Arrhythmias may not cause any signs or symptoms. In fact, your doctor might find you have an arrhythmia before you do, during a routine examination.

Some people do have noticeable arrhythmia symptoms, which may include:

- A fluttering in your chest
- A racing heartbeat (tachycardia)
- A slow heartbeat (bradycardia)
- Chest pain
- Shortness of breath
- Lightheadedness
- Dizziness
- Fainting (syncope) or near fainting

Noticeable signs and symptoms don't always indicate a serious problem. Some people who feel arrhythmias don't have a serious problem, while others who have life-threatening arrhythmias have no symptoms at all.

When to see a doctor

Arrhythmias may cause you to feel premature heartbeats, or you may feel that your heart is racing or beating too slowly. Other signs and symptoms may be related to reduced blood output from your heart. These include shortness of breath or wheezing, weakness, dizziness, lightheadedness, fainting or near fainting, and chest pain or discomfort. Seek urgent medical care if you suddenly or frequently experience any of these signs and symptoms at a time when you wouldn't expect to feel them.

Ventricular fibrillation is one type of arrhythmia that is deadly. It occurs when the heart beats with rapid, erratic electrical impulses. This causes pumping chambers in your heart (the ventricles) to quiver uselessly, instead of pumping blood. Without an effective heartbeat, blood pressure plummets, cutting off blood supply to your vital organs. A person with ventricular fibrillation will collapse within seconds and soon won't be breathing or have a pulse. If this occurs, follow these steps:

- Call 911 or the emergency number in your area.
- If you or someone nearby knows cardiopulmonary resuscitation (CPR), begin providing it if it's needed. CPR can help maintain blood flow to the organs until an electrical shock (defibrillation) can be given.

Portable defibrillators, which can deliver an electric shock that may restart heartbeats, are available in an increasing number of places, such as airplanes, police cars and shopping malls. They can even be purchased for your home. Portable defibrillators come with built-in instructions for their use. They're programmed to allow a shock only when appropriate.