What Is It?
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), coronary artery disease or an abnormality of a heart valve. 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
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.
Diagnosis
Your doctor will ask about your family history of heart disease and cardiac arrhythmias. He or she also will review your personal medical history, and will ask whether you have any of the conditions that can lead to tachycardia, including coronary artery disease, heart valve abnormalities, heart valve disease resulting from rheumatic fever, lung disease, thyroid disorders, medications and dietary factors. You also will be asked to describe your symptoms.
During the physical examination, your doctor will check your heart rate and rhythm, together with your pulses. In tachycardia, your pulse may not match the heart sounds your doctor hears through a stethoscope. 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, tremors, muscle wasting 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, including blood tests to measure levels of thyroid hormones, an echocardiogram to check for heart valve abnormalities, a coronary angiogram to check for coronary artery disease, and other tests. 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.
Expected Duration
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.
Prevention
Tachycardia caused by coronary artery disease can be prevented by taking these actions to modify cardiac risk factors:
Tachycardia that occurs as a side effect of medication can be prevented by reducing the dose or changing medications. In general, people who are prone to tachycardia should avoid or limit their consumption of caffeinated beverages, chocolate and alcohol.
Not all episodes of tachycardia can be prevented.
Treatment
The treatment of tachycardia depends on its cause:
When To Call a Professional
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.
Prognosis
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.
Additional Info
American Heart Association (AHA)
7272 Greenville Ave.
Dallas, TX 75231
Toll-Free: 1-800-242-8721
http://www.americanheart.org/
National Heart, Lung, and Blood Institute (NHLBI)
P.O. Box 30105
Bethesda, MD 20824-0105
Phone: 301-592-8573
TTY: 240-629-3255
Fax: 301-592-8563
http://www.nhlbi.nih.gov/
American College of Cardiology
Heart House
2400 N Street NW
Washington, DC 20037
Phone: 202-375-6000
Fax: 202-375-7000
http://www.acc.org/
