During a heart attack, your heart muscles receive less blood.
This can be because one or more arteries are unable to deliver a sufficient flow of blood to the heart muscles. 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.
Blockages and artery spasms can both restrict blood flow to the heart. This reduction in blood flow can start causing damage to heart muscles within minutes.
This lack of oxygen leads to the breakdown of the heart muscle at the cellular level. As the oxygen depletion continues, this damage continues.
The following can affect how much damage your heart will take during an attack:
- how quickly you receive treatment
- how much blood flow the blockages stop
- the size of the area the blockage affects
Since the heart muscle cannot easily regenerate itself, the heart heals after an attack by forming scar tissue. The heart tissue not affected by the oxygen loss may get bigger over time, and the heart may change shape.
By definition, a heart attack is a disruption of blood flow to the heart muscle that damages heart muscle tissue. However, the nature of that disruption and how the heart responds can differ.
There are three 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
The ST segment is part of the pattern on an electrocardiogram (ECG). This is a test that measures your heart’s electrical activity and displays it on a monitor as a continuous line. A person’s ST segment will typically appear as a flat period between peaks.
STEMI Heart Attacks
STEMI is what you think of as a traditional heart attack. During a STEMI, something completely blocks a coronary artery.
| Heart rate during a STEMI | Symptoms |
| 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. the back (posterior) part of the heart being involved |
Chest pain or discomfort, dizziness or lightheadedness, nausea, shortness of breath, palpitations, anxiety, fainting or loss of consciousness |
NSTEMI Heart Attacks
An NSTEMI reduces blood flow to the heart but does not cut it off completely. As a result, these types of heart attacks are not as severe as STEMIs but are still serious.
There are different types of NSTEMIs.
In type I NSTEMIs, a plaque rupture or erosion causes a partial blockage of an artery. Whereas in type II NSTEMIs, other factors such as artery spasms or dysfunctions cause a blood supply-demand imbalance.
In all NSTEMI types, no ST segment elevation appears on an ECG.
| Heart rate during an NSTEMI | Symptoms |
| 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. This is where the demand for 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. This limits blood flow to the heart.
A coronary spasm is less common than STEMI or NSTEMI.
| Heart rate during a coronary spasm | Symptoms |
| Sometimes, there’s 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 |
Certain medications can affect heart rate during a heart attack or assist in preventing one from occurring.
These include:
- Beta-blockers. These block the effects of adrenaline and help reduce heart rate.
- Nitrates. Nitrates help keep blood flow high by relaxing and widening arteries.
- Antiplatelet agents. This type of medication can help stop potentially dangerous blood clots from forming.
- Anticoagulants. Like antiplatelet agents, these help stop clots from forming, but by different means.
- Calcium channel blockers. These medications can reduce blood pressure and help treat abnormal heart rhythms.
Effect of medical conditions
Tachycardia, a condition in which your heart always or frequently beats abnormally fast, can cause your heart rate to remain at unusually high rates during a heart attack.
Bradycardia can have the opposite effect. This condition results in an abnormally slow heart rate, which may continue during a heart attack.
Other conditions, such as sepsis, can also increase your heart rate before, and during, a heart attack. It can also increase your heart rate unrelated to a heart attack.
Blood pressure is the force of blood pushing against the inside walls of your arteries as blood circulates. Just as heart rate changes are unpredictable during a heart attack, so are blood pressure changes.
A heart attack can damage the muscles of the heart. This can mean that it may not be able to pump as strongly as it normally does, 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 while your heart struggles to keep blood circulating. This can also cause a dip in blood pressure.
A rapid heart rate is one of many possible symptoms of a heart attack. However, it is usually not 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
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.
The main three risk factors of a heart attack. These risk factors are:
- high blood pressure (hypertension)
- high cholesterol
- smoking
Some other common conditions that raise your risk for a heart attack include:
- advancing age
- having obesity
- diabetes
- family history of heart disease
- personal history of heart disease or stroke
A person’s resting heart rate is thought to be a factor in determining a person’s risk of a heart attack.
For most people, a heart rate that’s consistently above or below 60 to 100Trusted Source beats per minute should prompt a visit to a doctor for a heart health evaluation.
Regular exercise can help lower your resting heart rate and improve your aerobic capacity. Some exercises that can improve heart health are:
- brisk walking or running
- swimming
- bicycling
- other aerobic activities
A doctor can work with you to help lower the risk of a heart attack. They can help you identify ways to improve your heart health, such as lifestyle changes or medications.
Takeaway
Multiple factors can influence your heart rate during a heart attack. In many cases, your heart rate will increase, but several conditions and medications may cause it to stay at the same pace or even slow down.
However, a high resting heart rate can sometimes be a risk factor for developing heart attacks.
Maintaining a healthy resting heart rate and a normal blood pressure are two factors you can usually manage with lifestyle changes and medications if necessary. These steps can help preserve your heart health and reduce your risk of a serious heart attack.
If you or someone around you is showing heart attack symptoms, call local emergency services immediately.
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