Acute Coronary Syndrome (ACS)

How acute coronary syndrome happens

The coronary arteries supply the heart muscle with oxygen. Over decades, cholesterol-rich plaques build up in their walls (atherosclerosis). ACS starts when a plaque cracks or erodes. The body treats this as an injury: platelets stick to it and a clot forms, partly or completely blocking the artery.

• A partial or intermittent blockage causes unstable angina or an NSTEMI.
• A complete blockage usually causes a STEMI, the most urgent type.

Heart muscle starts to die within 20 to 40 minutes of complete blockage, and the damage grows over hours. That is why the saying "time is muscle" drives every step of treatment.

Types of acute coronary syndrome

Troponin is a protein released into the blood when heart muscle cells are damaged. Modern high-sensitivity troponin tests detect very small amounts.

Symptoms

The classic symptom is chest discomfort:

• pressure, squeezing, tightness, heaviness or a crushing feeling in the center of the chest
• lasting more than a few minutes, or coming and going
• occurring at rest or with minimal effort
• spreading to one or both arms, the neck, jaw, back or upper belly

Other symptoms:

• shortness of breath
• cold sweat
• nausea or vomiting
• lightheadedness or fainting
• unusual tiredness

Women, older adults and people with diabetes more often have less typical symptoms, such as breathlessness, indigestion-like discomfort, back or jaw pain, or overwhelming fatigue, sometimes without obvious chest pain.

Risk factors

• high cholesterol
• high blood pressure
• smoking or vaping nicotine
• diabetes
• obesity and physical inactivity
• family history of early heart disease (a male relative before 55 or female before 65)
• age over 45 in men and 55 in women
• chronic kidney disease
• inflammatory conditions such as rheumatoid arthritis and psoriasis
• cocaine and amphetamine use

What to do if you think you are having ACS

1. Call 911 or your local emergency number. Ambulance crews can start treatment, record an ECG and alert the hospital.
2. Chew aspirin (one regular 325 mg tablet or four low-dose 81 mg tablets), unless you are allergic or have been told not to take it.
3. Use nitroglycerin if you have been prescribed it for angina, as directed.
4. Rest and stay calm. If you are alone, make sure responders can get in.
5. If the person collapses and is not breathing normally, start CPR and use an AED.

Diagnosis in hospital

• ECG within 10 minutes of arrival, repeated if symptoms change. ST elevation means the STEMI pathway.
• High-sensitivity troponin tests at arrival and repeated within 1 to 3 hours.
• Examination and blood tests for kidney function, blood count and cholesterol.
• Echocardiogram to see how well the heart is pumping.
• Coronary angiography: dye injected into the coronary arteries through a catheter in the wrist or groin, showing blockages on X-ray.

Treatment

Opening the artery

• STEMI: emergency percutaneous coronary intervention (PCI), where a balloon opens the artery and a stent is placed, ideally within 90 minutes of first medical contact. If PCI is not available quickly, clot-busting drugs (thrombolysis) are given.
• NSTEMI and unstable angina: angiography usually within 24 to 72 hours, sooner in high-risk patients, followed by stenting or bypass surgery if needed.
• Coronary artery bypass graft (CABG) surgery for people with disease in several arteries or the left main artery.

Medicines

• Dual antiplatelet therapy: aspirin plus a second agent such as ticagrelor, prasugrel or clopidogrel, usually for 12 months
• Anticoagulants such as heparin in the acute phase
• High-intensity statins, regardless of starting cholesterol
• Beta blockers, especially when heart function is reduced
• ACE inhibitors or ARBs for heart muscle protection
• Nitrates and pain relief for symptoms

Complications

• Arrhythmias, including ventricular fibrillation, which causes cardiac arrest
• Heart failure from damaged muscle
• Cardiogenic shock
• Mechanical complications such as valve or wall rupture (rare)
• Pericarditis
• Recurrent ACS and stroke

Recovery and preventing another event

• Cardiac rehabilitation: a supervised exercise and education program that lowers the risk of death and readmission. Ask for a referral.
• Take medicines as prescribed and do not stop antiplatelet drugs without speaking to your cardiologist, especially after a stent.
• Stop smoking: the risk of another heart attack falls sharply after quitting.
• Control blood pressure, cholesterol and diabetes.
• Eat a Mediterranean-style diet, stay active and keep a healthy weight.
• Get vaccinated against flu and COVID-19.
• Most people return to driving, work and sexual activity within weeks, as advised by their care team.

Frequently asked questions

What is acute coronary syndrome?

Acute coronary syndrome is a group of emergencies caused by a sudden reduction in blood flow to the heart, usually from a ruptured plaque and clot. It includes unstable angina and two types of heart attack: NSTEMI and STEMI.

Is acute coronary syndrome the same as a heart attack?

Not exactly. ACS includes heart attacks (NSTEMI and STEMI) and unstable angina, where blood flow is dangerously reduced but heart muscle has not yet been measurably damaged. All are treated as emergencies because unstable angina can progress to a heart attack.

What are the symptoms of acute coronary syndrome?

Chest pressure, squeezing or tightness lasting more than a few minutes, often spreading to the arm, jaw, neck or back, with sweating, nausea, breathlessness or lightheadedness. Women, older adults and people with diabetes may have breathlessness or fatigue without typical chest pain.

What is the difference between STEMI and NSTEMI?

A STEMI shows ST-segment elevation on the ECG and usually means an artery is completely blocked, needing immediate reopening. An NSTEMI shows heart damage on troponin tests without ST elevation, usually from a partial blockage, and is treated with medicines and angiography within days.

Can you fully recover from acute coronary syndrome?

Many people recover well, especially with fast treatment that limits heart damage. Cardiac rehabilitation, medicines and lifestyle changes greatly reduce the risk of another event. Some people are left with heart failure or angina that needs ongoing treatment.