Dana Karem

Electrocardiography ECG

What is ECG

Illustration of the electrical activities of the heart.

Normal Cardiac Electrical Distribution

Electrode Placement

ECG PRINT

Normal ECG Pattern

Interpretation P wave: Atrial depolarisation

QRS complex: Ventricular depolarisation

T wave: Ventricular repolarisation

Meanings

Depolarisation happens when a cell membrane's charge develops into positive to produce action potential. This is induced by the influx of Ca++ and Na+ into the cell.

Repolarisation happens when a cell membrane's charge develop into (returns to) negative. This is induced by the escape of K+

out of the cell.

Intervals

The Heart Rate

Rule of 300 When the rhythm is regular, count the

number of large squares between two R waves

Divide 300 by how many squares there are between two R waves

The Heart Rate

(300 / 6) = 50 beats per minutes

Six squares

The Rhythm

R-R distances are fixed (the same)

Irregular Rhythm

R-R distances are variable (not the same)