Symptoms, Causes and Diagnosis

Frequently Asked Questions (FAQs)


Find answers to your questions about cardiac arrhythmias.



Find definitions of technical terms in our glossary.

Understanding Cardiac Arrhythmias 

In simple terms, your heart is both an electrical system and a fluid-pumping system. The electrical system delivers signals to the heart, starting a four-step pumping action, which circulates the right amount of blood to the rest of your body. A normal heart beats about 60 to 100 beats per minute. 

Abnormal heart rhythms or contractions can develop if your heart’s electrical signals become blocked or irregular because of disease, injury, other medical issues or lifestyle choices. If this happens to you, you have what is called an arrhythmia (a-RITH-me-ah), or rhythm disorder. Your heart may beat too fast, too slow or out of sync. In each case, this means that the heart may pump blood less effectively and you may experience symptoms as a result. Lack of blood flow can damage the brain, heart and other organs, potentially causing blood clots, strokes and sudden cardiac arrest. 

There are three types of arrhythmias:

  • A heartbeat that is too fast is called tachycardia. 
  • A heartbeat that is too slow is called bradycardia.
  • An extra heartbeat is called a premature ventricular contraction. 


Bradycardia, a heartbeat of less than 60 beats per minute, occurs when signals to the heart beat too slowly, irregularly or not at all. You may feel tired, confused or have short of breath because your body is not getting enough oxygen. There are two main types of bradycardia:

  • Sick sinus syndrome
  • Heart block

Learn more about bradycardia.


Tachycardia, a heartbeat faster than 100 beats per minute, is caused by faulty electrical signals that tell your heart to beat fast. The signals can originate in the upper or lower chambers of your heart. Symptoms can include:

  • Heart palpitations
  • Feeling overtired
  • Feeling out of breath
  • Dizziness

Types of tachycardia include:

  • Atrial fibrillation, which is the most common heart rhythm disorder
  • Atrial flutter
  • Supraventricular tachycardia
  • Ventricular tachycardia

One other type of tachycardia is ventricular fibrillation, which is more serious and is the cause of half of all cardiac deaths.

Learn more about tachycardia.

Premature ventricular contractions

A premature ventricular contraction, or early heartbeat, is an arrhythmia in which the heart’s lower chambers contract an extra time between two normal heartbeats. Medications, caffeine and stress can cause early heartbeats, or they can occur spontaneously. The extra contractions can make your heart seem to flip-flop or skip a beat.

Learn more about premature ventricular contractions (PVCs)