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Causes

By Mayo Clinic staff

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Illustration showing a normal heartbeat Normal heartbeat

Tachycardia is caused by something that disrupts the normal electrical impulses that control the rhythm of your heart's pumping action. Many things can cause or contribute to problems with the heart's electrical system. These factors include:

  • Damage to heart tissues from heart disease
  • Abnormal electrical pathways in the heart present at birth (congenital)
  • Disease or congenital abnormality of the heart
  • High blood pressure
  • Smoking
  • Heavy alcohol consumption
  • Heavy caffeine consumption
  • Adverse reaction to medications
  • Abuse of recreational drugs, such as cocaine
  • Imbalance of electrolytes, mineral-related substances necessary for conducting electrical impulses
  • Overactive thyroid (hyperthyroidism)

In some cases, the exact cause of tachycardia can't be determined.

Electrical circuitry of the heart
Your heart is made up of four chambers — two upper chambers (atria) and two lower chambers (ventricles). The rhythm of your heart is normally controlled by a natural pacemaker — the sinus node — located in the right atrium. The sinus node produces electrical impulses that initiate each heartbeat.

From the sinus node, electrical impulses travel across the atria, causing the atria muscles to contract and pump blood into the ventricles. The electrical impulses then arrive at a cluster of cells called the atrioventricular node (AV node) — usually the only pathway for signals to travel from the atria to the ventricles.

The AV node slows down the electrical signal before sending it to the ventricles. This slight delay allows the ventricles to fill with blood. When electrical impulses reach the muscles of the ventricles, they contract, causing them to pump blood either to the lungs or to the rest of the body.

Types of tachycardias
Tachycardia occurs when a problem in electrical signals produces a heartbeat that is faster than normal. Common types of tachycardia include the following:

  • Atrial fibrillation is a rapid heart rate caused by chaotic electrical impulses in the atria. These signals result in rapid, uncoordinated, weak contractions of the atria. The chaotic electrical signals bombard the AV node, usually resulting in an irregular, rapid rhythm of the ventricles. Episodes of atrial fibrillation may last a few hours or several days. Some episodes won't end unless treated.

    Most people with atrial fibrillation have some structural abnormalities of the heart related to such conditions as heart disease or high blood pressure. Other factors that may contribute to atrial fibrillation include heart valve disorder, hyperthyroidism or heavy alcohol consumption.

  • Atrial flutter is a very fast, but regular rate of the atria caused by irregular circuitry within the atria. The fast rate results in weak contractions of the atria. The rapid signals entering the AV node cause a rapid and sometimes irregular ventricular rate. Episodes of atrial flutter may also last a few hours or several days, or the condition may persist unless treated.

    Various forms of heart disease can contribute to the onset of atrial flutter, and it is sometimes a complication of heart surgery. People who experience atrial flutters often experience atrial fibrillation as well.

  • Supraventricular tachycardias (SVTs), which originate somewhere above the ventricles, are caused by abnormal circuitry in the heart, usually present at birth, that creates a loop of overlapping signals. Episodes may last only a few seconds or several hours.

    In one form of SVT, an abnormality in the AV node may "split" an electrical signal into two, sending one signal to the ventricles and another back to the atria. Another common abnormality is the presence of an extra electrical pathway from the atria to the ventricles that bypasses the AV node. This may result in a signal going down one pathway and up the other. Wolff-Parkinson-White syndrome is the most common disorder featuring an extra pathway.

  • Ventricular tachycardia is a rapid rate that originates with abnormal electrical signals in the ventricles. The rapid beat doesn't allow the ventricles to fill and contract efficiently to pump enough blood to the body. Ventricular tachycardia is often a life-threatening medical emergency.

    Ventricular tachycardia is usually related to damage to the heart muscle from a previous heart attack or disease of the heart muscle (cardiomyopathy).

  • Ventricular fibrillation occurs when rapid, chaotic electrical impulses cause the ventricles to quiver ineffectively instead of pumping necessary blood to the body. This serious malfunction results in death if the heart isn't restored to a normal rhythm within minutes.

    Most people who experience ventricular fibrillation have an underlying heart disease or have experienced serious trauma, such as being struck by lightning.

