Pediatric ECG Learning App

This page is designed to assist students and doctors in learning and understanding pediatric ECGs. It provides a comprehensive guide to reading and interpreting electrocardiograms in children, highlighting the unique aspects and variations compared to adult ECGs. Whether you're a student aiming to master ECG interpretation or a healthcare professional seeking to refine your skills, this resource offers valuable insights into the nuances of pediatric cardiac monitoring.

Explore detailed sections on ECG basics, waveforms, intervals, and common pathologies to enhance your knowledge and diagnostic accuracy. The content is tailored to address the specific challenges of pediatric ECG interpretation, making it an essential tool for anyone involved in the care and assessment of young patients. Dive into the information provided to gain a clearer understanding of how to accurately read and analyze pediatric ECGs.

ECG Basics:

The pediatric electrocardiogram (ECG) is a valuable tool for assessing the electrical activity of a child's heart. Here are the basic components:

  • Electrodes: Sensors placed on the skin to detect electrical activity.
  • Leads: Views of the heart's electrical activity from different angles.
  • Paper speed: Usually 25 mm/sec, which affects the interpretation of wave durations.
  • Calibration: Standard calibration is 1 mV = 10 mm.

P Wave:

The P wave represents atrial depolarization. It is the first positive deflection in the ECG waveform.

  • Normal duration: < 0.08 seconds in infants and children.
  • Normal amplitude: < 2.5 mm in the limb leads.
  • Abnormalities can indicate atrial enlargement or other atrial pathology.

QRS Complex:

The QRS complex represents ventricular depolarization. It consists of three waves: Q wave, R wave, and S wave.

  • Normal duration: 0.04 - 0.08 seconds in infants and children.
  • Pathological Q waves can indicate previous myocardial infarction.
  • Wide QRS complex can indicate ventricular hypertrophy or bundle branch block.

T Wave:

The T wave represents ventricular repolarization. It follows the QRS complex.

  • Normal T waves are asymmetrical.
  • T wave inversion can be normal in children up to the age of 8 years, especially in the right precordial leads.
  • Peaked T waves can indicate hyperkalemia.

U Wave:

The U wave represents the repolarization of the Purkinje fibers. It is sometimes seen following the T wave.

  • Usually small and not always visible.
  • Prominent U waves can indicate hypokalemia or bradycardia.

PR Interval:

The PR interval is the time from the beginning of the P wave to the start of the QRS complex, indicating the time taken for electrical activity to travel from the atria to the ventricles.

  • Normal duration: 0.10 - 0.14 seconds in infants and children.
  • Prolonged PR interval can indicate first-degree heart block.
  • Shortened PR interval can indicate pre-excitation syndromes like Wolff-Parkinson-White syndrome.

QRS Interval:

The QRS interval represents the duration of ventricular depolarization.

  • Normal duration: 0.04 - 0.08 seconds in infants and children.
  • Wide QRS complex can indicate ventricular hypertrophy or bundle branch block.
  • Narrow QRS complex is typically seen in supraventricular tachycardia.

QT Interval:

The QT interval is the time from the start of the QRS complex to the end of the T wave, representing the total time for ventricular depolarization and repolarization.

  • Normal duration varies with heart rate; QTc (corrected QT) is used for standardization. In children, the upper limit of normal QTc is around 0.44 seconds.
  • Prolonged QT interval can indicate risk for ventricular arrhythmias like torsades de pointes.
  • Shortened QT interval can indicate hypercalcemia.

Myocardial Infarction:

Myocardial infarction (MI) in children presents with several key ECG changes:

  • Presence of Q waves.
  • ST-segment elevation in the leads corresponding to the affected area.
  • T wave inversion.

Atrial Fibrillation:

Atrial fibrillation in children is characterized by an irregularly irregular rhythm with no distinct P waves.

  • Irregular R-R intervals.
  • Absence of discrete P waves, replaced by fibrillatory waves.

Ventricular Tachycardia:

Ventricular tachycardia (VT) is a fast heart rhythm originating from the ventricles.

  • Wide QRS complexes (>0.12 seconds).
  • Regular rhythm with a fast rate (>100 bpm in children).

Heart Block:

Heart blocks in children are categorized into first, second, and third-degree blocks, each with distinct ECG features:

  • First-degree: Prolonged PR interval (>0.20 seconds).
  • Second-degree: Dropped beats (Mobitz type I and II).
  • Third-degree: Complete dissociation between atrial and ventricular activity.

