Heart Attack Without Blocked Arteries

Q: I recently had a heart attack, but a cardiac catheterization found no blocked arteries. Is this possible?

A: Yes, this type of heart attack is called a myocardial infarction in the absence of obstructive coronary artery disease, or MINOCA. It accounts for 5 to 6% of heart attacks.

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Compared with other types of heart attacks, patients are usually younger and more likely to be female.

Causes of MINOCA include:

Minor plaque build-up is disturbed leading to temporary clotting in your coronary artery.
Short-lived (transient) spasm of a large coronary artery.
Narrowing of the small blood vessels that branch off the coronary arteries, called microvessel disease or microvascular coronary disease.
A spontaneous tear or dissection of the coronary artery.
A blood clot or embolism in a coronary artery.

MINOCA is diagnosed based on abnormalities in blood enzymes that show damage to the heart’s muscle. A catheterization will show no evidence of obstruction (blockage) and confirm that no artery is blocked 50% or more. Other imaging tests will identify a limited (localized) area of heart muscle injury.

Cardiac MRI or direct imaging of the interior of your coronary artery may be helpful if the diagnosis is unclear.

You should be evaluated for an increased tendency to form blood clots. It’s important to rule out other causes that may masquerade as a heart attack.

Because MINOCA has a variety of causes, uncovering the correct one is necessary for your doctor to choose the appropriate treatment. These may include calcium channel blockers for spasm or intensive use of blood thinners (anticoagulants) to try to prevent blood clot formation.

The likely course of your disease depends on its underlying cause and treatment strategy.

Ongoing studies are still needed to better understanding the likelihood of recovery from MINOCA. But research suggests that those with MINOCA who receive standard heart attack therapy (aspirin, beta-blockers, ACE inhibitors and statins) have a better long-term outcome than those who don’t.

— Cardiologist Leslie Cho, MD