Facts and definition of arrhythmias (heart rhythm disorders)
The four types of arrhythmias are premature beats, supraventricular, ventricular, and bradyarrhythmias.
- A heart rhythm disorder is an abnormal variation from the normal heartbeat. Heart rhythm disorders involve abnormalities of one or more of the following: heart rate, regularity of beats, sites where electrical impulses originate, or sequence of activation of heartbeats. Heart rhythm disorder is also referred to as an arrhythmia.
- The primary function of the heart is to supply blood and nutrients to the body. The regular beating, or contraction, of the heart, moves the blood throughout the body. Each heartbeat is controlled by electrical impulses traveling through the heart. In the normal heart, these electrical impulses occur in regular intervals. When something goes wrong with the heart's electrical system, the heart does not beat regularly. The irregular beating results in a heart rhythm disorder, or arrhythmia.
- The electrical system regulating heartbeat consists of two main areas of control that are connected to a series of conducting pathways, similar to the electrical wiring in a house.
- The sinoatrial, or SA, node is located in the right atrium. It provides the main control and is the source of each beat. The SA node also keeps up with the body's overall need for blood and increases the heart rate when necessary, such as during exercise, emotional excitement, or illness such as fever. The SA node is sometimes called the "natural pacemaker" of the heart.
- Electrical impulses leave the SA node and travel through special conducting pathways in the heart to the other controller, the atrioventricular, or AV, node. The purpose of the AV node is to provide a pathway for impulses from the atria to the ventricles. It also creates a delay in conduction from the atria to the ventricle. This causes the atria to contract first and allow the ventricles to fill with blood before they contract themselves.
- The delay ensures proper timing so that the lower chambers of the heart (ventricles) have time to fill before they contract.
- Normally, the heart beats about 60 to 100 times a minute. This state is called "normal sinus rhythm" or "normal rhythm" or "normal heartbeat." Depending upon the needs of the body, it may beat faster (sinus tachycardia) due to stress or slower (sinus bradycardia) such as during sleep.
What is an arrhythmia (heart rhythm disorder)?
Arrhythmias are abnormalities of the heartbeat. There are many types of arrhythmias, and they are classified by some
researchers and doctors by where they begin in the heart (the atria, AV node, or the ventricles). Others classify arrhythmias as one of four types -- premature beats, supraventricular, ventricular, and bradyarrhythmias. Generally speaking, those that do not originate from the ventricles are called supraventricular arrhythmias while those that come from the ventricles are called ventricular arrhythmias. The arrhythmias that can often lead to death in minutes are ventricular fibrillation and ventricular tachycardia. Although others may also cause death, these two arrhythmias can quickly and severely alter the heart's ability to effectively pump blood. Immediate electrocardioversion to put the heart back into a more effective rhythm that allows the heart to pump blood effectively can be life-saving.
What are the more common types of arrhythmias (heart rhythm disorders)?
The following are some of the more commonly encountered arrhythmias, starting with the supraventricular arrhythmias.
- Premature atrial contractions, sometimes called PAC or APC, or premature supraventricular contractions: This happens when another part of the atria sends an electrical impulse soon after the previous beat, causing the heart to contract earlier than expected. This arrhythmia is a very common occurrence in all ages and usually is not serious.
- Supraventricular tachycardia, or paroxysmal SVT or PSVT: SVT occurs when any structure above the ventricle (usually the atria or the AV node) produces a regular, rapid electrical impulse resulting in a rapid heartbeat.
- Sick sinus syndrome: Irregular electrical impulses generated by the SA node cause a slower-than-normal heart rate (sometimes alternating with rapid heart rates if the electrical impulses switch to a high rate).
- Wolff-Parkinson-White (WPW) syndrome: This is an arrhythmia people are born with because they have extra electrical pathways leading from the atrium to the ventricle that can cause tachycardia and particular types of rapid arrhythmias.
- Atrial fibrillation: This is a common condition caused by electrical impulses discharged at a rapid rate from many different areas of the atria. It usually causes a fast and irregular heartbeat.
- Atrial flutter: This condition is caused by a rapid discharge from a single place in the right atrium. Typically, the right atrium produces electrical impulses at a rate of 300 beats per minute, but only every other beat is conducted through the AV node, meaning that the ventricular rate is classically about 150 beats per minute.
What are the types of arrhythmias (heart rhythm disorders) in people with serious heart disease?
Arrhythmias arising in the ventricle (ventricular arrhythmias) are more likely to be found in people with more serious heart disease but may also be found in healthy individuals.
- Premature ventricular complex or PVC: This electrical impulse starts in the ventricle causing the heart to beat earlier than expected. Usually, the heart returns to its normal rhythm right away.
- Ventricular tachycardia: Fast and usually regular impulses come from the ventricles and cause a very rapid heart rate. This is usually a life-threatening tachycardia and needs immediate medical attention, possibly electrical shock or defibrillation that can stop or override these impulses.
