An arrhythmia is an abnormal heartbeat that may be unusually fast (tachycardia) or unusually slow (bradycardia). It may be related to a previous heart condition (e.g., damage from a heart attack) or to other factors (e.g., caffeine, stress, medications).
In the majority of cases, a skipped beat is not medically significant. The most serious arrhythmias, however, contribute to almost 500,000 deaths in the United States each year according to the American Heart Association, with annual deaths attributable to the condition rising steadily. Also, one type of arrhythmia called ventricular fibrillation causes most of the 330,000 sudden cardiac deaths that occur each year. Other kinds of arrhythmias contribute to stroke and the formation of blood clots.
Diagnosing an arrhythmia is very important, because the longer an arrhythmia lasts without detection or treatment, the greater the chances of permanent damage and additional heart dysfunction. Diagnosis may be done through noninvasive tests such as an EKG (electrocardiogram) or an event monitor, or it may be done through a more invasive test such as an electrophysiology study.
Most nonsustained (temporary) arrhythmias need no treatment, although a physician may recommend certain lifestyle changes. When arrhythmias do require treatment, it may include medications, cardioversion, a catheter ablation, and/or surgery to implant either a pacemaker or an implantable defibrillator (ICD).
About arrhythmias
An arrhythmia is an abnormal heart rhythm resulting from any change, deviation or malfunction in the heart's conduction system – the system through which normal electrical impulses are generated and travel through the heart. An arrhythmia may result in a heartbeat that is unusually fast (tachycardia), unusually slow (bradycardia), regular or irregular. Some arrhythmias are signs of more serious heart problems while others are not. An arrhythmia may be brief and unnoticeable, or it may be startling, obvious or even fatal.
Skips, pauses and palpitations (strong, fast, “galloping” heartbeats) commonly occur in the general population. In the majority of cases, a skipped beat is not medically significant. The most serious arrhythmias, however, contribute to approximately 500,000 deaths in the United States each year according to the American Heart Association. One type of arrhythmia (ventricular fibrillation) causes most of the 330,000 sudden cardiac deaths (SCD) that occur each year. SCD occurs when a patient dies following an episode of cardiac arrest, in which the heart suddenly stops beating. It is fatal unless the patient receives immediate medical attention.
In general, the probable outcome of an arrhythmia is largely dependent on any structural heart abnormalities. Outcomes tend to be worse among patients with poor heart function such as patients who have experienced large heart attacks or cardiomyopathy.
Risk factors and causes for arrhythmias
To understand what causes abnormal heart rhythms, one must first have a basic understanding of what causes a normal heart rhythm.
The heart is a large muscle that contracts to pump blood around the body. Each of the heart’s contractions or heartbeats, is triggered by electrical impulses. These electrical impulses are sent from the sinoatrial node (the heart’s natural pacemaker), located at the top of the upper-right chamber of the heart or right atrium. From there, the electrical impulses travel through the upper chambers of the heart (atria), stimulating them to pump blood through the atrial valves to the ventricles. The electrical impulse then travels to the atrioventricular (AV) node, which rests between the upper and lower chambers of the heart (atria and ventricles). From there, they are transmitted to the ventricles via the bundle branches, which stimulate the ventricles to contract, pushing blood through the ventricular valves and out of the heart. The closing of each set of valves as the atria and ventricles contract accounts for the distinctive "lub-dub" sound of a healthy heart. A normal heart will beat approximately 60 to 100 times per minute.
In general, one of the following abnormalies is usually responsible for an arrhythmia:
Abnormal function of the cells in the sinoatrial node (sick sinus syndrome), such that these cells either do not fire or transmit impulses improperly.
Delayed or improperly produced/conducted impulses through the atrioventricular node (which could cause heart block) or the ventricles (which could cause bundle block branch).
An extra pathway in the conduction system, causing additional heartbeats.
Electrical impulses that arise from places in the heart other than the sinoatrial node and interfere with the heartbeat.
There are a number of heart-related factors associated with arrhythmias, including:
Previous heart damage from a heart attack or atherosclerosis (hardening of the arteries).
Congenital heart disease or defects (e.g., long syndrome QT, Brugada syndrome, hypertrophic cardiomyopathy).
Abnormalities of heart structure or function. These include cardiomyopathy (in which the heart muscle is abnormally enlarged, thickened and/or stiffened) or valvular heart disease.
Side effects from medications.
There are other causes of arrhythmias that are not heart-related. These include:
High stress, anger or hostility.
Caffeine consumption (including chocolate).
