Multifocal atrial tachycardia is a rapid heart rate that occurs when too many signals (electrical impulses) are sent from the upper heart (atria) to the lower heart (ventricles).

The human heart gives off electrical impulses, or signals, which tell it to beat. Normally, these signals begin in an area of the upper right chamber called the sinoatrial node (sinus node or SA node). This node is considered the heart's "natural pacemaker." It helps control the heartbeat. When the heart detects a signal, it contracts (or beats).

The normal heart rate in adults is about 60 to 100 beats per minute. The normal heart rate is faster in children.

In multifocal atrial tachycardia (MAT), multiple locations in the atria fire signals at the same time. Too many signals lead to a rapid heart rate -- usually from 100 to 130 beats per minute in adults. The rapid heart rate causes the heart to work too hard and inefficiently. If the heartbeat is very fast, the heart has less time to fill up with blood, so it doesn't have the right amount of blood to pump to the brain and the rest of the body.

MAT is most common in people age 50 and over. It is often seen in people with conditions that lower the amount of oxygen in the blood. These conditions include:

• Bacterial pneumonia
• Chronic obstructive pulmonary disease (COPD)
• Congestive heart failure
• Lung cancer
• Lung failure
• Pulmonary embolism

You may be at higher risk for MAT if you have:

• Coronary heart disease
• Diabetes
• Had surgery within the last 6 weeks
• Overdosed on the drug theophylline
• Sepsis

When the heart rate is less than 100 beats per minute, the arrhythmia is called "wandering atrial pacemaker."

Some people may have no symptoms. When symptoms occur, they can include:

• Chest tightness
• Light-headedness
• Fainting
• Sensation of feeling the heart beat (palpitations)
• Shortness of breath
• Weight loss and failure to thrive in infants

Other symptoms that can occur with this disease:

• Breathing difficulty when lying down
• Dizziness

An examination shows a fast irregular heartbeat, usually of 100 to 130 beats per minute. Blood pressure is normal or low. There may be signs of poor circulation.

Tests to diagnose MAT include:

• ECG
• Electrophysiologic study (EPS)

Heart monitors are used to record the rapid heartbeat. These include:

• 24-hour Holter monitor
• Portable, long-term loop recorders -- allow you to start recording if symptoms occur
• If you are in the hospital, your heart rhythm will be monitored 24 hours a day

If you have a condition that can lead to MAT, that condition should be treated first.

Treatment for MAT includes:

• Improving blood oxygen levels
• Giving magnesium or potassium through a vein
• Stopping medications, such as theophylline, which can increase the heart rate
• Taking medicines to slow the heart rate (if the heart rate is too fast), such as such as calcium channel blockers (verapamil, diltiazem) or beta-blockers

MAT can be controlled if the condition that causes the rapid heartbeat is treated and controlled.

• Cardiomyopathy
• Congestive heart failure
• Reduced pumping action of the heart

Call your health care provider if:

• You have a rapid or irregular heartbeat with other MAT symptoms
• You have MAT and your symptoms get worse, do not improve with treatment, or you develop new symptoms

To reduce the risk of developing MAT, promptly treat the disorders that cause it.

Olgin JE, Zipes DP. Specific arrhythmias: diagnosis and treatment. In: Bonow RO, Mann DL, Zipes DP, Libby P, eds. Braunwald's Heart Disease: A Textbook of Cardiovascular Medicine. 9th ed. St. Louis, Mo: WB Saunders; 2011:chap 39.

Zimetbaum P. Cardiac arrhythmia with supraventricular origin. In: Goldman L, Schafer AI, eds. Cecil Medicine. 24th ed. Philadelphia, Pa: Saunders Elsevier; 2011:chap 64.