Ege Üniversitesi Pediatrik Kardiyoloji Bilim Dalı: Interpreting Pediatric ECG by Pediatric cardiology at The University of Chicago

2.4.09

Interpreting Pediatric ECG by Pediatric cardiology at The University of Chicago

Pediatric cardiology at The University of Chicago

Interpreting Pediatric ECG

First, bring the ECG you want to interpret.
Do you have it in front of you? Good, let's proceed.
Take a deep breath and stop cursing. In few minutes you will have the ECG completely read!

Things you MUST note prior to starting the interpretation process:
What is the patients age? many of the values will be affected by this.
Is the ECG "full standard"? A full standard means that the ECG was not reduced in size so as to fit on the paper. Full standard is represented by a rectangle at the onset of each line on the ECG paper. the rectangle's height is 2 big squares if it is full standard. If the ECG is half standard, then the rectangle will be one large square high. Occasionally you'll see that the rectangle goes up to 2 large squares, the descends to only one large square, this means that the limb leads (I, II, II, aVR, aVL and aVF) are full standard, while the chest leads V1 to V6 are half standard.
Important: If the ECG is half standard you MUST multiply all waves by 2 to normalize them.

Full standard 10mm/mV

Half standard 5 mm/mV

Full/Half standard 10/5 mm/mV

Is the ECG "standard speed"? The standard speed of paper is 25 mm/sec. Occasionally it is made to run at a double speed (50 mm/sec) in cases of tacharrhythmia to enable the visualization of an otherwise hidden p waves. If the speed is doubled, then calculated heart rate should be doubled and measured durations (PR, QRS and QT) must be halved to obtain actual rate and durations.

Heart rate:
Count the number of big squares between two consecutive R waves (RR duration). Now divide 300 by the number of squares counted. That's the heart (or more accurately the ventricular) rate.
If you were anal and into inflicting pain onto yourself, you can be more accurate by counting the number of small squares, then dividing 1,500 by that number.
If there is sinus arrhythmia, causing variation in the heart rate during the respiratory cycle, then you can do the above mentioned heart rate measurement twice. Once with the shortest RR cycle and again with the longest RR cycle, then average the two.

How to determine axis?
ECG waves, such as "p" , "QRS" have an axis which determines its spatial relationship. This helps to understand where the particular wave is origniating from and where it is heading to. The various ECG leads determines this. A positive deflection of a p wave in a particular lead means that the direction of that wave is within 90 degrees on each side of that lead. By using two or three leads one can determine the direction of that wave. Therefore an upright p wave in leads I and aVF indicates that it is within the range of 0-90 degrees, this is normal for a sinus node originating p wave.

When calculating a "QRS" axis, the net deflection is calculated. This is the net summation of the positive and negative deflection of the various components of the QRS complex. For example, if the R wave is 10 mm high and the S wave is 3 mm deep, then the net QRS is 7 mm high, or generally speaking is an "upward deflection" in that lead, i.e. it is within 90 degrees of either side of that lead.

Where's the P?
The "p" wave represents the stimulation from the sinus node (cardiac pace maker) as it travels through the atria. Because of its origin from the high right atrium and travel towards the AV node at the atrio-ventricular junction, it assumes a positive (upward) configuration in leads I and aVF.

If the p wave is upright in leads I and aVF, then it is most likely originating normally from the sinus node. On the other hand a P wave of an axis other than 15 to 110 is unlikely to be from the sinus and is most probably from an ectopic atrial focus acting as a pace maker, either due to malfunction of the sinus node and an escape atrial rhythm, or due to an abnormal ectopic tachycardia firing at a rate faster than the sinus node, thus taking over the pace maker function.

Durations
P wave: Normally less than 2-3 small squares (0.08-0.12 sec) wide. Wide P waves indicate left atrial enlargement.
PR interval: If longer than what is appropriate for age (see Normal Values table below), that's first degree AV block.

