Yasmine Ali, MD, is board-certified in cardiology. She is an assistant clinical professor of Medicine at Vanderbilt University School of Medicine and an award-winning physician writer.
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.
There are many causes, including changes to heart tissue (reduced blood flow, scarring), exertion or stress, blood imbalances (electrolytes, hormones), medications or supplements, or disorders in electrical signaling.1 It can be caused by genetic disorders, such as long QT syndrome or Brugada syndrome. Sometimes the cause is unknown.
Many arrhythmias cause no symptoms, so you may not even know you have one unless you get a heart screening. Arrhythmias can occur suddenly without warning, and symptoms can include palpitations, lightheadedness, syncope (fainting), and cardiac arrest.
Treatments vary and will depend on the type of arrhythmia. They may include antiarrhythmic drugs, pacemakers, implantable defibrillators, and ablation procedures. If someone goes into cardiac arrest, cardiopulmonary resuscitation (CPR) and use of an automated external defibrillator (AED), if available, improves the chances of survival and recovery outcomes.
Atrial fibrillation (AFib) is an arrhythmia caused by rapid and chaotic electrical impulses originating in the heart's atria (upper heart chambers). AFib is not typically life-threatening but can cause significant symptoms, including palpitations, shortness of breath, and fatigue, and can contribute to more serious conditions, such as stroke.
The heart generates its own electrical impulse (also called an electrical signal) to create heartbeats. Electrical impulses are produced by the sinus node, a small structure in the right atrium (upper chamber). The signal causes the atria to contract, moving blood to the ventricles (lower chambers), and moves to the atrioventricular (AV) node, triggering a contraction in the ventricles.
The number of times your heart beats per minute. Heart rate varies from person to person, but a resting heart rate may range from 60 to 100 beats per minute. Tachycardia is a resting heart rate of more than 100 beats per minute, and bradycardia is a resting heart rate below 60 (mostly considered a problem if it is accompanied by symptoms).
Ventricular fibrillation (VF) is an arrhythmia caused by chaotic electrical impulses in the heart’s ventricles (lower chambers). The ventricles quiver and can prevent the heart from effectively pumping blood throughout the body. Ventricular fibrillation can become a medical emergency that leads to sudden cardiac arrest and death within minutes.
National Heart, Lung, and Blood Institute. Arrhythmia. Updated September 1, 2011.
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
Cleveland Clinic. Pulse and heart rate. Updated November 18, 2018.
National Heart, Lung, and Blood Institute. Arrhythmia.