The Most Severe Type of Heart Attack

By Richard N. Fogoros, MD 

Updated on November 27, 2023

 Medically reviewed by Jeffrey S. Lander, MD

A STEMI, or ST elevation myocardial infarction, is a heart attack that occurs when a major artery feeding into the heart is completely blocked. This changes the blood flow to the organ and the electrical current in the lower chambers.

A STEMI is the most serious and deadly type of heart attack. Following an attack, between 30% and 38% of people die within five years.¹

This article explains what a STEMI heart attack is. It also covers symptoms, diagnosis, and treatment options.

 The Heart: Anatomy, Function, and Conditions

What Is a STEMI Heart Attack?

STEMI is the most severe type of acute coronary syndrome (ACS), which describes conditions where there is a rapid decrease of blood flow to the heart.

STEMI pathophysiology, or how one comes about, is as follows:²

• A fatty substance called plaque builds up in the coronary arteries, which supply blood to the heart.

• This stressor leads to a tear within that plaque buildup; as a result, blood clots, or clumps of blood form within the blood vessel to try and cover up the tear.

• This leads to a complete blockage in the artery.

• When blocked, the part of the heart muscle serviced by that artery will quickly suffer from a lack of oxygen, also called ischemia.

• Some of the heart muscle will begin to die resulting in a myocardial infarction, or heart attack.

STEMI vs. NSTEMI vs. Unstable Angina

Other, less severe, types of ACS are notably different from the STEMI type. They include:

• Unstable angina: With this type of ACS, blood clots will form, dissolve, and re-form without causing a complete blockage. When this happens, an individual may have random chest pain, even when resting.³

• Non-ST-segment elevation myocardial infarction (NSTEMI): This occurs when the blockage doesn't completely stop the blood flow in a major artery or totally blocks a minor artery. It may be called a "partial heart attack."

 Mini Heart Attack: Don’t Doubt Yourself With Suspected Symptoms

Symptoms of a STEMI Heart Attack

Symptoms can vary from person to person. Some STEMI symptoms may include: 

• Pain around the shoulder blades, arm, chest, jaw, left arm, or upper stomach

• Pain or pressure around chest area, also known as angina

• Sweating, or feeling out of breath

• Discomfort or tightness in the neck or arm

• Indigestion, which is discomfort in the stomach and chest

• Heartburn, which describes when you have an acidic taste in your mouth and upper chest discomfort

• Nausea and vomiting

• Fatigue or sudden exhaustion

• Dizziness

• Increased or irregular heart rate

Anyone who is at risk of a heart attack should pay close attention to any unusual symptoms and seek medical attention right away if any are noticed.

Verywell / Laura Porter

 Signs and Symptoms of a Heart Attack

Types of STEMI Attacks

Blood flows into the heart from three different arteries. STEMI heart attacks are classified depending on which part of the heart the blocked artery is supplying.

• Anterior STEMI: A blockage in the artery supplies blood to the front wall of the heart, the left anterior descending (LAD) artery.⁴

• Inferior or Lateral STEMI: A blockage in the arteries that supply blood to the bottom walls of the heart. This type of STEMI can be caused by the blockage of the right coronary artery (RCA) or the left circumflex coronary artery (LCx).⁵

• Posterior STEMI: A blockage in the arteries that supply blood to the back wall of the heart.⁶

 Coronary Arteries: Anatomy and Function

How STEMI Is Diagnosed

To diagnose a STEMI, a healthcare provider will go over your symptoms. They will also run diagnostic tests like an ECG. In addition, your healthcare provider may also run blood tests, known as cardiac biomarkers, to check for heart muscle damage and rapidly begin treatment.

To confirm the diagnosis, images of the coronary arteries are taken to assess where the blockage is located.

 How a Heart Attack Is Diagnosed

STEMI Treatment

Because a STEMI is a severe heart attack, treatment will begin as soon as possible. Keep in mind, the longer it takes to unblock the artery, the more damage there may be. 

STEMI treatment may include:

• Drugs that help stabilize the heart and reduce pain like morphine, beta-blockers, and statin medications

• Oxygen therapy to increase the oxygen sent to your tissues

• Medication, like aspirin, that helps to deter blood clots

• An angioplasty, a minimally invasive surgery that restores blood flow to the impacted artery

• Stenting, which involves the insertion of a mesh tube to reopen the blocked artery

• Medications to dissolve the blood clot, called thrombolytics

After treatment, the recovery period begins. This may include an exercise-based rehabilitation program, dietary changes, and the use of medications like blood thinners, such as antiplatelets. Cardiac rehab typically starts once you are cleared by your healthcare provider.

 How Many People Survive a Heart Attack?

STEMI Heart Attack Prognosis

STEMI is the most deadly type of heart attack. Mortality rates, or the number of people who die due to this type of heart attack, differ by the location of the blockage, as well as other factors, such as age, sex, risk factors, and medical history.

In general, the 30-day mortality rate for people with STEMI ranges from 2.5% to 10%:⁷

Keep in mind that mortality can rise to about 38% if an individual experiences a complication, like sudden cardiac arrest, before making it to the hospital.⁸

Prognosis also depends greatly on the time it takes to receive definitive care. This factor can include distances from a qualified facility, as in some rural locations, or within the system itself. A study of 114, 871 STEMI patients across 648 hospitals in the United States found in-hospital mortality was lower for those treated within target times established by national guidelines.⁹

Other factors that increase the risk of death from STEMI include a history of:

• A prior heart attack

• Hypertension

• High cholesterol

• Diabetes

• Heart failure

• Smoking

In addition, the older a person is, the more likely STEMI will be fatal. Research shows people age 80 and older have a 45.9% mortality rate from STEMI.

How Long Can You Live After a STEMI Heart Attack?

Individuals who survive past the year mark have a life expectancy similar to that of the general population.¹⁰

Prevention

While you can't control all factors that help prevent a STEMI heart attack, there are some things you can do to reduce your risk, including:¹¹

• Maintaining a healthy weight

• Getting regular exercise

• Decreasing alcohol intake

• Quitting smoking

• Reducing stress

• Managing cholesterol, blood pressure, and diabetes

 Causes and Risk Factors of Heart Disease

Why It's Called a STEMI Heart Attack

A STEMI is so-named because it causes an increase in the ST segment of an electrocardiogram (ECG)—a diagnostic test that uses sensors to monitor the heart's electrical activity and records it on a line graph.

The ST segment refers to a part of the test that shows the heart's activity in a wave pattern. When a person has the most severe type of heart attack, this segment will appear abnormally elevated, instead of flat. This indicates a total blockage.

Summary

STEMI is the most severe type of acute coronary syndrome. With this type of heart attack, there is a complete blockage in one of the coronary arteries.

Symptoms of a STEMI may vary from person to person, but generally include discomfort, pain, or pressure around the chest area.

To diagnose a STEMI, your healthcare provider will go over your symptoms, as well as run various diagnostic tests. Treatment will begin as soon as possible and may include various medications and procedures to help unblock the artery and reduce discomfort.