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Atrial Fibrillation and Atrial Flutter

How does a normal heart beat?

The heart is a hollow muscular organ – approximately the size of your clenched fist – that beats 40 million times per year (between 60 and 100 beats per minute). The heart's pumping action is controlled by its electrical system, which gives rise to the heart rhythm.

Normal cardiac rhythm results from electrical impulses that begin in a special group of cells that form the sinoatrial (SA) node, also called the sinus node. Located in the right upper chamber of the heart, sinus node cells act as the heart's natural pacemaker. Impulses spread from the sinus node to the right and left atria (the upper chambers of the heart), causing them to contract at the same time. The impulses then travel to the AV (atrioventricular) node, the region that manages impulse traffic from the atria to the ventricles (the lower chambers of the heart). Here, impulses are slowed slightly to give the atria time to contract before the signal reaches the ventricles.

From the AV node, the impulses travel through a system of specialized heart tissue. Located in the wall that separates the two ventricles, this conducting system splits to form the right and left bundle branches that travel to the respective ventricles. Via this conducting pathway, powerful electrical 'jump-start' signals are delivered to the ventricular muscle of the heart. In the healthy heart, these impulses travel at the same speed so that the two ventricles contract at the same time, and oxygen-rich blood from the lungs is pumped throughout the body.

What is atrial fibrillation?

Atrial fibrillation is the most common type of arrhythmia, affecting about 1.5 million Americans. During atrial fibrillation, electrical signals in the atria occur in a very fast, uncontrolled, and chaotic manner so that the atria quiver instead of contract. This produces ineffective and disorganized atrial contractions. These disorganized electrical signals then arrive at the ventricles in an irregular fashion.

What is atrial flutter?

Atrial flutter is a rapid heart rhythm in which electrical signals in the atria are abnormally fast. Unlike atrial fibrillation in which the upper chambers beat erratically, in atrial flutter the upper chambers beat rapidly but regularly.

In atrial flutter, electrical impulses get "caught" in a single large circuit and travel in an endless loop around the atrium. The right atrium is particularly susceptible to this type of "reentrant" electrical conduction. This common arrhythmia usually occurs in older patients and patients with previous heart disease, although atrial flutter can even occur in younger patients and those with no structural heart disease. Patients with atrial flutter may also have atrial fibrillation.

What are the symptoms of atrial fibrillation and atrial flutter?

Some patients do not feel atrial fibrillation or atrial flutter; others find the symptoms disabling. Typical signs and symptoms include weakness – especially with exercise – rapid or pounding heartbeat (palpitations), dizziness, or shortness of breath.

What are the causes of atrial fibrillation and atrial flutter?

Atrial fibrillation and atrial flutter become more common as people age. These disorders are also associated with hypertension, valvular heart disease, or a history of coronary disease or heart attacks. They occur occasionally in young or middle age without any clear precipitating factors.

What risks are associated with atrial fibrillation and atrial flutter?

Atrial fibrillation and atrial flutter are not directly life threatening. The primary danger from these conditions is stroke because these arrhythmias prevent the atria from pumping blood effectively. As a result, blood pools in the atria and may form small clots. If these clots reach the brain, they can cause a stroke. In fact, about 15 percent of strokes occur in persons with atrial fibrillation. The risk of stroke can be minimized by treatment with blood "thinning" medication.

When atrial fibrillation occurs in young patients in the absence of heart disease or high blood pressure, it is called "lone atrial fibrillation". Patients with lone atrial fibrillation are considered at very low risk for stroke.

How are atrial fibrillation and atrial flutter treated?

Several treatment options are available for atrial fibrillation, including:

• Medication to control heart rate
  Many patients have no significant symptoms during atrial fibrillation. In such cases, restoring sinus rhythm may not be necessary. Typically, medication is prescribed to prevent the lower chambers of the heart from beating too rapidly.
• Blood thinners
  Blood clots and strokes are the most serious concern from atrial fibrillation and flutter. This danger can be largely prevented with proper blood "thinning" medications. Warfarin (also known as Coumadin) is a potent blood thinner. Proper dosing of this medication requires blood testing and monitoring by a physician. This medication is the treatment of choice for most patients with atrial fibrillation and risk factors for stroke. The degree of blood "thinning" is monitored by a blood test called an INR. An INR value between 2.0 and 3.0 is usually optimal for anticoagulation to be achieved.
• Cardioversion
  Atrial fibrillation and atrial flutter can usually be converted back to normal sinus rhythm. This may be done with medications or electrical current (called DC cardioversion). During electric cardioversion, an electrical impulse is delivered between two patches on the patient's chest. This resynchronizes electrical conduction in the atria and allows the sinus node to resume control. Electric cardioversion is highly effective and safe for restoring normal heart rhythm. However, because cardioversion itself has no long-lasting influence on the heart's rhythm, atrial fibrillation may recur following cardioversion. The likelihood of recurrence depends upon the underlying heart disease of an individual patient.
• Medications to Maintain Normal Rhythm
  Your cardiologist may recommend medications to maintain the normal heart rhythm. These antiarrhythmic medications may be used after a cardioversion to prevent the recurrence of atrial fibrillation or flutter.
• AV Node Ablation
  In some patients, medications are not effective at controlling the heart rate – or maintaining normal sinus rhythm. Such patients may not tolerate the rapid and irregular heartbeat caused by atrial fibrillation. These patients may feel symptoms such as palpitations, fatigue, and shortness of breath – particularly with exercise. One effective treatment for such patients is AV node ablation. This procedure blocks conduction of the disorganized electrical impulses to the lower chambers of the heart. A permanent pacemaker is implanted as part of this procedure to ensure that the heart keeps beating at a safe rate.
• Catheter Ablation of Atrial Fibrillation
  Catheter ablation may provide a cure for atrial fibrillation in selected patients. This invasive catheter-based procedure is based on the recognition that while atrial fibrillation can originate anywhere in the right or left atrium, it commonly originates in the pulmonary veins, which carry blood from the lungs to the left atrium. During the procedure, a catheter is inserted into the groin area advanced to the heart. The areas responsible for initiating or maintaining the atrial fibrillation – commonly the pulmonary veins – are treated an energy source. The most commonly used energy source is radiofrequency current. This treatment electrically "isolates" the treated area and prevents extra heartbeats from initiating atrial fibrillation.
• Catheter Ablation of Atrial Flutter
  Catheter ablation can cure atrial flutter. In this procedure, a catheter is inserted into a vein in the leg and is advanced to the heart. In the heart, energy is applied throught the catheter to destroy the abnormal electrical pathway that is causing the arrhythmia. The most commonly used energy source for treating atrial flutter is radiofrequency current. This procedure is extremely effective for eliminating atrial flutter.