Normal ECG Parameters – Vocabulary Flashcards

Vocabulary flashcards summarizing the components and normal values of a standard electrocardiogram (ECG).

P wave

Represents atrial depolarization; normally 0.07–0.12 s in duration, ≤2.5 mm in amplitude, rounded and positive in all leads except aVR where it is negative.

PR interval (P–R interval)

The time for impulse conduction from atria to ventricles (AV node); normal length 0.12–0.20 s.

QRS complex

Depicts ventricular depolarization; Q wave < 2 mm, total duration < 0.10 s, r/S ratio in V1 < 1, and SV2 + RV5 < 35 mm (>50 yrs) or < 45 mm (<50 yrs).

RR interval

Time between successive R waves, used to calculate heart rate; at rest, 0.75–1 s between QRS complexes.

ST segment

Isoelectric segment marking the beginning of ventricular repolarization.

T wave

Reflects the end of ventricular repolarization; normally rounded, asymmetric, positive in all leads except negative in aVR.

QT interval

Encompasses ventricular depolarization and repolarization (electrical systole). Measured where T wave is most visible (lead II or V5).

Corrected QT (QTc)

Heart-rate–adjusted QT using QTc = QTm + 0.154 (1000 − RR); normal < 450 ms in adult males and < 460 ms in adult females.