In a typical heart rhythm, a tiny cluster of cells at the sinus node sends out an electrical signal. The signal then travels through the atria to the atrioventricular (AV) node and into the ventricles, causing them to contract and pump blood.
A heart arrhythmia (uh-RITH-me-uh) is an irregular heartbeat. Heart rhythm problems (heart arrhythmias) occur when the electrical signals that coordinate the heart's beats don't work properly. The faulty signaling causes the heart to beat too fast (tachycardia), too slow (bradycardia) or irregularly.
Heart arrhythmias may feel like a fluttering or racing heart and may be harmless. However, some heart arrhythmias may cause bothersome — sometimes even life-threatening — signs and symptoms.
However, sometimes it's normal for a person to have a fast or slow heart rate. For example, the heart rate may increase with exercise or slow down during sleep.
Heart arrhythmia treatment may include medications, catheter procedures, implanted devices or surgery to control or eliminate fast, slow or irregular heartbeats. A heart-healthy lifestyle can help prevent heart damage that can trigger certain heart arrhythmias.
In general, heart arrhythmias are grouped by the speed of the heart rate. For example:
- Tachycardia (tak-ih-KAHR-dee-uh) is a fast heart. The resting heart rate is greater than 100 beats a minute.
- Bradycardia (brad-e-KAHR-dee-uh) is a slow heartbeat. The resting heart rate is less than 60 beats a minute.
Fast heartbeat (tachycardia)
Types of tachycardias include:
- Atrial fibrillation (A-fib). Chaotic heart signaling causes a rapid, uncoordinated heart rate. The condition may be temporary, but some A-fib episodes may not stop unless treated. A-fib is associated with serious complications such as stroke.
- Atrial flutter. Atrial flutter is similar to A-fib, but heartbeats are more organized. Atrial flutter is also linked to stroke.
- Supraventricular tachycardia. Supraventricular tachycardia is a broad term that includes arrhythmias that start above the lower heart chambers (ventricles). Supraventricular tachycardia causes episodes of a pounding heartbeat (palpitations) that begin and end abruptly.
- Ventricular fibrillation. This type of arrhythmia occurs when rapid, chaotic electrical signals cause the lower heart chambers (ventricles) to quiver instead of contacting in a coordinated way that pumps blood to the rest of the body. This serious problem can lead to death if a normal heart rhythm isn't restored within minutes. Most people who have ventricular fibrillation have an underlying heart disease or have experienced serious trauma.
- Ventricular tachycardia. This rapid, regular heart rate starts with faulty electrical signals in the lower heart chambers (ventricles). The rapid heart rate doesn't allow the ventricles to properly fill with blood. As a result, the heart can't pump enough blood to the body. Ventricular tachycardia may not cause serious problems in people with an otherwise healthy heart. In those with heart disease, ventricular tachycardia can be a medical emergency that requires immediate medical treatment.
Slow heartbeat (bradycardia)
Although a heart rate below 60 beats a minute while at rest is considered bradycardia, a low resting heart rate doesn't always signal a problem. If you're physically fit, your heart may still be able to pump enough blood to the body with fewer than 60 beats a minute at rest.
If you have a slow heart rate and your heart isn't pumping enough blood, you may have a type of bradycardia. Types of bradycardias include:
- Sick sinus syndrome. The sinus node is responsible for setting the pace of the heart. If it doesn't work properly, the heart rate may alternate between too slow (bradycardia) and too fast (tachycardia). Sick sinus syndrome can be caused by scarring near the sinus node that's slowing, disrupting or blocking the travel of impulses. Sick sinus syndrome is most common among older adults.
- Conduction block. A block of the heart's electrical pathways can cause the signals that trigger the heartbeats to slow down or stop. Some blocks may cause no signs or symptoms, and others may cause skipped beats or bradycardia.
Premature heartbeats are extra beats that occur one at a time, sometimes in patterns that alternate with the normal heart beat. The extra beats may come from the top chamber of the heart (premature atrial contractions) or the bottom chamber (premature ventricular contractions).
A premature heartbeat may feel like your heart skipped a beat. These extra beats are generally not concerning, and they seldom mean you have a more serious condition. Still, a premature beat can trigger a longer-lasting arrhythmia, especially in people with heart disease. Occasionally, very frequent premature beats that last for several years may lead to a weak heart.
Premature heartbeats may occur when resting. Sometimes premature heartbeats are caused by stress, strenuous exercise or stimulants, such as caffeine or nicotine.
Heart arrhythmias may not cause any signs or symptoms. A doctor may notice the irregular heartbeat when examining you for another health reason.
In general, signs and symptoms of arrhythmias may include:
- A fluttering in the chest
- A racing heartbeat (tachycardia)
- A slow heartbeat (bradycardia)
- Chest pain
- Shortness of breath
Other symptoms may include:
- Lightheadedness or dizziness
- Fainting (syncope) or near fainting
When to see a doctor
If you feel like your heart is beating too fast or too slowly, or it's skipping a beat, make an appointment to see a doctor. Seek immediate medical help if you have shortness of breath, weakness, dizziness, lightheadedness, fainting or near fainting, and chest pain or discomfort.
