A heart attack occurs due to a loss of blood supply to part of the heart. It often results from a blockage in a nearby artery. However, when a person experiences a heart attack that is not due to a blockage in an artery, experts may refer to it as a MINOCA.

A heart attack, or myocardial infarction, can be life threatening and requires immediate medical attention. It is crucial to recognize the warning signs, such as pain in the chest and difficulty breathing, as soon as possible and seek prompt treatment.

In this article, we will discuss what a MINOCA is, how its symptoms differ, and the possible causes.

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MINOCA stands for “myocardial infarction with nonobstructive coronary arteries.” This refers to a heart attack that occurs without any blockage in the arteries.

Clinicians define a MINOCA as an acute myocardial infarction without obstructive coronary heart disease and no obvious cause. Research suggests that 6–14% of heart attacks occur without obstruction in the arteries.

Most heart attacks result from blocked arteries due to plaque buildup, known as atherosclerosis. Plaque consists of cholesterol, deposits, and other substances. When it builds up in the arteries, it can narrow or block them, which may slow the flow of oxygenated blood to the heart, raising the risks of a heart attack.

Nonobstructive coronary heart disease is when there is an interruption to the heart’s blood supply, but a person does not have an obstruction in their arteries. To diagnose this condition, the plaque in the blood vessel must block less than 50% of the arteries.

MINOCA and heart attacks that result from blocked arteries tend to be similar. However, their underlying causes and who they affect can differ.

Different types of MINOCA may include:

Spontaneous coronary artery dissection (SCAD)

SCAD occurs when the wall of an artery suddenly tears. Arterial walls have layers. When a tear occurs, blood can build up between these layers and create a bulge that can disrupt blood flow. Evidence suggests that 90% of SCAD cases occur in females, accounting for roughly a quarter of heart attacks in females under the age of 60 years.

Doctors are not certain what causes such a sudden tear in an artery, but they believe it may be a combination of factors, including:

  • genetics
  • hormones
  • systemic inflammatory diseases
  • fibromuscular dysplasia

Coronary artery vasospasm

A coronary artery vasospasm describes the spontaneous tightening of a heart artery. This may occur if a person takes certain medications or stimulants that can cause blood vessels to constrict. When this happens, it can disrupt blood flow. Also known as vasospastic angina, it is a common cause of MINOCA.

Microvascular disease

Microvascular disease refers to a condition that affects the walls and inner lining of small blood vessels that branch off arteries in the heart. Damage to these walls and linings can restrict blood flow to the heart and cause spasms in the blood vessels. A 2022 study found that roughly half of people experiencing MINOCA had microvascular disease.

Stress cardiomyopathy

Stress cardiomyopathy, also known as broken heart syndrome or takotsubo syndrome, occurs when a person experiences sudden stress that may weaken the left ventricle of the heart, making it less able to pump blood effectively.

Although the exact mechanism is not known, doctors believe it may be due to a sudden surge in stress hormones that impact the muscles and blood vessels connected to the left ventricle. However, research has shown that 1 in 5 people do not report any stressful event before their symptoms, and it can also occur after positive life events.

Muscle issues

Another potential cause of myocardial infarction is an issue with the muscles in the heart. For example, when heart tissue becomes inflamed, known as myocarditis, it can cause muscle damage and make it harder for the heart to pump blood. Myocarditis can occur due to infections, drugs, and autoimmune conditions. Evidence suggests that myocarditis is present in 33% of MINOCA cases.

A 2018 study suggests that MINOCA occurs more frequently in younger people and people assigned female at birth, with females being 5 times more likely to experience MINOCA than males.

Some evidence also suggests that people who experience MINOCA are less likely to have traditional cardiovascular risk factors, such as a history of smoking, diabetes, and obesity, and a family history of coronary artery disease.

However, some potential risk factors may include:

  • an increased risk of blood clotting problems
  • anxiety and depression
  • cancer
  • autoimmune conditions
  • infectious diseases, such as pneumonia, sepsis, and respiratory infections
  • hormones related to pregnancy, contraception, and hormone replacement therapy

Heart attacks occur when there is a lack of blood supply to the heart. Symptoms include:

  • chest pain, pressure, or tightness
  • pain that may spread to arms, neck, jaw, or back
  • nausea and vomiting
  • sweaty or clammy skin
  • feeling of heartburn or indigestion
  • shortness of breath
  • coughing or wheezing
  • lightheadedness or dizziness
  • anxiety that can feel similar to a panic attack

If someone has these symptoms:

1. Dial 911 or the number of the nearest emergency department.
2. Stay with them until the emergency services arrive.

If a person stops breathing before emergency services arrive, perform manual chest compressions:

1. Lock fingers together and place the base of hands in the center of the chest.
2. Position shoulders over hands and lock elbows.
3. Press hard and fast, at a rate of 100–120 compressions per minute, to a depth of 2 inches.
4. Continue these movements until the person starts to breathe or move.
5. If needed, swap over with someone else without pausing compressions.

Use an automatic external defibrillator (AED) available in many public places:

1. An AED provides a shock that may restart the heart.
2. Follow the instructions on the defibrillator or listen to the guided instructions.

MINOCA tends to have similar symptoms to heart attacks that occur due to other causes. Some possible heart attack symptoms include chest pain, pain radiating elsewhere, shortness of breath, and nausea. It is also worth noting that MINOCA is more common among females, who may experience slightly different symptoms, such as fatigue and a general sense of feeling unwell.

If a person thinks they may be experiencing heart attack symptoms, it is important that they seek immediate medical attention. The sooner a person receives help, the more likely they are to recover.

A doctor may diagnose MINOCA when a person shows signs of myocardial infarction without obstruction in their arteries. They will perform other tests to help them exclude other possible causes of the symptoms a person is experiencing.

For example, to look for blockages in the arteries, a doctor may use a special type of X-ray called a coronary angiography. This is a diagnostic test that uses X-rays and a contrasting dye to help detect blockages in a person’s arteries. Other diagnostic tests that may help determine the underlying cause of MINOCA may include:

MINOCA can occur for several reasons, so a doctor will manage each case individually by treating the underlying cause. Depending on the exact cause, a doctor may use one or a combination of the following treatments:

If a person is concerned about their heart health, they may wish to consult a doctor to discuss their concerns and ways to minimize their risk of cardiovascular disease. If a person suspects symptoms of a heart attack, it is vital that they seek emergency help immediately, since faster medical intervention can reduce the amount of damage to the heart.

Heart attacks that occur without plaque obstruction in the arteries are known as MINOCA. This term stands for “myocardial infarction with nonobstructive coronary arteries.”

Symptoms of MINOCA are largely similar to signs of a heart attack that occurs due to an obstruction. However, they have different risk factors and occur more often in younger females.

There are many different types and causes of MINOCA, which may require specific diagnostic tests for a doctor to find. A healthcare professional may prescribe various treatments depending on the underlying cause.