- Ventricular fibrillation: Electrical impulses arise from the ventricles in a fast and disordered sequence. The resulting uncoordinated contractions cause the heart to quiver (appearing like a bag of worms) and lose the ability to beat and pump blood, leading to immediate cardiac arrest; electrical shock therapy may be life-saving.
What are other types of arrhythmias (heart rhythm disorders)?
Bradyarrhythmias produce heart rates that are too slow to allow enough blood to be pumped during either time of demand (stress or increased activity) or even during normal activity. Bradyarrhythmias are usually slower than 60 beats per minute. For example,
the person may become dizzy and pass out when they try to stand up because not enough blood is pumped into the brain.
Arrhythmias can be frightening, but in many cases, especially in younger
people with normal underlying arrhythmias, they are not life-threatening and can be effectively treated with medications.
- Supraventricular arrhythmias are very common in middle-aged and elderly adults. The older a person becomes, the more likely they are to experience an arrhythmia, especially atrial fibrillation.
- Many supraventricular arrhythmias are temporary and not serious, especially if no underlying heart disease is present. These arrhythmias can be a response to normal activities or emotions.
- Even if an arrhythmia has a serious underlying cause, the arrhythmia itself may not be dangerous. The underlying problem can often be treated effectively.
The purpose of this article is to give the reader an introduction to
arrhythmias. Each disorder or arrhythmia has been studied in great detail by many investigators so there are books and articles devoted to each type of arrhythmia. The reader is advised to click onto the references for more detail on each type of arrhythmia for more in depth details about diagnosis, treatments, and outcomes. Specific details for each type and subtype of disorder are far beyond the scope of this introductory article.
Heart Disease: Causes of a Heart Attack
What are the signs and symptoms of arrhythmias (heart rhythm disorders)?
Many arrhythmias cause no or minimal symptoms. Other people, however, can actually feel the arrhythmia when it happens.
Common symptoms include the following:
- Palpitations, feeling "skipped beats"
- Thumping or fluttering in the chest
- Sensation of the heart racing
In addition, some can experience symptoms that are more generalized, including the following:
- Feeling faint or tired
- Light-headedness or passing out (syncope)
- Shortness of breath
- Chest pain or discomfort
On the other hand, people may feel many of the sensations described above and have no arrhythmias whatsoever. These symptoms may be due to anxiety, stress, or other causes besides an abnormal heartbeat.
What causes arrhythmias (heart rhythm disorders)?
Among individuals without known heart disease, arrhythmias are generally random, isolated occurrences that do not carry any significance. However, an evaluation by a physician is advised if a person notices any unusual or abnormal heart beats, especially if they reoccur or are sustained.
A variety of heart diseases cause arrhythmias. Heart disease can refer to patients with coronary artery disease, heart valve problems, heart failure, or disorders with heart conduction, or high blood pressure. Remember, however, that having an arrhythmia does not necessarily mean that a person has heart disease. Arrhythmias have many causes; sometimes the cause of an arrhythmia is never determined, other times the cause may be easy to determine and treat.
Sometimes, conditions other than heart disease may cause or aggravate arrhythmias. These conditions include the following:
- Infection or fever
- Physical or emotional stress
- Diseases such as anemia or thyroid disease
- Drugs and other stimulants, such as caffeine, tobacco, alcohol, cocaine, amphetamines, and certain over-the-counter and prescription medications, including medicine used to treat arrhythmias
- Certain arrhythmias can be genetically determined such as Wolff-Parkinson-White (WPW) syndrome.
When to seek medical care if you have an arrhythmias (heart rhythm disorder)
Most people have noticed their heart racing, a fluttering in the chest, or a sensation that the heart skipped a beat. If this happens once, or very infrequently, with no other symptoms, it is usually not serious and medical care is usually not needed. However, any questions or concerns should be discussed with a health care professional. If the person is prescribed a medication, the health care professional should also be notified if a recommended treatment does not alleviate the symptoms.
More serious symptoms should be evaluated immediately at the nearest hospital emergency department. These symptoms include:
- Any unexplained shortness of breath
- Loss of consciousness
- Light-headedness or feeling faint
- Feeling that the heart is beating too slowly or too quickly
- Chest pain with normal activity
- Chest pain with any of the above symptoms
People experiencing these symptoms should not drive to the emergency department. They should call 9-1-1 for emergency medical transport.
How are arrhythmias (heart rhythm disorders) diagnosed?
Evaluation of rhythm disorders usually requires a detailed discussion of symptoms and a physical exam with a health care professional.
In addition, an electrocardiogram (ECG or EKG) is mandatory to establish the exact type of arrhythmia. If the rhythm disturbance is present while the ECG is being recorded, the problem may be identified immediately. Otherwise, more specialized testing may be required. A 24-hour (or longer) recording of the heartbeat is often necessary to detect any rhythm problem that occurs daily but not constantly. (For examples of EKGs of various arrhythmias, the reader is urged to see the references provided in this introductory article.)
