What is the difference between heart attack and cardiac arrest

If you’re confused by the terms used to describe heart attacks, you’re not alone. They’re often described as “mild” or “massive,” or even the ominous-sounding “widow maker.” But these terms are not necessarily helpful, and they may create confusion and anxiety.

The good news: most people who have a heart attack survive. The bad news? “Any heart attack can be fatal, no matter how big, how small, or where it occurs in the heart,” says Dr. James Januzzi, a cardiologist at Harvard-affiliated Massachusetts General Hospital. “Furthermore, there’s a lot of misunderstanding among the general public about what a heart attack actually is,” he says.

The connection between heart attack vs. cardiac arrest

Perhaps the most common source of confusion is the difference between a heart attack and cardiac arrest. A heart attack (what doctors call a myocardial infarction or MI) is defined as damage to part of the heart muscle caused by inadequate blood flow to that area. Most of the time, this happens due to a blockage in one of the heart’s arteries. Known as a type 1 heart attack, such blockages typically occur when cholesterol-laden plaque lining an artery ruptures. A clot forms, obstructing the vessel.

While a heart attack is a plumbing problem, a cardiac arrest is an electrical problem. Cardiac arrest happens when the heart’s electrical system malfunctions, causing it to beat rapidly and chaotically — or to stop beating altogether. Without blood circulating to the brain, lungs, and other organs, the person gasps or stops breathing and becomes unresponsive within seconds.

A heart attack is a common cause of cardiac arrest, but most heart attacks do not lead to cardiac arrest. Other possible causes of cardiac arrest include heart failure, a clot in the lungs, a serious imbalance of potassium, magnesium, or other minerals in the blood, a drug overdose, or a blow to the chest.

Does size matter?

Some heart attacks cause more harm than others. During a heart attack, blood levels of a protein released by damaged muscle (troponin) give some sense of severity. Afterwards, an ultrasound of the heart (echocardiogram) can reveal the extent of the damage. “A large heart attack will significantly reduce the squeezing strength of the heart muscle,” says Dr. Januzzi.

The term “widow maker” refers to a heart attack caused by a blockage near the top of the left anterior descending (LAD) artery, the main artery that supplies blood to the front of the heart. However, heart attacks that involve the LAD are not necessarily fatal, and those involving other arteries can be deadly, too.

What to do

Call 911 right away if you or someone near you has symptoms of a heart attack or cardiac arrest. Common heart attack symptoms include:

• uncomfortable pressure, squeezing, or pain in the chest
• pain or other uncomfortable sensations in an arm, the back, neck, jaw, or stomach
• shortness of breath
• sudden nausea or vomiting
• lightheadedness or dizziness
• unusual fatigue.

Signs of cardiac arrest are a sudden loss of responsiveness and abnormal breathing (either not breathing or only gasping). Give hands-only cardiopulmonary resuscitation (CPR) until help arrives.

Ask the doctor

Q. My grandfather had a heart attack in his mid-70s, but he survived and lived until age 93. My father also had heart disease, but he died of cardiac arrest when he was just 67. What’s the difference between a heart attack and cardiac arrest?

A. These two terms often confuse people because they’re sometimes used interchangeably. But a heart attack and cardiac arrest are not the same thing.

A heart attack is a circulation problem that happens when a blocked artery prevents blood flow to part of the heart muscle. If the artery isn’t reopened to restore blood flow, the heart cells supplied by that artery start to die. Symptoms include intense discomfort in the center of the chest or other parts of the upper body, breathlessness, sweating, and nausea. But the heart continues to beat, and the person remains awake.

In contrast, cardiac arrest is most often an electrical problem that causes the heart to abruptly and unexpectedly stop beating. An electrical misfire causes the heart’s lower chambers (ventricles) to flutter or quiver, known as ventricular fibrillation (v-fib). During cardiac arrest, a person suddenly collapses or faints, stops breathing normally, and can’t be roused. Other symptoms can include irregular, odd gasping or choking sounds (known as agonal breathing) and twitching muscles.

Most heart attacks do not trigger cardiac arrest. However, when cardiac arrest does occur, a heart attack is often to blame. Sometimes, the oxygen-starved heart muscle triggers v-fib during a heart attack. Scar tissue from a heart attack can also damage the heart, leaving it unable to pump effectively. A weakened heart is more prone to v-fib.

Because cardiac arrest is so closely tied to coronary artery disease (the root cause of heart attacks), the underlying risks are largely the same. These include smoking, diabetes, high cholesterol, physical inactivity, obesity, high blood pressure, and a family history of early heart disease.

Other heart conditions that can predispose people to cardiac arrest include weak heart muscle (cardiomyopathy), heart valve problems, and inherited conditions that affect the heart’s electrical system, such as long QT syndrome. Some drug use increases risk as well, particularly using drugs such as cocaine or amphetamines or overdosing on opioids or other pain medications.

Finally, the risk of cardiac arrest rises slightly during and for up to 30 minutes after strenuous exercise, especially in people who are out of shape. But the odds are estimated at one in 1.5 million during any one exercise episode, which is far outweighed by the overall heart-protecting benefits of exercise.

— Deepak L. Bhatt, M.D., M.P.H.
Editor in Chief, Harvard Heart Letter

Image: © Moyo Studio/Getty Images

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