Electrical Sequence Of The Heart Ekg

The synchronized electrical sequence of the heart is initiated by the SA node, the heart's natural pacemaker. The firing of the SA node sends out an electrical impulse via its neurons to the right atrium, left atrium, and AV node simultaneously. Since the right atrium is closer to the SA node, it depolarizes first, resulting in pumping action by the right atrium before the left atrium. At the AV node, the impulse is delayed to allow for the ventricles to fill up with blood. After the delay, the AV node sends the impulse to the Bundle of His and the Purkinje fibers. This triggers the contraction of the ventricles to send blood either to the lungs or out to the body.

Component of the electrical sequence

Association in the heart

P Wave

Firing of the SA node and depolarization of the atria.

PR Interval

Delay of the electrical impulse at the AV node and the depolarization of the atrium.

Ventricular depolarization

QRS Complex

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Q-wave = first negative deflection

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S-wave = second negative deflecton

R-wave = first positive deflection

ST Segment

The beginning of ventricular repolarization. Should be isoelectric (flat at baseline).

T Wave

Ventricular repolarization.

Electrocardiograms The electocardiogram or ECG is a major diagnostic tool for the assessment of the health of the heart. It is a measurement taken at the surface of the skin which reflects the electrical phenomena in the heart when the SA node triggers the electrical sequence that controls heart action.