The heart normally beats at a rate of about 60 to 100 beats per minute at rest. A rate faster than 100 beats a minute in an adult is called tachycardia. Most people experience transient rapid heartbeats, called sinus tachycardia, as a normal response to excitement, anxiety, stress, or exercise. If tachycardia occurs at rest or without a logical cause, however, it is considered abnormal.
The two main types of tachycardia are abnormal supraventricular tachycardias (which originate in the upper chambers of the heart, the atria) and ventricular tachycardias (which originate in the lower chambers of the heart, the ventricles).
The most common forms of tachycardias are:
1. Paroxysmal supraventricular tachycardia, which generally has a rate of 140 to 200 beats per minute, develops spontaneously, and stops and starts suddenly, but may recur
2. Atrial flutter, in which the atria beat at 240 to 300 beats per minute, although the actual pulse rate is much slower, because not all of these impulses are translated into contractions of the ventricles
3. ventricular tachycardia, a very serious arrhythmia initiated in the ventricles, in which the heart rate is usually between 150 and 250
4. atrial fibrillation (see Health Profile on Atrial Fibrillation).Causes
Sinus tachycardias are most likely to occur in those who are easily excitable, suffer anxiety, or drink a lot of caffeine-containing beverages. They may also been seen in people with thyroid disease, with fevers, or with certain drugs (especially asthma and allergy medications).
The occurrence of tachycardias under any of these circumstances does not necessarily imply underlying heart disease.
More severe types of tachycardia tend to occur in those who have underlying heart disease. They may be caused by an electrical disturbance within the heart without an anatomic deformity, or by congenital defects, coronary artery disease, chronic disease of the heart valves, or chronic lung disease.
Tachycardias may also occur in the course of a heart attack (or myocardial infarction).Diagnosis
Your physician will take a complete medical history and perform a physical examination. Blood tests may be done. He or she may perform an electrocardiogram (EKG) or use a heart monitor to assess your heart's electrical activity.Treatment
Medical treatment depends on the cause and type of the tachycardia. Sinus tachycardias usually do not require treatment other than therapy for the underlying cause, if any. A supraventricular paroxysmal tachycardia may respond to certain simple maneuvers that your physician will explain to you. This may involve holding one's breath for a minute, bathing the face in cold water, or massaging the carotid artery in the neck. In other cases, medication may be prescribed to slow the heartbeat on a continual basis.
If tachycardia is severe, or arises from the ventricle, immediate injectable medication or electric shock (electroconversion) may be required to stimulate the heart to return to a normal rate. In rare, severe and resistant cases of ventricular tachycardias, a defibrillation device (AICD, similar to a pacemaker) may be implanted surgically to help maintain a normal heart rhythm.
In elderly people or those with underlying heart disease, it is important to treat tachycardias within a few hours, if at all possible, because a prolonged rapid rate may result in decreased heart function and complications.Questions
What tests need to be done to determine the cause of the tachycardia?
How serious is this?
What are the chances of having a heart attack?
What treatment will you be recommending?
Will any medication need to be prescribed? What are the side effects?