Tachycardia is the medical term for a heart rate that is faster than 100 beats per minute. Tachycardia can occur as a normal or an abnormal heart rate response. When tachycardia occurs as a normal response, it is called sinus tachycardia. It can be caused by exercise, fever, pain, anxiety, anemia, hyperthyroidism, or fright. However, tachycardia is considered abnormal when one’s heart rate increases abruptly and/or is disproportionate to the activity a person is performing. Causes for the latter can be abnormalities in the heart’s electrical system, heart scarring, certain drugs, and heart failure, among others.

When a person has abnormal tachycardia, the faster-than-normal heartbeat can prevent the chambers of the heart from filling efficiently with blood between contractions of the heart muscle. This, in turn, can result in a reduction of cardiac output, or in other words, reduced blood supply to the rest of the body's organs. When people don’t get the proper blood flow throughout their body, they may experience the symptoms, such as palpitations, fainting sensation, lightheadedness, loss of consciousness, dizziness, weakness, and shortness of breath.

Older adults, particularly those with structural heart disease, are at increased risk of specific types of tachycardia. However, tachycardia could also occur in patients without structural heart disease and may affect younger adults and children.

Because some causes of tachycardia are life-threatening, people who recognize signs of tachycardia should seek medical attention immediately. Anyone who experiences shortness of breath and chest pain should call 911.

Although it can be uncontrolled, undiagnosed tachycardia may lead to health complications or even death; when tachycardia is diagnosed and treated in a timely fashion, patients can live normal lives.

To sustain life, the heart beats continually and pumps oxygen-rich blood to muscles and tissues throughout the body. The heart adjusts how much blood it pumps and how fast it beats to meet the changing oxygen needs of muscles and tissues around the body. For instance, during exercise, when muscles and tissues require more oxygen than they do at rest, the heart contracts with increased force and beats faster to pump more blood—and oxygen—to the body’s muscles and tissues.

The heart’s rhythm and the rate at which it beats are regulated by the sinus node (also called the sinoatrial node), the heart’s natural pacemaker. Located in the right atrium (the upper right chamber of the heart), the sinus node generates electrical signals that travel through the heart, causing the heart muscle to contract and pump blood. In response to increased levels of adrenaline, such as during exercise or at times of emotional stress, the sinus node speeds up, sending electrical signals at a faster rate than normal, thereby causing the heart rate to increase. Conversely, when a person is at rest or sleeping, the sinus node slows down, thereby causing the heart rate to slow down.

A normal, healthy adult typically has a resting heart rate between 60 and 100 beats per minute. Tachycardia is defined as a heart rate over 100 beats per minute. Tachycardia that occurs as a response to stimuli, is called sinus tachycardia and is a normal heart response to meet the body's needs.

However, tachycardia that occurs abruptly and without a clear cause, or when the heart rate increases out of proportion to the amount of activity a person is performing, is considered abnormal. During a tachycardia episode, the heart rate usually increases abruptly without relation to the body's needs.

There are different types of tachycardia:

• Sinus tachycardia is an elevated heart rate that occurs when the sinus node generates and transmits faster electrical signals. It is often a response to an external stimulus, such as fear, stress, exercise, pain, or drugs. In some cases, it may be caused by a thyroid condition, anemia, bleeding, or fever. However, very infrequently, it can also be an inappropriate sinus response, causing fatigue and exercise intolerance that should be evaluated by a health care professional.
• Supraventricular tachycardia is an elevated resting heart rate that originates in the upper chambers of the heart or the atrioventricular (AV) node, a structure located between the upper (atria) and lower chambers (ventricles) of the heart. The AV node regulates the transmission of electrical signals from the sinus node to the ventricles. Atrial fibrillation, atrial flutter, atrial tachycardia, AV nodal reentry tachycardia (AVNRT), and AV reentry tachycardia (AVRT) are all types of supraventricular tachycardia.
• Ventricular tachycardia is an elevated heart rate that originates in the heart’s lower chambers.

Supra-ventricular and ventricular tachycardia often occur without warning and are linked to an abnormal electrical pathway in the heart or a specific area in the heart that acts independently. Conditions linked with these types of tachycardia include:

• High blood pressure
• Structural heart disease
• Heart attack
• Heart surgery
• Heart failure
• Myocarditis, a heart infection
• Sleep apnea
• Having obesity
• A family history of tachycardia
• Congenital electrical extra connection or bypass tract

Sinus tachycardia, on the other hand, may be caused by external stimuli such as:

• Stress
• Elation
• Fear
• Anxiety
• Caffeine
• Tobacco
• Hyperthyroidism
• Anemia
• Shortness of breath
• Heart failure
• Medications
• Cocaine or other illegal drugs

Some people with tachycardia do not have any symptoms. However, people with tachycardia who do have symptoms may experience:

• Fainting
• Palpitations
• Lightheadedness
• Loss of consciousness
• Dizziness
• Weakness
• Shortness of breath
• Anxiety
• Decrease in exercise capacity
• Breaking out in a cold sweat
• Chest pain
• Cardiac arrest, in some instances

People with the following conditions may be at increased risk of tachycardia:

• Chronic pain
• High blood pressure
• Heart disease
• A family history of tachycardia
• Advanced age
• Pregnancy
• Anemia
• Stress
• Fever
• Thyroid disease
• Smoking
• Using cocaine and other illegal drugs
• Heavy alcohol usage

Tachycardia is diagnosed when your heart rate is above 100 beats per minute. Doctors can diagnose the cause of the tachycardia and whether treatment is necessary—for instance, if it is considered abnormal—after learning about a patient’s medical history, giving a physical exam, and performing diagnostic tests.

