Acute Coronary Syndrome: Complete Guide to Symptoms, Causes, Diagnosis, and Treatment

4 days ago

9 min read

Updated: 2 days ago

Medically reviewed by Dr. Baraa Alnahhal, MD · Last reviewed: September 2026

Quick Answer: What Is Acute Coronary Syndrome?

Acute coronary syndrome is a medical emergency describing conditions caused by a sudden drop in blood flow to the heart, usually when fatty plaque bursts inside a heart artery and a blood clot blocks it. It includes two conditions: a heart attack (when heart muscle cells die or are damaged) and unstable angina (when blood flow drops but tissue doesn't die, still raising heart attack risk). Get emergency help right away, and never drive yourself to the hospital.

TL;DR

What it is: A sudden reduction in blood flow to the heart, which is a medical emergency.
The two conditions: A heart attack (myocardial infarction) and unstable angina.
The cause: Plaque (fatty deposits) in the heart's arteries breaks open, a clot forms, and blood flow is blocked.
The classic sign: Sudden chest pain or discomfort (pressure, tightness, aching, burning), often spreading to the arms, jaw, neck, back, or upper belly.
The hidden trap: Women, older adults, and people with diabetes often have symptoms without chest pain: nausea, sweating, fatigue, dizziness.
What to do: Call emergency services immediately. Do not drive yourself to the hospital.

Acute Coronary Syndrome at a Glance

What it is: A range of conditions from sudden reduced blood flow to the heart.
The two conditions: Heart attack (myocardial infarction) and unstable angina.
The cause: Plaque in heart arteries bursts, a blood clot forms, and blood flow is blocked.
Most common symptom: Chest pain or discomfort (angina), usually starting suddenly.
Pain can spread to: Shoulders, arms, upper belly, back, neck, jaw.
Silent signs: Nausea, heavy sweating, shortness of breath, racing heartbeat, dizziness, fainting, unusual fatigue.
Who may skip chest pain: Women, older adults, and people with diabetes.
Key tests: ECG/EKG, blood tests for heart proteins, coronary angiogram, echocardiogram, stress test.
Emergency medicines: Clot busters, nitroglycerin, aspirin and other antiplatelets, beta blockers, statins.
Procedures: Angioplasty with stenting; bypass surgery (CABG).
What to do now: Call emergency services. Never drive yourself to the hospital.

What Is Acute Coronary Syndrome?

Acute coronary syndrome is a term that describes a range of conditions related to a sudden reduction in blood flow to the heart. These conditions include a heart attack and unstable angina, a type of chest pain.

When blood flow to the heart is reduced, the heart muscle doesn't get enough oxygen. If heart tissue cells die or are damaged, a heart attack happens. A heart attack is also known as a myocardial infarction.

Unstable angina occurs when blood flow to the heart decreases, but it's not severe enough to kill heart tissue cells or cause a heart attack. The reduced blood flow may still increase your risk of a heart attack.

Acute coronary syndrome often causes severe chest pain or discomfort. It is a medical emergency that needs diagnosis and care right away. The goals of treatment are to improve blood flow and to treat and prevent complications.

Symptoms: The Warning Signs That Vary by Person

The symptoms of acute coronary syndrome usually start suddenly. They include:

Chest pain or discomfort: it may feel like aching, pressure, tightness, or burning. Chest pain is also called angina.
Pain that spreads: starting in the chest and moving to the shoulders, arms, upper belly area, back, neck, or jaw.
Nausea or vomiting
Pain or burning in the upper belly (indigestion)
Shortness of breath (dyspnea)
Sudden, heavy sweating
Racing heartbeat
Feeling lightheaded or dizzy
Fainting
Unusual fatigue

Chest pain or discomfort is the most common symptom. But symptoms can vary a lot depending on age, sex assigned at birth, and other medical conditions.

Important: Women, older adults, and people with diabetes are more likely to have symptoms without chest pain or discomfort. Nausea, sweating, unusual fatigue, or shortness of breath alone can be the warning.

When to See a Doctor

Acute coronary syndrome is a medical emergency. Chest pain or discomfort can be a symptom of many life-threatening conditions. Get emergency help right away for a diagnosis and appropriate care. Do not drive yourself to the hospital.

Causes: How Plaque Turns Into an Emergency

Acute coronary syndrome is usually caused by a buildup of fatty deposits in and on the walls of the heart's arteries. These fatty deposits are also called plaque.

The chain of events:

Fats, cholesterol, and other substances build up and narrow the arteries.
When a fatty deposit breaks open, a blood clot can form.
The clot blocks blood flow to the heart.
The heart muscle doesn't get enough oxygen.
The lack of oxygen can cause cells in the heart muscle to die, and the damage can lead to a heart attack.

