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Heart Procedures - Signal-Average Electrocardiogram - Page 2

Signal-Average Electrocardiogram

Overview

EKG may also be done for other reasons, including, but not limited to, the following:

During a physical examination, an EKG may be performed to obtain a baseline tracing of the heart's function. This baseline tracing may be used later as a comparison with future EKGs to determine if any changes have occurred.
An EKG may be performed as part of a work-up prior to a procedure such as surgery, to determine if there is a pre-existing heart condition that may cause complications during or after the procedure.
An EKG may be performed to assess the function of an implanted pacemaker.
An EKG may be performed to determine the effectiveness of certain heart medications.
An EKG may be performed to assess the heart's status after an MI, or after a heart-related procedure such as a cardiac catheterization, heart surgery, electrophysiological studies, etc.

click image to enlarge

So Just What Do All Those Funny Squiggles Mean?
Almost everyone knows what a basic EKG tracing looks like. But what does it mean?

The first little upward notch of the EKG tracing is called the "P wave." The P wave indicates that the atria (the two upper chambers of the heart) are contracting to pump out blood.

The next part of the tracing is a short downward section connected to a tall upward section. This next part is called the "QRS complex." This part indicates that the ventricles (the two lower chambers of the heart) are contracting to pump out blood.

The next short upward segment is called the "ST segment." The ST segment indicates the amount of time from the end of the contraction of the ventricles to the beginning of the rest period before the ventricles begin to contract for the next beat.

The next upward curve is called the "T wave." The T wave indicates the resting period of the ventricles.

When your physician studies your EKG, he/she looks at the size and length of each part of the EKG. Variations in size and length of the different parts of the tracing may be significant. The tracing for each lead of a 12-lead EKG will look different, but will have the same basic components as described above. Each lead of the 12-lead EKG is "looking" at a specific part of the heart, so variations in a lead may indicate a problem with the part of the heart associated with a particular lead.

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