Approach to Pediatric ECGs

Click for pdf: ECG basics

First thing’s first

• Check the name on the top of the ECG – is this your patient?
• Check the date – is this the one you ordered?
• Check for old ECGs – just like a chest xray, it’s always a good idea to compare with an old one
• Check for the age of the patient – the heart physiology and the normal values differ in different age groups in the pediatric population

Note: You may want to cover the top part of the ECG sheet now.  Do not rely on the computer calculated numbers; it may be wrong.  Trust yourself!

Technical Aspects

• Is the ECG full standard?
• Full standard means that the ECG was not reduced in size so that it can fit on the paper
• Look at the left hand side of each line

If it is full standard, the rectangle’s height should be 2 big squares

If it is half standard, the rectangle’s height is only 1 big square.  You will need to double all the waves to normalize them

What is the paper speed?

• The standard speed is 25mm/sec
• That means each little box is 0.04 seconds, each big box is 0.2 seconds, the whole strip is 6 seconds
• Now look at the top of the ECG, there should be a print out of what speed the ECG was ran at
• For tachyarrhythmias, the speed of the ECG may have been increased to 50 mm/sec in order to visualize the p waves; in this case, the speed and duration of the ECG components will need to be doubled

Rate

• Normal, Fast or Regular Rates
• Find 2 adjacent R waves, count the number of big squares between the R’s
• Divide 300 by the number of big squares : this is your rate
• Or . . . .Find a QRS complex that starts on a thick line, then count the thick lines using these numbers “300-150-100-75-60-50” to the next QRS

Slow or Irregular Rates

• The easiest way to calculate the rate is to count the total number of QRS complex along the length of the entire strip and multiply it by 10: this is your rate (bpm)

• Note: The normal value for heart rate ranges dramatically depending on your patient’s age.  Please compare your patient’s age and heart rate with Table 1.

Rhythm

Analysis

• Is the rhythm sinus?

Sinus rhythm:

• Is there a P wave before each QRS complex?
• Is there a QRS complex after every P wave?
• Are the P waves upright in leads I, II, III?
• Do all P waves should look the same?
• Are all P wave axis normal (0° to +90°)?
• Are the PR intervals constant?
• Is the rhythm fast or slow? (refer to Table 1 values)
• Is the rhythm regular or irregular? Do the P waves and QRS follow a regular pattern?
• If it is irregular, is it consistently irregular or consistently irregular?

Consistently irregular = some form to the pattern of irregular complex i.e. predictable
Inconsistently irregular = no pattern at all i.e. unpredictable

Abnormal Rhythms

Axis

• Axis is the “conduction flow” of the heart
• Normal axis varies with age – i.e. newborns have a right axis deviation because the left and right ventricles are the same size due to fetal circulation

• Look at the QRS complex of Lead I and Lead aVF
• Is the QRS complex of Lead I more negative (downgoing or conduction away from the lead) or positive (upgoing or conduction towards the lead)?
• Is the QRS complex of Lead aVF more negative or positive?

P Wave and PR Interval

• PR = beginning of P to beginning of QRS
• P wave normal is 2-3 little squares (0.08-0.12); if wide P wave = left atrial enlargement
• If P wave is taller than 2-3 little squares = right atrial enlargement
• PR interval is dependent on age (Table 1); if PR is wide = first degree AV block

QRS Complex

• If beginning of Q to end of S is longer than 2-3 small squares: bundle branch block
• Look for the “M” sign in either V1 or V6
• If the “M” is on V1:  Right bundle branch block (RBBB)

• If the “M” is on V6 : Left bundle branch block (LBBB)

QTc Interval

• Beginning of Q to end of T
• QT corrected interval for heart rate because as HR decrease, QT lengthens and vice versa
• Normal: <0.45 (<6 months), <0.44 (>6 months)
• QTc = QT / square root of RR interval
• DDx prolonged QT: long QT syndrome, hypokalemia, hypomagnesemia, hypocalcemia, neurologic injury
• Prolonged QT predisposes to ventricular tachycardia and associated with sudden death

T wave

• DDx of peaked, pointed T = hyperkalemia, LVH
• DDx of flattened T waves = hypokalemia, hypothyroidism

Ventricular Hypertrophy

Right ventricular hypertrophy

If any of the following:

• R wave >98% in V1 or S wave >98% in I or V6
• Increased R/S ratio in V1 or decreased R/S in V6
• RSR’ in V1 or V3R in the absence of complete RBBB
• Upright T wave in V1 (>3 days)
• Presence of Q wave in V1, V3R, V4R
• DDx of RVH: ASD, TAPVR, pulmonary stenosis, TOF, large VSD with pulmonary HTN

Left ventricular hypertrophy

If any of the following:

• R >98% in V6, S >98% in V1
• Increased R/S ratio in V6 or decreased R/S in V1
• Q >5mm in V6 with peaked T
• DDx: VSD, PDA, anemia, complete AV block, aortic stenosis, systemic HTN

Appendix

a) Table 1:  Normal Values

References

Garcia, Tomas and Neil Holtz. 12-Lead ECG: The Art of Interpretation. Jones and Bartlett Publishers Canada. 2001

Interpreting Pediatric ECG. Pediatric Cardiology at the University of Chicago.  http://pediatriccardiology.uchicago.edu/MP/ECG/ECG-submenue.htm

Acknowledgments

Written by: Jasmine Lam

Edited by: Jeff Bishop