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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 AV Block, 1st degree

EKG of AV Block, 2nd degree

EKG of AV Block, Complete

EKG of Left Bundle Branch Block

EKG of Right Bundle Branch Block

EKG of Long QT Syndrome

EKG of Right Ventricular Hypertrophy (RVH)

EKG of Sinus Tachycardia

EKG of Supraventricular Tachycardia (SVT)

EKG of Wolff-Parkinson-White (WPW) rhythm

EKG of premature atrial complexes (PACs)

EKG of premature ventricular contractions (PVC's)