Electrocardiogram

An electrocardiogram or electrocardiograph (ECG or EKG) is a recording of the electrical activity of the heart obtained non-invasively via skin electrodes. Its name is made of different parts: electro, because it is related to electrical activity, cardio, Greek for heart, graph, a Greek root meaning "to write".

Electrical impulses in the heart originate in the sinoatrial node and travel through the heart muscle where they impart electrical initiation of systole or contraction of the heart. The electrical impulses can be measured at selectively placed electrodes on the skin over the heart. Electrodes on different sides of the heart measure the activity of different parts of the heart muscle. The ECG cannot reliably measure the pumping ability of the heart or rule out blockages in the heart arteries; for which other tests as echocardiogram, nuclear stress tests , cardiac CT or catheterization may be done.