Automatic Tachycardias

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Rapid cardiac arrhythmias, or tachycardias, can be caused by two major types of electrical disturbances in the heart. These are the reentrant tachycardias, and the automatic tachycardias. Both types can lead serious problems, potentially including syncope (loss of consciousness), and even sudden death.

“Automatic tachycardias” are caused by the spontaneous generation of abnormal electrical impulses from somewhere in the heart. You can think of these automatic tachycardias as being produced by an “irritable focus” at some location within the heart muscle. This irritable focus rapidly fires off electrical impulses, causing the heart to beat too rapidly.

Causes of Automatic Tachycardias

The word tachycardia simply means a heart rate of greater than 100 beats per minute. Because sometimes it is a good thing to have a heart rate above 100, not all tachycardias are bad or abnormal.

There are three general causes of tachycardia:

  • Normal tachycardia (or sinus tachycardia) is a normal phenomenon most of us experience each day. It occurs because the sinus node speeds up the rate at which it generates electrical impulses in response to exertion or stress.
  • Reentrant tachycardia is a cardiac arrhythmia caused by an abnormal electrical connection somewhere in the heart that creates a potential circuit. The tachycardia occurs when an electrical impulse becomes “trapped” within this circuit, and begins spinning off heart beats at a rapid rate. Reentrant tachycardias characteristically start and stop very suddenly and for no apparent reason, and most they often occur in people who are otherwise completely healthy.
  • Automatic tachycardias do not involve an abnormal electrical circuit. Instead they are caused by the spontaneous, abnormal generation of electrical impulses from some location in the heart. These arrhythmias are often seen in people who are medically unstable.

Characteristics of Automatic Tachycardia

With automatic tachycardias, an abnormal focus of cardiac cells begin producing their own electrical impulses faster than the sinus node does, thus taking over the rhythm of the heart and producing tachycardia.

Automatic tachycardias can be either supraventricular (so-called “automatic atrial tachycardia,” which means that the cells that are "automatically" firing are be located within the atria), or ventricular(“automatic ventricular tachycardia,” in which the abnormal electrical impulses are coming from the ventricles). As with reentrant tachycardia, the ventricular form of automatic tachycardia is by far the more dangerous type.

In addition, automatic junctional tachycardia can occur when the abnormal impulses arise near the AV node, which is near the "junction" of the atria and the ventricles).

There is even a type of automatic tachycardia that originates in the sinus node itself, called inappropriate sinus tachycardia, or IST.

In stark contrast to the reentrant tachycardias, automatic tachycardias are most commonly seen in people who are acutely ill. This is because various types of acute illness may create the conditions necessary for cardiac to produce abnormal electrical impulses.

In particular, automatic arrhythmias tend to occur in people who have acute lung disease (such as pulmonary embolus or pneumonia), acute myocardial infarction (heart attacks), or in people who have various severe abnormalities in their metabolic condition — such as low blood oxygen levels, low potassium or magnesium blood levels, or very high levels of adrenalin.

As a result, automatic tachycardias are most commonly seen in particularly unstable patients in the hospital setting, especially in people who are sick enough to be in intensive care units.

There are exceptions to this common pattern, however. IST, for instance, occurs in younger people who are otherwise entirely healthy.

Also, a rare condition called automatic atrial tachycardia (also called “ectopic atrial tachycardia”) is also seen in young, healthy people. Unlike reentrant atrial tachycardia, automatic atrial tachycardia tends to be persistent instead of intermittent, and can lead to tachycardia-induced heart failure. Persistent automatic atrial tachycardia is usually treated with ablation therapy.

Treatment of Automatic Tachycardia

In general, the most effective treatment for automatic tachycardia is to identify and reverse the underlying medical problem, as rapidly as possible. Once the underlying lung condition, cardiac condition, or metabolic abnormalities are stabilized, the arrhythmia virtually always goes away. So in nearly all cases, the treatment for automatic tachycardias is to rapidly stabilize the medical disorder that is producing it.

Usually, when a person who has had an automatic tachycardia has become healthy enough to leave the hospital, the arrhythmia has already resolved. There is generally no reason to consider using chronic antiarrhythmic drugs, or other long-term therapy aimed at treating cardiac arrhythmias. Preventing any further arrhythmias is a matter of taking whatever steps are possible to prevent a recurrence of the medical problem that caused the arrhythmia in the first place.

A Word From Verywell

Automatic tachycardias are caused by the spontaneous generation of electrical impulses from somewhere in the heart. They can be thought of as a cardiac arrhythmia due to an “irritation” of cardiac cells, usually as the result of an acute, severe medical condition. In general, these arrhythmias go away when the underlying medical condition is successfully treated, and no long-term antiarrhythmic therapy is required.

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Article Sources

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