Tachycardia is a common type of heart rhythm disorder (arrhythmia) in which the heart beats faster than normal while at rest.
It's normal for your heart rate to rise during exercise or as a physiological response to stress, trauma or illness (sinus tachycardia). But in tachycardia (tak-ih-KAHR-dee-uh), the heart beats faster than normal in the upper or lower chambers of the heart or both while at rest.
Your heart rate is controlled by electrical signals sent across heart tissues. Tachycardia occurs when an abnormality in the heart produces rapid electrical signals that quicken the heart rate, which is normally about 60 to 100 beats a minute at rest.
In some cases, tachycardia may cause no symptoms or complications. But if left untreated, tachycardia can disrupt normal heart function and lead to serious complications, including:
- Heart failure
- Stroke
- Sudden cardiac arrest or death
Treatments, such as drugs, medical procedures or surgery, may help control a rapid heartbeat or manage other conditions contributing to tachycardia.
Types of tachycardia
There are many different types of abnormal tachycardia. They're classified according to the origin and cause of the abnormally fast heartbeat. Common types of tachycardia include:
- Atrial fibrillation. Atrial fibrillation is a rapid heart rate caused by chaotic, irregular electrical impulses in the upper chambers of the heart (atria). These signals result in rapid, uncoordinated, weak contractions of the atria.
Atrial fibrillation may be temporary, but some episodes won't end unless treated.
Atrial fibrillation is the most common type of tachycardia. Most people with atrial fibrillation have some structural abnormalities of the heart related to underlying conditions such as heart disease or high blood pressure. Other factors that may contribute to atrial fibrillation include a heart valve disorder, hyperthyroidism or heavy alcohol use.
- Atrial flutter. In atrial flutter, the heart's atria beat very fast but at a regular rate. The fast rate results in weak contractions of the atria.
Atrial flutter is caused by irregular circuitry within the atria. Episodes of atrial flutter may resolve themselves or may require treatment.
People who experience atrial flutter also often experience atrial fibrillation at other times.
- Supraventricular tachycardia (SVT). Supraventricular tachycardia is an abnormally fast heartbeat that originates somewhere above the ventricles. It's caused by abnormal circuitry in the heart that is usually present at birth and creates a loop of overlapping signals.
- Ventricular tachycardia. Ventricular tachycardia is a rapid heart rate that originates with abnormal electrical signals in the lower chambers of the heart (ventricles). The rapid heart rate doesn't allow the ventricles to fill and contract efficiently to pump enough blood to the body.
Ventricular tachycardia episodes may be brief and last only a couple of seconds without causing harm. But episodes lasting more than a few seconds can become a life-threatening medical emergency.
- 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 can be fatal if the heart isn't restored to a normal rhythm within minutes with an electric shock to the heart (defibrillation).
Ventricular fibrillation may occur during or after a heart attack. Most people who experience ventricular fibrillation have an underlying heart disease or have experienced serious trauma, such as being struck by lightning.
When your heart is beating too fast, it may not pump blood effectively to the rest of your body. This can deprive your organs and tissues of oxygen and can cause the following tachycardia-related signs and symptoms:
- Shortness of breath
- Lightheadedness
- Rapid pulse rate
- Heart palpitations — a racing, uncomfortable or irregular heartbeat or a sensation of "flopping" in the chest
- Chest pain
- Fainting (syncope)
Some people with tachycardia have no symptoms, and the condition is only discovered during a physical examination or with a heart-monitoring test called an electrocardiogram.
Tachycardia is caused by something that disrupts the normal electrical impulses that control the rate of your heart's pumping action. Many things can cause or contribute to problems with the heart's electrical system. These include:
- Damage to heart tissues from heart disease
- Abnormal electrical pathways in the heart present at birth (congenital heart conditions, including long QT syndrome)
- Disease or congenital abnormality of the heart
- Anemia
- Exercise
- Sudden stress, such as fright
- High or low blood pressure
- Smoking
- Fever
- Drinking too much alcohol
- Drinking too many caffeinated beverages
- Medication side effects
- Abuse of recreational drugs, such as cocaine
- Imbalance of electrolytes, mineral-related substances necessary for conducting electrical impulses
- Overactive thyroid (hyperthyroidism)
In some cases, the exact cause of tachycardia can't be determined.
The heart's electrical system
To understand the causes of heart rate or rhythm problems such as tachycardia, it helps to understand how the heart's internal electrical system works.
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 called the sinus node, which is 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 atrial muscles to contract and pump blood into the ventricles.
The electrical impulses then arrive at a cluster of cells called the atrioventricular (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.
When anything disrupts this complex system, it can cause the heart to beat too fast (tachycardia), too slow (bradycardia) or with an irregular rhythm.
Any condition that puts a strain on the heart or damages heart tissue can increase your risk of tachycardia. Lifestyle changes or medical treatment may decrease the risk associated with the following factors:
- Heart disease
- High blood pressure
- Sleep apnea
- Overactive or underactive thyroid
- Smoking
- Diabetes
- Heavy alcohol use
- Heavy caffeine use
- Use of recreational drugs
- Psychological stress or anxiety
- Anemia
Other risk factors
Other factors that may increase the risk of tachycardia include:
- Older age. Aging-related wear on the heart makes you more likely to develop tachycardia.
- Family. If you have a family history of tachycardia or other heart rhythm disorders, you may have an increased risk of tachycardia.
Complications of tachycardia vary in severity depending on factors such as the type of tachycardia, the rate and duration of rapid heart rate, and the existence of other heart conditions. Possible complications include:
- Blood clots that can cause a stroke or heart attack
- Inability of the heart to pump enough blood (heart failure)
- Frequent fainting spells or unconsciousness
- Sudden death, usually only associated with ventricular tachycardia or ventricular fibrillation
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