Risk factors Symptoms
References
  1. Mitchell LB. Arrhythmias and conduction disorders: Introduction. The Merck Manuals: The Merck Manual for Healthcare Professionals. http://www.merck.com/mmpe/sec07/ch075/ch075a.html. Accessed April 19, 2009.
  2. Olgin JE, et al. Specific arrhythmias: Diagnosis and treatment. In: Libby P, et al., eds. Braunwald's Heart Disease: A Textbook of Cardiovascular Medicine. Philadelphia, Pa.: Saunders Elsevier; 2007. http://www.mdconsult.com/book/player/book.do?method=display&type=aboutPage&decorator=header&eid=4-u1.0-B978-1-4160-4106-1..X5001-8--TOP&isbn=978-1-4160-4106-1&uniq=134565520#lpState=open&lpTab=contentsTab&content=4-u1.0-B978-1-4160-4106-1..50038-8%3Bfrom%3Dtoc%3Btype%3DbookPage%3Bisbn%3D978-1-4160-4106-1. Accessed April 19, 2009.
  3. Ventricular tachycardia. American Heart Association. http://americanheart.org/print_presenter.jhtml?identifier=3062877. Accessed April 22, 2009.
  4. Atrial or supraventricular tachycardia. American Heart Association. http://www.americanheart.org/presenter.jhtml?identifier=3062868. Accessed April 18, 2009.
  5. Mitchell LB. Atrial fibrillation (AF). The Merck Manuals: The Merck Manual for Healthcare Professionals. http://www.merck.com/mmpe/sec07/ch075/ch075e.html. Accessed April 20, 2009.
  6. Mitchell LB. Ventricular tachycardia (VT). The Merck Manuals: The Merck Manual for Healthcare Professionals. http://www.merck.com/mmpe/sec07/ch075/ch075k.html. Accessed April 20, 2009.
  7. Mitchell LB. Reentrant supraventricular tachycardias (SVT, PSVT). The Merck Manuals: The Merck Manual for Healthcare Professionals. http://www.merck.com/mmpe/sec07/ch075/ch075g.html. Accessed April 20, 2009.
  8. Mitchell LB. Ventricular fibrillation. The Merck Manuals: The Merck Manual for Healthcare Professionals. http://www.merck.com/mmpe/sec07/ch075/ch075m.html. Accessed April 20, 2009.
  9. Hebbar AK, et al. Management of common arrhythmias: Part I. Supraventricular arrhythmias. American Family Physician. 2002;65:2479.
  10. Hebbar AK, et al. Management of common arrhythmias: Part II. Ventricular arrhythmias and arrhythmias in special populations. American Family Physician. 2002;65:2491.
  11. Mitchell LB. Atrial flutter. The Merck Manuals: The Merck Manual for Healthcare Professionals. http://www.merck.com/mmpe/sec07/ch075/ch075f.html. Accessed April 20, 2009.
  12. What are Holter, event and transtelephonic monitors? American Heart Association. http://www.americanheart.org/presenter.jhtml?identifier=3005149. Accessed Jan. 15, 2009.
  13. Calkins H. Supraventricular tachycardia: AV nodal reentry and Wolff-Parkinson-White syndrome. In: Fuster V, et al., eds. Hurst's The Heart. 12th ed. New York, N.Y.: McGraw-Hill; 2008. http://www.accessmedicine.com/content.aspx?aID=3050545. Accessed April 19, 2009.
  14. Prystowsky EN, et al. Approach to the patient with cardiac arrhythmias: Introduction. In: Fuster V, et al., eds. Hurst's The Heart. 12th ed. New York, N.Y.: McGraw-Hill; 2008. http://www.accessmedicine.com/content.aspx?aID=3048673. Accessed April 20, 2009.
  15. Delacretaz E. Supraventricular tachycardia. New England Journal of Medicine. 2006;354:1039.
  16. Prystowsky EN, et al. Atrial fibrillation, atrial flutter, and atrial tachycardia: Introduction. In: Fuster V, et al., eds. Hurst's The Heart. 12th ed. New York, N.Y.: McGraw-Hill; 2008. http://www.accessmedicine.com/content.aspx?aID=3048772. Accessed April 20, 2009.
  17. Grogan M (expert opinion). Mayo Clinic, Rochester, Minn. April 29, 2009.

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