However, if the arrhythmia is even more infrequent, an event recorder may be used. These recorders can be hand-held machines that are activated by the patient whenever he or she feels symptoms. These event recorders can be worn for variable amounts of time from days to weeks in order to detect changes in the heart's rhythm. Some recorders are placed surgically under the skin and left there for up to 1 year.
An ultrasound of the heart, called an echocardiogram, is often used for an evaluation of the structure and function of the heart that may help identify underlying causes that lead to arrhythmias.
In general, arrhythmias in children are diagnosed with most of the same tests that are used in adults.
What is the treatment for arrhythmias (heart rhythm disorders)?
The treatment of arrhythmias varies depending on the presence or absence of symptoms, how frequent the arrhythmia occurs, and the seriousness of any underlying heart condition. The majority of arrhythmias are either not treated or are treated with medications taken by mouth. Some arrhythmias must be treated emergently with electrocardioversion or the patient will die. For others, the treatment may range from vagal maneuvers (for example, the Valsalva, a maneuver of breath holding and bearing down) to medication to more advanced surgical procedures, such as an internal implanted pacemaker or cardiac defibrillator (ICD). Sometimes, no treatment is necessary because the arrhythmia resolves.
Except in life-threatening emergencies, a person should have a detailed discussion of the tests and treatment options with the health care professional to be clear about the tests and potential treatment options before any tests or surgery is done. This discussion should include the risks and benefits the patient may have if they choose to have or not have specific treatments or surgical procedures done.
What medications treat arrhythmias (heart rhythm disorders)?
The choice and use of medications depends on the specific type of arrhythmia present. Although detailed discussion about this is beyond the scope of this article, the reader is encouraged to click onto the links to the predominant arrhythmias to determine the common medications and common surgical methods used to treat these heart beat disorders.
Although some arrhythmias may require some special uses of medications (for example, IV adenosine for PSVT), most utilize various beta-blockers and calcium channel blockers to control fast rates. Although atropine may be used for a short time to speed up heart rates, usually the treatment will be a pacemaker.
What electrical and surgical treatments are available for arrhythmias (heart rhythm disorders)?
The most common electrical and surgical treatments are listed as follows:
- Electrical: These include pacemakers and defibrillators (several types including ones that can either pace, defibrillate, or even cardiovert manually ) and automatic external defibrillators (AEDs) that are available to the public, and function with external sources of electricity.
- Ablation: This technique is done by surgically placing small probes that can destroy tissue and then are removed once the tissue is altered. (Technically, ablation -- which kills cells found usually in the atria, thus stopping arrhythmia-generating cells -- may be done with hot or cold probes.) This is sometimes termed a modified MAZE procedure (see below).
- Surgical implants: These are pacemakers that regulate heartbeat rates by either including extra beats if the heartbeat is too slow or "overdrive pacing" if the rate is too fast (for example, ventricular tachycardia); defibrillators that detect and then interrupt ventricular fibrillation; and devices that can both pace and defibrillate, all of which are surgically implanted and battery-powered.
- Surgery: This is open-heart surgery (termed MAZE surgery or MAZE procedure) where small cuts are made in the heart tissue to induce scar formation that blocks electrical impulses or removes cells causing impulses (currently infrequently done).
Electrical cardioversion is most often used in emergencies, although patients with certain arrhythmias who are stable may have electrical cardioversion done non-emergently. Most of the surgical procedures (implants) are done in patients whose arrhythmias are under medical control (temporarily or longer-term).
Do I need to follow-up with my doctor after being diagnosed with an
Follow-up is usually done with the primary care professional and often with a heart specialist (cardiologist). The patient is monitored for effectiveness of treatment, recurrence of symptoms or arrhythmia, side effects of medication, additional routine testing, and overall condition. For those requiring pacemakers, follow-up on a regular basis is mandatory. Patients are advised to make all follow-up appointments and should not attempt to change their medications without first consulting their doctor(s).
What is the outlook or life-expectancy for a person with an arrhythmia (heart rhythm disorder)?
The detection and management of heart rhythm disorders are undergoing constant improvement. The past years have seen an unprecedented explosion of information about these conditions. Detection and management of heart rhythm disorders has improved the quality and quantity of life. However, patients need to keep follow-up appointments and maintain their medications because not doing this can severely reduce a person's outcome. Untreated, ignored, or "undertreated" serious arrhythmias can result in syncope, strokes, heart failure, and sudden death.
Reviewed on 8/6/2021
Medically reviewed by Robert J. Bryg, MD; Board Certified Internal Medicine with subspecialty in Cardiovascular Disease
Bocka, Joseph J., MD. "Automatic External Defibrillation." Medscape. Updated: May 30, 2014.