What is an arrhythmia?

An arrhythmia is an abnormal heart rhythm.

Some arrhythmias can cause problems with contractions of your heart chambers by:

  • Not allowing the lower chambers (ventricles) to fill with enough blood, because an abnormal electrical signal is causing your heart to pump too fast or too slow.
  • Not allowing enough blood to be pumped out to your body, because an abnormal electrical signal is causing your heart to pump too slowly or too irregularly.
  • Not allowing the top chambers (atria) to work properly. 


An arrhythmia can occur in the
sinus node, the atria, or the atrioventricular node. These are called supraventricular
arrhythmias. A ventricular arrhythmia is caused by an abnormal electrical focus within
your ventricles. This results in abnormal conduction of electrical signals within your
ventricles. Arrhythmias can also be listed as slow (bradyarrhythmia) or fast
(tachyarrhythmia). “Brady-” means slow, and “tachy-” means fast.

In any of these situations, your body’s vital organs may not get enough blood to meet their needs.

What causes an arrhythmia?

An arrhythmia occurs when there is
a problem with the electrical system that is supposed to control a steady heartbeat.
With a problem in the electrical system, your heart may beat too fast, too slow, or


Who is at risk for an arrhythmia?

Many things can affect the
electrical system of your heart and cause an arrhythmia. Substances such as caffeine,
alcohol, tobacco, illegal drugs, diet medicines, some herbs, and even prescription
medicines can trigger an arrhythmia. Health conditions such as coronary heart disease,
high blood pressure, and diabetes raise your risk for arrhythmias. Arrhythmias become
more common as you get older.

What are the symptoms of arrhythmias?

The effects on the body are often
the same, whether the heartbeat is too fast, too slow, or too irregular. Some symptoms
of arrhythmias include:

  • A sensation of fluttering or irregular
    heartbeat (palpitations) 
  • Weakness
  • Tiredness (fatigue)
  • Low blood pressure
  • Dizziness
  • Fainting
  • Heart failure
  • Collapse and cardiac arrest
  • Difficulty feeding (in babies)

The symptoms of an arrhythmia may
look like other conditions. Always see your healthcare provider for a diagnosis.

How are arrhythmias diagnosed?

Several tests may be used to
diagnose arrhythmias. Some of these are discussed below.

Electrocardiogram (ECG) measures the electrical activity of your heart. Small
sticky patches called electrodes are placed at specific locations on your body such as
your chest, arms, and legs. The electrodes are connected to wires that pick up the
heart’s electrical activity and send it to the machine. The machine interprets the
activity and makes a graph (tracing). An ECG can show:

  • An arrhythmia
  • Damage to the heart from a lack of oxygen to the heart
    muscle (ischemia). This is also called a heart attack (myocardial infarction).
  • A problem with one or more of the valves
  • Another type of heart condition


The ECG has several variations:

  • Exercise ECG, or stress test. You are
    attached to the ECG machine as described above. But you walk on a treadmill or pedal
    a stationary bike while the ECG is recorded. This test is done to check for changes
    in the ECG during stress, such as exercise.
  • Signal-averaged ECG. This procedure is done in the same
    manner as a regular an ECG, except that your heart’s electrical activity is recorded
    over a longer period of time, usually 15 to 20 minutes. Signal-averaged ECGs are done
    when your healthcare provider thinks you may have an arrhythmia, but it’s not seen on
    a regular ECG. The signal-averaged ECG has more sensitivity to problems in the
    ventricles called “late potentials.” Signal-averaged ECG is used in research and
    seldom used in for patients.
  • Electrophysiologic studies (EPS).
    This is a nonsurgical but invasive test in which a small, thin tube (catheter)
    is put into a large blood vessel in your leg or arm and moved to your heart. This
    lets your healthcare provider find where the arrhythmia originates within your heart
    tissue. Your provider can then figure out how to best treat it. Sometimes, your
    provider can treat the arrhythmia by doing an ablation at the time of the
  • Holter monitor. A Holter monitor is a
    continuous ECG recording done over a period of 24 or more hours. Electrodes are
    attached to your chest and connected to a small portable ECG recorder by lead wires.
    Holter monitoring may be done when your healthcare provider thinks you may have an
    arrhythmia. Arrythmias may last only a very short time and not be seen on during the
    shorter recording time of a regular ECG. While wearing a Holter monitor, you can go
    about your daily activities. But you should not do activities that cause a lot of
    sweating. This could cause the electrodes to become loose or fall off. You should
    also not take a shower or swim while wearing a a Holter monitor.
  • Event monitor. This is similar to a
    Holter monitor, except that you start the ECG recording only when you feel symptoms.
    Event monitors are typically worn longer than Holter monitors. You can remove the
    monitor to shower or bathe. 
  • Mobile cardiac monitoring. This is
    similar to Holter and event monitors. The ECG is checked constantly to spot
    arrhythmias. The ECG is recorded and sent to your healthcare provider regardless of
    whether you have symptoms. You can also start recordings yourself when you have
    symptoms. These monitors can be worn up to 30 days. 
  • Implantable loop recorder. This is a
    miniature heart recording device that is implanted underneath the skin over your
    heart. It can record the heart rhythm for up to 3 years. It is useful in diagnosing
    arrhythmias that happen only now and then or rarely..