Tachycardia

Overview

Tachycardia (tak-ih-KAHR-dee-uh) is the medical term for a heart rate over 100 beats a minute. Many types of irregular heart rhythms, called arrhythmias, can cause tachycardia.

A fast heart rate isn't always a concern. For instance, the heart rate usually rises during exercise or as a response to stress.

Tachycardia may not cause any symptoms or complications. But sometimes it's a warning of a medical condition that needs attention. Some forms of tachycardia can lead to serious health problems if left untreated. Such problems may include heart failure, stroke or sudden cardiac death.

Treatment for tachycardia may include specific actions or movements, medicine, cardioversion, or surgery to control a rapid heartbeat.

Types

There are many different types of tachycardia. Sinus tachycardia refers to a usual increase in the heart rate often caused by exercise or stress.

Other types of tachycardia are grouped according to cause and the part of the heart causing the fast heart rate. Common types of tachycardia caused by irregular heart rhythms include:

• Atrial fibrillation, also called AFib. This is the most common type of tachycardia. Chaotic, irregular electrical signals start in the upper chambers of the heart, called the atria. These signals trigger a fast heartbeat. A-fib may be temporary. But some episodes won't end unless treated.
• Atrial flutter. Atrial flutter is similar to A-fib, but heartbeats are more organized. Episodes of atrial flutter may go away by themselves or may need treatment. People who have atrial flutter also often have A-fib at other times.
• Ventricular tachycardia. This irregular heart rhythm starts in the lower heart chambers, called the ventricles. The fast heart rate doesn't let the ventricles fill and squeeze to pump enough blood to the body. Episodes may be brief and last only a couple of seconds without causing harm. But episodes lasting more than a few seconds can be life-threatening.
• Supraventricular tachycardia (SVT). Supraventricular tachycardia is a broad term that includes irregular heart rhythms that start above the lower heart chambers. Supraventricular tachycardia causes episodes of a pounding heartbeat that begin and end abruptly.
• Ventricular fibrillation. This serious condition can be deadly if the heart rhythm isn't reset within minutes. Rapid, chaotic electrical signals cause the lower heart chambers to quiver instead of squeezing in a coordinated way. Most people with this type of irregular heart rhythm have heart disease or have had a serious injury, such as being struck by lightning.

Causes

Tachycardia is an increased heart rate for any reason. If a fast heart rate is caused by exercise or stress, it's called sinus tachycardia. Sinus tachycardia is a symptom, not a condition.

Most heart conditions can lead to different forms of tachycardia. Irregular heart rhythms, called arrhythmias, are one cause. An example of an irregular heart rhythm is atrial fibrillation (AFib).

Other things that may lead to tachycardia include:

• Fever.
• Excessive alcohol use, which is defined as 14 or more drinks a week for a man or seven or more drinks a week for a woman.
• Alcohol withdrawal.
• Too much caffeine.
• High or low blood pressure.
• Changes in the level of minerals in the body, called electrolytes. Examples include potassium, sodium, calcium and magnesium.
• Certain medicines.
• Overactive thyroid, called hyperthyroidism.
• A low number of red blood cells, called anemia.
• Smoking or nicotine use.
• Use of illegal stimulants such as cocaine or methamphetamine.
• Heart attack.

Sometimes the exact cause of tachycardia is not known.

How does the heart beat?

To understand the cause of tachycardia, it may be helpful to know how the heart usually works.

The heart has four chambers:

• The two upper chambers are called the atria.
• The two lower chambers are called the ventricles.

Inside the upper right heart chamber is a group of cells called the sinus node. The sinus node makes the signals that start each heartbeat.

The signals move across the upper heart chambers. Then the signals arrive at a group of cells called the AV node, where they usually slow down. The signals then go to the lower heart chambers.

In a healthy heart, this signaling process usually goes smoothly. The resting heart rate is typically 60 to 100 beats a minute. But in tachycardia, something causes the heart to beat faster than 100 beats a minute.

