Arrhythmias are divided up by the place where they happen. If they start in the ventricles, or lower chambers of your heart, they’re called ventricular. When they begin in the atria or upper chambers, they’re called supraventricular.

Doctors also group them by how they affect your resting heart rate. Bradycardia is a heart rate of fewer than 60 beats per minute. Tachycardia is more than 100 beats per minute.

Supraventricular arrhythmias include:

• Premature atrial contractions. These are early extra beats. They’re harmless and generally don't need treatment.

• Atrial fibrillation (AFib). The upper chambers of your heart contract in an unusual way. Your heart might beat more than 400 times a minute.

• Atrial flutter. This is usually more organized and regular than atrial fibrillation. It happens most often in people who have heart disease and in the first week after heart surgery. It frequently changes to atrial fibrillation.

• Paroxysmal supraventricular tachycardia (PSVT). This is a rapid heart rate, typically with a regular rhythm. It begins and ends suddenly.

• Accessory pathway tachycardia. You can have a rapid heart rate because of an extra pathway between your heart's upper and lower chambers. Think of it as an extra road on your way home, as well as your usual route. When that happens in your heart, it can cause a fast rhythm.

• AV nodal reentrant tachycardia (AVNRT). This is caused by an extra pathway through a part of your heart called the AV node. It can cause heart palpitations, fainting, or heart failure.

Ventricular arrhythmias include:

• Premature ventricular contractions (PVCs). These are among the most common arrhythmias. They're the "skipped heartbeat" that many of us feel sometimes.

• Ventricular tachycardia (V-tach). This is a rapid heart rhythm starting from the heart's lower chambers. Because your heart is beating too fast, it can't fill with enough blood. This can be a serious arrhythmia, especially in people who have heart disease, and it may be linked to other symptoms.

• Ventricular fibrillation (V-fib). This happens when your heart's lower chambers quiver and can't contract or pump blood to the rest of your body. It’s a medical emergency that must be treated with CPR and defibrillation as soon as possible.

• Long QT syndrome. Your heart’s lower chambers take too long to contract and release. This may cause dangerous rhythm problems and death.

Another type of arrhythmia, bradyarrhythmia, is a slow rhythm because of disease in your heart's electrical system or because of medication. It may make you pass out or feel like you will. Types of bradyarrhythmia include:

• Sinus node dysfunction. This is caused by an issue with your heart's sinus node, its natural pacemaker.

• Heart block. There’s a delay or a block of the electrical impulse as it travels from your heart's sinus node to its lower chambers.