Pediatric ECG Interpretation Guide¶
Systematic approach to pediatric ECG interpretation with age-based normal values.
Systematic Approach¶
The 10-Step Method¶
- Rate - Calculate ventricular rate
- Rhythm - Sinus vs non-sinus
- Axis - Frontal plane QRS axis
- Intervals - PR, QRS, QTc
- P waves - Morphology, RAE/LAE
- QRS morphology - RVH, LVH, RBBB, LBBB
- Q waves - Pathologic?
- ST segments - Elevation/depression
- T waves - Inversion, peaked
- Comparison - Prior ECGs if available
Rate Calculation¶
Methods¶
- 300 Rule: 300 / (# large boxes between R-R)
- 1500 Rule: 1500 / (# small boxes between R-R)
- 6-Second Strip: Count QRS complexes × 10
Normal Heart Rate by Age¶
| Age | Awake (bpm) | Sleeping (bpm) |
|---|---|---|
| Newborn | 100-180 | 80-160 |
| 1-3 months | 100-180 | 80-160 |
| 3-6 months | 90-120 | 70-120 |
| 6-12 months | 80-120 | 70-120 |
| 1-3 years | 70-110 | 60-100 |
| 3-6 years | 65-110 | 60-100 |
| 6-12 years | 60-95 | 55-90 |
| >12 years | 55-85 | 50-80 |
Axis¶
Normal Axis by Age¶
| Age | Normal QRS Axis |
|---|---|
| Newborn | +60° to +180° (RAD normal!) |
| 1-4 weeks | +60° to +160° |
| 1-3 months | +30° to +110° |
| 3-12 months | +10° to +110° |
| 1-3 years | +10° to +100° |
| >3 years | 0° to +90° |
| Adult | -30° to +90° |
Key Point¶
Rightward axis is NORMAL in neonates - reflects RV dominance in utero
Quick Axis Determination¶
| Lead I | aVF | Axis |
|---|---|---|
| + | + | Normal (0 to +90°) |
| + | - | LAD (-30° to -90°) |
| - | + | RAD (+90° to +180°) |
| - | - | Extreme axis |
Intervals¶
PR Interval (seconds)¶
| Age | Normal Range | Upper Limit |
|---|---|---|
| <1 year | 0.08-0.14 | 0.16 |
| 1-3 years | 0.08-0.14 | 0.16 |
| 3-6 years | 0.09-0.16 | 0.17 |
| 6-12 years | 0.09-0.17 | 0.18 |
| >12 years | 0.10-0.18 | 0.20 |
Short PR: WPW (<0.08), Pompe disease, glycogen storage Long PR: 1st degree AV block, myocarditis, rheumatic fever
QRS Duration (seconds)¶
| Age | Upper Limit |
|---|---|
| <1 year | 0.08 |
| 1-3 years | 0.08 |
| 3-6 years | 0.09 |
| 6-12 years | 0.10 |
| >12 years | 0.10 |
Wide QRS: Bundle branch block, ventricular rhythm, WPW, hyperkalemia
QTc Interval (Bazett Correction)¶
QTc = QT / √RR
| QTc (ms) | Interpretation |
|---|---|
| <440 | Normal |
| 440-470 | Borderline |
| >470 | Prolonged |
| ≥480 | Definite LQTS (or ≥460 with symptoms) |
| <340 | Short QT syndrome |
Causes of Long QT: - Congenital LQTS (LQT1, LQT2, LQT3) - Medications (Class IA/III antiarrhythmics, macrolides, fluoroquinolones, antipsychotics) - Electrolyte abnormalities (↓K, ↓Mg, ↓Ca) - Myocarditis, hypothermia
P Wave Abnormalities¶
Right Atrial Enlargement (RAE)¶
- P wave amplitude >3 mm in lead II
- Tall, peaked P waves ("P pulmonale")
- Seen in: Tricuspid atresia, Ebstein, pulmonary hypertension
Left Atrial Enlargement (LAE)¶
- P wave duration >0.08 sec (infants) or >0.10 sec (older children)
- Notched P wave in lead II ("P mitrale")
- Terminal negative deflection in V1 >1 mm deep and >1 small box wide
- Seen in: Mitral stenosis, VSD, PDA, cardiomyopathy
Ventricular Hypertrophy¶
Right Ventricular Hypertrophy (RVH)¶
Criteria (must use age-appropriate norms): - R in V1 > upper limit for age - S in V6 > upper limit for age - R/S ratio in V1 > upper limit for age - Upright T in V1 after day 3 of life (abnormal until ~8 years) - qR pattern in V1 - RAD for age
