STEMI Heart Attacks and Why They Are So Dangerous

An ST elevation myocardial infarction (STEMI) is a heart attack that occurs when a major artery feeding into the heart is completely blocked, changing 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.

STEMI symptoms may include upper body pain and discomfort, as well as exhaustion and nausea. Treatment will vary but may include drugs that stabilize the heart or reduce blood clots, oxygen therapy, or procedures, such as an angioplasty or stenting.

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

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:

• A fatty substance called plaque builds up in the coronary arteries, which supply blood to the heart.
• This stress triggers a tear in the artery, which blood clots, or clumps of blood, cover up.
• This causes 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 fixed blockage. When this happens, an individual may have random chest pain, even when resting.
• 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."

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.

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.

Types of STEMI Attacks

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

Anterior STEMI

An anterior STEMI refers to an attack resulting from an infarction in the left anterior descending (LAD) artery. The LAD supplies more oxygen to the heart than other arteries, pumping blood into the anterior (front) side of your heart. Thus, this type of blockage is associated with the greatest risk of heart failure and fatality.

Inferior STEMI

An inferior or lateral STEMI involves a blockage in one of the following arteries:

• Right coronary artery (RCA): The RCA supplies blood to the bottom side of your heart (right ventricle and the right atrium).
• Left circumflex artery (LCX): The LCX supplies the left side wall of your heart.

Inferior STEMI attacks are less severe than anterior ones because the RCA and LCX are smaller than the LAD. Thus, infarctions in these arteries don't disrupt the blood flow as much. While 40% to 50% of myocardial infarctions are related to inferior infarctions, people with these conditions tend to have low rates of hospitalization and risk of death compared to anterior STEMI patients.

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, or magnetic resonance imaging (MRI), which creates a detailed image of your heart. In addition, your healthcare provider may also run blood tests, known as cardiac biomarkers, to check for heart muscle damage.

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 stop blood clots
• An angioplasty, a minimally invasive surgery that repairs the impacted artery
• Stenting, which involves the insertion of a mesh tube to reopen the blocked artery

After treatment, the recovery period begins. This may include an exercise-based rehabilitation program, dietary changes, and the use of medications like blood thinners, which prevent blood clots.

STEMI Heart Attack Prognosis

STEMI is the most deadly type of heart attack. Mortality rates, or the amount 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 hospital mortality rate for:

• A STEMI ranges from 4% to 24%
• An anterior STEMI is 21.4%
• An inferior localized STEMI is 12.2%

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

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.

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:

• Maintaining a healthy weight
• Getting regular exercise
• Decreasing alcohol intake
• Quitting smoking
• Reducing stress
• Managing cholesterol, blood pressure, and diabetes
  
  

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.