If you have MAT, your heart beats much faster than normal. This happens when the upper chambers of your heart send too many electrical signals to the lower chambers.

For an adult, a heart rate of 60 to 100 heartbeats per minute is normal. If you have MAT, your heart rate can be anywhere between 100 to 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, their heart rate will be 111 to 253 beats per minute.

According to a 1994 study in The Journal of Emergency Medicine, MAT isn’t common. It’s most frequently seen in people with a severe cardiopulmonary (heart-lung) illness.

Many people see no signs of MAT. If you do experience symptoms, it’s likely that they’ll come and go. The most common symptoms of MAT are rapid pulse, shortness of breath, and fainting.

Rapid pulse

An increased pulse rate can occur while you’re active or at rest. It’s usually accompanied by tightness in the chest, shortness of breath, and often lightheadedness or dizziness.

Shortness of breath

Difficult or uncomfortable breathing or feeling like you can’t get enough air usually accompanies the rapid pulse.

Fainting

If you have MAT, you should be wary of fainting. It can be caused by 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.

MAT causes several different areas of your heart to emit electrical signals simultaneously. This results in a much faster heart rate — anywhere between 100 and 250 beats per minute.

MAT most commonly affects people over the age of 50. It’s also found in people suffering from conditions that reduce the amount of oxygen in the blood. These include:

  • COPD, which is 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:

  • diabetes
  • 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

Your doctor may suspect you’re suffering from MAT if your heartbeat is between 100 and 250 beats per minute, your blood pressure is low to normal, and you have signs of poor circulation. If this is the case, your doctor may order the following tests:

  • Electrocardiogram (ECG). This is an electrocardiogram that monitors and records heartbeat activity.
  • Electrophysiological study (EPS). This is 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’re in hospital, your heart activity will be monitored 24 hours a day.

Your doctor will first treat the underlying cause of your MAT. That can include hypoxia, or 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. This involves the surgical removal of the tissue that sends signals to the heart for it to beat and the permanent implantation of a pacemaker.

The symptoms of MAT can be managed as long as the condition causing the rapid heart rate is controlled.

However, a number of long-term complications are linked to MAT. These conditions may develop over time if the condition isn’t treated or if you’re suffering from additional heart conditions. Complications may include:

  • a reduction in your heart’s pumping action
  • heart failure, which is when your heart is unable to pump blood through your body
  • cardiomyopathy, a weakening or changing of your heart muscle

Contact you doctor if you experience rapid or irregular heartbeat with shortness of breath, lightheadedness, or fainting. Treating disorders that lead to MAT is the best prevention.