Introduction to ECG Changes in Electrolyte Imbalances

Key Concepts:

  • ECG is a crucial tool in identifying electrolyte disturbances
  • Changes may be subtle in early stages
  • Multiple electrolyte abnormalities can coexist
  • Serial ECGs help monitor treatment response

Normal Pediatric Reference Values:

  • Potassium: 3.5-5.5 mEq/L
  • Sodium: 135-145 mEq/L
  • Calcium: 8.5-10.5 mg/dL
  • Magnesium: 1.5-2.5 mg/dL
  • Phosphate: 4.5-6.5 mg/dL (varies by age)

Hypokalemia (K+ < 3.5 mEq/L)

ECG Manifestations:

  • ST segment depression
  • Decreased T wave amplitude (flattening)
  • Prominent U waves (best seen in V2-V4)
  • Prolonged PR interval
  • Increased QT interval

Severity-Based Changes:

  • Mild (K+ 3.0-3.4 mEq/L):
    • T wave flattening
    • ST segment depression
  • Moderate (K+ 2.5-2.9 mEq/L):
    • Prominent U waves
    • Depression of ST segment
    • Decreased T wave amplitude
  • Severe (K+ < 2.5 mEq/L):
    • U waves larger than T waves
    • Apparent QT prolongation (QU interval)
    • Risk of Torsades de Pointes

Hyperkalemia (K+ > 5.5 mEq/L)

Progressive ECG Changes:

  • Peaked T waves (tall, narrow, symmetric)
  • Shortened QT interval
  • PR prolongation
  • P wave flattening/disappearance
  • QRS widening
  • Sine wave pattern in severe cases

Severity-Based Changes:

  • Mild (K+ 5.5-6.0 mEq/L):
    • Peaked T waves (tent-shaped)
    • Shortened QT interval
  • Moderate (K+ 6.1-7.0 mEq/L):
    • PR interval prolongation
    • P wave flattening
    • QRS widening
  • Severe (K+ > 7.0 mEq/L):
    • Loss of P wave
    • Wide QRS complex
    • Sine wave pattern
    • Risk of ventricular fibrillation

Hyponatremia (Na+ < 135 mEq/L)

ECG Changes:

  • Prolonged QT interval
  • ST segment depression
  • T wave changes (usually nonspecific)
  • Decreased QRS voltage

Clinical Correlation:

  • Changes more prominent with acute onset
  • Severity of ECG changes correlates with:
    • Rate of sodium decline
    • Absolute sodium level
    • Presence of symptoms

Hypernatremia (Na+ > 145 mEq/L)

ECG Manifestations:

  • Shortened QT interval
  • Peaked T waves (less prominent than hyperkalemia)
  • ST segment elevation (nonspecific)

Notable Features:

  • ECG changes less specific than other electrolyte disorders
  • Changes more prominent when:
    • Na+ > 155 mEq/L
    • Rapid onset

Hypocalcemia (Ca2+ < 8.5 mg/dL)

Classic ECG Changes:

  • Prolonged QT interval (hallmark finding)
  • Prominent U waves
  • T wave alterations
  • ST segment changes

Detailed Findings:

  • Early changes:
    • QT interval prolongation
    • T wave flattening
  • Progressive changes:
    • ST segment depression
    • T wave inversion
    • Risk of Torsades de Pointes

Hypercalcemia (Ca2+ > 10.5 mg/dL)

Key ECG Changes:

  • Shortened QT interval (primary finding)
  • J point elevation
  • Broad T waves with increased amplitude
  • Shortened ST segment
Hypercalcaemia causing marked shortening of the QT interval (260ms). (source)

41-year old man with a parathyroid adenoma- Bizarre-looking QRS complexes, Very short QT interval, J waves = notching of the terminal QRS, best seen in lead V1. (source)

Progressive Changes:

  • Moderate elevation:
    • QT interval shortening
    • T wave peaking
  • Severe elevation:
    • Osborn waves
    • Risk of AV block
    • Cardiac arrest (very severe cases)
    Electrocardiographic readings show the Osborn waves (arrows) in our severely hyper-calcemic patient.
    After correction of the hypercalcemia, the electrocardiogram was normal. (source)

Hypomagnesemia (Mg2+ < 1.5 mg/dL)

ECG Manifestations:

  • Prolonged QT interval
  • ST segment depression
  • T wave flattening or inversion
  • Prominent U waves

Clinical Significance:

  • Often associated with:
    • Hypokalemia
    • Hypocalcemia
  • Increased risk of:
    • Supraventricular arrhythmias
    • Ventricular arrhythmias
    • Torsades de Pointes

Hypermagnesemia (Mg2+ > 2.5 mg/dL)

ECG Changes:

  • Prolonged PR interval
  • Widened QRS complex
  • Peaked T waves

Progressive Changes:

  • Moderate elevation:
    • First-degree AV block
    • QRS widening
  • Severe elevation:
    • Complete heart block
    • Asystole (extreme cases)

Hyperphosphatemia (PO4 > 6.5 mg/dL)

ECG Manifestations:

  • QT interval prolongation
  • T wave abnormalities
  • Bundle branch blocks

Associated Findings:

  • Often seen with:
    • Hypocalcemia
    • Renal dysfunction
  • ECG changes may reflect:
    • Calcium-phosphate interactions
    • Secondary electrolyte disturbances

Hypophosphatemia (PO4 < 4.5 mg/dL)

ECG Changes:

  • Decreased QRS voltage
  • ST segment depression
  • T wave flattening

Clinical Considerations:

  • Changes more prominent in severe cases
  • Associated findings:
    • Decreased myocardial contractility
    • Impaired energy metabolism
  • May see:
    • Atrial arrhythmias
    • Conduction disturbances


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