Tuesday, July 24, 2007
ECG lecture
Theoretical Basis of the ECG:
An electrical current in the direction towards the positive end of a bipolar electrode causes a positive deflection of the stylus of the ECG. If the number of myocardial cells (dipoles) in this direction increases, the current will increase as well. The greater the current, the more positive the voltage. An electrical current in the direction away from the positive end of a bipolar electrode causes a negative deflection of the stylus of the ECG. If the number of myocardial cells (dipoles) in this direction increases, the current will increase as well. The greater the current, the more negative the voltage.
ECG Leads:
An electrocardiographic lead is a recording electrode or a pair of recording electrodes at a specified location. In clinical practice, twelve leads are usually used in the diagnostic ECG, although there is no limitation to the number of leads one may select for special purposes. The leads are usually placed on the elbows and stifles. A right leg electrode is used as the ground.
ECG Standard Leads:
Leads I, II and III are all bipolar (i.e., they detect a change in electric potential between two points) and detect an electrical potential change in the frontal plane. Lead I is between the right arm and left arm electrodes, the left arm being positive. Lead II is between the right arm and left leg electrodes, the left leg being positive. Lead III is between the left arm and left leg electrodes, the left leg again being positive.
Sometimes, the acronym EKG is used instead of ECG.
Labels: ECG introduction
# posted by Dr. Ulman @ 11:06 PM 
