Heart arrhythmia – Symptoms and causes – Mayo Clinic

Overview

Heart rhythm problems (heart arrhythmias) occur when the electrical impulses that coordinate your heartbeats don't work properly, causing your heart to beat too fast, too slow or irregularly.

Heart arrhythmias (uh-RITH-me-uhs) 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.

Heart arrhythmia treatment can often control or eliminate fast, slow or irregular heartbeats. In addition, because troublesome heart arrhythmias are often made worse or are even caused by a weak or damaged heart, you may be able to reduce your arrhythmia risk by adopting a heart-healthy lifestyle.

Arrhythmias may not cause any signs or symptoms. In fact, your doctor might find you have an arrhythmia before you do, during a routine examination. Noticeable signs and symptoms don't necessarily mean you have a serious problem, however.

Noticeable arrhythmia symptoms may include:

Arrhythmias may cause you to feel premature or extra heartbeats, or you may feel that your heart is racing or beating too slowly. Other signs and symptoms may be related to your heart not pumping effectively due to the fast or slow heartbeat. These include shortness of breath, weakness, dizziness, lightheadedness, fainting or near fainting, and chest pain or discomfort.

Seek urgent medical care if you suddenly or frequently experience any of these signs and symptoms at a time when you wouldn't expect to feel them.

Ventricular fibrillation is one type of arrhythmia that can be deadly. It occurs when the heart beats with rapid, erratic electrical impulses. This causes pumping chambers in your heart (the ventricles) to quiver uselessly instead of pumping blood. Without an effective heartbeat, blood pressure plummets, cutting off blood supply to your vital organs.

A person with ventricular fibrillation will collapse within seconds and soon won't be breathing or have a pulse. If this occurs, follow these steps:

Find out if an automated external defibrillator (AED) is available nearby. These portable defibrillators, which can deliver an electric shock that may restart heartbeats, are available in an increasing number of places, such as in airplanes, police cars and shopping malls. They can even be purchased for your home.

No training is required. The AED will tell you what to do. It's programmed to allow a shock only when appropriate.

Many things can lead to, or cause, an arrhythmia, including:

Your heart is made up of four chambers two upper chambers (atria) and two lower chambers (ventricles). The rhythm of your heart is normally controlled by a natural pacemaker (the sinus node) located in the right atrium. The sinus node produces electrical impulses that normally start each heartbeat.

From the sinus node, electrical impulses travel across the atria, causing the atria muscles to contract and pump blood into the ventricles.

The electrical impulses then arrive at a cluster of cells called the atrioventricular node (AV node) usually the only pathway for signals to travel from the atria to the ventricles.

The AV node slows down the electrical signal before sending it to the ventricles. This slight delay allows the ventricles to fill with blood. When electrical impulses reach the muscles of the ventricles, they contract, causing them to pump blood either to the lungs or to the rest of the body.

In a healthy heart, this process usually goes smoothly, resulting in a normal resting heart rate of 60 to 100 beats a minute.

Doctors classify arrhythmias not only by where they originate (atria or ventricles) but also by the speed of heart rate they cause:

Not all tachycardias or bradycardias mean you have heart disease. For example, during exercise it's normal to develop a fast heartbeat as the heart speeds up to provide your tissues with more oxygen-rich blood. During sleep or times of deep relaxation, it's not unusual for the heartbeat to be slower.

Tachycardias originating in the atria include:

Atrial fibrillation. Atrial fibrillation is a rapid heart rate caused by chaotic electrical impulses in the atria. These signals result in rapid, uncoordinated, weak contractions of the atria.

The chaotic electrical signals bombard the AV node, usually resulting in an irregular, rapid rhythm of the ventricles. Atrial fibrillation may be temporary, but some episodes won't end unless treated.

Atrial fibrillation may lead to serious complications such as stroke.

Tachycardias occurring in the ventricles include:

Ventricular fibrillation. Ventricular fibrillation occurs when rapid, chaotic electrical impulses cause the ventricles to quiver ineffectively instead of pumping necessary blood to the body. This serious problem is fatal if the heart isn't restored to a normal rhythm within minutes.

Most people who experience ventricular fibrillation have an underlying heart disease or have experienced serious trauma, such as being struck by lightning.

Long QT syndrome. Long QT syndrome is a heart disorder that carries an increased risk of fast, chaotic heartbeats. The rapid heartbeats, caused by changes in the electrical system of your heart, may lead to fainting, and can be life-threatening. In some cases, your heart's rhythm may be so erratic that it can cause sudden death.

You can be born with a genetic mutation that puts you at risk of long QT syndrome. In addition, several medications may cause long QT syndrome. Some medical conditions, such as congenital heart defects, may also cause long QT syndrome.

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, you may have an efficient heart capable of pumping an adequate supply of blood with fewer than 60 beats a minute at rest.

In addition, certain medications used to treat other conditions, such as high blood pressure, may lower your heart rate. However, if you have a slow heart rate and your heart isn't pumping enough blood, you may have one of several bradycardias, including:

Conduction block. A block of your heart's electrical pathways can occur in or near the AV node, which lies on the pathway between your atria and your ventricles. A block can also occur along other pathways to each ventricle.

Depending on the location and type of block, the impulses between the upper and lower halves of your heart may be slowed or blocked. If the signal is completely blocked, certain cells in the AV node or ventricles can make a steady, although usually slower, heartbeat.

Some blocks may cause no signs or symptoms, and others may cause skipped beats or bradycardia.

Although it often feels like a skipped heartbeat, a premature heartbeat is actually an extra beat. Even though you may feel an occasional premature beat, it seldom means you have a more serious problem. Still, a premature beat can trigger a longer lasting arrhythmia especially in people with heart disease.

Premature heartbeats are commonly caused by stress, strenuous exercise or stimulants, such as caffeine or nicotine.

Certain factors may increase your risk of developing an arrhythmia. These include:

Certain arrhythmias may increase your risk of developing conditions such as:

Stroke. When your heart quivers, it's unable to pump blood effectively, which can cause blood to pool. This can cause blood clots to form. If a clot breaks loose, it can travel from your heart to your brain. There it might block blood flow, causing a stroke.

Certain medications, such as blood thinners, can greatly lower your risk of stroke or damage to other organs caused by blood clots. Your doctor will determine if a blood-thinning medication is appropriate for you, depending on your type of arrhythmia and your risk of blood clots.

To prevent heart arrhythmia, it's important to live a heart-healthy lifestyle to reduce your risk of heart disease. A heart-healthy lifestyle may include:

Read the rest here:
Heart arrhythmia - Symptoms and causes - Mayo Clinic