Arm Numbness Can Be an Overlooked Sign of a Heart Attack

What would you say if asked to identify a classic sign of a heart attack? Most people would cite crushing chest pain as the number-one smoking gun, but there's another lesser-known indication that your cardiovascular health may be in jeopardy: arm numbness.

Read more: Is It a Heart Attack or Something Else? Things Mistaken for a Heart Attack

According to the Centers for Disease Control and Prevention (CDC), every 40 seconds an American has a heart attack. Similarly, every 40 seconds an American has a stroke, according to the CDC.

Both occur when the normal blood flow to one's heart or brain becomes blocked, setting in motion a cellular shutdown that eventually manifests as an emergency. When that happens, time is of the essence. National Institutes of Health experts warn that when the heart goes without blood for too long a period of time — meaning roughly 20 minutes or more — the damage can prove irreversible.

This means it's critical for people to be able to immediately spot key signs of a cardiovascular crisis in progress, so help can be sought as quickly as possible.

According to Harvard Health Publishing, chest pain is actually just one of many possible signs of a heart attack underway. Other indicators include shortness of breath or a sudden feeling of nausea, dizziness or fatigue. In addition, if one or both of your arms suddenly feel painful, uncomfortable, heavy, weak or numb, that can be a sign of cardiac trouble too.

"There are many different potential causes of hand or arm numbness," says Gregg Fonarow, MD, director of the Ahmanson-UCLA Cardiomyopathy Center. In fact, the U.S. National Library of Medicine lists a wide array of alternate explanations, ranging from nerve or spine injury to vitamin deficiencies to simply sitting or standing too long in the same position. So how can you tell what your arm numbness actually means?

"Pain or numbness that is very localized and brought on by touch or position is less likely to represent a cardiac-related symptom," Fonarow says. "But arm numbness is associated with shortness of breath, sudden nausea or vomiting, lightheadedness or dizziness, cold sweat and/or generalized fatigue would greatly increase the likelihood that this symptom may represent a heart attack."

It's worth noting that very often men and women experience different symptoms when a heart attack strikes. Fonarow says the jury is still out on whether arm numbness is a shared symptom.

"Some studies have suggested that numbness as a symptom of a heart attack is more common in men," he says. "Yet others have not shown any difference between men and women. These symptoms should be considered of concern in both men and women. And if symptoms develop which raise any concern, it is critical to call 911 to summon emergency medical services."

Still, according to the American Stroke Association (ASA), the sudden onset of arm weakness or numbness is actually less often an indicator of a heart attack than it is a sign of another serious cardiac emergency: stroke.

In fact, arm numbness is a marquee feature of ASA's helpful shorthand for identifying stroke symptoms: "F.A.S.T." While "F" stands for face drooping and "S" stands for slurred speech, the letter "A" stands for arm weakness or numbness. ("T" stands for time to call 911 when any of these symptoms develop.)

To get a better sense if your arm numbness might signal a stroke, ASA experts advise anyone with sudden arm weakness or numbness to try to raise both arms. If one arm starts to drift downward in the process, a stroke may be underway.

The ASA also warns that one's arm may not be the only body part afflicted by numbness when a stroke occurs. Sudden numbness or weakness of the leg or face — particularly if it only affects one side of the body — is another strong indication of stroke trouble.

Read more: Numbness and Tingling in the Left Arm After a Workout