Multifocal atrial tachycardia
Multifocal atrial tachycardia (MAT) is a rapid heart rate. It occurs when too many signals (electrical impulses) are sent from the upper heart (atria) to the lower heart (ventricles).
What makes your heart beat? - Animation
The cardiac conduction system is a group of specialized cardiac muscle cells in the walls of the heart that send signals to the heart muscle causing it to contract. The main components of the cardiac conduction system are the SA node, AV node, bundle of His, bundle branches, and Purkinje fibers. The SA node (anatomical pacemaker) starts the sequence by causing the atrial muscles to contract. From there, the signal travels to the AV node, through the bundle of His, down the bundle branches, and through the Purkinje fibers, causing the ventricles to contract. This signal creates an electrical current that can be seen on a graph called an electrocardiogram (EKG or ECG). Doctors use an EKG to monitor the cardiac conduction system's electrical activity in the 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 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.
Conduction system of the heart
The intrinsic conduction system sets the basic rhythm of the beating heart by generating impulses which stimulate the heart to contract.
In MAT, many locations in the atria fire signals at the same time. Too many signals lead to a rapid heart rate. It most often ranges from 100 to 130 beats per minute or more in adults. The rapid heart rate may cause the heart to work too hard and not move blood efficiently. If the heartbeat is very fast, there is less time for the heart chamber to fill with blood between beats. Therefore, not enough blood is pumped to the brain and the rest of the body with each contraction.
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:
- 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
- Had surgery within the last 6 weeks
- Overdosed on the drug theophylline
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
- Sensation of feeling the heart is beating irregularly or too fast (palpitations)
- Shortness of breath
- Weight loss and failure to thrive in infants
Other symptoms that can occur with this disease:
Exams and Tests
A physical exam shows a fast irregular heartbeat of over 100 beats per minute. Blood pressure is normal or low. There may be signs of poor circulation.
Tests to diagnose MAT include:
Heart monitors may be used to record the rapid heartbeat. These include:
- 24-hour Holter monitor
- Portable, long-term loop recorders that allow you to start recording if symptoms occur
If you are in the hospital, your heart rhythm will be monitored 24 hours a day, at least at first.
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 medicines, such as theophylline, which can increase heart rate
- Taking medicines to slow the heart rate (if the heart rate is too fast), 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.
Complications may include:
When to Contact a Medical Professional
Contact 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 for developing MAT, treat the disorders that cause it right away.
Michael A. Chen, MD, PhD, Associate Professor of Medicine, Division of Cardiology, Harborview Medical Center, University of Washington Medical School, Seattle, WA. Also reviewed by David C. Dugdale, MD, Medical Director, Brenda Conaway, Editorial Director, and the A.D.A.M. Editorial team.
Kalman JM, Sanders P. Supraventricular tachycardias. In: Libby P, Bonow RO, Mann DL, Tomaselli GF, Bhatt DL, Solomon SD, eds. Braunwald's Heart Disease: A Textbook of Cardiovascular Medicine. 12th ed. Philadelphia, PA: Elsevier; 2022:chap 65.
Zimetbaum P. Supraventricular cardiac arrhythmias. In: Goldman L, Schafer AI, eds. Goldman-Cecil Medicine. 26th ed. Philadelphia, PA: Elsevier; 2020:chap 58.