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
- 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.
When to see a doctor
A number of conditions can cause a rapid heart rate and tachycardia symptoms. It's important to get a prompt, accurate diagnosis and appropriate care. See your doctor if you or your child experiences any tachycardia symptoms.
If you faint, have difficulty breathing or have chest pain lasting more than a few minutes, get emergency care, or call 911 or your local emergency number. Seek emergency care for anyone experiencing these symptoms.
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
- Sudden stress, such as fright
- High or low blood pressure
- 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
- Heavy alcohol use
- Heavy caffeine use
- Use of recreational drugs
- Psychological stress or anxiety
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