Alcohol consumption.
Side effects from prescription medications, including those used to treat arrhythmias.
Some over-the-counter medications, including those for coughs, colds or weight loss. This includes certain “natural” or herbal remedies. Guarana, ginseng and ephedra (ma huang) are all stimulants that can increase heart rate, interfere with sleeping, and cause palpitations and other symptoms of arrhythmia.
Some illegal drugs. Cocaine, inparticular, over-stimulates the heart, regardless how it enters the body (e.g., snorted, injected, smoked, dissolved on the tongue). This could result in fatal arrhythmias.
Sleep disorders, such as insomnia or sleep apnea.
Other risk factors include age, hypertension, diabetes, left ventricular hypertrophy, pulmonary disease and electrolyte abnormalities such as low potassium and magnesium.
Types and differences of arrhythmias
Arrhythmias are classified and treated based upon where in the heart they originate, how they manifest themselves and what cardiac functions they affect. For example, sinus arrhythmia is a type of heart rhythm that originates in the heart’s natural pacemaker (sinus node). It is characterized by changing heart rates often associated with breathing. For instance, heart rate may increase when inhaling and decrease when exhaling. It is almost always harmless.
More dangerous is sudden arrhythmia death syndrome (SADS), which is any disorder of the conduction system (e.g., long QT syndrome) that increases the risk of sudden cardiac death. Other types of arrhythmias include:
Bradycardia(a heart rate of fewer than 60 beats per minute)
Sick sinus syndrome (also known as sinus node dysfunction, brady-tachy syndrome or tachy-brady syndrome). A group of symptoms that indicate bradycardia originating at the sinus node (sinus bradycardia).
Heart block (also known as atrioventricular block or AV block). May be classified as first degree, second degree (type 1 and 2) or third degree (complete). Heart block refers to a “blockage” in the passage of electrical signals from the atria to the ventricles, resulting in abnormally slow contractions.
Bundle block branch. Involves the left and/or right bundle branches, which transmit the heart signal to the ventricles. Left bundle branch block (LBBB) is further classified as complete or partial (anterior fascicular block or posterior fascicular block). Right bundle branch block (RBBB) is also classified as complete or partial. Other types of bundle branch block include bifascicular block and trifascicular block.
Tachycardia(a heart rate of over 100 beats per minute)
Supraventricular tachycardia (paroxysmal or sustained).Can be paroxysmal (acute attacks) or sustained. Supraventricular tachycardia may involve the AV node (also known as junctional tachycardia) or the atrium. It may be caused by factors such as premature contraction of the upper chambers of the heart or extra conduction pathways that “short circuit” the electrical signal. One of the most common types of sustained supraventricular tachycardia is atrial fibrillation, which affects two million people each year in the United States. Atrial fibrillation is the result of rapid, disorganized signals in the atria that prompt the ventricles to contract irregularly. Although this condition is not directly life-threatening, when the atria fibrillate (or quiver) instead of beating, blood is not effectively passed through the heart’s chambers and may pool in the atria. A blood clot may form and travel throughout the body, which could lead to a stroke or heart attack.
Ventricular tachycardias. Affecting the heart’s ventricles, these are generally more serious than supraventricular tachycardias. Among the most serious is ventricular fibrillation, which causes the heart to quiver (fibrillate) rather than beat efficiently. Ventricular fibrillation often leads to sudden cardiac death if not treated immediately. Often, the first sign of ventricular fibrillation is sudden fainting (syncope).
Signs and symptoms of arrhythmias
Symptoms of arrhythmias vary from person to person, and depend on the source of the abnormality. Some people with mild arrhythmias have no symptoms at all. If symptoms are experienced, these may include any of the following:
Palpitations (strong or “galloping” heartbeat)
Skipped heartbeat
Dizziness, fatigue or fainting (syncope) as a result of the brain not getting enough oxygen-rich blood. This could manifest as unexplained falls, particularly in elderly individuals.
Angina (chest pain, pressure or discomfort)
Shortness of breath (dyspnea)
In severe cases, it could also result in cardiac arrest and death.
Diagnosis methods for arrhythmias
Diagnosing an arrhythmia is very important because the longer the arrhythmia lasts without detection or treatment, the greater the chances of permanent damage and heart dysfunction. If someone experiences what feels like a flutter, skipped beat or any other unusual beat activity, a medical opinion and diagnosis should be obtained as soon as possible.
