Atrium (plural: Atria) — ECG/EKG Terminology

Definition: One of two upper chambers of the heart. The right atrium receives blood from the body; the left atrium receives blood from the lungs.

Key Facts

• Right atrium receives deoxygenated blood from the body
• Left atrium receives oxygenated blood from the lungs
• Thin-walled chambers designed for receiving, not powerful pumping
• Atria contract gently to help fill the ventricles below

ECG Connection: Atrial depolarization creates the P wave on the ECG—a small, rounded deflection at the beginning of each heartbeat.

Why It Matters: Recognizing P wave abnormalities helps you identify atrial rhythm problems early.