reduce events after MI
In CLEAR SYNERGY, 7,062 patients received colchicine, an anti-inflammatory that blocks tubulin (ChEMBL), or placebo soon after a heart attack. After 3 years, cardiovascular death, new heart attack, stroke or urgent revascularization occurred in 9.1% vs 9.3%, even though CRP fell, and diarrhea was more common (Jolly, NEJM, 2024). Inflammation, measured by CRP, remains a research target.
Complete revascularization, including after 75
In the FIRE trial, 1,445 patients aged 75 or older (median 80) were randomized: treating all significant narrowings lowered death, heart attack, stroke or repeat procedures at one year from 21.0% to 15.7% (Biscaglia, NEJM, 2023). COMPLETE-2 (NCT05701358, 5,100 patients, results expected after 2028) compares two ways of choosing which narrowings to treat.
Faster troponin tests
A new high-sensitivity troponin T test, validated in 1,415 emergency patients, safely ruled out a heart attack in 54% of them with the 0/1-hour approach, with a negative predictive value of 99.5% (Völschow, 2026): shorter waits with the same safety.
Which tests can help?
A heart attack is diagnosed in the hospital, never at home. But routine blood tests reveal your risk years before and track your recovery: lipid panel, lipoprotein(a) once in a lifetime, HbA1c and fasting glucose, creatinine with eGFR, a complete blood count, and BNP when heart failure is suspected. Read together with your blood pressure and history, they give a far clearer picture than any single number.
Glossary
- Myocardial infarction: death of part of the heart muscle from lack of blood flow; a heart attack.
- Acute coronary syndrome (ACS): STEMI, NSTEMI and unstable angina.
- Troponin: a heart muscle protein released into the blood when heart cells are damaged.
- 99th percentile URL: the troponin level exceeded by only 1 in 100 healthy people.
- PCI: opening an artery with a balloon and stent through a catheter.
- DAPT: aspirin plus a P2Y12 inhibitor.
- Ejection fraction: the share of blood the left ventricle pumps out with each beat.
- MINOCA: heart attack without obstructed coronary arteries.
Frequently asked questions
What are the signs and symptoms of myocardial infarction?
Chest pain or pressure lasting more than a few minutes, pain spreading to the arm, back, neck or jaw, shortness of breath, cold sweat, nausea and light-headedness. Some heart attacks are silent.
Is there a difference between a heart attack and a myocardial infarction?
No, they are the same thing. Acute coronary syndrome is the broader term that also includes unstable angina.
What should you never do during a heart attack?
Never wait for the pain to pass, never drive yourself and never delay calling 911 to take aspirin. Take aspirin only if the dispatcher or your doctor advises it and you are not allergic.
What is the life expectancy of someone with myocardial infarction?
It depends on the damage, the speed of treatment, the ejection fraction and risk factor control. Most people survive; in recent trials of patients on modern care, about 4 in 100 died over three and a half years (REDUCE-AMI, BETAMI-DANBLOCK).
What is the difference between STEMI and NSTEMI?
A STEMI shows ST elevation on the ECG and needs the artery opened immediately. An NSTEMI raises troponin without ST elevation; angiography is usually done within hours to a day.
What troponin level indicates a heart attack?
No single number: troponin above the test's 99th percentile (for example 16 ng/L in women and 34 ng/L in men with one hs-troponin I test) that rises or falls between samples, with symptoms or ECG changes.
Sources
- Rao SV et al. — 2025 ACC/AHA/ACEP/NAEMSP/SCAI Guideline for Acute Coronary Syndromes — Circulation, 2025 — doi.org
- Restrepo VJ, Rao SV — Uncertainties in the 2025 ACS Guidelines — Curr Cardiol Rep, 2026 — doi.org
- Thygesen K et al. — Fourth Universal Definition of Myocardial Infarction (2018) — Eur Heart J, 2019 — doi.org
- Byrne RA et al. — 2023 ESC Guidelines for acute coronary syndromes — Eur Heart J, 2023 — doi.org
- van Oosterhout REM et al. — Sex Differences in Symptom Presentation in ACS — J Am Heart Assoc, 2020 — doi.org
- Burgos LM et al. — ESC 0/1-hour algorithm: meta-analysis — Eur Heart J Acute Cardiovasc Care, 2020 — doi.org
- Chiang CH et al. — Safety and efficacy of the ESC 0/1-hour algorithm — Heart, 2020 — doi.org
- Gunsolus I et al. — Renal Dysfunction and High-Sensitivity Troponin I — J Am Soc Nephrol, 2018 — doi.org
- Christenson RH et al. — HIGH-US study of a hs-troponin I assay — Clin Biochem, 2020 — doi.org
- van der Hagen EAE et al. — Fast 0/1-h algorithm for NSTEMI — Clin Chem Lab Med, 2019 — doi.org
- Völschow B et al. — Validation of a novel hs-troponin T assay — Eur Heart J Acute Cardiovasc Care, 2026 — doi.org
- Yndigegn T et al. — REDUCE-AMI — N Engl J Med, 2024 — doi.org
- Ibanez B et al. — REBOOT — N Engl J Med, 2025 — doi.org
- Munkhaugen J et al. — BETAMI-DANBLOCK — N Engl J Med, 2025 — doi.org
- Rossello X et al. — Beta blockers with mildly reduced ejection fraction: meta-analysis — Lancet, 2025 — doi.org
- Zuin M et al. — Fragility of beta-blocker evidence after MI — Am Heart J Plus, 2026 — doi.org
- Jolly SS et al. — Colchicine in Acute Myocardial Infarction (CLEAR SYNERGY) — N Engl J Med, 2024 — doi.org
- Biscaglia S et al. — Complete or Culprit-Only PCI in Older Patients (FIRE) — N Engl J Med, 2023 — doi.org
- COMPLETE-2 (NCT05701358) — ClinicalTrials.gov — clinicaltrials.gov
- Ojha N, Dhamoon AS — Myocardial Infarction — StatPearls, 2023 — pubmed.ncbi.nlm.nih.gov
- CDC — About Heart Attack Symptoms, Risk, and Recovery — cdc.gov
- CDC — Heart Disease Facts — cdc.gov
- NHLBI — Heart Attack (symptoms, causes, treatment, recovery, women) — NIH — nhlbi.nih.gov
- MedlinePlus — Heart attack — NLM — medlineplus.gov
- MedlinePlus — Troponin test — NLM — medlineplus.gov
- MedlinePlus — Cholesterol levels; metabolic syndrome; HbA1c test — NLM — medlineplus.gov
- MedlinePlus — Aspirin and heart disease — NLM — medlineplus.gov
- ChEMBL — aspirin, ticagrelor, clopidogrel, atorvastatin, colchicine, metoprolol — EMBL-EBI — ebi.ac.uk
Further reading
- Troponin blood test: what a high result means
- Cardiac markers: troponin, BNP and CK explained
- Broken heart syndrome vs heart attack
- New rapid troponin test speeds ER diagnosis
- CK-MB blood test: why troponin is preferred
- Stroke: signs, causes, tests and treatment
- ApoB test: a clearer heart-risk number
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