Your heart rate changes frequently due to factors ranging from how active you are to the temperature of the air around you. A heart attack can also trigger a slowing or accelerating of your heart rate.

Likewise, your blood pressure during a heart attack may increase or decrease depending on such factors as the type of heart tissue injured during the event or whether certain hormones were released that spiked your blood pressure.

In some cases, a person’s resting heart rate can signal a higher risk for a heart attack. It’s one of several important risk factors — some of which are manageable, while others are beyond your control.

Knowing your specific risk factors, as well as the common signs of a heart attack, can help protect against the life threatening consequences of a heart attack.

Keep reading to learn more about what happens to your heart and heart rate during a heart attack.

Your heart rate is the number of times your heart beats per minute. A normal or healthy resting heart rate for an adult is between 60 and 100 beats per minute. In general, the lower your heart rate, the more efficient your heart is at pumping.

Heart rate during exercise

During exercise, your heart rate increases to meet your muscles’ demand for oxygenated blood. At rest, your heart rate slows because demand isn’t as strong. While you’re sleeping, your heart rate slows down.

Heart rate during a heart attack

During a heart attack, your heart muscle receives less blood because one or more arteries that supply the muscle are blocked or spasming and unable to deliver a sufficient flow of blood. Or, the cardiac demand (the amount of oxygen the heart needs) is higher than the cardiac supply (the amount of oxygen the heart has) available.

Your heart rate isn’t always predictable

How this cardiac event affects the heart rate isn’t always predictable.

Certain medications may slow your heart rate

For example, if you’re on a medication that slows your heart rate, such as a beta-blocker for heart disease, your heart rate may remain slow during a heart attack. Or if you have a type of heart rhythm disturbance (arrhythmia) called bradycardia, in which your heart rate is perpetually slower than normal, a heart attack may do nothing to increase the rate.

There are certain types of heart attacks that can lead to an abnormal slowing of the heart rate because they affect the electrical tissue cells (the pacemaker cells) of the heart.

Tachycardia may speed your heart rate

On the other hand, if you have tachycardia, in which your heart always or frequently beats abnormally fast, then that pattern could continue during a heart attack. Or, certain types of heart attacks can cause the heart rate to increase.

Finally, if you have some other condition that’s causing your heart to beat fast, such as sepsis or infection, then it could be causing the stress on your heart rather than being a result of the blockage to blood flow.

Many people live with tachycardia and have no other symptoms or complications. However, if you consistently have a rapid resting heart rate, you should absolutely have your cardiovascular health evaluated.

Research shows that people with an elevated heart rate at the time they arrive at a hospital with a heart attack have a higher risk of death.

A rapid heart rate is one of many possible symptoms of a heart attack. But it usually isn’t the only sign of trouble if your heart is truly in distress. The most common symptoms of a heart attack include:

  • chest pain that may feel like a sharp pain, tightness, or pressure on the chest
  • pain in one or both arms, chest, back, neck, and jaw
  • cold sweat
  • shortness of breath
  • nausea
  • lightheadedness
  • a vague sense of impending doom

If you think you or a loved one may be having a heart attack, call 911 immediately.

The sooner you can get diagnosed and treated, the less damage the heart will endure. You should never try to drive yourself to the emergency room if you’re having heart attack symptoms.

By definition, a heart attack is a disruption of blood flow to the heart muscle that damages heart muscle tissue. But the nature of that disruption and how the heart responds can differ.

There are three different types of heart attacks and each can affect heart rate in different ways:

  • STEMI (ST segment elevation myocardial infarction)
  • NSTEMI (non-ST segment elevation myocardial infarction), which has many subtypes
  • coronary spasm

STEMI heart attacks

STEMI is what you think of as a traditional heart attack. During a STEMI, a coronary artery is completely blocked.

The ST segment refers to a portion of a heartbeat as seen on an electrocardiogram (ECG).

Heart rate during a STEMISymptoms
Heart rate usually increases, especially if the front (anterior) part of the heart is affected.

