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Arrhythmias

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.

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:

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:

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.

References

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 www.ncbi.nlm.nih.gov/pubmed/22975230.

    • Arrhythmias

      Arrhythmias

      Animation

    •  

      Arrhythmias - Animation

      This animation shows the cardiac conduction system and the arrhythmias of a fast and slow beating heart.

    • Cardiac arrhythmia: Heart palpitations and other symptoms

      Cardiac arrhythmia: Heart palpitations and other symptoms

      Animation

    •  

      Cardiac arrhythmia: Heart palpitations and other symptoms - Animation

      A wide range of symptoms, including palpitations, dyspnea, syncope, fatigue, dizziness, chest pain, and lightheadedness can be produced by different types of cardiac arrhythmia.

    • Cardiac conduction system disorders - overview

      Cardiac conduction system disorders - overview

      Animation

    •  

      Cardiac conduction system disorders - overview - Animation

      A look at different types of cardiac accessory pathway problems including tachycardias and Wolff-Parkinson-White syndrome.

    • Heart, section through the middle

      Heart, section through the middle - illustration

      The interior of the heart is composed of valves, chambers, and associated vessels.

      Heart, section through the middle

      illustration

    • Heart, front view

      Heart, front view - illustration

      The external structures of the heart include the ventricles, atria, arteries and veins. Arteries carry blood away from the heart while veins carry blood into the heart. The vessels colored blue indicate the transport of blood with relatively low content of oxygen and high content of carbon dioxide. The vessels colored red indicate the transport of blood with relatively high content of oxygen and low content of carbon dioxide.

      Heart, front view

      illustration

    • Normal heart rhythm

      Normal heart rhythm - illustration

      An electrocardiogram (ECG) test measures the electrical activity of the heart. A normal resting heart rate is 60 to 100 beats per minute.

      Normal heart rhythm

      illustration

    • Bradycardia

      Bradycardia - illustration

      Bradycardia heart rhythms are characterized by a slowness of the heartbeat, usually at a rate under 60 beats per minute (normal resting rate is 60 to 100 beats per minute).

      Bradycardia

      illustration

    • Ventricular tachycardia

      Ventricular tachycardia - illustration

      Ventricular tachycardia is a rapid resting heart rate initiated within the ventricles, typically at 160 to 240 beats per minute (normal resting rate is 60 to 100 beats per minute).

      Ventricular tachycardia

      illustration

    • Atrioventricular block,  ECG tracing

      Atrioventricular block, ECG tracing - illustration

      This picture shows an ECG (electrocardiogram, EKG) of a person with an abnormal rhythm (arrhythmia) called an atrioventricular (AV) block. P waves show that the top of the heart received electrical activity. Each P wave is usually followed by the tall (QRS) waves. QRS waves reflect the electrical activity that causes the heart to contract. When a P wave is present and not followed by a QRS wave (and heart contraction), there is an atrioventricular block, and a very slow pulse (bradycardia).

      Atrioventricular block, ECG tracing

      illustration

    • Conduction system of the heart

      Conduction system of the heart - illustration

      The intrinsic conduction system sets the basic rhythm of the beating heart by generating impulses which stimulate the heart to contract.

      Conduction system of the heart

      illustration

    • Arrhythmias

      Animation

    •  

      Arrhythmias - Animation

      This animation shows the cardiac conduction system and the arrhythmias of a fast and slow beating heart.

    • Cardiac arrhythmia: Heart palpitations and other symptoms

      Animation

    •  

      Cardiac arrhythmia: Heart palpitations and other symptoms - Animation

      A wide range of symptoms, including palpitations, dyspnea, syncope, fatigue, dizziness, chest pain, and lightheadedness can be produced by different types of cardiac arrhythmia.

    • Cardiac conduction system disorders - overview

      Animation

    •  

      Cardiac conduction system disorders - overview - Animation

      A look at different types of cardiac accessory pathway problems including tachycardias and Wolff-Parkinson-White syndrome.

    • Heart, section through the middle

      Heart, section through the middle - illustration

      The interior of the heart is composed of valves, chambers, and associated vessels.

      Heart, section through the middle

      illustration

    • Heart, front view

      Heart, front view - illustration

      The external structures of the heart include the ventricles, atria, arteries and veins. Arteries carry blood away from the heart while veins carry blood into the heart. The vessels colored blue indicate the transport of blood with relatively low content of oxygen and high content of carbon dioxide. The vessels colored red indicate the transport of blood with relatively high content of oxygen and low content of carbon dioxide.

      Heart, front view

      illustration

    • Normal heart rhythm

      Normal heart rhythm - illustration

      An electrocardiogram (ECG) test measures the electrical activity of the heart. A normal resting heart rate is 60 to 100 beats per minute.

      Normal heart rhythm

      illustration

    • Bradycardia

      Bradycardia - illustration

      Bradycardia heart rhythms are characterized by a slowness of the heartbeat, usually at a rate under 60 beats per minute (normal resting rate is 60 to 100 beats per minute).

      Bradycardia

      illustration

    • Ventricular tachycardia

      Ventricular tachycardia - illustration

      Ventricular tachycardia is a rapid resting heart rate initiated within the ventricles, typically at 160 to 240 beats per minute (normal resting rate is 60 to 100 beats per minute).

      Ventricular tachycardia

      illustration

    • Atrioventricular block,  ECG tracing

      Atrioventricular block, ECG tracing - illustration

      This picture shows an ECG (electrocardiogram, EKG) of a person with an abnormal rhythm (arrhythmia) called an atrioventricular (AV) block. P waves show that the top of the heart received electrical activity. Each P wave is usually followed by the tall (QRS) waves. QRS waves reflect the electrical activity that causes the heart to contract. When a P wave is present and not followed by a QRS wave (and heart contraction), there is an atrioventricular block, and a very slow pulse (bradycardia).

      Atrioventricular block, ECG tracing

      illustration

    • Conduction system of the heart

      Conduction system of the heart - illustration

      The intrinsic conduction system sets the basic rhythm of the beating heart by generating impulses which stimulate the heart to contract.

      Conduction system of the heart

      illustration

    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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