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

Premature Atrial Contraction (PAC)	Length of two cycles (R-R) usually shorter Preceded by P wave, followed by normal QRS No hemodynamic significance
Premature Ventricular Contraction (PVC)	Premature, wide QRS, no P waves, T wave opposite to QRS I.e. multifocal, bigeminy, trigeminy, couplets Maybe normal if uniform and decrease with exercise
Atrial Flutter	Rapid atrial rate (~300 bpm) with varying ventricular rate Sawtooth pattern Suggests significant pathology
Atrial Fibrillation	Very fast atrial rate (350-600 bpm) Irregularly irregular No P waves, normal QRS Suggests significant pathology
Ventricular Tachycardia	Wide, unusually shaped QRS T waves opposite direction of QRS HR 120-200 bpm Suggests significant pathology
Ventricular Fibrillation	Very irregular QRS Rate is rapid and irregular “terminal arrhythmia”

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?

Lead I	Lead aVF	Axis
+	+	Normal
+	–	Left Axis Deviation
–	+	Right Axis Deviation
–	–	Extreme Right Axis Deviation

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

Age	HR bpm	QRS axisdegrees	PR intervalseconds	QRS intervalseconds	R in V1mm	S in V1mm	R in V6mm	S in V6mm
1st week	90-160	60-180	0.08-0.15	0.03-0.08	5-26	0-23	0-12	0-10
1-3wks	100-180	45-160	0.08-0.15	0.03-0.08	3-21	0-16	2-16	0-10
1-2 mo	120-180	30-135	0.08-0.15	0.03-0.08	3-18	0-15	5-21	0-10
3-5 mo	105-185	0-135	0.08-0.15	0.03-0.08	3-20	0-15	6-22	0-10
6-11 mo	110-170	0-135	0.07-0.16	0.03-0.08	2-20	0.5-20	6-23	0-7
1-2 yr	90-165	0-110	0.08-0.16	0.03-0.08	2-18	0.5-21	6-23	0-7
3-4 yr	70-140	0-110	0.09-0.17	0.04-0.08	1-18	0.5-21	4-24	0-5
5-7 yr	65-140	0-110	0.09-0.17	0.04-0.08	0.5-14	0.5-24	4-26	0-4
8-11 yr	60-130	-15-110	0.09-0.17	0.04-0.09	0-14	0.5-25	4-25	0-4
12-15 yr	65-130	-15-110	0.09-0.18	0.04-0.09	0-14	0.5-21	4-25	0-4
> 16 yr	50-120	-15-110	0.12-0.20	0.05-0.10	0-14	0.5-23	4-21	0-4

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