A type of arrhythmia called ventricular fibrillation can cause a dramatic drop in blood pressure. Collapse can occur within seconds and soon the person's breathing and pulse will stop. If this occurs, follow these steps:
- Call 911 or the emergency number in your area.
- If there's no one nearby trained in cardiopulmonary resuscitation (CPR), provide hands-only CPR. Push hard and fast on the center of the chest at a rate of 100 to 120 compressions a minute until paramedics arrive. You don't need to do rescue breathing.
- If you or someone nearby knows CPR, start CPR. CPR can help maintain blood flow to the organs until an electrical shock (defibrillation) can be given.
- If an automated external defibrillator (AED) is available nearby, have someone get the device and follow the instructions. An AED is a portable defibrillation device that can deliver a shock that may restart heartbeats. No training is required to operate an AED. The AED will tell you what to do. It's programmed to allow a shock only when appropriate.
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To understand the cause of heart arrhythmias, it may be helpful to know how the heart typically works.
How does the heart beat?
The heart is made of four chambers — two upper chambers (atria) and two lower chambers (ventricles).
The heart's rhythm is normally controlled by a natural pacemaker (the sinus node) in the right upper chamber (atrium). The sinus node sends electrical signals that normally start each heartbeat. These electrical signals move across the atria, causing the heart muscles to squeeze (contract) and pump blood into the ventricles.
Next, the signals arrive at a cluster of cells called the AV node, where they slow down. This slight delay allows the ventricles to fill with blood. When the electrical signals reach the ventricles, the chambers contract and pump blood to the lungs or to the rest of the body.
In a healthy heart, this heart signaling process usually goes smoothly, resulting in a normal resting heart rate of 60 to 100 beats a minute.
Things that can cause an irregular heartbeat (arrhythmia) include:
- Current heart attack or scarring from a previous heart attack
- Blocked arteries in the heart (coronary artery disease)
- Changes to the heart's structure, such as from cardiomyopathy
- High blood pressure
- Infection with COVID-19
- Overactive thyroid gland (hyperthyroidism)
- Sleep apnea
- Underactive thyroid gland (hypothyroidism)
- Certain medications, including cold and allergy drugs bought without a prescription
- Drinking too much alcohol or caffeine
- Drug abuse
- Stress or anxiety
Things that may increase the risk of heart arrhythmias include:
- Coronary artery disease, other heart problems and previous heart surgery. Narrowed heart arteries, a heart attack, abnormal heart valves, prior heart surgery, heart failure, cardiomyopathy and other heart damage are risk factors for almost any kind of arrhythmia.
- High blood pressure. This condition increases the risk of developing coronary artery disease. It may also cause the walls of the left lower heart chamber (left ventricle) to become stiff and thick, which can change how electrical signals travel through the heart.
- Congenital heart disease. Being born with a heart condition may affect the heart's rhythm.
- Thyroid disease. Having an overactive or underactive thyroid gland can raise the risk of irregular heartbeats.
- Obstructive sleep apnea. This condition causes pauses in breathing during sleep. It can lead to a slow heartbeat (bradycardia) and irregular heartbeats, including atrial fibrillation.
- Electrolyte imbalance. Substances in the blood called electrolytes — such as potassium, sodium, calcium and magnesium — help trigger and send electrical impulses in the heart. An imbalance in electrolytes — for example, if they are too low or too high — can interfere with heart signaling and lead to irregular heartbeats.
- Certain drugs and supplements. Some prescription drugs and certain cough and cold medications bought without a prescription can cause arrhythmias.
- Excessive alcohol. Drinking too much alcohol can affect the electrical impulses in your heart and can increase the chance of developing atrial fibrillation.
- Caffeine, nicotine or illegal drug use. Caffeine, nicotine and other stimulants can cause your heart to beat faster and may lead to the development of more-serious arrhythmias. Illegal drugs, such as amphetamines and cocaine, may greatly affect the heart and cause many types of arrhythmias or sudden death due to ventricular fibrillation.
Complications depend on the type of arrhythmia. In general, complications of heart arrhythmias may include stroke, sudden death and heart failure.
Heart arrhythmias are associated with an increased risk of blood clots. If a clot breaks loose, it can travel from the heart to the brain, causing a stroke. Blood thinners can lower the risk of stroke related to atrial fibrillation and other arrhythmias. Your doctor will determine if a blood-thinning medication is right for you.
If an arrhythmia is causing heart failure symptoms, methods to control the heart rate may improve heart function.
Lifestyle changes to reduce the risk of heart disease may help prevent heart arrhythmias. A heart-healthy lifestyle includes:
- Eating a heart-healthy diet
- Staying physically active
- Maintaining a healthy weight
- Not smoking
- Limiting or avoiding caffeine and alcohol
- Reducing stress, as intense stress and anger can cause heart rhythm problems
- Using medications as directed and telling your doctor about all the medicines you take, including those bought without a prescription
By Mayo Clinic Staff