Pediatric EKG Interpretation
Before you read the EKG, look for:
 Patient age, as many values change with age
 Standardization: Full standard is two large squares (1 mV, 10 mm) and half standard is one large square (0.5mV, 5 mm)
 Paper speed: the standard is 25 mm/sec. The faster the paper speed the slower the HR will look and vice versa
Basic EKG interpretation
 Heart rate: The standard paper speed is 25 mm (5 large squares)/sec. This means that if the distance between two beats (RR) is 5 large squares, the HR is 60 beat/min. If the distance between two beats is one large square, the HR is 300 beat/min. Two squares →150, 3 squares →100, 4 squares → 75, 5 squares → 60, 6 squares → 50 beat/min. The HR may be counted by simply dividing 300 by the number of the large squares between two heart beats (RR).
 Axis: Make sure to determine both P wave and QRS axes. Net summation of positive and negative deflection is used. Look for two perpendicular leads (usually lead I and aVF). When QRS is positive in both lead I and aVF, the axis is in the left lower quadrant (090 degrees). If it is negative in lead I and positive in aVF, the axis is in the right lower quadrant (90180 degrees) and so forth.
 Rhythm: The sinus node is located at the SVC/right atrial junction. Sinus rhythm is characterized by:
a) One P wave preceding each QRS complex.
b) All P waves are uniform in shape.
c) Normal P wave axis is in the left lower quadrant (090 degrees), i.e. upright in both lead I and aVF (unless there is dextrocardia).  Durations/Intervals:
a) P wave: Normally it is 2.5 mm wide and 2.5 mm high. Tall P waves indicate RA enlargement (RAE), wide P waves indicate LA enlargement (LAE), wide and bipeaked P waves indicates biatrial enlargement (BAE).
b) PR interval varies with age and heart rate and is <0.2 sec at any age
c) QRS duration (23 small squares or 0.080.12 sec). Wide QRS may indicate bundle branch block or ventricular beats.
d) QT interval (measured from the beginning of Q to the end of T waves). QTc is the QT interval corrected for the heart rate. QTc=QT (in seconds)/square root of preceding RR interval (in seconds).  Chamber Hypertrophy/Enlargement: a) Right ventricular hypertrophy: I Voltage criteria (tall R in V1 and deep S in V6>95% for age) II Extreme right axis deviation III rSR' in V1 with a tall R' IV qR pattern in V1 V Upright T wave in V1 > 1 week of age b) Left ventricular hypertrophy: Less well defined than RVH. I Voltage criteria (tall R in V6 and deep S in V1) II Left axis deviation III Strain pattern in left precordial leads (inverted T waves in V5 and V6)
Summary of Normal Values 

Age Group 
Heart Rate (beats/min)* 
Frontal Plane QRS Vector (degrees) 
PR Interval (sec) 
QRS Duration V5 
Q III (mm) †‡ 
Q V6 (mm) † 
RV1 (mm) 
SV1 (mm) 
R/SV1 
RV6 (mm) 
SV6 (mm) 
R/SV 6 
SV1+ RV 6 (mm) † 
R + S V 4 (mm) † 

Less than 1 day 
93154 
+59 to 163 
0.080.16 (.11) 
.030.07 (.05) 
4.5

2

526 (14) 
023 (8) 
.1U (2.2) 
011 (4) 
09.5 (3) 
.1U (2.0)

28

52.5

1 to 2 days 
90159 (123) 
+64 to 161 
0.080.14 (.11) 
.030.07 (.05) 
6.5 
2.5 
527 (14) 
021 (9) 
.1U (2.2) 
012 (4.5) 
09.5 (3) 
.1U (2.5)

29 
52 
3 to 6 days 
91166 (129) 
+77 to 163 
0.070.14 (.11) 
.030.14 (.05) 
5.5 
3 
324 (13) 
017 (7) 
.1U (2.2) 
.512 (5) 
010 (3.5) 
.1U (2.2)

24.5 
49 
1 to 3 wks 
107182 (148) 
+65 to +161 
0.070.14 (.10) 
.030.08 (.05) 
6 
3 
312 (11) 
011 (4) 
.1U (2.2) 
2.516.5 (7.5) 
010 (3.5) 
.1U (3.3)

21 
49 
1 to 2 mo 
121179 (14)9 
+31 to +113 
0.070.13 (.10) 
.030.08 (.05) 
7.5 
3 
38 (10) 
012 (5) 
.1U (2.2) 
521.5 (11.5) 
06.5 (3) 
.2U (4.8)

29 
53.5 
3 to 5 mo 
106186 (141) 
+7 to +104 
0.070.15 (.11) 
.030.08 (.05) 
6.5 
3 
320 (10) 
017 (6) 
.1U (2.2) 
6.522.5 (13) 
010 (3) 
.2U (6.2)

35 
61.5 
6 to 11 mo 
109169 (134) 
+6 to +99 
0.070.16 (.11) 
.030.08 (.05) 
8.5 
3 
1.520 (9.5) 
.518 (4) 
.1U (2.2) 
622.5 (12.5) 
07 (2) 
.2U (7.6)

37 
53 
1 to 2 yr 
89151 (119) 
+7 to +101 
0.080.15 (.11) 
.040.08 (.06) 
6 
3 
2.517 (9) 
.521 (8) 
.1U (2.2) 
622.5 (13) 
06.5 (2) 
.3U (9.3)

39 
49.5 
3 to 4 yr 
73137 (108) 
+6 to +104 
0.090.16 (.12) 
.040.08 (.06) 
5 
9.5 
118 (8) 
.221 (10 
.1U (2.2) 
824.5 (15) 
05 (1.5) 
.6U (10.8)

42 
53.5 
5 to 7 yr 
65133 (100) 
+11 to +143 
0.090.16 (.12) 
.040.08 (.06) 
4 
4.5 
.514 (4) 
.324 (12) 
.1U (2.2) 
8.526.5 (16) 
04 (1) 
.9U (11.5)

47 
54 
8 to 11 yr 
62130 (91) 
+9 to +114 
0.080.16 (.11) 
.040.09 (.06) 
3 
3 
012 (5.5) 
.325 (12) 
.1U (2.2) 
925.5 (16) 
04 (1) 
1.5U (14.3)

45.5 
53 
12 to 15 yr 
60119 (85) 
+11 to 130 
0.080.16 (.11) 
.040.09 (.07) 
3 
3 
010 (4) 
.321 (11) 
.1U (2.2) 
6.523 (14) 
04 (1) 
1.4U (14.7

41 
50 
_{* 2 to 98% (mean)} 