(Also known as: Heart rhythm disorders, irregular heartbeat)
An arrhythmia is a disorder that affects the normal heart rate. With an arrhythmia, the heart tends to beat too slow (bradycardia), too fast (tachycardia), or irregularly.


These disorders can affect the amount of blood pumped by the heart.

The heartbeat is controlled by electrical impulses that normally travel on a smooth path through the heart, causing the ventricles and atria to contract in a specific order, pushing blood through the lungs and body. These electrical impulses are controlled by the heart’s sinoatrial (SA) node, or sinus node, the heart’s natural pacemaker.

Although many arrhythmias will never cause health problems, they can cause troublesome symptoms, such as dizziness or chest discomfort. Other, more dangerous arrhythmias can impact blood supply and require medical management. Left untreated, they can eventually lead to stroke, heart attackheart failure, or sudden death.

Atrial fibrillation (afib) is the most common arrhythmia. Different types of atrial fibrillation may last for seconds or be permanent. The condition is more common in older people and can have many different causes.

Ventricular fibrillation is the most dangerous type of arrhythmia. With this condition, the heart’s ventricles lose the ability to contract, stopping blood flow to the body and brain. Ventricular fibrillation rapidly leads to loss of consciousness and death, and requires electrical shock (defibrillation) to restart the heartbeat.


Tests commonly used to diagnose arrhythmias include:

  • Electrocardiogram: to identify problems with heart rhythm

  • Holter monitor: a portable electrocardiogram machine used to continuously monitor the heartbeat over one or two days

  • Event monitor: similar to a Holter monitor, but used for weeks or months. An event recorder is turned on by the patient when symptoms occur

  • Electrophysiology studies: to track and stimulate electrical impulses in the heart

  • Stress (exercise) testing: to test whether an arrhythmia occurs when the heart is challenged to work harder than normal