What Is Multifocal Atrial Tachycardia?
If you have multifocal atrial tachycardia (MAT), your heart is beating much faster than it normally does. This happens when the upper chambers of your heart send too many electrical signals to the lower chambers. It is multifocal, which means that the signals come from tissue throughout the atria (upper heart chambers) rather than only from the sinoatrial node.
For an adult, a heart rate of 60 to 100 heartbeats per minute is considered normal. If you have MAT, your heart rate can be anywhere between 100 and 250 beats per minute.
MAT is rare in infants and children. They normally have higher heart rates than adults—100 to 130 beats per minute. When an infant or child has MAT, his or her heart rate will be 111 to 253 beats per minute. (Bradley et al., 2001)
Your heart is comprised of four chambers. The heart’s two uppermost chambers are called the right atrium and the left atrium; the two below are called the right ventricle and the left ventricle. The beating of your heart is stimulated by electrical impulses that begin in an area of the right atrium known as the sinoatrial node (sinus node or SA node). You could think of the SA node as your heart’s pacemaker—setting the pace at which your heart beats. As the electrical signal spreads through the walls of the upper chambers, it causes them to contract. Before the signal passes through to the ventricles, it slows to allow the upper chambers to contract before the lower ones do.
According to The Journal of Emergency Medicine, multifocal atrial tachycardia (MAT) is not common and is most frequently seen in people with severe cardiopulmonary (heart-lung) illness.
What Are the Causes of MAT?
MAT causes several different areas of your heart to emit electrical signals simultaneously. This results in a must faster heart rate—anywhere between 100 and 250 beats per minute.
MAT most commonly affects people over the age of 50. It is also found in people suffering from conditions that reduce the amount of oxygen in the blood. These include:
- COPD—caused by exposure to lung irritants
- bacterial pneumonia—a respiratory disorder in which the lungs are infected
- congestive heart failure—a condition that makes the heart unable to pump enough blood
- pulmonary embolism—a blockage in the main artery of the lung
- lung cancer
- lung failure
You may also be at an increased risk of MAT if you have:
- coronary heart disease
- sepsis—a severe inflammatory response to bacteria or other germs
- surgery within the last six weeks
- overdosed on the medication theophylline—a drug used to treat breathing disorders such as emphysema or asthma
What Are the Symptoms of MAT?
Many people see no signs of MAT. But if you do experience symptoms, it is likely that they will come and go. The most common symptoms of MAT are rapid pulse and fainting.
An increased pulse rate can occur while you are active or at rest and is usually accompanied by a feeling of tightness in the chest, a shortness of breath, and often a feeling of lightheadedness or dizziness
If you have MAT, you should be wary of fainting as a result of a shortness of breath that persists for some time.
The severity of these symptoms will vary considerably, depending on your age and general health. They tend to be worse in individuals whose pulse rate is most rapid.
Symptoms in Infants
When MAT occurs in infants, it may cause wheezing and weight loss.
How Is MAT Diagnosed?
Your doctor may suspect you are suffering from MAT if your heartbeat is between 100 and 250 beats per minute, your blood pressure is in the low to normal range, and you are also showing signs of poor circulation. If this is the case, your doctor may order the following tests:
- ECG—an electrocardiogram that monitors and records heartbeat activity
- electrophysiological study (EPS)—a minimally invasive procedure performed to monitor the heart’s electrical activity
Your doctor may also recommend that your heart be monitored to record the rate of your heartbeats. Monitoring can be done in several ways:
- Holter monitor—this monitor is usually worn for 24 to 48 hours during normal activity
- portable loop monitor—this is a long-term monitor that allows you to record heart activity as symptoms arise
- in-hospital monitoring—if you are in hospital, your heart activity will be monitored 24 hours a day.
What Are the Treatments for MAT?
Your doctor will first treat the underlying cause of your MAT. That can include hypoxia (inadequate oxygen), congestive heart failure, and theophylline toxicity. You may receive therapies to improve your blood oxygen levels. If the problem is theophylline toxicity, your doctor will stop that medication. Magnesium and potassium may be given intravenously to treat MAT. Your doctor may also prescribe medications like certain beta-blockers or calcium channel blockers that have proved effective in treating MAT.
Individuals with uncontrollable MAT may benefit from atrioventricular ablation (surgical removal) of the tissue that is sending the signals to beat and the permanent implantation of a pacemaker.
What Is the Long-Term Outlook for MAT?
The symptoms of MAT can be adequately managed as long as the underlying condition causing the rapid heart rate is controlled.
There are a number of long-term complications linked to MAT. These conditions may develop over time if the condition is not treated or if you are also suffering from additional heart conditions. Complications may include:
- reduction in the heart’s pumping action
- heart failure—the heart is unable to pump blood through the body
- cardiomyopathy—weakening or changing of the heart muscle.