There are two general types of arrhythmias: rapid heart rhythms and slow heart rhythms. These two arrhythmias may require an EP study.

Rapid Heart Rhythms (Tachycardias):
Rapid heart rhythms possibly originate in the atria, AV node, or ventricles. Rapid rhythms in the ventricles are potentially more serious because there pumps the blood.

• Supraventricular Tachycardia (SVT) is a series of rapid heartbeats that involves in the upper chambers of the heart.
• AV nodal re-entry tachycardia (AVNRT) is a common form of SVT where there is an extra pathway in or next to the AV node. An electrical impulse may enter this pathway, resulting in a very rapid heartbeat.
• Wolff-Parkinson-White (WPW) Syndrome is an abnormal "bridge" of tissue connecting the atria and ventricles. This causes a short circuit which can result in tachycardia.
• Atrial Fibrillation is when multiple impulses fire in the atria in a haphazard fashion. The atria then beats very quickly and ineffectively.
• Ventricular Tachycardia (VT) is when there is an abnormal electrical pathway located in the ventricles which may result in a rapid heartbeat.
• Ventricular Fibrillation is when multiple impulses fire rapidly in the ventricles in a haphazard fashion causing the ventricles to quiver and cease to pump blood efficiently.

Slow Heart Rhythms (Bradycardias):

• Sick Sinus Syndrome (SSS) is when the sinus node does not act as the heart's natural pacemaker.
• Some other variations of SSS are: Sinus Bradycardia (heart beats too slowly), Sinus Pause (heart pauses for too long), Bradycardia-Tachycardia Syndrome (heartbeat may alternate between too slow or fast)