Overview of Non-ST Segment Myocardial Infarction

heart attack, also known as myocardial infarction, which occurs when blood flow to the heart muscle is blocked, starving it of oxygen. It is one of several conditions called acute coronary syndrome (ACS) in which blood flow to the heart is suddenly reduced or blocked.

Many people don’t realize that there is more than one form of heart attack. Some involve only partial blood flow obstruction. Cardiologists call this non-ST-segment elevation myocardial infarction (NSTEMI). NSTEMI is a milder form of heart attack that accounts for about two-thirds of all cases.

This article explains what NSTEMI is and how it differs from a “classic” heart attack. It also describes how NSTEMI is diagnosed and how treatment can be changed based on an assessment of a person’s risk factors for serious heart attack.

Types of acute coronary syndromes

All forms of ACS are usually caused by the rupture of plaque in the coronary (heart) arteries, resulting in a partial or complete blockage. Depending on the severity of the blockage, ACS can be divided into three different types:

  • Unstable angina is the partial rupture of an artery that causes chest pain. Unlike stable angina that occurs during exertion, unstable angina It can happen at any time and is considered more serious. Unstable angina does not cause permanent heart damage.
  • ST-segment elevation myocardial infarction (STEMI) is considered a “classic” heart attack. It occurs when a ruptured plaque completely blocks a major coronary artery, causing extensive heart damage.
  • NSTEMI is complete blockage of a small coronary artery or partial blockage of a major coronary artery. The symptoms may be the same as STEMI, but the damage to the heart is much less.


NSTEMI is a type of heart attack caused by complete blockage of a small coronary artery or partial blockage of a major coronary artery. It can cause symptoms typical of a heart attack, but tends to cause less damage to the heart muscle.


NSTEMI is usually diagnosed when a patient presents with symptoms of unstable angina. These include:

  • Tenderness or tightness in the chest that may spread to the shoulders or other parts of the upper body
  • chest pain that occurs when you are not exercising
  • shortness of breath
  • sweat
  • anxiety

Doctors can use an electrocardiogram (ECG), which records the electrical activity of the heart, to differentiate between STEMI and NSTEMI.

On an EKG, there is usually a flat line between heartbeats, called the “ST segment.” During a typical heart attack, the ST segment will be elevated. For NSTEMI, there is no evidence of ST-segment elevation.

Because NSTEMI can cause damage to the heart muscle, it is still considered a heart attack. Even so, NSTEMI has more in common with unstable angina and generally has a better outcome.

NSTEMI rarely causes STEMI because they tend to involve different blood vessels. NSTEMI is more likely to occur in patients with diffuse coronary artery disease. This form of heart disease involves a network of tiny blood vessels (called collateral vessels) that serve the heart only occasionally. In contrast, STEMI will involve the major coronary arteries.

Even so, if NSTEMI involves a partial blockage of a major coronary artery, it can develop into STEMI within hours, weeks, or months if not treated properly.


NSTEMI is differentiated from STEMI using an electrocardiogram (ECG). NSTEMI rarely progresses to STEMI because it tends to affect the small blood vessels that serve the heart.

emergency treatment

Treatment for NSTEMI is the same as for unstable angina. If you have heart symptoms, the emergency medical team will start intensive treatment to stabilize the heart and prevent further damage to the heart muscle.

Stability focuses on two things:

  • eliminate acute ischemia (insufficient blood flow)
  • prevent the formation of blood clots

acute ischemia

During acute ischemia, the heart does not get enough oxygen, resulting in cell death. Doctors can help eliminate this by using medications called beta-blockers and statins.

These drugs work in different ways:

  • Beta-blockers prevent damage caused by overproduction of adrenaline. Adrenaline is released in times of crisis; it causes narrowing of blood vessels and increased pressure in the heart. Beta-blockers can reverse this effect and help restore circulation.
  • Statins stabilize ruptured plaques and reduce arterial inflammation. This helps prevent further blockages.

Beta-blockers and statins usually relieve acute ischemia within minutes. Oxygen and morphine may be given to improve breathing and reduce pain.

blood clot formation

During NSTEMI, the emergency medical team will provide medicines to prevent blood clots from forming around the blockage. Doing this prevents “total occlusion” in which the blood vessel is completely blocked.

