When the heart beats too slowly, it is called bradycardia, a type of arrhythmia.

An arrhythmia is any disorder of your heart rate or rhythm. It means that your heart beats too quickly, too slowly or with an irregular pattern.

Many factors can affect your heart's rhythm, such as having had a heart attack, blood chemistry imbalances or abnormal hormone levels. Some substances or medicines may also cause arrhythmias.

Symptoms can include: fast or slow heart beat, skipping beats, lightheadedness, dizziness, chest pain, shortness of breath, paleness and sweating.