However, it may slow due to:

1. beta-blocker use
2. damage to the conduction system (the special heart muscle cells that tell the heart when to contract)
3. if the back (posterior) part of the heart is involved
Chest pain or discomfort,
dizziness or lightheadedness,
nausea,
shortness of breath,
palpitations,
anxiety,
fainting or loss of consciousness

NSTEMI heart attacks

NSTEMI refers to a partially blocked coronary artery. It’s not as severe as a STEMI, but it’s still very serious.

No ST segment elevation is found on an ECG. ST segments are likely to be depressed.

Heart rate during an NSTEMISymptoms
Heart rate is similar to those associated with STEMI.

Sometimes, if another condition in the body, such as sepsis or arrhythmia, is causing the heart rate to increase, it can cause a supply-demand mismatch, where the demand of oxygen of the heart muscle increases due to fast heart rate, and supply is limited because of blockages in the blood vessels.
Chest pain or tightness,
pain in neck, jaw or back,
dizziness,
sweating,
nausea

Coronary spasms

A coronary spasm occurs when the muscles within one or more coronary arteries suddenly constrict, narrowing the blood vessels. In this case, blood flow to the heart is limited.

A coronary spasm is less common than STEMI or NSTEMI.

Heart rate during a coronary spasmSymptoms
Sometimes, little or no change in heart rate, though a coronary spasm can cause tachycardia. Brief (15 minutes or less), but recurring episodes of
chest pain, often while asleep at night, but can be so strong it wakes you;
nausea;
sweating;
feeling as though you may pass out

Blood pressure is the force of blood pushing against the inside walls of your arteries as it circulates throughout the body. Just as heart rate changes are unpredictable during a heart attack, so too are blood pressure changes.

Because blood flow in the heart is blocked and a portion of heart tissue is denied oxygen-rich blood, your heart may not be able to pump as strongly as it normally does, thus lowering your blood pressure.

A heart attack may also trigger a response from your parasympathetic nervous system, causing your heart and the rest of your body to relax and not fight while your heart struggles to keep blood circulating. This can also cause a dip in blood pressure.

On the other hand, the pain and stress from the heart attack can raise the blood pressure during a heart attack.

Blood pressure-lowering medications, such as diuretics or angiotensin converting enzyme inhibitors, can keep your blood pressure low during a heart attack, too.

Risk factors for a heart attack include modifiable factors, such as your weight, as well as those beyond your control, such as your age. Some of the most common conditions that raise your risk for a heart attack include:

  • advancing age
  • obesity
  • diabetes
  • high cholesterol
  • high blood pressure
  • inflammation
  • smoking
  • sedentary lifestyle
  • family history of heart disease
  • personal history of heart disease or stroke
  • poorly controlled stress

Can your heart rate reveal your risk for a heart attack?

A very high or very low heart rate may reveal your risk for heart attack. For most people, a heart rate that’s consistently above 100 beats per minute or below 60 beats per minute for nonathletes should prompt a visit to a doctor for a heart health evaluation.

Long-distance runners and other types of athletes often have a low resting heart rate and a high aerobic capacity — the ability of the heart and lungs to deliver sufficient oxygen to the muscles. So, their heart rates are usually low.

Both of these traits are associated with a lower risk of heart attack and death. Regular exercise — such as brisk walking or running, swimming, bicycling and other aerobic activities — can help lower your resting heart rate and improve your aerobic capacity.

Though a rapid resting heart rate can be a risk factor for a heart attack in certain patients, a myocardial infarction isn’t always characterized by a fast-beating heart. Sometimes, your heart rate may slow down during a heart attack due to problems with the heart’s electrical system.

Likewise, your blood pressure may or may not change much during a heart attack.

Still, maintaining a healthy resting heart rate and a normal blood pressure are two steps you can usually control with lifestyle choices and, if necessary, medications. These steps can help preserve your heart health and reduce your odds of a serious heart attack.