There are a number of tests that physicians may use to diagnose an arrhythmia. The type of test(s) used will depend on a number of factors, including the specific symptoms of a patient as well as his or her personal and family medical history. These include:
An electrocardiogram (EKG), often considered the best diagnostic tool when an arrhythmia is suspected. It measures the heart’s electrical activity either at rest or under stress (known as a stress test). EKGs can be done by a physician in an office or hospital setting, or they can be portable and measured over time using a Holter Monitor or event recorder.
An echocardiogram of the heart uses sound waves to track the structure and function of the heart. A moving image of the patient’s beating heart is played on a video screen, where a physician can study the heart’s thickness, size and function.
Cardiac catheterization procedures may be used to help a physician learn more about a patient’s specific arrhythmia. One such test is an electrophysiology study (EPS), which uses controlled electrical stimuli to locate the exact origin and nature of an arrhythmia. Once the electrical malfunction is pinpointed, catheter ablation may be used to treat it. An implantable cardioverter defibrillator (ICD) may be recommended based on the results of EPS testing.
A tilt table test may be used to evaluate causes of fainting spells (syncope) that are unrelated to arrhythmias. In the test, the patient is strapped onto a table. Then the table is tilted upright and the heart rate and blood pressure are monitored. This is not a direct test for arrhythmias. However, symptoms common with arrhythmia may also be caused by other medical problems. Tilt table tests may be used to rule out these other causes.
Treatment options for arrhythmias
The method of treatment depends upon the type and severity of the arrhythmia. Most nonsustained arrhythmias do not need treatment, although physicians may recommend making some lifestyle changes. These changes include:
Quitting or reducing caffeine intake
Limiting alcohol use
Avoiding certain medications (e.g., decongestants)
Using stress management techniques
Also, medications called beta-blockers, calcium channel blockers or inotropes (e.g., digoxin) may be prescribed. In severe cases, antiarrhythmics may be recommended. These medications should be monitored carefully to prevent any side effects, which can include increased or worsened arrhythmias. Patients on such medications are encouraged to learn how to take their own pulse so any abnormal rhythm will be promptly detected.
Sometimes more invasive treatments are helpful, including:
Pacemaker implantation. For a slow heartbeat (bradycardia), the most common treatment is an electronic pacemaker. This device, implanted under the skin of the chest and permanently attached to the heart, delivers steady electrical impulses that stimulate the heart to beat at a healthy rate.
Implantable cardioverter defibrillator (ICD) implantation. An ICD monitors and, if necessary, corrects an abnormally fast or quivering heartbeat. These devices may be lifesaving for patients with ventricular fibrillationor ventricular tachycardia. Modern ICDs may also be programmed to pace the heart after an abnormal heart beat.
Cardioversion. A treatment to correct certain types of arrhythmia by converting an abnormal cardiac rhythm to a normal one. A defibrillator is used to deliver carefully timed and well-controlled electrical shocks to the chest wall. It may be used in the treatment of atrial fibrillation or ventricular tachycardia.
Electrophysiology study with catheter ablation. This is a procedure in which catheters are introduced into the heart from blood vessels in the legs and/or neck and radiofrequency energy is used to very carefully destroy (ablate) the abnormal areas of the heart that are creating the arrhythmias.
Left cardiac sympathetic denervation (LCSD). A procedure in which part of the nerves leading to the heart are removed to reduce the heart's control over the sympathetic nervous system. The sympathetic nervous system controls involuntary functions such as breathing and heart rate. LCSD is a potential treatment for long QT syndrome, which can cause the heart to beat extremely fast.
Maze procedure. An open-heart surgery in which the surgeon creates a new pathway through which the heart’s electrical signals can travel. While it is a treatment option for atrial fibrillation, it is usually reserved only for patients who are having severe symptoms despite other treatments (e.g., medications, cardioversion and ablation).
Many arrhythmia patients are able to live normal, active lives. If after receiving diagnosis and treatment, symptoms such as excessive lightheadedness or fainting (syncope) occur, patients are urged to consult their physicians immediately.
Prevention methods for arrhythmias
By preventing or delaying the onset of such diseases as atherosclerosis, a person is less likely to encounter dangerous arrhythmias. If a person has already been diagnosed with heart disease, the best way to prevent arrhythmia is to closely follow a treatment plan for the original disease. This will most likely include healthy lifestyle changes (e.g., reducing use of alcohol and caffeine and stop smoking). Patients will also be asked to visit their physician for regular testing to monitor their heart function.
