The Process - ECG Interpretation

From the AHA Arrhythmia Media Library link, you can explore a wide variety of visual images and text related to cardiac topics.
http://watchlearnlive.heart.org/CVML_Player.php?moduleSelect=arrhyt

Isoelectric Line

Straight line seen when no electrical activity occurs.
The baseline of the tracing.

P wave

Represents atrial depolarization.
Impulse fired from SA node and spreads through atrial tissue.
Usually upright and rounded.

P-R Interval

The time required for the impulse to travel through the atria to A-V node.
0.12 - 0.20 seconds
Measured from beginning of P wave to beginning of QRS complex.

QRS Complex

Represents ventricular depolarization.
0.06 - 0.08 seconds
Measured from beginning of Q wave to end of S wave.

J-Point

Represents junction where QRS complex ends and ST segment begins.

S-T Segment

Represents time interval between completion of ventricular depolarization and onset of ventricular repolarization.
Measured from the end of QRS complex to beginning of T wave.

Q-T Segment

Represents the time required for ventricles to depolarize and repolarize.
0.32 - 0.40 seconds
Measured from onset of QRS complex to end of T wave.

T wave

Represents ventricular repolarization.
Usually same deflection as QRS complex.

U wave

Represents late ventricular repolarization.
Small, usually positive deflection following the T wave
Uncertain significance - typically seen with hyokalemia

Electrocardiogram Primer video: A weblink to view an ECG video http://www.hhmi.org/biointeractive/echocardiogram