Complications

When the heart beats too fast, it may not pump enough blood to the body. As a result, the organs and tissues may not get enough oxygen.

Complications of tachycardia depend on:

• The type of tachycardia.
• How fast the heart is beating.
• How long the rapid heart rate lasts.
• Whether there are other heart conditions.

Potential complications of tachycardia may include:

• Blood clots that can cause a heart attack or stroke. Blood-thinning medicine may be used to lower this risk.
• Frequent fainting or unconsciousness.
• Heart failure.
• Sudden cardiac death. This is usually only associated with ventricular tachycardia or ventricular fibrillation.

Diagnosis

To diagnose tachycardia, a healthcare professional examines you and asks questions about your symptoms, health habits and medical history.

Tests

Tests may be done to confirm an unusually fast heartbeat and to look for the cause. Tests to diagnose tachycardia may include:

• Electrocardiogram (ECG or EKG). This quick test checks the heartbeat. Sticky patches, called electrodes, are attached to the chest and sometimes to the arms or legs. An ECG shows how fast or how slow the heart is beating.

  Some personal devices, such as smartwatches, can do ECGs. Ask your care team if this is an option for you.

• Holter monitor. This portable ECG device is worn for a day or more to record the heart's activity during daily activities. This test can detect irregular heartbeats that aren't found during a regular ECG exam.
• Event monitor. This device is like a Holter monitor, but it records only at certain times for a few minutes at a time. It's typically worn for about 30 days. You usually push a button when you feel symptoms. Some devices automatically record when an irregular heart rhythm is noticed.
• Echocardiogram. Sound waves are used to create images of the beating heart. This test can show how blood flows through the heart and heart valves.
• Chest X-ray. A chest X-ray shows the condition of the heart and lungs.
• MRI scan of the heart. Also called a cardiac MRI, this test uses magnetic fields and radio waves to create detailed images of the heart. It's most often done to find a cause of ventricular tachycardia or ventricular fibrillation.
• CT scan of the heart. Also called a cardiac CT, this test takes several X-ray images to provide a more detailed look of the heart. It may be done to find the cause of ventricular tachycardia.
• Coronary angiogram. A coronary angiogram is done to check for blocked or narrowed blood vessels in the heart. It uses a dye and special X-rays to show the inside of the coronary arteries. The test may be done to look at the heart's blood supply in people who have ventricular tachycardia or ventricular fibrillation.

• Electrophysiological (EP) study. This test may be done to confirm a diagnosis of tachycardia. It can help find where in the heart the incorrect signaling occurs. An EP study is mostly used to diagnose some specific types of tachycardias and irregular heartbeats.

  During this test, one or more flexible tubes are guided through a blood vessel, usually in the groin, to various areas in the heart. Sensors on the tips of the tubes record the heart's electrical signals.

• Stress tests. Exercise can trigger or worsen some types of tachycardia. Stress tests are done to see how exercise affects the heart. They often involve walking on a treadmill or pedaling a stationary bike while the heart is checked. If you can't exercise, you may be given medicine that increases the heart rate like exercise does. Sometimes an echocardiogram is done during a stress test.
• Tilt table test. This test may be done to learn if a fast heartbeat leads to fainting. The heart rate and rhythm and blood pressure are checked while you lie flat on a table. Then, under careful supervision, the table is tilted to a standing position. A member of your care team watches how your heart and the nervous system that controls it respond to the changes in position.

Lifestyle and home remedies

If you have tachycardia or any type of heart disease, it's important to take steps to keep your heart healthy. Steps include lifestyle changes such as eating a heart-healthy diet, getting regular exercise, and not smoking or using tobacco. Your care team also may suggest that you limit or avoid caffeine.

Coping and support

If you have a plan to manage an episode of a fast heartbeat, you may feel calmer and more in control when one occurs. Ask your care team:

• How to take your pulse and what heart rate is best for you.
• When and how to do treatments called vagal maneuvers, if appropriate.
• When to seek emergency care.