The ECG pt 1 Flashcards
What does the P wave reflect
Atrial depolarization
What does the P-R segment reflect
An isoelectric period showing the time it takes for the wave to pass through the AV node, AV bundle and bundle branches
What does the QRS complex reflect
Ventricular depolarization
What does the P-R interval reflect
The time taken for the wave to pass from atria to ventricles
What does the T wave reflect
Ventricular repolarisation
What does the ST segment reflect
Isoelectric period, plateau of ventricular AP
Vector representation. What does the direction and length of the vector represent?
Direction represents the direction of the dipole (current)
The length represents the strength of the dipole
On an ECG recording do you get a positive or negative deflection of the positive dipole faces the electrode?
Positive.
What do measured potentials depend on?
Magnitude of the charges
Orientation of the dipole and electrodes
Distance between dipole and electrodes
What is a dipole
A pair of equal but opposite charges separated by a small distance
Why can we measure the dipoles using electrodes at distal parts of the body
Because of Faraday’s law stating that current flow at proximal and distal parts of the body equally
Describe Einthovens triangle including location of leads, and positive negative corners for each.
Top of triangle (horizontal) Lead 1. Negative RA Positive LA
Left side of triangle Lead 2 RA negative, LL positive
Right side triangle Lead 3 LL positive, LA negative
What is the range of normal mean QRS vector?
-30- 110 degrees
