What is an arrhythmia?
An arrhythmia is an abnormality in the timing or pattern of the heartbeat. When you have an arrhythmia, your heart may beat too quickly or too slowly, or you may experience an irregular rhythm in which your heart feels as if it is "skipping a beat."
Some types of arrhythmia may not be serious. Other types may be of great concern because they can cause fainting, heart failure or even sudden death. If you think you have an arrhythmia, consult your doctor.
How does a normal heart rhythm work?
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The heart is a four-chambered muscle that pumps blood, which carries oxygen and nutrients, throughout the body. The two upper chambers of the heart, the right and left atria (plural of atrium), receive and collect the blood. The lower chambers, the right and left ventricles, pump the blood to other parts of the body.
In the same beat, the left atrium receives oxygen-rich blood from the lungs and pushes it to the left ventricle. The left ventricle pumps it through a large artery, called the aorta, to the rest of the body.
Heart Rhythms Depend on Electricity
The heart uses muscle contractions to pump blood through the body. A small burst of electricity causes the muscle to contract.
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In normal heart function, an electrical impulse starts in the upper right chamber of the heart in the sinus node (sinoatrial node), often thought of as the heart’s natural pacemaker. The sinus node is a group of specialized cells capable of generating a momentary electrical current. The current spreads through the atria (upper chambers), causing them to contract and squeeze blood into the ventricles (lower chambers).
The electrical signal then travels to the atrioventricular (AV) node, located between the atria and the ventricles. The AV node delays the signal for a fraction of a second. This delay allows the ventricles time to fill completely with blood.
Once the ventricles are filled, the electrical impulse travels rapidly through the bundle of His, a network of specialized fibers. The bundle of His splits into the right and left bundle branches, which conduct the electrical impulse into the right and left ventricles. With that burst of electricity, the ventricles contract and pump blood out to the body.
Normally, the heart’s electrical system triggers the resting heart to beat in this precise sequence 60 to 100 times each minute. This is referred to as normal sinus rhythm. With exercise, the heart rate will increase to above 100 times per minute. A person’s peak heart rate can be calculated by subtracting their age from 220. For example, the peak heart rate for a 40 year old is 220 - 40 = 180.
What are the symptoms of arrhythmia?
Cardiac arrhythmias may cause a wide variety of symptoms, such as:
- Palpitations: a racing, skipping or fluttering sensation in your chest
- Dizziness or light-headedness
- Low blood pressure
- Chest pain
- Shortness of breath
- Heart failure: heart can’t pump enough oxygenated blood through the body
- Cardiac arrest: heart stops beating
- Difficulty feeding (in infants)
Sometimes arrhythmias are silent, meaning they cause no obvious symptoms. A doctor can detect an irregular heartbeat during a physical exam by taking your pulse, listening to your heart or by performing diagnostic tests.
When should I call an ambulance?
- If someone experiences severe chest pain, shortness of breath, prolonged palpitations or racing heart
- If someone loses consciousness. You may need to perform cardiopulmonary resuscitation (CPR) if the heartbeat or breathing has stopped
What are the different types of arrhythmias?
: heartbeat that is out of rhythm. Occurs when the electrical signal does not originate from the sinus node
Supraventricular tachycardia — rapid heartbeat involving the atria (upper chambers of the heart). There are several types of supraventricular tachycardia:
- Atrial fibrillation: ineffective contractions of the atria caused by rapid, irregular signals from multiple sites in the upper half of the heart
- Atrial tachycardia: rapid beating of the atria, much faster than the ventricles, due to a "short circuit" in the upper half of the heart
- Atrial flutter: extremely rapid beating of the atria (between 240 and 340 times per minute) due to a "short circuit" in the upper half of the heart
- Paroxysmal supraventricular tachycardia (PSVT): rapid heartbeat caused by a "short circuit" resulting from an extra electrical pathway in the heart
: rapid, inefficient contractions of the ventricles
: slow heartbeat due to a failing sinus node or a blockage in the electrical circuit
What causes arrhythmia?
Arrhythmias have many different causes. Here are some examples:
Congenital abnormality of the heart’s electrical system: For example, some patients are born with an abnormal muscle fiber connecting the upper and lower chambers of the heart. The presence of this extra fiber can lead to paroxysmal supraventricular tachycardia (PSVT) later in life.
Inherited heart disease that causes abnormalities over time, setting the stage for an arrhythmia. One example is arrhythmogenic right ventricular dysplasia (ARVD): Patients with this inherited condition are born with normal hearts. But over time the heart muscle is replaced by fat and scar tissue, which can cause arrhythmias.
Acquired conditions: A heart attack, for example, can cause part of the heart muscle to turn to scar. Scar tissue may be the site of a "short circuit" and set the stage for ventricular tachycardia.
Changes over time: The heart may change as years pass, eventually developing an arrhythmia. The best example is atrial fibrillation, which is rare before age 50 but increases dramatically afterward. By the age of 80, one person in 10 has atrial fibrillation.
How are arrhythmias diagnosed?
Some diagnostic tests take place on site in a doctor’s office or hospital. Other tests provide monitoring at home as you follow your daily routine. Click each method to learn more.
On-Site Diagnostic Tests
(ECG or EKG): wires taped to various parts of your body to create a graph of your heart’s electrical rhythm
Exercise stress test
: ECG recorded while strenuously exercising
or transesophageal echocardiogram: ultrasound of the heart
Magnetic resonance imaging
(MRI): imaging of the heart that does not involve radiation and can diagnose certain rare heart conditions
(CT): high-resolution X-rays; can be performed extremely quickly (ultrafast CT scans), which results in very low radiation exposure
Tilt table test
: measurement of heart rate and blood pressure in response to upright tilt, which simulates prolonged standing; used to diagnose syncope (fainting)
(EP): test that examines the heart’s electrical activity from the inside; used to diagnose many heart rhythm disorders and performed prior to catheter ablation
In-Home Diagnostic Monitors
: a portable ECG you wear continuously from one to seven days to record your heart rhythms over time
: a portable ECG you wear for one or two months, which records only when triggered by an abnormal heart rhythm or when you manually activate it
: a tiny event monitor with a battery life of several years, inserted under your skin to record very occasional events
How are arrhythmias treated?
Treatment decisions are based on a thorough analysis of your condition, medical history, lifestyle and other factors. Click each treatment to learn more.
- Catheter ablation: procedure to cauterize the specific heart cells that cause abnormal heart rhythms
- Cardioversion: procedure delivering a precisely controlled shock to your heart to “reset” an atrial fibrillation or atrial flutter; performed under anesthesia
- Your doctor may recommend medications based on your type of arrhythmia, medical history and current medications and medical conditions
- Implanted devices
- Pacemakers: inserted under the skin below the collarbone, pacemakers deliver regular electrical pulses through thin, highly durable wires attached to the heart. Pacemakers are used to treat bradycardia, heart block and some types of heart failure
- Implantable cardioverter defibrillators (ICDs): a small implanted device that delivers an electrical pulse to the heart to reset a dangerously irregular heartbeat. Often used to treat ventricular tachycardia or heart failure
- Cardiac resynchronization therapy (CRT): a pacemaker or ICD used to treat certain types of heart failure that are caused by dyssynchronous contractions (when the chambers of heart beat out of time with each other)
- Lifestyle changes
- Controlling hypertension
- Losing weight
- Limiting alcohol
- Treating sleep apnea
To learn more, visit the Johns Hopkins Electrophysiology and Arrhythmia Service.