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Abnormal heart rhythms; Bradycardia; Tachycardia; Fibrillation

An arrhythmia is a disorder of the heart rate (pulse) or heart rhythm. The heart can beat too fast (tachycardia), too slow (bradycardia), or irregularly.

An arrhythmia can be harmless, a sign of other heart problems, or an immediate danger to your health.

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  • Causes

    Normally, your heart works as a pump that brings blood to the lungs and the rest of the body.

    To help this happen, your heart has an electrical system that makes sure it contracts (squeezes) in an orderly way.

    • The electrical impulse that signals your heart to contract begins in an area of the heart called the sinoatrial node (also called the sinus node or SA node). This is your heart's natural pacemaker.
    • The signal leaves the SA node and travels through the heart along a set electrical pathway.
    • Different nerve messages signal your heart to beat slower or faster.

    Arrhythmias are caused by problems with the heart's electrical conduction system.

    • Abnormal (extra) signals may occur.
    • Electrical signals may be blocked or slowed.
    • Electrical signals travel in new or different pathways through the heart.

    Some common causes of abnormal heartbeats are:

    • Abnormal levels of potassium or other substances in the body
    • Heart attack, or a damaged heart muscle from a past heart attack
    • Heart disease that is present at birth (congenital)
    • Heart failure or an enlarged heart
    • Overactive thyroid gland


    Arrhythmias may also be caused by some substances or drugs, including:

    • Alcohol, caffeine, or stimulant drugs
    • Heart or blood pressure medicines
    • Cigarette smoking (nicotine)
    • Drugs that mimic the activity of your nervous system
    • Medicines used for depression or psychosis

    Sometimes medicines used to treat one type of arrhythmia will cause another type of abnormal heart rhythm.

    Some of the more common abnormal heart rhythms are:

    • Atrial fibrillation or flutter
    • Atrioventricular nodal reentry tachycardia (AVNRT)
    • Heart block or atrioventricular block
    • Multifocal atrial tachycardia
    • Paroxysmal supraventricular tachycardia
    • Sick sinus syndrome
    • Ventricular fibrillation or ventricular tachycardia
    • Wolff-Parkinson-White syndrome
  • Symptoms

    When you have an arrhythmia, your heartbeat may be:

    • Too slow (bradycardia)
    • Too quick (tachycardia)
    • Irregular, uneven, or skipping beats

    An arrhythmia may be present all of the time or it may come and go. You may or may not feel symptoms when the arrhythmia is present. Or, you may only notice symptoms when you are more active.

    Symptoms can be very mild, or they may be severe or even life threatening.

    Common symptoms that may occur when the arrhythmia is present include:

    • Chest pain
    • Fainting
    • Lightheadedness, dizziness
    • Paleness
    • Palpitations (feeling your heart beat fast or irregularly)
    • Shortness of breath
    • Sweating
  • Exams and Tests

    The health care provider will listen to your heart with a stethoscope and feel your pulse. Your blood pressure may be low or normal.

    An ECG will be the first test done.

    Heart monitoring devices are often used to identify the rhythm problem, such as a:

    • Holter monitor (where you wear a device that records and stores your heart rhythm for 24 hours)
    • Event monitor or loop recorder (worn for 2 weeks or longer, where you record your heart rhythm when you feel an abnormal rhythm)

    An echocardiogram is often ordered to examine the size or structure of your heart.

    Coronary angiography to see how blood flows through the arteries in your heart.

    A special test, called an electrophysiology study (EPS), is done to take a closer look at the heart's electrical system.

  • Treatment

    When an arrhythmia is serious, you may need urgent treatment to restore a normal rhythm. This may include:

    • Electrical "shock" therapy (defibrillation or cardioversion)
    • Implanting a short-term heart pacemaker
    • Medicines given through a vein or by mouth

    Sometimes, better treatment for your angina or heart failure will lower your chance of having an arrhythmia.

    Medicines called anti-arrhythmic drugs may be used:

    • To prevent an arrhythmia from happening again
    • To keep your heart rate from becoming too fast or too slow

    Some of these medicines can have side effects. Take them as prescribed by your provider. DO NOT stop taking the medicine or change the dose without first talking to your provider.

    Other treatments to prevent or treat abnormal heart rhythms include:

    • Cardiac ablation, used to destroy areas in your heart that may be causing your heart rhythm problems
    • An implantable cardiac defibrillator, placed in people who are at high risk of sudden cardiac death
    • Permanent pacemaker, a device that senses when your heart is beating irregularly, too slowly, or too fast. It sends a signal to your heart that makes your heart beat at the correct pace.
  • Outlook (Prognosis)

    The outcome depends on several factors:

    • The kind of arrhythmia you have. (Some abnormal heart rhythms may be life threatening if not treated right away, or DO NOT respond well to treatment.)
    • Whether you have coronary artery disease, heart failure, or valvular heart disease.
  • When to Contact a Medical Professional

    Call your provider if:

    • You develop any of the symptoms of a possible arrhythmia.
    • You have been diagnosed with an arrhythmia and your symptoms worsen or DO NOT improve with treatment.
  • Prevention

    Taking steps to prevent coronary artery disease may reduce your chance of developing an arrhythmia.


Related Information

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Olgin JE. Approach to the patient with suspected arrhythmia. In: Goldman L, Schafer AI, eds. Goldman's Cecil Medicine. 25th ed. Philadelphia, PA: Elsevier Saunders; 2016:chap 62.

Rubart M, Zipes DP. Genesis of cardiac arrhythmias, electrophysiologic considerations. In: Bonow RO, Mann DL, Zipes DP, Libby P, Braunwald E, eds. Braunwald's Heart Disease: A Textbook of Cardiovascular Medicine. 10th ed. Philadelphia, PA: Elsevier Saunders; 2015:chap 33.

Tracy CM, Epstein AE, Darbar D, et al. 2012 ACCF/AHA/HRS focused update of the 2008 guidelines for device-based therapy of cardiac rhythm abnormalities: a report of the American College of Cardiology Foundation/American Heart Association Task Force on Practice Guidelines. J Am Coll Cardiol. 2012;60(14):1297-1313. PMID: 22975230



Review Date: 5/5/2016  

Reviewed By: Michael A. Chen, MD, PhD, Associate Professor of Medicine, Division of Cardiology, Harborview Medical Center, University of Washington Medical School, Seattle, WA. Also reviewed by David Zieve, MD, MHA, Isla Ogilvie, PhD, and the A.D.A.M. Editorial team.

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