When acute coronary syndrome doesn't cause heart muscle cells to die, it is called unstable angina.

Risk Factors

The risk factors for acute coronary syndrome are the same as those for other types of heart disease:

Older age
High blood pressure
High blood cholesterol
Smoking or tobacco use
Not enough physical activity
An unhealthy diet
Obesity or overweight
Diabetes
Personal or family history of chest pain (angina), heart attacks, or stroke
History of high blood pressure, preeclampsia, or diabetes during pregnancy
Early menopause
COVID-19 infection

How Acute Coronary Syndrome Is Diagnosed

Acute coronary syndrome is an emergency, so it's usually diagnosed at a hospital. The healthcare team runs tests to check the heart and find the cause of symptoms, and some tests happen while they ask about your symptoms and medical history.

Electrocardiogram (ECG or EKG). This quick test shows how the heart is beating. Sticky sensor patches attach to the chest and sometimes to the arms or legs. Changes in the heartbeat may mean the heart is not working as it should, and patterns help find the general location of any blockages.
Blood tests. Some heart proteins slowly leak into the blood after heart damage. Blood tests check for these proteins.

Your healthcare team combines symptoms and test results to diagnose acute coronary syndrome and to classify your condition as a heart attack or unstable angina. Other tests may rule out different causes or help determine treatment:

Coronary angiogram: a thin flexible catheter is guided to the heart (usually through the groin or wrist); dye makes the arteries show up on images to reveal blockages. Some treatments can even be done during this test.
Echocardiogram: sound waves create pictures of the beating heart, showing blood flow through the heart and valves, and whether it's pumping properly.
Myocardial perfusion imaging: a tiny, safe amount of radioactive substance tracks through the heart's blood vessels via a special camera, finding areas of poor blood flow or damage.
CT angiogram: a powerful X-ray machine creates images of the heart and its blood vessels, finding plaque buildup in the coronary artery walls.
Exercise stress test: shows how the heart works during exercise (treadmill or bike); medicine that mimics exercise is used if you can't exercise. It is only done when you have no symptoms at rest.

Treatment Options

The immediate goals of treatment are to relieve pain and distress, improve blood flow, and restore heart function quickly and as much as possible. The long-term goals are to help the heart work better, manage risk factors, and lower the risk of a heart attack.

Treatment may include medicine and heart procedures or surgery.

Medicines

Clot busters (thrombolytics): break up a blood clot blocking an artery.
Nitroglycerin: improves blood flow by temporarily widening blood vessels.
Antiplatelet drugs: prevent blood clots from forming. Examples: aspirin, clopidogrel (Plavix), prasugrel (Effient).
Beta blockers: relax the heart muscle, slow the heart rate, decrease demand on the heart, and lower blood pressure. Examples: metoprolol (Lopressor, Toprol-XL), nadolol.
ACE inhibitors: widen blood vessels and improve blood flow, helping the heart work better. Examples: lisinopril (Qbrelis, Zestril), benazepril (Lotensin).
ARBs: help control blood pressure. Examples: irbesartan (Avapro), losartan (Cozaar).
Statins: lower blood cholesterol and may stabilize fatty deposits so they're less likely to rupture and form a clot. Examples: atorvastatin (Lipitor, Atorvaliq), simvastatin (Zocor, Flolipid).
Other cholesterol-lowering drugs: lower cholesterol further. Example: ezetimibe (Zetia).

Surgery and Other Procedures

Angioplasty and stenting. A thin, flexible tube and tiny balloon open clogged heart arteries. The tube is inserted into a blood vessel, usually in the groin or wrist, and guided to the narrowed artery. A wire with a deflated balloon on the tip inflates to widen the artery, then is deflated and removed. A mesh tube called a stent is usually placed in the artery to keep it open.
Coronary artery bypass grafting (CABG, pronounced "cabbage"). This major surgery takes a healthy blood vessel from the chest or leg area (the graft). The surgeon attaches the ends of the graft below a blocked heart artery, creating a new path for blood to flow to the heart.

