Tachycardia

What Is It?

Tachycardia is a heart rate of more than 100 beats per minute. In normal adults, the heart beats regularly 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 fever, rapid blood loss or strenuous exercise. It also can be caused by an abnormally high level of thyroid hormones, called hyperthyroidism, or by an adrenal gland tumor called pheochromocytoma. In some patients, 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. In other cases, tachycardia can be a side effect of some foods and drinks, including coffee, tea, alcohol and chocolate; tobacco; or medication, including epinephrine (used in various medications), ephedrine (used in various medications), aminophylline (Phyllocontin, Truphylline), atropine (used in various medications), digoxin (Lanoxin) and others.

Symptoms

Although tachycardia is a symptom in itself, it can occur with associated symptoms, such as:

• Dizziness, lightheadedness and (sometimes) fainting
• Fatigue (an abnormally tired feeling due to decreased cardiac output)
• Palpitations (awareness of a rapid heartbeat)
• Breathlessness

If tachycardia is caused by an underlying medical illness, there will be additional symptoms that are specific to that medical 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.

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, including any possible risk factors for tachycardia (coronary artery disease, heart valve abnormalities, heart valve disease resulting from rheumatic fever, thyroid disorders, medications, dietary factors). You also will be asked to describe your specific cardiac symptoms, including any possible triggers for those symptoms.

During the physical examination, your doctor will check your heart rate and rhythm, together with your pulses. This is because certain cardiac arrhythmias cause a mismatch of the pulse, which reflects the activity of the ventricles, and the heart sounds. Your doctor also will check for an enlarged heart, for heart murmurs (one sign of a heart-valve problem) and for physical signs of thyroid abnormalities (enlarged thyroid gland, tremors, muscle wasting, and an abnormal protrusion of the eyes).