The Electrical Heart

Every heartbeat starts with an electrical signal. This signal originates in an area called the sinus node in the upper chamber of the heart (right atrium) and then travels through specialized electrical pathways to excite the lower chambers (ventricles) to contract. This process happens about 60 times a minute, resulting in a pulse.

When an electrocardiogram (EKG) is performed, we are looking at this electrical signal as it is picked up from the skin. A normal EKG is shown here:

Each tall spike shows the electrical impulse as it races through the lower chambers (ventricles) – a process that takes less than a tenth of a second in a normal individual! We will discuss next in the heart rhythm problem section what can cause abnormally slow and fast heart rhythms.

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