An electrocardiogram (EKG, ECG) is a test that measures the
electrical signals that control heart rhythm. The test measures how electrical
impulses move through the heart muscle as it contracts and relaxes.
The electrocardiogram 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
The QRS complex is a record of the
movement of electrical impulses through the lower heart chambers
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
ByHealthwise Staff Primary Medical ReviewerRakesh K. Pai, MD, FACC - Cardiology, Electrophysiology Specialist Medical ReviewerGeorge Philippides, MD - Cardiology
Current as ofMarch 12, 2014
WebMD Medical Reference from Healthwise
March 12, 2014
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