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

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 heart beat. When the heart detects a signal, it contracts (or beats). The normal heart rate in adults about 60 to 100 beats per minute. The normal heart rate is faster in children.

In multifocal atrial tachycardia (MAT), multiple locations within the heart "fire" signals at the same time. Too many signals lead to a rapid heart rate -- anywhere from 100 to 250 beats per minute. The rapid heart rate causes the heart to work too hard. If the heart beat 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 aged 50 and over. It is often seen in people with conditions that lower the amount of oxygen in the blood. These conditions include:

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

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

• Coronary heart disease
• Had surgery within the last 6 weeks
• Overdosed on the drug theophylline
• Diabetes
• Sepsis (widespread systemic infection)

• Sensation of feeling the heart beat (palpitations)
• Light-headedness
• Fainting
• Shortness of breath
• Chest tightness
• Infants may have weight loss and failure to thrive

Additional symptoms that may be associated with this disease:

• Dizziness
• Breathing difficulty when lying down

An examination shows a rapid heart beat of 100 to 180 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 heart beat. These include:

• 24-hour Holter monitor
• Portable, long-term loop recorders -- allow you to start recording if symptoms occur
• If the patient is in the hospital, the heart rhythm is 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:

• Methods to improve blood oxygen levels
• Magnesium given by IV (intravenous) line
• Stopping medications, such as theophylline, which can increase the heart rate
• Medicines to control the heart rate, such as such as calcium channel blockers (verapamil, diltiazem) or selective beta-blockers

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

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

Call your health care provider if:

• Rapid or irregular heartbeat is associated with other MAT symptoms.
• Symptoms worsen, do not improve with treatment, or new symptoms develop.

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

Ferri FF. Ferri’s Clinical Advisor: Instant Diagnosis and Treatment. 8th ed. St. Louis, Mo: Mosby; 2006:540.

Marx J. Rosen’s Emergency Medicine: Concepts and Clinical Practice. 5th ed. St. Louis, Mo: Mosby; 2002:1080-1081.