Otherwise, because there are so many different forms of arrhythmia, there is no single strategy that can prevent them, especially arrhythmias that occur without warning. However, people may be able to notice a pattern in their arrhythmias. For example, the heart may race after exercise or heavy exertion and may slow considerably when sleeping or resting. Additionally, certain high-stress situations can cause rhythm abnormalities. People are encouraged to identify any situations in their lives that appear to trigger arrhythmias, and consider how they might avoid those situations as much as possible.
Ongoing research for arrhythmias
A large body of scientific research into the mechanisms and therapies of arrhythmias has been accumulated over the past two decades. Ongoing studies are:
Attempting to more accurately identify patients at high risk for life-threatening ventricular arrhythmias and defining which populations would benefit the most from a particular therapy (e.g., drugs, ICD). This includes the development of advanced new diagnostics. One new technique involves using a CT scan and 3-D electro-anatomical maps to create a very realistic picture of where the faulty electrical signal is originating from and affecting.
Attempting to better understand which forms of arrhythmia indicate higher risk for potentially life-threatening events. For instance, researchers have learned that abnormal heart rhythms affecting the ventricles (ventricular arrhythmias) indicate a higher risk of heart attack or sudden cardiac death. Ventricular arrhythmias that occur during the recovery phase of exercise have been found to be a strong indicator of risk.
Attempting to better understand the genetic disorders that can predispose to arrhythmias in order to better understand how to treat these disorders with conventional medications, as well as with the hope of using gene-based therapies in the future. For instance, researchers have recently identified an inherited cardiac arrhythmia syndrome that occurs because of a mutation in a gene called ankyrin-B. Such discoveries may eventually lead to genetic testing in patients with a family history of arrhythmias. This, in turn, could aid in the early diagnosis, treatment or prevention of potentially life-threatening conditions.
Attempting to better understand the role of lifestyle factors (e.g., diet, exercise, stress management) in arrhythmia prevention and treatment. For instance, researchers have found that people who regularly eat fish have slower heart rates and therefore a reduced risk of sudden cardiac death.
Working to improve catheter ablation technology so that arrhythmias like atrial fibrillation and ventricular tachycardia can be successfully cured with a catheter-based procedure. Researchers are working on technology that will help them better guide catheter ablation devices to the site of very specific arrhythmias.
Working to improve the reliability and diagnostic capabilities of pacemakers, and using pacemakers in the successful treatment of fainting, heart failure and atrial fibrillation (e.g., biventricular pacemakers). Biatrial pacing, for example, is a newer strategy to reduce the number of episodes of atrial fibrillation. This involves delivering electrical impulses to the right atrium and to the coronary sinus (the area of the heart that receives the cardiac veins and opens into the right atrium).
Developing new medications that can reduce the risk of coronary events (e.g., heart attack, sudden cardiac death) in patients with arrhythmias. Such medications (e.g., the experimental JTV519) works by preventing molecular defects in the heart from resulting in an abnormal rhythm. These “molecular-based” therapies may eventually be beneficial for patients at high risk of developing potentially fatal arrhythmias, such as those with heart failure.
Determining the potential of medications typically used in the management of other heart-related conditions in the treatment or prevention of arrhythmias. For example, researchers have found that atrial fibrillation patients taking statins, a cholesterol-reducing drug, after cardioversion had a decreased risk of their arrhythmias returning. Whether statins directly influence heart rhythm or provide benefit for some other reason is not yet known. In other research, taking potassium supplements may help some patients with long QT syndrome.
Developing new technology for detecting abnormal heart rhythms in high-risk patients. For instance, researchers have developed sensors to detect arrhythmias that can be sewn into bras or shorts. The sensors then clip into a module to monitor signals and then either trigger an alarm or link with a mobile phone should an abnormal heart rhythm occur. While such devices are not likely to be widely available for some time, they may become a part of the treatment landscape in the future.
Questions for your doctor about arrhythmias
Preparing questions in advance can help patients to have more meaningful discussions with their physicians regarding their conditions. Patients may wish to ask their doctor the following questions about arrhythmia:
Sometimes I feel my heart racing, could this be arrhythmia?
What may be causing my arrhythmia?
What kind of arrhythmia do I have? Is it life-threatening?
Could my arrhythmia be an indication of a more serious condition?
Can I still exercise with arrhythmia?
What lifestyle changes can I make to improve my arrhythmia?
What tests can I take to determine if I have arrhythmia?
Should I go to the hospital if I experience symptoms consistent with arrhythmia?
Are there any prescription or over-the-counter medications I should avoid due to arrhythmia?
