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 (10 mV) and half standard is one (5mV)
- Paper speed: the standard is 25 mm/sec
Basic EKG interpretation
Heart rate: the paper speed determines the heart rate. The standard paper speed is 25 mm (5 large squares)/sec. This means that if the distance between two beats 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. The HR may be counted by simply dividing 300 by the number of the large squares between two heart beats.
Axis: make sure to determine both P wave and QRS axes. Net summation of positive and negative deflections 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 (0-90 degrees). If it is negative in lead I and positive in AVF, the axis is in the right lower quadrant (90-180 degrees).
Rhythm: the sinus node is located at the SVC-RA junction. Sinus rhythm is characterized by:
- One P wave preceding each QRS complex.
- All P waves are uniform in shape.
- P wave axis in the left lower quadrant (0-90 degrees), i.e. upright in both lead I and AVF.
Durations/Intervals:
- P wave: normally it is 2.5 mm wide and 2.5 mm high. Tall P wave indicate RA enlargement and wide P wave indicate LA enlargement.
- PR interval (varies with age and heart rate) (table)
- QRS duration (2-3 small squares or 0.08-0.12 sec). Wide QRS may indicate bundle branch block or ventricular beats.
- QT interval (measured from the beginning of Q to the end on T waves). QTc is the QT interval corrected for the heart rate. QTc= QT (in seconds)/ square root of RR interval (in seconds) (table)
Chamber hypertrophy/enlargement:
- Left ventricular hypertrophy: I- Voltage criteria (tall R in V6 and deep S in V1), II- Left axis deviation, III- Strain pattern in left leads
- Right ventricular hypertrophy: I- Voltage criteria (tall R in V1 and deep S in V6 >95 % for age), II- qR or rSR' pattern inV1, III- Upright T wave in V1 > 1 week, IV- Extreme right axis deviation.
Links to EKG images:
EKG of Left Bundle Branch Block
EKG of Right Bundle Branch Block
EKG of Right Ventricular Hypertrophy (RVH)
EKG of Supraventricular Tachycardia (SVT)
EKG of Wolff-Parkinson-White (WPW) rhythm