Lifestyle Changes That Protect Your Heart

Lifestyle changes can help keep the heart healthy. Here are the nine habits the sources recommend:

Don't smoke or use tobacco. Quit if you smoke, and ask your healthcare team for help. Avoid secondhand smoke too.
Eat healthy foods. Choose fruits, vegetables, and whole grains. Limit sugar, salt, and saturated fats.
Be active. Aim for at least 30 minutes of moderate or vigorous activity five or more days a week. Ask your team about the right amount and type for you.
Check your cholesterol. Get regular blood cholesterol checks and avoid high-fat, high-cholesterol meat and dairy. Medicine may be recommended if cholesterol is high.
Control your blood pressure. Uncontrolled high blood pressure raises the risk of serious conditions, so get it checked regularly and ask what reading is best for you.
Keep a healthy weight. Too much weight strains the heart and can lead to high cholesterol, high blood pressure, diabetes, and heart disease.
Manage stress. Try more exercise, mindfulness, and support groups.
Limit alcohol. If you drink, keep it moderate: up to one drink a day for women, up to two for men.
Practice good sleep habits. Adults should get 7 to 9 hours of sleep daily, going to bed and waking at the same time every day, including weekends.

Preparing for Emergency Care

If you have sudden chest pain or other symptoms of acute coronary syndrome, get emergency care right away or call 911.

How you describe your symptoms helps the emergency medical team make a diagnosis. Be prepared to answer these questions:

When did the symptoms start?
How long did they last?
What symptoms are you currently having?
How would you describe the pain?
Where is the pain located?
On a scale of 1 to 10, with 10 being the worst, how bad is the pain?
Does anything make the symptoms better or worse?

Frequently Asked Questions

What is acute coronary syndrome?

Acute coronary syndrome is a medical emergency describing conditions caused by a sudden reduction in blood flow to the heart. It includes two conditions: a heart attack (myocardial infarction), where heart muscle cells die or are damaged, and unstable angina, where blood flow decreases but tissue does not die, still raising heart attack risk.

What causes acute coronary syndrome?

It's usually caused by fatty deposits (plaque) building up in and on the walls of the heart's arteries. When a fatty deposit breaks open, a blood clot can form and block blood flow to the heart. Without enough oxygen, heart muscle cells can die, causing a heart attack.

What are the symptoms of acute coronary syndrome?

Symptoms usually start suddenly: chest pain or discomfort (aching, pressure, tightness, or burning) that may spread to the shoulders, arms, upper belly, back, neck, or jaw. Nausea, sudden heavy sweating, shortness of breath, a racing heartbeat, dizziness, fainting, and unusual fatigue are also common. Notably, women, older adults, and people with diabetes may have symptoms without any chest pain.

How do I know if it's a heart attack or unstable angina?

The difference is whether heart tissue dies. In a heart attack, the blood flow blockage causes heart muscle cells to die or become damaged. In unstable angina, blood flow drops but isn't severe enough to kill tissue, though it still increases your risk of a heart attack. Hospitals use ECGs and blood tests for heart proteins to tell the two apart.

What should I do if I think I'm having acute coronary syndrome?

Get emergency help right away: call emergency services and do not drive yourself to the hospital. The goals of immediate treatment are to relieve pain, improve blood flow, and restore heart function as quickly as possible through medicines (like clot busters, nitroglycerin, aspirin, and beta blockers) and procedures such as angioplasty with stenting or bypass surgery.

How can acute coronary syndrome be prevented?

The risk factors are the same as other heart disease: older age, high blood pressure, high cholesterol, smoking, lack of physical activity, unhealthy diet, obesity, diabetes, and family history. Protect your heart by not smoking, eating fruits, vegetables, and whole grains, getting at least 30 minutes of activity most days, checking your cholesterol and blood pressure, keeping a healthy weight, managing stress, limiting alcohol, and sleeping 7 to 9 hours a night.

Conclusion: What to Remember About Acute Coronary Syndrome

Acute coronary syndrome is one of the clearest "time is muscle" situations in medicine, and knowing the facts beforehand can save a life. The three lessons to carry from this guide are:

Sudden chest symptoms are never "just wait and see." Pressure, tightness, or burning in the chest, especially when it spreads to the arm, jaw, neck, or back, is a medical emergency. Call for help immediately, and never drive yourself to the hospital.
Don't wait for the classic chest pain. Women, older adults, and people with diabetes often experience acute coronary syndrome without chest pain. Nausea, sweating, shortness of breath, and unusual fatigue can be the only warning.
Prevention starts long before the emergency. The same habits that lower risk (no smoking, healthy eating, daily activity, controlled blood pressure and cholesterol, and good sleep) are your best long-term protection against the plaque that causes this emergency.

If you or someone near you ever feels sudden chest pain or pressure, treat it as serious until a medical team says otherwise.

This article is for informational purposes only and is not a substitute for professional medical advice. If you have sudden chest pain or other emergency symptoms, call emergency services right away. Never drive yourself to the hospital.