Nonobstructive coronary artery disease (CAD) occurs when the coronary arteries have a plaque buildup.

Experts usually view it as less severe than obstructive CAD. However, research reveals nonobstructive CAD may also increase the risk of a heart attack.

In this article, we examine the differences between nonobstructive and obstructive CAD. We also discuss whether nonobstructive CAD is dangerous and the potential risk factors and treatments for the condition.

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Nonobstructive CAD differs from obstructive CAD in that people with nonobstructive CAD do not have as much plaque buildup in their arteries.

With obstructive CAD, the plaque buildup is significant (usually greater than 70%) and can narrow or block the arteries. This slows oxygenated blood flow to the heart and raises the risk of a heart attack.

The plaque is still present with nonobstructive CAD. However, it does not block the arteries. For a doctor to diagnose a person with nonobstructive CAD, the plaque must block less than 50% of the arteries.

The evidence points to the possibility that nonobstructive CAD could also be dangerous.

Historically, experts have tended to dismiss nonobstructive CAD as less severe than obstructive CAD because of an assumption that it is the physical blocking of the arteries that leads to a higher risk for heart attack. However, around 5–6% of people who have heart attacks do not have obstructive CAD.

The authors of a 2020 article in the European Heart Journal also note that treating the blockages in people with obstructive CAD is often ineffective in reducing heart attacks from occurring in the future.

The American Heart Association states that nonobstructive CAD is associated with a 28–44% increased risk of a major cardiac event, such as a heart attack or death.

As a result of research findings, experts are looking more closely at the extent of plaque forming in the arteries as a possible indicator of a future heart attack rather than the physical blockage itself.

It is worth noting there are two types of heart attacks.

One type includes heart attacks that occur due to something suddenly blocking blood flow, such as a piece of plaque. The other type is when the amount of blood oxygen required by the body is not supplied. This second type tends to occur with obstructive CAD, while the first type can occur with nonobstructive CAD.

If there is little plaque blockage present, nonobstructive CAD will not cause any symptoms.

If there is enough plaque buildup to reduce blood flow, a person may experience symptoms similar to those occurring due to obstructive CAD.

Symptoms of CAD may include:

  • chest pain or discomfort
  • pain in the arm, neck, or back
  • feeling lightheaded, weak, or nauseated
  • breaking out in a cold sweat
  • shortness of breath
  • fatigue after activity

For some people, the first sign of CAD is a heart attack.

According to the Centers for Disease Control and Prevention (CDC), the plaque buildup in the walls of the arteries that pump blood to the heart and other parts of the body causes CAD.

Plaque forms from cholesterol and other substances and may narrow or block the arteries, limiting blood flow to the heart or increasing the risk for heart attack, known as atherosclerosis.

Certain factors could increase the risk of CAD, including:

  • high levels of “bad” cholesterol and low levels of “good” cholesterol
  • high blood pressure
  • a family history of heart disease
  • diabetes
  • overweight
  • postmenopause
  • being a male over age 45
  • physical inactivity
  • diet
  • smoking tobacco
  • increased levels of lipoprotein (a)

A doctor may recommend some of the following tests and scans to diagnose CAD:

  • Electrocardiogram (ECG or EKG): Measures the activity of the heart.
  • Exercise stress test: Measures heart rate during physical activity on a treadmill.
  • Pharmacologic stress test: This test uses medication instead of exercise to speed up the heart rate.
  • Chest X-ray: Takes a picture of the heart, lungs, and other chest organs.
  • Coronary angiogram: This uses an X-ray to check blood flow through the arteries.
  • Coronary artery calcium scan: Examines the arteries for plaque and calcium buildup.
  • Blood tests: Measures factors that affect the arteries, such as cholesterol.
  • Echocardiogram: Uses ultrasound to create an image of the heart alongside stress testing.
  • Nuclear imaging: Creates a picture of the heart using radioactive tracers alongside stress testing.

Treatment for nonobstructive CAD depends on whether a person has had a major cardiac event, such as a heart attack, or whether another underlying health condition is present.

Doctors may recommend:

  • lifestyle and dietary changes, such as eating a healthier diet, getting more exercise, reducing stress, and quitting smoking
  • medication to treat risk factors for CAD, such as high cholesterol or high blood pressure
  • a daily aspirin to prevent blood clots
  • medication to treat chest pains, such as nitroglycerin sprays and patches

Nonobstructive CAD does not block the arteries, so it is unlikely a doctor will recommend surgery. However, if plaque continues to build up, they may suggest surgery.

Surgical interventions to treat obstructive CAD by restoring blood flow to the heart may include:

  • Percutaneous coronary revascularization: A doctor inserts a catheter into the artery and uses a balloon to push the blockage to the artery walls. They insert a stent to help keep the artery open.
  • Coronary artery bypass surgery: A doctor uses a healthy artery from elsewhere in the body to reroute the blood flow around the blockage.

There is a risk that nonobstructive CAD can develop into obstructive CAD if plaque buildup blocks more than 50% of the artery.

Complications of CAD that affect arteries close to the heart may include:

  • chest pain
  • abnormal heart rhythm
  • heart attack
  • heart failure

Experts sometimes view nonobstructive CAD as less severe than obstructive CAD. However, recent research suggests it can also result in major cardiac events.

The symptoms, risk factors, diagnosis, and treatment for nonobstructive CAD are the same as obstructive CAD. However, a person may not require surgery if plaque buildups have not blocked the arteries.

Lifestyle changes and medication to treat risk factors, such as high cholesterol, may help to reduce the risk of a heart attack.