Basic Cardiology:
ELECTROCARDIOGRAPHY
The Basics
What is an ECG?
An ECG is a graphic interpretation of the electrical output of the heart. The heart's conduction system is translated into different waveforms, known collectively as an ECG. The ECG records changes in magnitude and direction of the electrical activity of the heart.
What is an EKG?
Kardiogram is the German spelling. Since Einthoven, the inventor of the ECG/EKG was German, EKG is a commonly used abbreviation. Ode to Einthoven.
Why do we use the ECG/EKG?
The ECG is a noninvasive diagnostic tool that medical personnel can use to continuously monitor for cardiac conduction abnormalities.
Electrodes:
We use electrodes to create the leads in which we view the ECG. Modern electrodes are usually pre-packaged with conductive gel on the side which attaches to the body of the patient. Some have a medal diode to which the ECG wires attach. Some have a tab that ECG wires are clipped to. It is important to follow the manufacturers recommendations on the storage of these electrodes. The conductive gel may lose it's worth if left out.
The standard placement of each electrode is on all four extremities. The distal portion of the extremity is ideal and recommended for accurate ECGs. This has been modified by many clinicians for purpose of ease. The shoulders and lower abdomen or thighs are commonly used locations. Doing this increases the magnitude of the wave forms and reduces artifact from movement.
The wires are attached to the electrodes at specific locations. The white wire goes to the right shoulder/arm of the patient. The black wire should be located at the left shoulder/arm, and the red wire below that one on the left leg/thigh or abdomen. The green wire should be attached to the right leg/thigh or abdomen.
There are common tricks of the trade when it commons to remembering electrode/wire placement. Smoke over fire, meaning black over the red. I personally teach the condiment method; salt, pepper, ketchup, relish (white, black, red, green). Starting clockwise on the right arm/shoulder of the patient, the condiment method never fails.
Note: Torso placement of electrodes is not ideal for a patient with dyspnea. This will increase artifact from movement of the chest wall and abdomen.
Why do some monitors only have three wires?
All of the limb leads can be obtained from the three lead system. The green electrode/wire is known as the neutral.
Einthoven:
At this point of my tutorial I am going to send you over to another tutorial, and a whole other blog. Instead of writing everything I have learned about Einthoven from Tom B's blog, I am just going to let you read it from where I learned it on the Prehospital 12-lead blog. All of you really need to read at this point is part 1. I will cover most of the information from the rest of his tutorial. I dare you to try and not read the rest though.
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