Week 2 ECG Interpretation Parts of a Normal ECG

P Wave

Atrial depolarization; represents the electrical activation that causes the atria to contract.

PR Interval

Time from the beginning of atrial depolarization to the beginning of ventricular depolarization; represents conduction of the electrical impulse from the atria through the AV node toward the ventricles.

QRS Complex

Ventricular depolarization; represents the electrical activation that causes the ventricles to contract.

ST Segment

Period after ventricular depolarization and before ventricular repolarization; normally should be close to the baseline.

T Wave

Ventricular repolarization; represents the electrical recovery of the ventricles after contraction.

R-R Interval

Time between one R wave and the next R wave; used to assess heart rate and whether the ventricular rhythm is regular.

P-P Interval

Time between one P wave and the next P wave; used to assess whether the atrial rhythm is regular.

Q Wave

First negative deflection of the QRS complex; represents the beginning of ventricular depolarization.

R Wave

First positive deflection of the QRS complex; represents the main phase of ventricular depolarization.

S Wave

Negative deflection that follows the R wave; represents the final phase of ventricular depolarization.