By Rachel Nania, AARP.org

Despite its depiction in the movies, a heart attack doesn’t always produce pain or pressure so intense it causes a person to clutch their chest and collapse to the floor. Most people who have a heart attack experience a much less dramatic version. And some have no symptoms at all — or symptoms that are so subtle they’re mistaken for something else entirely.

These so-called silent heart attacks account for about 20 percent of all heart attacks, according to the American Heart Association. Some experts estimate that number is even higher — closer to 50 percent.

What is a silent heart attack?
A heart attack happens when the arteries that carry blood to the heart become blocked, thereby depriving the heart muscle of oxygen and nutrients. If a person having a heart attack feels pain or pressure, it’s because of this blockage, says Eduardo Marban, M.D., executive director of the Smidt Heart Institute at Cedars-Sinai Medical Center in Los Angeles.

Symptoms of a silent heart attack
Few people actually exhibit no symptoms. But signs of a heart attack can be muted or confused with other conditions. Here’s what to look out for:

1.Shortness of breath
2.Weakness or fatigue
3.A general feeling of unease or discomfort
4.Sweating
5.Nausea or vomiting
6.Lightheadedness or dizziness
7.Mild pain in the throat or chest
8.Pain in the back or arms, like a sprained or pulled muscle

The same thing happens during a silent heart attack — blocked arteries make it so that oxygen-rich blood can’t reach the heart. The only difference is the problem goes unnoticed. “It’s not necessarily that there were no symptoms; it may just be that the patient didn’t recognize them as heart symptoms and wasn’t concerned,” Marban says.

For example, it’s not uncommon for silent heart attacks to be written off as indigestion, a sprained or strained muscle, fatigue, or “just feeling run-down,” Marban says.

People who later realize they’ve had a silent heart attack may also recall experiencing shortness of breath at the time, or a general state of discomfort that led to a night of lost sleep, says Robert Lager, M.D., an interventional cardiologist at MedStar Washington Hospital Center in Washington, D.C. Nausea, sweating, dizziness and an overall feeling of unease are also signs of a silent heart attack.
If you experience any of these symptoms, “don’t sit around and wonder” what could be wrong. “Time is muscle,” Lager says, referring to the damage that decreased blood flow can inflict on the heart. “The longer one waits to get evaluated, the more likely that there will be irreversible damage.”

That said, some people truly experience no symptoms — understated or otherwise — when they have a heart attack. Diabetics who have nerve issues that interfere with pain signals (called neuropathy), for example, are at higher risk for having a literal silent heart attack, Lager says. Women and older adults are also more likely to have an event without warning signs.

Is it a heart attack … or something else?
Silent heart attacks don’t just fool patients; they can be misdiagnosed in health care settings, too. Shortness of breath may be mistaken for a pulmonary problem, for instance. And pain in the shoulder or arm can be misdiagnosed as an orthopedic issue. “So there are lots of different forms of symptoms that are referred pain from the heart that can be very confusing and sometimes can be misleading,” Lager says.
One way to tell if the symptoms you’re experiencing are due to a heart attack or another condition is to know that the warning signs of heart trouble are “not positional,” Lager says. This means that the sprain-like pain in your neck and arm won’t get better if you stretch it or shake it out. And shortness of breath or sweating won’t subside if you take it easy and lie down.

“That’s a really good rule of thumb,” Lager says. “If you’re not sure if you’re having a symptom, see if you can manipulate it in some way. Can you press on the chest? Can you change your position? Can you stand up or sit down? Does it make a difference, positionally? Because the heart has no gyroscope; it doesn’t know where it is in space. And it doesn’t matter if you put the heart upside down or right side up, it’s going to give you the same signals if it’s in trouble.”

Another thing to keep in mind: Any symptom that results from the loss of oxygen to the heart will generally get worse if you increase demand on the heart. “So if someone has chest discomfort at rest and gets up and walks around, you’re increasing the heart’s demand for oxygen, so the symptoms usually will get worse if it’s a heart issue,” Lager says.

The risks factors for silent heart attacks are the same as those for a heart attack with symptoms. The most common include:

•Age (for men, 45 and older; for women, 55 and older)
•Diabetes
•Excess weight
•High blood pressure
•High cholesterol
•Lack of exercise
•Prior heart attack
•Tobacco use
•A family history of heart disease

The dangers of having a heart attack and not knowing
Many people who have had a silent heart attack find out about it after the fact — sometimes months or years later — usually during a routine electrocardiogram, or EKG. Symptoms that arise afterward can also bring patients in to see a health care provider. Lager says people who have suffered a silent heart attack may notice a faster heart rate or increased exercise intolerance, for example.

Usually when someone finds out they had a silent heart attack, the damage has already been done. But identifying a past heart attack can help you and your doctor mitigate risks for future cardiac events. After all, a silent heart attack can increase risk of heart failure by 35 percent, one study shows. It also increases the likelihood of sudden death, stroke and having another heart attack.

Dangerous heart arrhythmias are another concern your doctor may monitor for if you had an undetected heart attack in the past. These can develop when parts of the heart muscle are scarred from the loss of blood. And another worry: Because “our blood gets thicker under stress,” Lager says, blood clots are also more likely to crop up after you’ve had a heart attack.

“Once the diagnosis is made, either of a recognized heart attack or a silent heart attack, everything is put into a higher risk category in terms of the complications that can ensue,” Marban says. “So it’s not something that we should just consider a curiosity and do nothing about. … Detecting a heart attack and acknowledging it is the first step towards putting the patient back on the kind of effective therapy that we know is helpful.”

Don’t ignore out-of-the-blue issues
The take-home message, Lager says, is to pay attention to a change in patterns in your body.

“If you’re someone who occasionally has some chest discomfort that’s mild, transient and occurs in certain predictable patterns, then it’s not nearly the same as someone who has new symptoms never felt before,” he says.

And if you’re prone to indigestion and just ate a spicy meal, the burning feeling in your chest is likely heartburn. But if it comes on out of the blue and the symptoms get worse, especially as you walk around or exercise, “that’s a real warning sign that it’s not gastrointestinal,” Lager says.

Rachel Nania writes about health care and health policy for AARP. Previously she was a reporter and editor for WTOP Radio in Washington, D.C. A recipient of a Gracie Award and a regional Edward R. Murrow Award, she also participated in a dementia fellowship with the National Press Foundation.