Tachycardia is a heart rate of more than 100 beats per minute. The heart normally beats at a rate of 60 to 100 times per minute, and the pulse (felt at the wrist, neck or elsewhere) matches the contractions of the heart's ventricles, the heart's two powerful lower chambers.
Tachycardia can be part of the body's normal response to anxiety, fever, rapid blood loss or strenuous exercise. It also can be caused by medical problems, such as an abnormally high level of thyroid hormones, called hyperthyroidism. In some people, tachycardia is the result of a cardiac arrhythmia (a heart-generated abnormality of heart rate or rhythm). Tachycardia can also be caused by lung problems, such as pneumonia or a blood clot in one of the lung's arteries.
In other cases, tachycardia can be a side effect of some foods and drinks, including coffee, tea, alcohol and chocolate; tobacco; or medication.
Symptoms of tachycardia can include:
If tachycardia is caused by a medical illness, there will be additional symptoms that are specific to that illness. For example, people who have tachycardia caused by hyperthyroidism also can experience nervousness, insomnia, sweating, tremors and other symptoms related to high levels of thyroid hormones. Tachycardia caused by heart or lung disease often is accompanied by chest pain or shortness of breath or lightheadedness.
Your doctor will ask you to describe your symptoms. He or she will review your personal medical history and potential causes of tachycardia, including lung disease, thyroid disorders, and medications. Your doctor will want to know if you have a family history of heart disease and cardiac arrhythmias.
During the physical examination, your doctor will check your heart rate and rhythm. Your doctor also will check for an enlarged heart, for heart murmurs (one sign of a heart valve problem), for abnormal lung sounds and for physical signs of thyroid abnormalities (enlarged thyroid gland, hand tremor and an abnormal protrusion of the eyes).
To further evaluate your tachycardia, your doctor will order an electrocardiogram (EKG). However, because some forms of tachycardia come and go, a one-time office EKG may be normal. If this is the case, you may need a test called ambulatory electrocardiography. For this test, you will wear a portable EKG machine called a Holter monitor for a period, usually for 24 hours. If symptoms occur infrequently, you may have to wear a monitor for much longer. You will be taught to press a button to record EKG readings when symptoms occur.
Depending on the results of your physical examination, other tests may be necessary, such as blood tests to measure your red blood cell count and levels of thyroid hormones and an echocardiogram to see if there are any structural abnormalities of your heart. Sometimes, physicians do "electrophysiology testing," in which they insert special catheters within the heart to collect information on the patterns of the heart's electrical activities.
How long tachycardia lasts depends on its cause. For example, tachycardia resulting from fever will go away when body temperature returns to normal. Tachycardia resulting from blood loss will end when the patient is stabilized with intravenous (IV) fluids and/or blood transfusions. Tachycardia resulting from hyperthyroidism or an adrenal gland tumor will go away when the disorder is treated. Tachycardia caused by medications or diet will go away quickly, usually within hours, when the chemical that is causing the problem is used up by the body or excreted in the urine. Tachycardia caused by cardiac problems can last a long time.
Since tachycardia is usually a sign of some underlying medical problem, discovering and treating the cause is the best way to prevent recurrent tachycardia.
The first episode of an arrhythmia that causes a rapid heart beat usually cannot be prevented.
The treatment of tachycardia depends on its cause. For example:
Call your doctor if you experience unexplained tachycardia, not the normal increase in heart rate after exercise. This is especially important if you also have palpitations, dizziness, lightheadedness, fainting spells, fatigue, breathlessness or chest pain.
The long-term outlook is usually good when tachycardia is caused by fever, blood loss, hyperthyroidism, medication or diet. Many tachycardias related to heart or lung problems can be controlled with medication, surgery or other procedures.
American Heart Association (AHA)
7272 Greenville Ave.
Dallas, TX 75231
National Heart, Lung, and Blood Institute (NHLBI)
P.O. Box 30105
Bethesda, MD 20824-0105
American College of Cardiology
2400 N Street NW
Washington, DC 20037