Normal Values

Age	HR bpm	QRS axis degrees	PR interval seconds	QRS interval seconds	R in V1 mm	S in V1 mm	R in V6 mm	S in V6 mm
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

QRS duration: If longer than 2-3 square (0.08-0.12 sec), that's bundle branch block (BBB).
RBBB or LBBB? To determine if a block is right BBB versus left BBB, look for the "M" shaped QRS. If you see it in V1 (right chest lead) then it is RBBB, if you see it in V6 (left chest lead), then it is LBBB.

RBBB

LBBB

QT, QTc: measure the QT interval, which is the duration from the beginning of the QRS complex to the end of the T wave. To do so, count the number of small squares, then multiply by 0.04 seconds, that the QT in seconds. Normal QT is determined by the HR. Therefore, you can either use the following formula if you are a nerd and into calculation.
QTc = QT / square root of RR interval
Or just determine the QTc from the QTc table below.

QT Table

QT HR	0.20	0.25	0.30	0.35	0.40	0.45	0.50
50	0.18	0.23	0.27	0.32	0.37	0.41	0.46
52	0.19	0.23	0.28	0.32	0.37	0.42	0.46
54	0.19	0.23	0.28	0.33	0.38	0.42	0.47
56	0.19	0.24	0.29	0.34	0.38	0.43	0.48
58	0.20	0.24	0.29	0.34	0.39	0.44	0.49
60	0.20	0.25	0.30	0.35	0.40	0.45	0.50
63	0.21	0.25	0.31	0.36	0.41	0.46	0.51
66	0.21	0.26	0.31	0.36	0.42	0.47	0.52
68	0.22	0.26	0.32	0.37	0.43	0.48	0.53
71	0.22	0.27	0.33	0.38	0.44	0.49	0.55
75	0.23	0.27	0.34	0.39	0.45	0.51	0.56
79	0.24	0.28	0.34	0.40	0.46	0.52	0.57
83	0.24	0.29	0.35	0.41	0.47	0.53	0.69
88	0.25	0.29	0.36	0.43	0.49	0.55	0.61
94	0.26	0.30	0.38	0.44	0.50	0.56	0.63
100	0.27	0.31	0.39	0.45	0.52	0.58	0.65
107	0.28	0.32	0.40	0.47	0.53	0.60	0.67
115	0.28	0.35	0.42	0.49	0.55	0.63	0.69
125	0.29	0.36	0.43	0.51	0.58	0.65	0.72
136	0.30	0.38	0.45	0.53	0.60	0.68	0.75
150	0.32	0.40	0.47	0.56	0.63	0.71	0.79

What is the rhythm?
To determine rhythm, please go to Arrhythmia detection Device.
Is there chamber hypertrophy?

Are the P waves too tall (more than 2-3 small squares)?
If so: Right Atrial Enlargement (RAE)

The P wave is taller than two small squares (>0.08 sec) in infants and small children
and more than three small squares (> 0.12 sec) in older children and adults.
P waves are best seen in the inferior (I, II & aVF) and the right chest leads (V & V).

Are the P waves too wide (more than 2-3 small squares)?
If so: Left Atrial Enlargement (LAE)

The P waves are wide, more than two small squares (> 0.08 sec) in infants and small children
and more than three small squares (> 0.12 sec) in older children and adults.
These P waves are best seen in the inferior (I, II & aVF) and the left chest leads (V & V).

Do the QRS complexes in V1 have any of the following configurations?
If so: Right Ventricular Hypertrophy (RVH)

R in V1 taller than 95% of normal PLUS S in V deeper than 95%.

rsR’ in V1 & V2 without widening of QRS complex as in bundle branch block. (The upper case R in rsR’ indicate that the R’ deflection is taller than the r wave.

qR in V1 & V2 .

Pure R wave in V1 & V2 , with or without ST & T changes indicative of strain.

Is the R wave too tall in V6 and or the S wave too deep in V1?
If so: Left Ventricular Hypertrophy (LVH)

S in V deeper than 95% of normal and R in V taller than 95% of normal.
& R in V1 taller than 95% of normal PLUS S in V deeper than 95%, or other features of RVH