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., previous damage from a heart attack) or to other factors (e.g., caffeine, stress, not getting enough sleep). In the majority of cases, a skipped beat is not medically significant. Sudden cardiac death (“cardiac arrest”) is responsible for approximately one-half of all deaths due to heart disease.

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 malfunction. Diagnosis may be done through noninvasive tests such as an electrocardiogram (EKG) or an event monitor, or it may be done through a more invasive test such as an electrophysiology study.

Most nonsustained arrhythmias need no treatment (other than lifestyle changes, perhaps). Other arrhythmias require treatment, which may include medications, a catheter ablation and/or surgery to implant either an artificial pacemaker or an implantable cardioverter defibrillator.






What is an arrhythmia?
An arrhythmia is an abnormal heartbeat resulting from any change, deviation or malfunction in the heart's conduction system — the system through which normal electrical impulses travel through the heart. An arrhythmia may be unusually fast (tachycardia) or unusually slow (bradycardia). Some arrhythmias are signs of more serious heart problems, and 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) may commonly occur in the general population. In the majority of cases, a skipped beat is not medically significant. Sudden cardiac death (“cardiac arrest”) is responsible for approximately one-half of all deaths due to heart disease.





What causes arrhythmias?
To understand what causes abnormal heart rhythms, one must first have a basic understanding of what causes a normal heart rhythm. 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), which is 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 and to the atrioventricular (AV) node, where they are transmitted to the lower chambers of the heart ventricles via the "bundle branches." Thus, the electrical impulses travel from the sinoatrial node to the ventricles, to trigger and regulate the heartbeat.

In general, the abnormality that results in an arrhythmia is one of the following:

• Abnormal function of the cells in the sinoatrial node (sick sinus syndrome), such that these cells are either not firing or transmitting impulses properly.
• Delayed or improperly produced/conducted impulses through the atrioventricular junction (which could cause heart block) or the ventricles (which could cause bundle branch block).
• An extra pathway in the conduction system, causing additional heartbeats.
• Electrical impulses arising from places in the heart other than the sinoatrial node.

There are a number of heart-related conditions that could lead to arrhythmias, which include the following:

• Previous heart damage from a heart attack or atherosclerosis (hardening of the arteries).
• Heart defects or congenital heart disease (e.g., long QT syndrome).
• 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.
• Effects from medications.

Other causes of arrhythmias are not heart-related, and these include the following:

• High stress.
• Caffeine consumption (including chocolate).
• Alcohol consumption.
• Smoking.
• Some over-the-counter medications, including those for coughs, colds or weight loss. This includes certain “natural” or herbal remedies. Guarana, ginseng and ephedra are all stimulants that can increase heart rate, interfere with sleeping, and cause palpitations and other symptoms of arrhythmia.
• Some illicit drugs. Cocaine overstimulates the heart, regardless how it enters the body (e.g., snorted, injected, smoked, dissolved on the tongue). This could result in fatal arrhythmias.
• Not getting enough sleep

What are the different types 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 normal area of the heart (sinus node) but is characterized by a variability in the heart rate. It is often associated with breathing, such that the heart rate increases when inhaling and decreases 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 the following:

Bradycardia

• Sinus bradycardia.
• Sick sinus syndrome (also known as sinus node dysfunction, brady-tachy syndrome or tachy-brady syndrome).
• Heart block (also known as atrioventricular block or AV block). This condition is classified as first degree, second degree (type 1 and 2) or third degree (complete).
• Bundle branch block. This condition involves the left and/or right bundle branches. 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

• Supraventricular tachycardia (paroxysmal or sustained)
• Junctional tachycardia or tachycardias involving the AV node
• Premature junctional contractions (PJCs, premature junctional beats, junctional extrasystoles, junctional ectopics)
• AV nodal reentrant tachycardia (AV node reentry, AV nodal reentry, AV reentrant tachycardia)
• AV reentrant tachycardia using an accessory bypass connection (e.g., Wolff-Parkinson-White syndrome and variants of this preexcitation syndrome)

Atrial tachycardia (focal or multifocal)

• Premature atrial contractions (PACs, premature atrial beats, PABs, atrial extrasystoles, atrial ectopics)
• Inappropriate sinus tachycardia (IST)
• Paroxysmal atrial tachycardia (PAT)
• Atrial flutter
• Atrial fibrillation (A-fib, AF, transient atrial fibrillation, lone atrial fibrillation)

Ventricular tachycardias

• Premature ventricular contractions (PVCs, premature ventricular complexes, ventricular extrasystoles, ventricular ectopics)
• Ventricular tachycardia (VT or "V-tach"; could be nonsustained or sustained, monomorphic or polymorphic, stable or unstable, idiopathic or due to known causes)
• Ventricular fibrillation (VF, V-fib)

What are the symptoms of an arrhythmia?
Symptoms of arrhythmias vary from person to person, and depend largely on the source of the abnormality. Some people 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
• 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.

• 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 while exercising (an exercise stress test). EKGs can be done by a physician in an office or hospital setting, or can be portable and measured over time by 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) that uses controlled electrical stimuli to locate the exact origin and nature of an arrhythmia. Once the electrical malfunction is pinpointed, radiofrequency ablation may be used to treat it.
• A tilt table test may be used to evaluate causes of fainting spells (syncope) that are unrelated to arrhythmias. In the test, the patient lies down on a table and is strapped down. Then the table is tilted upright and the heart rate and blood pressure are monitored.

• Quitting or reducing caffeine intake
• Limiting alcohol use
• Quitting smoking
• Avoiding certain medications (e.g., decongestants)
• Using stress management techniques

• Surgery to implant an artificial pacemaker in the patient’s chest. For a slow heartbeat (bradycardia), the most common treatment is an electronic (artificial) pacemaker. This device, which is implanted under the skin and permanently attached to the heart, delivers an electrical impulse when a slowing or irregularity of the heart rhythm is detected.
• Surgery to implant an implantable cardioverter defibrillator (ICD) in the patient’s chest. An ICD monitors and, if necessary, corrects an abnormally fast heartbeat. These devices may be lifesaving for patients with ventricular 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.

• 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).
• 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.
• Working to improve catheter ablation technology so that arrhythmias like atrial fibrillation and ventricular tachycardia can be successfully cured with a catheter-based procedure.
• Working to improve the reliability and diagnostic capabilities of pacemakers, and using pacemakers in the successful treatment of fainting, congestive heart failure and atrial fibrillation. 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).