Basic ECG Interpretation

P wave- atrial depolarization
PR segment- conduction delay through AV node

PR interval- atrial depolarization and conduction delay through AV node

QRS- ventricular depolarization

ST segment- isoelectric; ventricles still depolarized

QT interval- ventricular depolarization and ventricular repolarization

T wave- Ventricular repolarization

Normal Cardiac Rhythm Parameters

Normal sinus rhythm -----------between 60 and 100 bpm

Sinus bradycardia-------------- less than 60 bpm

Sinus tachycardia --------------over 100 bpm

QRS width---------------------- between 0.08 and 0.12 sec

PR interval ----------------------between 0.12 and 0.20 sec

QT interval ----------------------0.30-0.40 sec

Atrial rate, inherent------------ 60-100 bpm

Junctional rate, inherent ------ 40-60 bpm

Ventricular rate, inherent ----- 20-40 bpm

FIGURING RATE (for regular rhythms only)

1. 1500 method

- divide 1500 by the number of small squares between two consecutive QRS complexes

2. R-R method

- find a QRS where the peak R wave falls on a heavy dark line. USe this QRS as reference then take note where the next QRS falls. Starting from the next heavy line, count 300, 150, 100, 75, 60, 50, 40.

3. 6-second method

- count the number of QRS complexes in a 6 second strip and multiply by 10