Which type of arrhythmia is characterized by premature contractions originating from the atrium?

Premature Atrial Complexes (PACs) are a type of arrhythmia characterized by early heartbeats that originate in the atria. These premature contractions lead to an early depolarization of the atrial tissue, resulting in a heartbeat that occurs earlier than expected in the cardiac cycle.

PACs can disturb the normal heart rhythm but are often considered benign, especially in individuals without structural heart disease or other underlying conditions. They typically show a distinctive pattern on an electrocardiogram, with an early P wave that may have a different shape compared to the normal sinus P waves.

In contrast, conditions like Atrial Flutter involve a rapid reentrant circuit in the atrium leading to a rapid, but organized contraction, while Atrial Fibrillation is characterized by disorganized electrical activity of the atria resulting in irregularly timed contractions. Ventricular Tachycardia refers to a rapid heart rhythm originating from the ventricles, making it quite distinct from the premature contractions originating in the atrium that define PACs.