What is an Electrocardiogram?
An electrocardiogram (ECG) is a "picture" of the conduction of electrical
impulses through the heart.
What information may be obtained
from an ECG?
An ECG can tell the physician many things about the heart such as:
- Heart Rate
- Type of heart rhythm that is present.
- Where the electrical pulses originate.
- Abnormalities of conduction.
- Heart chamber enlargement.
- Evidence of previous damage (heart attack).
How is an ECG obtained?
For a standard ECG, 10 leads are placed on the chest and limbs of the patient.
Electrode patches with a conduction gel are applied to the patient and lead wires are
attached to the patches.
Is there any preparation the
patient must do prior to the test?
The patient should wear comfortable clothing that will allow easy access to the chest.
The skin of the patient is usually cleansed with alcohol and hair shaved, if needed, were
the electrode patches will be applied to ensure the patches will adhere to the skin in
order to get a good lead hook-up.
When the patient is properly hooked up to the electrocardiograph the patient is asked
to just relax and within seconds the ECG is complete.
When are electrocardiograms necessary?
Here at the Helena Cardiology Clinic, Dr. Paustian gets a baseline ECG on every new
patient seen in the clinic. The ECG is like your heart’s own "fingerprint,"
it is unique to you. ECGs are also obtained when a patient is returning to the clinic from
open heart surgery or angioplasty. Dr. Paustian may also request an ECG when a patient has
complaints of chest pain or has new onset of an irregular pulse.
What information should the
patient supply before having an ECG?
Patients should keep a current list of medications indicating their doses and how often
the medications are taken as certain medications can have an effect on the outcome of the
ECG.
In order to understand some of the information provided
by an ECG the following is a simplified explanation of the heart's anatomy and function.
The heart is a hollow, muscular organ that pumps blood to the lungs for oxygenation and
then back to the rest of the body. The adult heart weighs about one pound and is
approximately the size of your fist.
The heart has four chambers: right atrium, left atrium (upper chambers): right
ventricle, left ventricle (lower chambers). The heart is further divided by a muscular
wall called the septum, which divides the heart into the right and left side. The right
side of the heart pumps blood to the lungs to be oxygenated and the left side pumps the
oxygenated blood to the body.
The atria contract at the same time followed by the contraction of the
ventricles. These contractions usually occur in a rhythmic beat.
The normal electrical conduction pathway begins in a place in the heart called the SA
node, which is located in the upper portion of the right atrium. The impulse travels
downward through both the right and left atrium to the AV node located in the lower right
atrium near the septum. From here the impulse is directed down the septum through the
Bundle of His located between the ventricles to the Purkinje’s fibers circling the
ventricles and into the ventricular muscle. The cycle is then repeated again which will
result in a normal heart rhythm.
Any disruption in the conduction pathway will be shown in the ECG making it possible
for the physician to determine where the electrical impulses are starting from and
finishing at, as well as areas of the heart that may have been damaged by an event such as
a heart attack or other disease processes.
An electrocardiogram is an easy, painless diagnostic tool that can assist the physician
in determining the cardiac health of his patients.
Return to Top
.gif)
