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Electrocardiogram (EKG, ECG) tracing

Electrocardiography (EKG, ECG) tracings show a characteristic pattern of electrical impulses that are generated by the heart. The different parts of an EKG tracing of a heartbeat are called the P wave, the QRS complex, the ST segment, and the T wave.

See a picture of EKG components and intervals .

The P wave is a record of the movement of electrical activity through the upper heart chambers (the atria) and is recorded when they contract.
The QRS complex is a record of the movement of electrical impulses through the lower heart chambers (the ventricles) and is recorded when they contract.
The ST segment appears as a straight, level line between the QRS complex and the T wave. Elevated or lowered ST segments may mean the heart muscle is damaged or not receiving enough blood.
The T wave corresponds to the period when the lower heart chambers are relaxing and preparing for their next muscle contraction.

Author	Robin Parks, MS
Editor	Kathleen M. Ariss, MS
Editor	Marianne Flagg
Associate Editor	Terrina Vail
Associate Editor	Pat Truman, MATC
Primary Medical Reviewer	Caroline S. Rhoads, MD - Internal Medicine
Specialist Medical Reviewer	Robert A. Kloner, MD, PhD - Cardiology
Last Updated	August 25, 2008

WebMD Medical Reference from Healthwise

Last Updated: August 25, 2008

This information is not intended to replace the advice of a doctor. Healthwise disclaims any liability for the decisions you make based on this information.