A normal heart beats in a steady, even rhythm; about 60 to 100 times each minute (that’s about 100,000 times each day). Cardiac arrhythmias are disturbances in the normal rhythm of the heartbeat. An occasional palpitation or fluttering is usually not serious, but a persistent arrhythmia may be life threatening.

There are many different types of cardiac arrhythmias. The heart may beat too rapidly, known as atrial tachycardia, or too slowly, known as bradycardia, or it may beat irregularly. Atrial fibrillation and atrial flutter are common cardiac arrhythmias, which lead to an irregular and sometimes rapid heart rate.

These atrial arrhythmias may interfere with the heart’s ability to pump blood properly from its upper chambers (atria). The atria may not always empty completely, and blood remaining there too long may stagnate and potentially clot. Such clots may travel to other parts of the body, where they may cause blockages in the blood supply to the limbs, brain or heart.
In ventricular fibrillation, the lower chambers of the heart (ventricles) quiver feebly instead of contracting powerfully. This is the most severe type of arrhythmia, causing death in minutes unless medical assistance is obtained immediately.

When to Call an Ambulance

If you experience severe chest pain, shortness of breath or prolonged palpitations
If someone loses consciousness; if heartbeat or breathing has stopped, perform (fix indent here) cardiopulmonary resuscitation (CPR).

Symptoms
An arrhythmia may be “silent” and not cause any 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. If you do experience symptoms of cardiac arrhythmia, they may include:

Palpitations or irregular-feeling heartbeats.
Shortness of breath.
Chest pain.
Dizziness, lightheadedness, and fainting spells.
Mental confusion.
Loss of consciousness.

Causes
There are many causes for arrhythmias, however a fast or slow heart rate does not always mean your heart rhythm is abnormal. Your heart rate is also related to anxiety, activity, medications or other normal causes. Arrhythmias can be caused by:

Disorders that damage the heart or its valves, such as endocarditis, myocarditis and rheumatic fever.
Disorders of the thyroid gland.
Dehydration or depletion of potassium or other electrolytes may trigger an arrhythmia.
Some drugs, including digitalis, stimulants, and diuretics, as well as overdoses of cocaine, marijuana, or antidepressants.
Injury to the heart due to a heart attack.
The healing process following some cases of chest or heart surgery.

Risk increases with smoking, excess consumption of caffeine or alcohol, advancing age, high blood pressure, kidney disease and stress.

Prevention
You can help reduce your risk for arrhythmia by engaging in regular aerobic exercise, and by avoiding cigarettes, illegal drugs and excessive amounts of alcohol and caffeine. You should also be aware that emotional stress can sometimes cause irregularities with your heartbeat. If you are taking prescription medication, it is important that you carefully follow instructions and be aware of possible side effects.

Diagnosis
Physicians at Johns Hopkins have been leaders in the field of electrophysiology — the study of the heart’s electrical activity — since the early 1970s. Dr. Hugh Calkins has been director of the Arrhythmia Service since 1992.
Evaluation for an abnormal heart rhythm begins with an examination by one of our physicians at our Outpatient Center (satellite facility) at Green Spring Station. Your doctor may recommend one or more tests to diagnose the arrhythmia and determine if it is causing your symptoms. Exercise treadmill tests and electrocardiograms are performed at the outpatient locations. The others are done in the electrophysiology laboratory located in the hospital’s Cardiovascular Diagnostic Laboratory.

An electrocardiogram (ECG, often identified as an EKG) records your heart’s electrical activity during rest to determine abnormal heart rhythms.
A special type of ECG called a signal-averaged ECG (SAECG).
To record your heart’s activity during a 24-hour period or longer, the doctor may ask you to wear a Holter monitor. Small sensors applied to your skin are connected to a small recording device that is strapped or belted to your body. This is useful for detecting abnormalities that may not occur during an electrocardiogram.
Similar to the Holter monitor, doctors also may use an event monitor, which records the heart rhythm only when activated. It is usually worn for about a month.
An exercise stress test, also known as a treadmill test, helps determine irregular heart rhythms during exercise. During this test, the heart’s electrical activity is monitored through small metal sensors applied to your skin while you exercise on a stationary bicycle or treadmill.
If you experience lightheadedness or fainting, a tilt table test may be in order. You are placed on a table that starts in a horizontal position and is then tilted upward at different angles, while your heart rate and blood pressure are measured.
An electrophysiology test (EP).

The electrophysiology lab provides state-of-the-art biplane fluoroscopy equipment that facilitates complex catheter ablation procedures and reduces the amount of X-ray exposure that patients receive. The doctor routinely checks in with the patient before the procedure to answer any questions.

Treatment
Based on your diagnostic exam and test results, the doctor will work with you on a treatment plan that may include one or more of the following options:

Medications. You may be prescribed medication to help manage any electrical abnormalities. Antiarrhythmic drugs (such as a beta-blockers, calcium channel blockers, amiodarone or procainamide) convert the arrhythmia to a normal sinus rhythm or work to prevent an arrhythmia. Anticoagulants (such as aspirin or warfarin, also called “blood thinners”) may be prescribed to prevent the formation of blood clots, particularly for atrial arrhythmias. For those with atrial arrhythmias, digitalis (a drug that slows ventricular response to the rapid impulses coming from the atrium) may be prescribed. In any case, you should know what medication you are taking and understand its function, as well as its possible side effects. Your doctor will provide you with specific dosage instructions that should be followed carefully.
Cardioversion. An electric shock (cardioversion) may be administered under non-emergency conditions to correct atrial arrhythmias. In this case, you receive a short-acting anesthesia, and then an electrical shock is delivered to your chest wall that synchronizes the heart and allows the normal rhythm to restart.
Catheter ablation. If the doctor can pinpoint specific areas of the heart causing the abnormal rhythm, an outpatient procedure called catheter ablation can destroy these areas using radio wave energy, removing damaged heart tissue. This can often be performed during an electrophysiologic study.
Pacemaker. If your heartbeat is dangerously slow, you may benefit by having a pacemaker implanted in your chest. This is a small device that supplies electrical triggers to the heart to help it along when it beats too slowly. Similarly, a defibrillator is a small implanted device that delivers a small electrical shock to the heart if a too-rapid rhythm occurs.

Treatment is also likely to include possible prevention-based lifestyle changes that can help reduce your risk. Your family may also want to learn to recognize your symptoms so that cardiopulmonary resuscitation (or CPR) can be applied in an emergency situation.

Content Resource: http://www.hopkinsmedicine.org/heart_vascular_institute/conditions_treatments/conditions/arryhthmias.html