EKG waves and intervals

the sequential activation (depolarization) of the right and left atria

right and left ventricular depolarization (normally the ventricles are activated simultaneously)

ventricular repolarization

time interval from onset of atrial depolarization (P wave) to onset of ventricular depolarization (QRS complex)

duration of ventricular muscle depolarization

duration of ventricular depolarization and repolarization