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How Does an EKG Work?

An electrocardiogram (EKG) is a machine that interprets and records electrical impulses of the heart for diagnostic purposes. Remember that it is not a method of treatment for a heart condition but a machine used to observe the activity of the heart.

The EKG records the heart’s electrical pulses to create an electrocardiograph which helps heart doctors learn more about the heart.

How EKG Testing Works

EKG electrodes are designed to listen to and record the strength and timing of pulses passing through the heart. The data is recorded on a graph with different parts of the graph showing each step of an electrical signal’s journey through the patient’s heart.

• All electrical signals start in a group of cells known as the sinus node or sinoatrial (SA) node located in the upper right chamber of the heart. In a healthy adult at rest, the SA sends 60-100 signals per minute.
• From the SA, heart impulses travel to the right and left atria causing the atria to contract thereby pumping blood into the heart’s lower chambers, the ventricles. Electrical signals in this phase are recorded as P waves.
• The electrical signals passing from the atria to the ventricles through the atrioventricular (AV) node are recorded on the EKG as a flat line between the end of the P wave and the beginning of the Q wave.
• From the AV, the signals travel through a group of cells called the bundle of HIS, and into the right and left bundle branches. This phase is recorded as the QRS wave.
• The last wave, recorded by the EKG device as the T wave, is captured as the heart recovers to its original electrical state.

EKG testing is completely invasive – it simply involves placing the EKG machine over the chest to record the heart’s electrical activity.

Uses of the EKG

An electrocardiogram is used to:

• Determine the rate of heart beats
• Determine the regularity of heart rhythms
• Determine the positioning of the heart chambers
• Measure the size of the heart’s chambers
• Monitor surgical repairs, pacemakers, and/or effects of drugs currently being used to treat an existing heart problem.

Note: An EKG machine doesn’t measure the blood pumping capability of the heart.

Contact Dr. Seldon

Dr. Seldon, a Heart Doctor and Cardiologist in New York City, offers same day appointments and all testing is done on site. Call us at (212) 367-8000.