This may involve drugs such as aspirin, Plavix (clopidogrel), and other drugs that thin the blood and prevent the clumping of blood cells called platelets.

This treatment does not include thrombolytic drugs (“thrombus busters”) used for STEMI. Avoid these drugs because they are often unhelpful and can lead to a medical emergency called cardiogenic shock. This occurs when the heart’s ventricles cannot deliver enough blood to the body, leading to a dangerous drop in blood pressure.


NSTEMI is treated with beta-blockers and statins, which improve circulation and prevent further damage to the heart muscle. Meanwhile, blood thinners such as aspirin or Plavix (clopidogrel) are used to prevent blood clots and complete blood vessel blockages.

How to Survive a Heart Attack

After stabilization

Once a person with NSTEMI is stable, a heart specialist (called a cardiologist) will assess whether further intervention is needed. Many cardiologists use the TIMI (Thrombosis in Myocardial Infarction) score to make decisions.

The TIMI score assesses whether a person has any of the following risk factors for a typical heart attack:

  • Age 65 or above
  • Presence of at least three risk factors for coronary heart disease
  • Previous coronary obstruction greater than 50%
  • Admission ECG ST-segment deviation
  • At least two angina attacks in the past 24 hours
  • Elevated cardiac enzymes
  • Have used aspirin in the past 7 days

If you have two or fewer risk factors (TIMI score 0-2), you may not need further intervention. If the score is higher, the cardiologist may want to take more aggressive steps.

This includes cardiac catheterization and angioplasty and stenting. The procedure involves inserting a flexible tube (called a catheter) through an artery in the arm or leg into the blockage. The end of the catheter is then inflated to widen the blood vessel, and a narrow length of tube (called a stent) is left to keep the blood vessel open.

Cardiac stress testing can also be used to determine if aggressive treatment is needed. The test measures blood pressure, blood oxygen, and the electrical activity of the heart when you run on a treadmill or ride a stationary bike.


Once a person with NSTEMI is stabilized, a cardiologist may use the TIMI score (which assesses a person’s risk of a serious heart attack) and a cardiac stress test to determine whether further treatment is needed.

how to treat heart disease


Non-ST-segment elevation myocardial infarction (NSTEMI) is a type of heart attack in which a small artery in the heart is completely blocked or a large artery in the heart is partially blocked. It is not as severe as a “classic” heart attack called ST-segment elevation myocardial infarction (STEMI).

NSTEMI can cause the same symptoms as STEMI, but usually does less damage to the heart. It differs from STEMI in the electrocardiogram (ECG), which can tell if the electrical activity (called the ST segment) between heartbeats is elevated or not.

Treatment of NSTEMI focuses on restoring circulation and preventing thrombosis. This usually involves beta-blockers, statins, and blood thinners such as aspirin or Plavix (clopidogrel). After the individual is stabilized, the cardiologist will determine if further treatment is needed.

Frequently Asked Questions

  • What is NSTEMI?

    NSTEMI stands for non-ST segment myocardial infarction. NSTEMI is an acute coronary syndrome that occurs when blood flow to the heart is suddenly reduced or blocked. NSTEMI is also known as a mild heart attack.

  • Is NSTEMI a heart attack?

    Yes, NSTEMI is a relatively mild heart attack. It occurs when a major coronary artery is partially blocked or a minor coronary artery is completely blocked.

    The symptoms of NSTEMI are the same as other types of heart attack — chest pain or tightness, shortness of breath, anxiety, and sweating that may spread to the shoulders or other parts of the upper body — but don’t do much damage to the heart muscle .

  • What is the difference between STEMI, NSTEMI, and unstable angina?

    All three are acute coronary syndromes (ACS) caused by coronary plaque rupture. Unstable angina is the least severe, and STEMI is the most severe of the three.

    Unstable angina is caused by a partial rupture of an artery without permanent damage to the heart muscle. NSTEMI is caused by blockage of a small artery or a partial blockage of a large artery. STEMI occurs when a ruptured plaque completely blocks a large artery.