By Christopher Bergland 

Updated on November 14, 2023

 Medically reviewed by Anisha Shah, MD

Acute coronary syndrome (ACS) is a medical term that categorizes three conditions that cause a sudden, life-threatening reduction of blood flow to the heart. When plaque build-up associated with coronary artery disease blocks oxygen-rich blood from reaching heart muscles, it often causes acute coronary syndromes. Tight, squeezing chest pain (angina) is the most common symptom.¹ All three types of ACS are life-threatening emergencies that require calling 911 for immediate medical attention.

Read on to learn what you need to know about each type of acute coronary syndrome, how ACS symptoms feel, testing procedures used to diagnose it, treatment options, and how to manage an ACS heart condition long-term.

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A Glance at Each Type of Acute Coronary Syndrome

There are three types of ACS are:

1. Unstable angina

2. NSTEMI (non-ST-elevation myocardial infarction) heart attacks

3. STEMI (ST-elevation myocardial infarction) heart attacks

Unstable angina is the least severe type of acute coronary syndrome. When someone is having an unstable angina attack, insufficient blood flow within the heart (cardiac ischemia) causes angina symptoms, but blood tests don't show detectable myocardial necrosis (heart muscle tissue death).²

Non-ST-elevation myocardial infarction (NSTEMI) is more severe than unstable angina because inadequate blood flow to the heart muscle has caused some of the heart's muscular tissue to die. NSTEMI is considered a heart attack.³

ST-elevation myocardial infarction (STEMI) is the most serious type of ACS. When an ECG shows ST-elevation, someone is having a "massive" heart attack. ST-segment elevation on an ECG usually means that a major coronary artery is completely blocked and that the heart could stop beating very soon because much of its muscular tissue is rapidly dying or already dead.⁴

Heart Attack vs. Cardiac Arrest

Cardiac arrest is triggered by "electrical" problems that cause the heart to stop beating abruptly. Heart attacks are triggered by "circulation" problems that block coronary blood flow and cause heart muscle tissue to die over minutes or hours, which can eventually cause the heart to stop beating if not treated quickly. Heart attacks are classified as acute coronary syndrome, but sudden cardiac arrest is not.⁵

Causes and Risk Factors in Acute Coronary Syndrome

Acute coronary syndrome heart conditions are caused by circulation problems that prevent coronary arteries from delivering enough oxygen-rich blood to the heart muscle. Without sufficient blood flow, heart muscle tissue is starved of oxygen. In medical terms, the death of heart muscle tissue from insufficient blood flow is called a myocardial infarction.

Atherosclerosis, characterized by plaque build-up inside coronary artery walls, is the most common underlying cause of ACS.⁶ The narrowing of artery walls due to atherosclerotic plaque build-up inhibits the flow of oxygen-rich blood to the heart muscle, which can cause angina symptoms.

Some of the risk factors associated with acute coronary syndrome include:⁷

• Family history of coronary heart disease

• High cholesterol or high triglycerides (hyperlipidemia)

• High blood pressure (hypertension)

• Diabetes

• Smoking

• Obesity

• Physical inactivity

Symptoms: How Do ACS Symptoms Feel?

Acute coronary syndrome symptoms typically feel like a tightness or heaviness in the chest area or as if an invisible hand is squeezing or pressing down on your heart.⁸ This chest discomfort or pain feeling is called "angina." The symptoms of acute coronary syndrome caused by insufficient blood flow.

Symptoms associated with acute coronary syndrome can include:⁸

• Chest pain that feels like squeezing, burning, or crushing

• Pain in the jaw, arm, belly, shoulder, or neck

• Nausea

• Sweating

• Anxiety

• Rapid or irregular heartbeat

• Lightheadedness

It is important to note that some people with acute coronary syndrome don't experience any of the above symptoms. Silent myocardial ischemia or a silent heart attack is the phenomenon of people with insufficient blood flow to the heart not experiencing noticeable chest pain or other symptoms during an acute coronary syndrome emergency.⁹

Emergency Symptoms

Non-emergency chest pain from stable angina is predictable. It is typically triggered by physical exertion that calms down after resting and lasts less than five minutes. On the other hand, emergency ACS symptoms associated typically last longer than ten minutes, aren't triggered by exertion, and are not alleviated by rest.¹⁰

Any ACS symptoms should be treated as a "call 911" emergency. All three types of acute coronary syndrome are time-sensitive and require prompt emergency medical treatment at a hospital.⁸

Anyone experiencing ACS symptoms shouldn't drive themselves to the hospital. Taking an ambulance is the best way to go for numerous reasons, such as getting treatment en route to the hospital and not wasting precious time sitting in the ER's waiting room upon arrival.

Ideally, someone with ACS receives emergency medical treatment within 60 minutes of symptom onset. This 60-minute period is called the "golden hour" because getting ACS treatment during this critical time window can mean the difference between life and death.¹¹

Vague Symptoms

People who are diagnosed with ACS at the hospital often experience vague or intermittent symptoms lasting less than ten minutes in the days or weeks leading up to having a medical emergency. Speaking to a healthcare provider at the first sign of any angina-like chest discomfort is always a good idea.

Duration of Symptoms

When someone is receiving emergency acute coronary syndrome care, healthcare providers try to establish when their heart attack symptoms started so they can provide appropriate treatment during the “golden hour.” Even if someone has been experiencing sporadic or vague symptoms, their official “symptom onset time” starts when ischemic symptoms last ten minutes or longer.¹⁰

Treatment for Each ACS Heart Type

The most common treatment for acute coronary syndrome is coronary angioplasty with stent insertion, also known as percutaneous coronary intervention or PCI. During this minimally invasive procedure, a tiny balloon is inflated to widen narrow or blocked arteries. Then, a small wire mesh tube is inserted to keep blood flowing through the reopened artery. It is typically done as emergency surgery.¹²

When someone has a heart attack, marked by a complete blockage of a major coronary artery, it is recommended that primary PCI is performed within less than 90 minutes of the patient making contact with the EMTs who bring them to the hospital via ambulance.¹³

Survival Rates

Depending on the type of ACS and heart attack severity, with prompt diagnosis and treatment, survival rates for people hospitalized with a heart attack range from about 90% to 97%.¹⁴

Testing to Confirm ACS

Troponin blood tests are the golden standard for testing to confirm acute coronary syndrome. Troponins are released into the bloodstream when the heart muscle is damaged or dies from insufficient blood flow. High-sensitivity cardiac troponin tests measure how much of this biomarker is circulating in the blood and confirm varying degrees of acute coronary syndrome.¹⁵

Long-Term: How to Manage ACS Symptoms and Complications

Long-term treatment and lifestyle changes are essential for preventing another cardiac event after experiencing an acute coronary syndrome event and being treated at the hospital. Common medications prescribed for secondary prevention of acute coronary syndrome after hospital discharge include:¹⁶

• Aspirin

• Angiotensin-converting enzyme (ACE) inhibitors

• Statins

• Beta-blockers

• P2Y12 inhibitors¹⁷

In addition to taking medication, staying physically active, eating a heart-healthy diet, stress relief, and getting high-quality sleep in an optimal sleeping environment can all lower the risk of having future acute coronary syndrome symptoms or complications.¹⁸

Summary

Unstable angina, NSTEMI, and STEMI are the 3 types of acute coronary syndrome (ACS). Although every type of ACS is very serious and requires emergency medical attention, STEMI is the most dangerous. Chest pain at rest that isn't caused by physical exertion and lasts longer than 10 minutes can be a symptom of ACS. If you or someone you know is having ACS symptoms, call 911 immediately and get to a hospital via ambulance.