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Electrocardiogram (EKG) components and intervals
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An electrocardiogram (EKG, ECG) translates the heart's electrical activity into line tracings on paper. The spikes and dips in the line tracings are called waves.
- The P wave is a record of the electrical activity through the upper heart chambers (atria).
- The QRS complex is a record of the movement of electrical impulses through the lower heart chambers (ventricles).
- The ST segment shows when the ventricle is contracting but no electricity is flowing through it. The ST segment usually appears as a straight, level line between the QRS complex and the T wave.
- The T wave shows when the lower heart chambers are resetting electrically and preparing for their next muscle contraction.
Last Updated:
May 5, 2009- Medical Review:
- Caroline S. Rhoads, MD - Internal Medicine
John A. McPherson, MD, FACC, FSCAI - Cardiology
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