Arrhythmias are abnormal beats of the heart, such as:

  • Heartbeats that are too slow ( bradycardia)
  • Heartbeats that are too fast (tachycardia)
  • Extra beats
  • Skipped beats
  • Beats coming from abnormal areas of the heart

Heartbeat: Anatomy of the Heart

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Arrythmias can also be classified by the point of origination within the heart muscle:

  • Arrhythmias originating within the atria
  • Arrhythmias originating within the ventricles

The heart is a muscular pump with its own power supply and internal controls. It generates its own electrical signals to prompt each heartbeat and can therefore beat independently of the rest of the body. The electrical signal begins in a "pacemaker" called the sinoatrial, or sinus, node, which is in the back of the right atrium (upper right heart chamber). Arrhythmias can arise from any part of the heart's circuitry. Those that come from the atria are called atrial and are usually benign. Most of the dangerous arrhythmias start in the ventricles (lower chambers) or are due to failure of conduction through the atrioventricular (AV) node or due to abnormal electrical activity within the ventricles. The AV node is the electrical connection point between the atria and ventricles.

For descriptions of the many types of arrhythmias, click here.