A heart

Cardiac Arrhythmias

Also known as abnormal heart rhythm or dysrhythmia

A cardiac arrhythmia is when your heartbeat is too fast (tachycardia), too slow (bradycardia), or beats in an irregular rhythm due to a disruption of your heart’s normal electrical system

The severity of arrhythmias can vary tremendously. Many arrhythmias are benign and inconsequential, such as premature atrial complexes (PACs) that can cause an extra beat and brief palpitations. Others are extremely dangerous and life-threatening, such as ventricular tachycardia (a sudden, rapid, potentially very dangerous cardiac arrhythmia ) that can cause sudden cardiac arrest

A diagnosis of an arrhythmia generally requires capturing it on an electrocardiogram (ECG) (where electrodes record heart activity) or echocardiogram (an ultrasound of the heart), and a physical exam, and complete medical history.

    Frequently Asked Questions

    Key Terms

    Electrocardiography
    Diagnosing and Treating Inappropriate Sinus Tachycardia
    Woman with fingers pressed on temples, eyes closed
    A Condition That Causes Fainting in Young People
    Nurse Adjusts the ECG Pads on a Male Hospital Patient's Chest
    Heart Palpitations Causes and Treatments
    doctor and patient
    What You Should Know About Brugada Syndrome
    men doing cpr on another man
    Common Causes of Sudden Cardiac Arrest
    Midsection Of Man Resuscitating Friend Lying On Road
    Cardiac Arrest: How to Tell If Someone Needs CPR
    Implantable defribillator
    What Is the Risk of Having an Implantable Defibrillator?
    young athlete hurdling
    Exercise Recommendations for Myocarditis
    man running
    Exercise Recommendations for People With Long QT Syndrome (LQTS)
    defibrillator paddles
    What Are Premature Ventricular Complexes?
    Doctor showing medical chart to patient in hospital room
    Treating Premature Ventricular Complexes
    explaining heart problem
    Why Left Bundle Branch Block Is Important
    Elderly man speaking to a nurse
    The Important Difference Between a Heart Attack and a Cardiac Arrest
    Heart Patient
    Bradycardia: When Is a Slow Heart Rate a Problem?
    Heart rhythm on a monitor
    Discover the Causes and Treatment of Premature Atrial Complexes (PACs)
    cardiac anatomy showing the electrical system of the heart
    How the Heart's Electrical System Works
    sinus rhythm illustration
    Sick Sinus Syndrome: Causes, Symptoms, and Treatment
    An image of a pacemaker
    When Is a Pacemaker Needed for Heart Block?
    Doctor analyzes the electrocardiogram results, close-up. Diagnosis of arrhythmia, heart rate and heart disease
    Sinus Nodal Reentrant Tachycardia (SNRT) Symptoms and Treatment
    Woman with heart palpitations
    Atrioventricular Nodal Reentrant Tachycardia (AVNRT) Overview
    ECG
    Wolff-Parkinson-White Syndrome (WPW)
    intensive care
    Automatic Tachycardias and the Heart's Electrical Impulses
    Woman clutching her chest
    Ivabradine Can Treat IST and Other Dysautonomia Syndromes
    ekg monitor defibrillator
    The Difference Between V-Fib and Cardiac Arrest
    Woman walking in snow and coughing
    What Is Amiodarone Lung Toxicity?
    normal sinus rhythm
    What to Know About Normal Sinus Rhythm
    athlete and blood vessels
    Exercise Recommendations for Young Athletes with Marfan Syndrome
    Medical experts are studying the ECG recording
    The Strange History of Amiodarone
    bundle branch block
    What Bundle Branch Block Looks Like on an ECG
    Tired jogger
    Long QT Syndrome Causes, Symptoms, and Treatment
    African man holding daily pill box with pills
    Side Effects You Should Watch for When Taking Amiodarone
    Senior woman assisted by doctor
    Atrioventricular Reentrant Tachycardia (AVRT) - What You Should Know
    Doctor using digital tablet to talk to senior man
    Why Right Bundle Branch Block Is Important
    Woman with shortness of breath
    Understanding SVT and Your Heart Rate
    Woman holding medicine bottle, close-up
    Medications Used to Treat Cardiac Arrhythmias
    Doctor performing heart checkup
    How Cardiac Arrhythmias Are Treated
    young athletes playing soccer
    Exercise Recommendations for People With Hypertrophic Cardiomyopathy
    Woman with shortness of breath
    When a Fast Heartbeat Needs Treatment
    Surgeon holding defibrillator
    Discover How the Implantable Defibrillator Can Affect Your Lifestyle
    football huddle
    What Causes Sudden Death in Young Athletes
    Elderly man taking a medicine with a cup of water
    The 4 Main Types of Drugs That Treat Cardiac Arrhythmias
    Preventing Sudden Death With an Implantable Defibrillator
    A newborn baby sleeps in an infant incubator.
    What Is Timothy Syndrome?
    Doctor showing patient ECG results on a tablet
    What Are the Symptoms and Treatment of Atrial Flutter?
    SVT
    Treatment Can Vary Among the Various Types of SVT
    Midsection Of Doctor Examining Male Patient With Stethoscope
    How Cardiac Arrhythmias Are Diagnosed
    echocardiogram and ECG
    ARVC: A Cause of Sudden Death in Young Athletes
    ecg
    Overview of the Atrioventricular Node (AV Node)
    Page Sources
    Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
    1. National Heart, Lung, and Blood Institute. Arrhythmia. Updated September 1, 2011.

    2. Pollack Ross A., Brown Siobhan P., Rea Thomas, et al. Impact of bystander automated external defibrillator use on survival and functional outcomes in shockable observed public cardiac arrests. Circulation. 2018;137(20):2104-2113. doi:10.1161/CIRCULATIONAHA.117.030700

    3. Cleveland Clinic. Pulse and heart rate. Updated November 18, 2018.

    Additional Reading
    • National Heart, Lung, and Blood Institute. Arrhythmia.