Tachycardia

Tachycardia

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

Symptoms of tachycardia can include:

• Dizziness, lightheadedness and fainting
• Fatigue (an abnormally tired feeling)
• Palpitations (awareness of a rapid heartbeat)
• Breathlessness

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 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.

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

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.

Treatment

The treatment of tachycardia depends on its cause. For example:

• Fever. Fever-related tachycardia can be treated with fever-reducing medications, such as acetaminophen (Tylenol) or ibuprofen (Advil, Motrin and others). If the fever is caused by a bacterial infection, antibiotics also may be needed.
• Blood loss. To treat blood loss, the patient first is stabilized with fluids given intravenously (into a vein) or blood transfusions. Then, the source of the bleeding is found and stitched, or corrected with surgery.
• Hyperthyroidism. Hyperthyroidism can be treated with antithyroid medications such as methimazole (Tapazole, generic versions). Alternative treatments include radioactive iodine, which destroys the thyroid with radiation, or removing most of the thyroid gland with a surgical procedure called subtotal thyroidectomy.
• Cardiac arrhythmias. The treatment depends on the cause of the arrhythmia. In some people, massaging the carotid sinus in the neck will stop the problem. Other people require medications such as digitalis (Lanoxin), beta-blockers, calcium channel blockers, or amiodarone (Cordarone, Pacerone, generic versions). Some patients respond only to radiofrequency catheter ablation, a procedure that destroys the area of abnormal heart tissue that is triggering the tachycardia. Other patients can be treated with electrical cardioversion, a procedure that delivers a timed electrical shock to the heart to restore normal heart rhythm.
• Lung disease. If the tachycardia is caused by a blood clot in the lungs, the usual treatment is medications that dissolve the clot and keep more clots from forming. Pneumonia or other lung problems can be treated with medications for those conditions.