Acute Coronary Syndrome

Written & reviewed by the BestDoctors.sg editorial team · Last updated 2 Sep 2026 · General information, not medical advice

Acute coronary syndrome describes what happens when the heart is suddenly starved of blood and oxygen. It is one of the most common medical emergencies in Singapore, and how quickly a person reaches treatment can make the difference between full recovery and lasting heart damage. This guide explains what ACS is, how to recognise it, why every minute counts, and what treatment and recovery involve.

What acute coronary syndrome is

Acute coronary syndrome is not a single illness but an umbrella term for a group of emergencies caused by a sudden reduction of blood flow to the heart. The coronary arteries are the vessels that supply the heart muscle itself. Over time, fatty deposits called plaques can build up and narrow these arteries — a process known as coronary artery disease. In ACS, one of these plaques cracks or ruptures, and a blood clot forms on top of it. The clot can partly or completely block the artery, cutting off the oxygen the heart muscle needs to keep beating. When the muscle is starved of oxygen, it becomes distressed and, if the blockage is not cleared quickly, it can begin to die. This is why ACS is treated as a true emergency.

The types in plain terms

Doctors group acute coronary syndrome into a few closely related conditions, which sit on a spectrum of severity.

Unstable angina is chest pain that comes on at rest, is new, or is suddenly more frequent and severe than before. The artery is severely narrowed but heart muscle has not yet been permanently damaged. It is a serious warning that a heart attack may be about to happen.

Heart attack — known medically as a myocardial infarction — means heart muscle has actually started to die from lack of blood. Doctors describe two main “flavours”. A STEMI is usually caused by a completely blocked artery and shows a distinctive pattern on the heart tracing; it needs the fastest possible action to reopen the vessel. An NSTEMI often involves a partly blocked artery; it is still an emergency but shows a different pattern on the tracing. You do not need to know which type you have — the message is the same for everyone: get to hospital urgently.

Symptoms to recognise

The most common symptom is discomfort in the centre of the chest — often described as pain, pressure, heaviness, squeezing or tightness rather than a sharp stab. It may spread to one or both arms, the shoulders, the jaw, the neck, the upper back or the stomach area. Other warning signs include:

• Breathlessness, with or without chest discomfort
• Breaking out in a cold sweat
• Nausea or vomiting
• Light-headedness or feeling faint
• Unusual tiredness or a sense of impending doom

Importantly, not everyone gets the “classic” crushing chest pain. Women, older people and people with diabetes may have quieter or less typical symptoms — such as breathlessness, fatigue, indigestion-like discomfort or simply feeling very unwell. If something feels seriously wrong, do not wait to see whether it passes.

Why it is an emergency

Cardiologists often say “time is muscle”. Once a coronary artery is blocked, the area of heart muscle it feeds begins to die within a short time, and the longer the blockage lasts, the more muscle is lost for good. Restoring blood flow quickly can save that muscle, protect the heart’s pumping strength and lower the risk of dangerous heart-rhythm problems, which can cause a cardiac arrest. This is why calling 995 straight away — rather than resting, taking a taxi or driving yourself — is so important. Paramedics can begin treatment on the way and take you to a hospital equipped to reopen the artery.

Causes and who is at higher risk

The underlying cause of most ACS is coronary artery disease, the gradual narrowing of the heart’s arteries by fatty plaque. Anything that speeds up this process raises the risk. Common risk factors include:

• Smoking
• High blood pressure
• High cholesterol
• Diabetes
• Being overweight and physically inactive
• A family history of early heart disease
• Older age

Many of these risk factors are common in Singapore and several can be improved with treatment and lifestyle change. Having one or more does not mean a heart attack is inevitable, but it does mean paying closer attention to heart health.

How it is diagnosed and treated urgently

In the emergency department, staff work quickly to confirm the diagnosis and act. An ECG (a heart tracing) is done within minutes to look for signs of a blocked artery. Cardiac blood tests check for a protein released when heart muscle is damaged, and are often repeated to track any change. Doctors may also arrange a chest X-ray or heart scans.

Treatment aims to restore blood flow as fast as possible and to steady the heart. This may include antiplatelet and other blood-thinning medicines to stop the clot growing, and medicines to ease the heart’s workload and relieve pain. To physically reopen the artery, doctors often perform angioplasty, in which a fine tube is guided to the blockage and a small mesh stent is placed to hold the artery open. In some settings, clot-busting medicine may be given to dissolve the clot. When several arteries are badly narrowed, bypass surgery may be recommended. The right approach depends on the type of ACS and the individual, and is decided by the hospital team.

Recovery and preventing another event

Recovery does not end at discharge. Cardiac rehabilitation — a supervised programme of gentle, gradually increasing exercise, education and support — helps the heart recover, rebuilds confidence and lowers the risk of another event. Just as important are the medicines prescribed to protect the heart, control cholesterol and keep blood flowing smoothly through any stent. These medicines must not be stopped without medical advice, even if you feel well, as stopping suddenly can be dangerous. Long-term prevention also means controlling risk factors: stopping smoking, managing blood pressure, cholesterol and diabetes, eating a heart-healthy diet, staying active and keeping to a healthy weight. Regular follow-up with a doctor helps keep everything on track.

When to call 995

Call 995 for an emergency ambulance immediately if you or someone else has:

• Chest pain, pressure or tightness lasting more than a few minutes, or that goes and comes back
• Chest discomfort with sweating, breathlessness, nausea or light-headedness
• Pain spreading to the arm, jaw, neck, back or stomach
• Sudden collapse, or someone who is unresponsive and not breathing normally

Do not drive yourself. While waiting, stay still and rest. If a person becomes unresponsive and is not breathing normally, start chest compressions if you are able and follow the ambulance operator’s instructions.

Common questions

Is acute coronary syndrome the same as a heart attack?

Not exactly. ACS is the umbrella term. A heart attack is one form of ACS, and unstable angina is another. Both are emergencies.

Can I just rest and see if the pain goes away?

No. Waiting wastes the time in which heart muscle can be saved. If chest discomfort lasts more than a few minutes or comes with other warning signs, call 995.

My symptoms don’t feel dramatic — could it still be ACS?

Yes. Women, older people and those with diabetes may have milder or unusual symptoms such as breathlessness, fatigue or indigestion-like discomfort. If you feel seriously unwell, seek help.

Why shouldn’t I drive myself to hospital?

Symptoms can worsen suddenly, and a dangerous heart rhythm can develop without warning. An ambulance can begin treatment on the way and take you to the right hospital.

Will I need to take medicines for life?

Many people take heart-protecting medicines long term after ACS. Never stop them on your own — always discuss any change with your doctor first.

Related guides

• Heart attack warning signs
• Coronary artery disease & angina
• Heart stent & angioplasty
• Chest pain
• Cardiac rehabilitation

Sources

National Heart Centre Singapore; Singapore Heart Foundation; HealthHub.