Most often, heart attacks are associated with blocked arteries. However, with MINOCA – a myocardial infarction with non-obstructive coronary arteries – this isn’t the case. And it seems that women are at an increased risk. 

Michael Fogli, M.D., a noninvasive cardiologist with Ascension St. John in Tulsa, explains that MINOCA is an umbrella term applied to patients who are experiencing what looks like a heart attack but, when examined via a coronary angiogram, “they do not have an obstructing coronary plaque of at least 50% of the diameter of one of the heart arteries.” 

(He adds that it’s important to understand that the 50% attribution is an arbitrary cutoff, based on history and convention.)

“We have come to realize that this type of clinical syndrome can occur due to many possible causes, including spasm or spontaneous tear – dissection – of one of the coronary arteries, or severe blockage in the tiny branch vessels that we cannot see with our contrast dye – microvascular disease,” says Fogli. “Also, sudden inflammation or stress on the heart muscle – myocarditis – completely unrelated to any heart artery problem, can mimic a heart attack.”

In addition, he says “other acute noncardiac disorders, such as a pulmonary embolus or pneumonia, can mimic a heart attack, can cause chest pain like a heart attack and can stress the heart muscle enough to lead to heart muscle injury on EKG and blood testing.”

While MINOCA is not well known, Fogli says it’s more common than people think, as it accounts for approximately 10% of patients who appear to be having a conventional heart attack. 

George Chrysant, M.D., an interventional cardiologist with INTEGRIS in Oklahoma City, says while MINOCA is “largely felt to be a problem of the microvasculature,” it affects women more than men and “patients often do not have any risk factors, or at least any traditional risk factors,” associated with heart attacks. 

Another condition with little to no blockages is INOCA – ischemia with non-obstructive coronary arteries. 

“INOCA is very different from MINOCA, as INOCA is a chronic condition, not acute. It is characterized by ongoing symptoms of angina or an equivalent of angina, like shortness of breath, or fatigue, due to a problem of the coronary arteries that you cannot see with the coronary artery dye injection, in what we call the micro-circulation. These are the tiny microscopic blood vessels in the heart muscle,” he says. “Often, you can see evidence of a problem on a stress test, but then the coronary angiogram does not show a blockage of greater than 50% of the blood vessel diameter. More specialized cath lab testing – called coronary functional testing – can be done, but most cath labs don’t customarily perform it.”

According to Chrysant, there are several new findings in regards to INOCA and MINOCA. 

“Diagnosis of INOCA and MINOCA should be confirmed with either a cardiac MRI, to look for signs of microvascular obstruction, and/or OCT – optical coherence tomography – inside the coronary arteries,” he says. “What is being found is that while angiographically, the arteries appear completely normal, a fairly significant portion of patients actually do have obstruction on OCT that is not appreciated by the angiogram. There are some new articles that go over these findings and recommendations.”

And while current treatment plans may vary, the medical community’s knowledge of these conditions continues to evolve. 

“We have learned in preliminary studies that conventional treatment of coronary risk factors, such as using statins for cholesterol, ACE inhibitors or ARBs for blood pressure control, and achieving a healthy weight, eating right, controlling stress and not smoking are likely to be effective,” says Chrysant. 

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