To learn about your medical history, your doctor may ask about your heart health and whether any heart conditions run in the family, including tachycardia, structural heart disease, cardiac arrest, or sudden death. They may also ask about a personal or family history of fainting, weakness, feeling dizzy, or noticing heart palpitations.

A physical exam, ECG, heart ultrasound, and heart monitoring may be used to assess your heart function, structure, and electrical activity. By placing a monitor, doctors try to capture a tachycardia episode and assess its cause. Providers will also look for signs of an underlying condition that could cause tachycardia, such as thyroid disease, anemia, and leg swelling, which may indicate that your heart isn’t pumping efficiently.

Diagnostic tests include:

• Electrocardiogram to record the heart’s electrical activity
• Wearable heart monitors to record heart rhythm. There are different types of monitors and that may be worn for various durations, starting from 24 hours (using a Holter monitor) to a continuous 30-day recording (using a mobile cardiac telemetry device).
• Implantable heart monitor, a small monitor that is placed under the skin. It helps diagnose arrhythmias that occur infrequently (usually only once every few months). The device can last for up to 4 years.
• Blood tests to detect medical conditions that predispose patients to tachycardia, such as anemia, thyroid disease, pulmonary embolus, and heart failure.
• Computed tomography (CT) scan or magnetic resonance imaging (MRI) allows doctors, together with an echocardiogram, to assess the heart for structural abnormalities
• Tilt table test, a test in which you lie on a motorized table with electrodes attached to your chest, blood pressure cuffs, and an intravenous (IV) in an arm or hand. During the test, the table is titled upward, until you are almost in a standing position. The test assesses how your blood pressure and heart rate change in response to different body positions, which may help to determine the cause of fainting and heart palpitations. The tilt table test may be used to diagnose postural orthostatic tachycardia syndrome (POTS), a type of tachycardia that occurs after standing up from sitting or lying down.
• Electrophysiology study (EP study), a procedure in which an electrode catheter—a thin tube equipped with electrodes—is inserted into a blood vessel and guided to the heart. During the test, doctors attempt to stimulate the arrhythmia, characterize it, and eventually permanently fix it. EP studies are performed in an electrophysiology lab.

Whenever tachycardia is caused by an underlying condition, doctors try to treat that condition to resolve the tachycardia; when tachycardia is due to an abnormal electrical pathway in the heart or originates in a specific area in the heart, medications or ablation (cautery inside the heart) tools can be used to treat it.

The following medications may be used to treat tachycardia:

• Beta-blockers, such as metoprolol, nadolol, and propranolol
• Calcium channel blockers, such as verapamil or diltiazem
• Anti-arrhythmic medications, such as potassium or sodium channel blockers
• Adenosine
• Digoxin
• Magnesium sulfate

If medications aren’t effective, doctors may recommend one or some of the following procedures:

• Cardioversion, which uses external electrical shocks to change the heart’s rhythm, restoring it to normal.
• Catheter ablation, in which a wire is threaded through blood vessels to the heart. Doctors can use radiofrequency waves (radiofrequency ablation), laser light (laser ablation), or extreme cold (cryoablation) to destroy the tiny area in the heart that is causing the tachycardia, creating scar tissue. Once that area has been treated, the heart rhythm abnormality should be under control.
• An implantable cardiac defibrillator can detect when the heart is in an abnormal rhythm or rate, then, in response, try to terminate the tachycardia by pacing, or delivering, a shock to the heart to terminate the tachycardia. Once the device is implanted, it remains in the body and monitors the heart for any abnormal rhythm.
• Pacemaker, a small device implanted in the chest to help prevent a slow heart rate. Although it only treats slow heart rate, it allows doctors to give patients medications that usually cannot be given to people with a slow heart rate who also have episodes of tachycardia.

For certain types of tachycardia, the use of vagal maneuvers can help terminate tachycardia. These maneuvers include:

• Lying down
• Putting ice water (or a towel soaked in ice water) on your face
• Coughing forcefully
• Holding your breath while pinching the nose closed and bearing down (as if making a bowel movement), similar to what people may do when trying to unclog their ears

Other lifestyle habits may also be effective, including:

• Cutting back on caffeine consumption
• Drinking less alcohol
• Getting more sleep
  

Untreated tachycardia may cause considerable symptoms and lead to a reduction in quality of life. Some types of tachycardia can be life-threatening or lead to stroke. However, once diagnosed, tachycardia is a very treatable condition. Medication and medical procedures can help keep the condition under control and eliminate the cause of the arrhythmia in the heart, respectively. Medical procedures are usually more effective than medication in treating abnormal tachycardia.

“Yale physicians will work with you diligently to assess the presence of tachycardia and its cause,” says Nimrod Lavi, MD, a Yale Medicine clinical cardiac electrophysiologist, a doctor who treats abnormal heart rhythms. “Yale physicians have at their disposal all the needed tools to diagnose it and pinpoint the mechanism for its cause. Once diagnosed, we have all the necessary equipment to treat it safely and effectively with a very high success rate.”