Corresponding address: Shakuntala Prabhu, Div. of Pediatric Cardiology, Dept. of Pediatrics, B.J.Wadia Hospital for Children, Mumbai.
Email : ssprabhu1@hotmail.com

Steps to read Pediatric Electrocardiograms :

The electrocardiogram must be read systematically in the following order to extract the maximum information possible:

Rate calculation:

Heart rate = 1500 / Number of small squares in one R-R interval
Count the number of big boxes between the 2 R waves, if: 1= 300 bpm, 2 = 150 bpm, 3 = 100 bpm, 4 = 70 bpm and 5 = 60 bpm (bpm = beats per minute)

In children, cardiac output is determined primarily by heart rate as opposed to stroke volume. With age, the heart rate decreases as the ventricles mature and stroke volume plays a larger role in cardiac output. Age and activity-appropriate heart rates thus must be recognized. Average resting heart rate varies with age; newborns can range from 90-160 beats per minute (bpm) and adolescents from 50-120 bpm. The average heart rate peaks about the second month of life and thereafter gradually decreases until adolescence. Heart rates grossly outside the normal range for age should be scrutinized closely for dysrhythmias

Axis detection:

Axis helps to interpret the major vector of depolarization. Determine if the net QRS voltage is positive or negative in lead I and lead aVF. For example, if the R wave height is 10 mm (above the isoelectric line) and S wave height is 4 mm (below the isoelectric line), then the net QRS voltage is positive (+6). If the R wave is short and S wave is longer, the net QRS voltage would be negative.

The QRS axis can be located using the following simple rule:

Lead I	Lead aVF	Interpretation	Comment
Positive	Positive	Normal axis	Abnormal in neonates and early infancy
Negative	Positive	Right axis deviation	Normal in neonates and in early infancy
Positive	Negative	Left axis deviation	Abnormal at any age
Negative	Negative	North-west axis	Abnormal at any age