Myocardial Infarction with Non-Obstructive Coronary Arteries (MINOCA)

Myocardial infarction with non-obstructive coronary arteries, or MINOCA, is a heart attack confirmed by a rise in troponin and signs of reduced blood flow, but coronary angiography finds no narrowing of 50 percent or more in the main coronary arteries. A systematic review found this condition in about 6 out of 100 people with a heart attack. MINOCA is more common in women and in younger people than heart attacks caused by a blockage.

The 2023 ESC guidelines treat MINOCA as a working diagnosis, meaning a starting point for finding the cause, not a final diagnosis. An overview of heart attacks is covered on the Myocardial Infarction / Heart Attack page.

Causes the Doctor Looks For

MINOCA has various causes. A small plaque can crack or erode and form a clot that then dissolves on its own, so the artery looks almost normal when examined. A coronary artery can go into spasm and temporarily shut off blood flow. The small blood vessels inside the heart muscle may not work properly. A clot from elsewhere can travel to a coronary artery. The artery wall can also tear without any injury, covered on the Spontaneous Coronary Artery Dissection page. Sometimes the heart's oxygen demand exceeds its supply, for example with severe anemia or a very fast heart rhythm.

Conditions That Mimic MINOCA

Some diseases cause similar symptoms and a similar rise in troponin, even though they are not heart attacks caused by reduced blood flow. Examples include inflammation of the heart muscle, covered on the Myocarditis page, and sudden weakening of the heart muscle often triggered by stress, covered on the Takotsubo Cardiomyopathy page. Telling them apart is important because their treatment differs, and this is where cardiac MRI plays a major role.

Not a Mild Condition

Finding no severe blockage often brings patients relief, but the risk of another cardiac event is still real. Research shows that the risk of death within a year in MINOCA is lower than in heart attacks caused by a blockage, but it is far from zero. Some patients also feel confused or anxious after being told their arteries are clear, and the doctor's explanation of the cause helps answer those doubts. For this reason, further tests, treatment based on the cause, and regular follow-up are still needed.

MINOCA is diagnosed in stages. First, the doctor confirms a heart attack according to the universal definition of myocardial infarction: troponin rises or falls with levels above the normal limit, together with symptoms, ECG changes, or signs on imaging. Second, coronary angiography finds no narrowing of 50 percent or more. Third, there is no other clear cause, such as pulmonary embolism or a severe infection.

After that, the search for the cause begins. The 2023 ESC guidelines recommend cardiac MRI for patients with MINOCA whose cause is still unclear, to distinguish infarction from myocarditis or Takotsubo cardiomyopathy. Imaging from inside the artery with IVUS or OCT during catheterization can find a cracked plaque or a small tear. A spasm provocation test may be done in selected patients. Echocardiography and blood tests help look for the source of a clot or a blood clotting disorder.

When symptoms like those of a heart attack appear, you cannot tell whether there is a blockage or not, so call an ambulance right away or go to the nearest emergency room if chest pain lasts more than 5 minutes. After you have been diagnosed with MINOCA, make a follow-up appointment with a cardiologist if:

• The cause of your MINOCA is still unclear and you have not had a cardiac MRI.
• Brief chest pain comes back, especially at rest, at night, or in the early morning.
• You feel palpitations, tire easily, or get short of breath with light activity.
• You are planning a pregnancy after having had a coronary artery tear.