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CHAPTER 47   Abnormal Heart Rhythms
TOPICS   Introduction ~ Premature Beats ~ Atrial Flutter and Atrial Fibrillation ~ Ventricular Tachycardia ~ Ventricular Fibrillation ~ Sinus Bradycardia and Sick Sinus Syndrome ~ Heart Block
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Atrial Flutter and Atrial Fibrillation

Atrial flutter and atrial fibrillation are very similar. In both arrhythmias, the atria beat much faster than normal. The main difference is that the atria beat regularly in atrial flutter and irregularly in atrial fibrillation.

Normally, the atria contract while the ventricles are resting. This contraction pumps blood into the ventricles. In atrial flutter and atrial fibrillation, the atria do not have time to fill with blood completely, and they do not pump blood into the ventricles in a coordinated way. Thus, the ventricles of the heart cannot fill with blood and pump it out efficiently.

Atrial flutter is usually temporary. Typically, it either goes away (with or without treatment) or changes into another arrhythmia, usually atrial fibrillation. Sometimes atrial fibrillation is intermittent. But it can become constant, with no periods of normal heart rhythm. Both atrial flutter and atrial fibrillation may lead to serious problems, such as blood clots and heart failure.

Atrial flutter and atrial fibrillation are more common among older people. Other than premature beats, atrial fibrillation is the most common abnormal heart rhythm among older people. About 1 out of 10 people over 80 have chronic atrial fibrillation.

In older people, the most common causes of atrial flutter are coronary artery disease and chronic obstructive pulmonary disease (COPD). The most common causes of atrial fibrillation are high blood pressure, coronary artery disease, mitral valve disorders, and heart failure.

In atrial flutter or atrial fibrillation, the ventricles often beat faster than normal. The faster the ventricles beat, the less well they fill with and pump blood. Generally, the faster they beat, the more serious the consequences. Consequences may include chest pain, a heart attack, or heart failure.

Also during these arrhythmias, the left atrium does not empty completely. Clots tend to form in the blood that remains in the atrium. The clots can break off, leave the heart, travel through arteries, and eventually block small arteries elsewhere in the body. As a result, the area that the blocked artery normally supplies with blood does not get enough blood. Atrial fibrillation is more likely to cause clots than atrial flutter. The risk of blood clots is high for older people with atrial fibrillation.

Symptoms

Symptoms of atrial flutter or atrial fibrillation depend largely on how fast the heart rate is. With a heart rate up to about 120 beats per minute, some older people have no symptoms, but a few develop heart failure. With a faster rate, many people have unpleasant palpitations or chest discomfort. People with atrial flutter tend to have a fast but regular pulse. Those with atrial fibrillation tend to have a fast, irregular pulse. If the conduction of electrical currents in the heart is also abnormal, the pulse may remain normal or may even be slower than normal, despite flutter or fibrillation.

People who have atrial flutter or atrial fibrillation may feel weak, faint, and short of breath. They may develop chest pain or heart failure. Sudden pain or cramping in a leg or an arm may develop if atrial fibrillation causes blood clots to form in the atrium and part of one breaks off and blocks an artery in the leg or arm. A stroke may occur if a blood clot blocks an artery to the brain.

Diagnosis and Treatment

Doctors may suspect atrial flutter or atrial fibrillation on the basis of symptoms. Sometimes one of the arrhythmias is detected during a routine examination in a person who has no symptoms. Electrocardiography (ECG) can confirm the diagnosis. If the arrhythmia is intermittent, a portable ECG (Holter) monitor or event recorder may be needed. Sometimes transesophageal echocardiography (ultrasonography of the heart) is done to determine whether clots have formed in the heart. For this test, an imaging device is passed down the person's throat into the esophagus. This test is safe but can cause gagging and anxiety. Therefore, doctors usually give the person a sedative beforehand.

In an emergency—when atrial flutter or atrial fibrillation results in chest pain or shock—doctors usually use a cardioverter-defibrillator to try to restore a normal rhythm quickly. For this procedure, an electrical shock is applied to the chest with two small paddles.

In nonemergencies, when blood pressure is adequate and no chest pain is felt, an antiarrhythmic drug is given intravenously to slow the fast heart rate so that the heart pumps blood more efficiently. For people who also have heart failure, digoxin is often used first. For other people, a drug such as diltiazem, verapamil, or propanolol may be used. Sometimes one of these drugs is given with digoxin. Although these drugs slow the rapid heart rate, they do not usually restore heart rhythm to normal. Other drugs, such as procainamide, ibutilide, or dofetilide may be given intravenously to restore heart rhythm back to normal very quickly. If the heart rhythm returns to normal and if atrial flutter or atrial fibrillation is unlikely to recur, the drugs may be discontinued. People are then monitored periodically by their doctor to check for recurrences of the arrhythmia.

If atrial fibrillation persists, antiarrhythmic drugs (such as amiodarone, propafenone, sotalol, or quinidine) may be given by mouth to restore the heart rhythm to normal. Some people may be given drugs such as diltiazem, verapamil, or propranolol (with or without digoxin) to control the heart rate, rather than trying to restore heart rhythm to normal. In either case, warfarin (an anticoagulant) may also be given to help prevent blood clots from forming. However, taking warfarin increases the risk of bleeding, especially for older people. For example, minor bumps may cause bleeding under the skin (bruises), cuts may bleed longer, and bleeding after surgery may be excessive. To keep this risk as low as possible, doctors periodically do blood tests to measure how long blood takes to clot and adjust the dose of warfarin accordingly. Warfarin is not given to people who have bleeding disorders and may not be given to people who are at high risk of falling.

In some people who have taken antiarrhythmic drugs for a few weeks, the heart rhythm returns to normal. If it does not, an electrical shock is often applied to the chest to restore a normal heart rhythm. This procedure may cause a clot to be dislodged from the heart and thus increases the risk of a stroke. Taking warfarin for 3 weeks before the procedure helps reduce the risk of blood clots. Warfarin is continued for several weeks after the electrical shock is applied and may be continued indefinitely in people at high risk for recurrence of atrial fibrillation.

In some people, an electrical shock does not restore a normal heart rhythm. In other people, an electrical shock returns heart rhythm to normal for several weeks or months, then atrial flutter or atrial fibrillation recurs. Some people do not wish to have an electrical shock applied to the chest. In all of these situations, most people must take antiarrhythmic drugs and warfarin for the rest of their life. If palpitations are uncomfortable despite the continued use of drugs or if heart failure develops, a procedure called catheter ablation may be recommended. In this procedure, part or all of the electrical connection between the atria and ventricles is destroyed. If all of the connection is destroyed, a permanent artificial pacemaker must be implanted.

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