Your Heart Rate Changes During a Heart Attack, but Probably Not for the Reason You Think

What you may not know, though, is that your heart rate can undergo significant change during a heart attack. Depending on the person, it can ramp up or slow down.

"Heart attacks will usually make your heart beat faster," says James Udelson, MD, chief of cardiology at Tufts Medical Center in Boston, Massachusetts. But in some instances they can also slow things down.

Here, learn how a heart attack can affect your "normal" heart rate, plus other heart attack signs to watch out for, and when to go to the doctor to protect your heart.

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First, what is an 'abnormal' versus 'normal' heart rate?

A typical resting heart rate (i.e., the rate your heart beats when you're sitting and feeling relaxed) can range from 60 to 100 beats per minute (bpm), according to the American Heart Association (AHA). This means, a "normal" heart rate will vary by age, level of physical activity, overall health, and more.

If you're a serious athlete, your resting heart rate might be a bit lower, as low as 40 bpm. "The heart is well-trained in people who're really fit," says Dr. Udelson. "With each beat, more blood is pumped and sent to the rest of the body, so they typically require fewer beats per minute," he adds.

Your resting heart rate might also be below 60 if you take beta blockers, which cause the heart to beat more slowly and with less force, per the Mayo Clinic. Or your heart rate may skew a little higher—around 100 bpm—if you've had caffeine, certain stimulant medications, or you've been exercising, per the Mayo Clinic.

So what's considered a dangerous heart rate? Anything below 60 bpm (that's not "normal" for you) or consistently above 100 bpm per minute can be dangerous. Pay attention to any other symptoms you might be having, call your doctor, and go to the nearest ER as soon as possible. You may have bradycardia (a dangerously low heart rate, per the Mayo Clinic) or tachycardia (a dangerously high heart rate, per the Mayo Clinic), which needs to be treated with certain heart medications.

"Any time you're stressed, your body makes more adrenaline, which raises your heart rate." —James Udelson, MD, cardiologist

What happens to your heart rate during a heart attack?

Your heart rate can change over the course of a heart attack. "It'll almost always go up, usually because of the pain," says Dr. Udelson. "And any time you're stressed, your body makes more adrenaline, which raises your heart rate," he adds.

Heart rate fluctuations can happen to anyone during a heart attack. In fact, there aren't any underlying conditions that would cause heart rate changes during an attack, other than the attack itself, says Dr. Udelson.

In rare cases, a heart attack can make your heart rate slow down. This may happen if the heart attack is from a blockage in an artery on the right side of your heart. "A branch of that artery feeds the main pacemaker of your heart. If that artery is affected and the pacemaker isn't getting enough blood, your heart rate can slow down," adds Dr. Udelson.

Your heart rate can also fluctuate depending on the type of heart attack. Some of the most common include:

STEMI

STEMI is short for ST-elevation myocardial infarction. This type of heart attack changes how your heart's electrical activity looks on tests like an EKG, per the Cleveland Clinic.

STEMI heart attacks often happen when an artery on the left side of your heart becomes totally blocked, stopping blood flow to that area and causing a severe heart attack, according to the Cleveland Clinic. "Heart attacks involving the left main artery may be associated with higher heart rates," says Ashesh Parikh, DO, a cardiologist at Texas Health Plano and Texas Health Physicians Group.

NSTEMI

NSTEMI is short for non-ST-segment elevation myocardial infarction. Unlike STEMI heart attacks, NSTEMIs don't cause a noticeable change to your heart's electrical activity as measured by an EKG. They also happen due to a partial artery blockage rather than a total blockage, so they may be less severe, notes the Cleveland Clinic. NSTEMI heart attacks may or may not raise your heart rate. It mostly just depends on the person and their heart.

Coronary spasm

Coronary spasm happens when the muscles in the wall of one of your heart's arteries temporarily gets tighter, reducing or blocking blood flow to the heart. They're not always noticeable, but sometimes they can cause chest pain and even a heart attack, per the Mayo Clinic. And if you're having chest pain, your heart rate might go up as a result.

Keep in mind: A heart attack is different from cardiac arrest. Heart attack is a often a circulation problem, caused by blocked arteries, while cardiac arrest is an electrical problem, where the heart suddenly stops, per the AHA. This means, your heart rate during cardiac arrest completely stops.

Does your blood pressure change during a heart attack?

While not common, it can happen. Many people can have a heart attack with "normal" blood pressure and pulse. But the pain and stress of a heart attack can sometimes cause a person's blood pressure to spike, says Dr. Udelson.

And sometimes, it can dip too low. "If you're having a very large heart attack, you could be in shock, which could cause your blood pressure to get very low. That's unusual, but very dangerous," he adds.

Once you get to the hospital, your blood pressure and other vitals, including your heart rate, will be closely monitored and regulated.

Other signs of a heart attack

A change in heart rate or blood pressure aren't the only signs of a heart attack. Other red flags include the following, per the Cleveland Clinic:

• Chest pressure or tightness, like something is sitting on your chest
• Heartburn-like sensation
• Shortness of breath
• Pain on your left side, like your shoulder, arm, neck, or jaw
• Fatigue
• Nausea
• Sweating

Call 911 for an ambulance if you or someone you know is having these symptoms, especially if they are severe, last longer than 10 minutes, or if they are high-risk for heart attacks (i.e., they have hypertension, heart disease, diabetes, or a family history of heart issues), per the Cleveland Clinic.

When to go to the ER

Call 911 immediately if you're having severe, persistent chest pain or other symptoms that feel like they could be a heart attack. "Even if you aren't sure, don't hesitate," says Dr. Udelson. "If you get treatment quickly, you can minimize any damage" to your heart, and increase your likelihood of a full recovery.

The bottom line

There is no typical heart rate in a heart attack. Your heart rate can fluctuate greatly. More often, heart rate increases due to pain and stress, but sometimes, it can lower if you have a blockage in one of your arteries. It's important to know the signs and symptoms of heart attacks so doctors can treat you and any heart abnormalities you may have.

FAQ

What is the timeline of a heart attack?

Some heart attacks strike suddenly without warning. Others can cause symptoms (like chest pain or pressure that eases up with rest) for days, weeks, or even months ahead of time, notes the Mayo Clinic.

How a heart attack ends depends on whether a person gets treated. At the hospital, the blocked artery can be opened back up to restore blood flow to your heart. But it needs to happen quickly. "Ideally, a heart attack should be treated within 90 minutes of symptom onset to preserve heart muscle strength," says Dr. Parikh.

Heart attacks that aren't treated (or aren't treated quickly enough) are often fatal. "If you stayed home and were lucky enough to survive, part of the heart muscle would die. The pain would fade away in a day or so, but the heart would be left with damage," says Dr. Udelson.

What should you never do during a heart attack?

Never hesitate to call for help. "The number-one thing to absolutely avoid is not calling 911," says Dr. Udelson. "Death from heart attack in the U.S. has continuously gone down, but it requires getting to the hospital to be treated."

While waiting for treatment, avoid exerting yourself or putting any pressure on your chest, Dr. Parikh recommends. That can increase the demand on your heart to pump more blood, which could make the heart attack even worse.

Can you have a healthy heart and still have a heart attack?

Yes, you can. While factors like high blood pressure, diabetes, and smoking greatly increase your risk for a heart attack, "about a third of people who come in with a heart attack don't have any of those and it's genetic," says Dr. Udelson. Either way, it's still important to prioritize your heart health, by eating a balanced diet, getting daily exercise, reducing stress, and going to the doctor regularly for checkups.

—reviewed by Jennifer Logan, MD, MPH