Causes: - Pulmonary stenosis, TOF, pulmonary hypertension - Tricuspid regurgitation, ASD - DORV, TGA
Left Ventricular Hypertrophy (LVH)¶
Criteria: - R in V6 > upper limit for age - S in V1 > upper limit for age - R in V6 + S in V1 > upper limit for age - Q in V6 >5 mm - Inverted T waves in V6 (LV strain pattern)
Causes: - Aortic stenosis, coarctation, systemic hypertension - Hypertrophic cardiomyopathy - VSD, PDA (volume overload)
Biventricular Hypertrophy¶
- Criteria for both RVH and LVH
- Large equiphasic QRS in mid-precordial leads (V3-V4)
- Seen in: Large VSD, complete AV canal, complex CHD
Q Waves¶
Normal Q Waves¶
- Leads I, II, III, aVL, aVF, V5-V6
- Small and narrow (<0.04 sec, <5 mm)
Abnormal Q Waves¶
- Deep Q waves in V5-V6 (>5mm): LVH with volume overload
- Q waves in V1: RVH, dextrocardia, septal hypertrophy
- Q waves in I, aVL: ALCAPA (anomalous left coronary)
- Absent Q waves in V5-V6: LBBB, cardiomyopathy
ALCAPA Pattern¶
Q waves in leads I and aVL with ST elevation - Classic for anomalous left coronary from pulmonary artery - Represents anterolateral MI pattern in infant
ST-T Wave Changes¶
ST Segment¶
Elevation: - Pericarditis (diffuse, concave up) - Myocardial infarction (localized, convex up) - Early repolarization (benign, common in adolescents) - Brugada syndrome (V1-V3, coved pattern)
Depression: - Ischemia - Digoxin effect (scooped) - LVH strain - Subendocardial injury
T Wave Abnormalities¶
T wave inversion: - Normal in V1-V3 until age 8-10 years - Abnormal: Ischemia, cardiomyopathy, pericarditis, PE
Peaked T waves: - Hyperkalemia - LVH (can have tall T waves) - Hyperacute MI
Flat T waves: - Hypokalemia - Hypothyroidism - Pericardial effusion
Classic ECG Patterns¶
Wolff-Parkinson-White (WPW)¶
- Short PR (<0.08-0.12 sec depending on age)
- Delta wave (slurred upstroke of QRS)
- Wide QRS
- Secondary ST-T changes
Long QT Syndrome (LQTS)¶
| Type | Gene | ECG Pattern | Triggers |
|---|---|---|---|
| LQT1 | KCNQ1 | Broad T wave | Exercise (swimming) |
| LQT2 | KCNH2 | Notched/Low amplitude T | Auditory stimuli, emotion |
| LQT3 | SCN5A | Long ST, late T | Rest, sleep |
Brugada Syndrome¶
- Type 1: Coved ST elevation ≥2mm in V1-V2
- Right bundle branch morphology
- Often unmasked by fever, drugs
Hypertrophic Cardiomyopathy (HCM)¶
- LVH voltage criteria
- Deep narrow Q waves (septal)
- ST-T abnormalities
- Can have WPW (consider Pompe, Danon)
Myocarditis/Pericarditis¶
Myocarditis: - Sinus tachycardia - Low voltage (if effusion) - ST-T changes - Arrhythmias (PVCs, heart block)
Pericarditis: - Diffuse ST elevation (concave up) - PR depression - Low voltage (if large effusion) - Electrical alternans (if tamponade)
ALCAPA¶
- Q waves and ST elevation in I, aVL
- Anterolateral MI pattern
- LVH may be present
Arrhythmia Recognition¶
SVT in Children¶
- Narrow complex tachycardia
- Rate often 220-320 in infants, 180-280 in children
- P waves often not visible
- Regular R-R intervals
- Most common: AVRT (accessory pathway)
Ventricular Tachycardia¶
- Wide QRS tachycardia
- AV dissociation (if visible)
- Fusion/capture beats
- In pediatrics, consider: CPVT, LQTS, ARVC, structural heart disease
Heart Block¶
| Degree | ECG Finding |
|---|---|
| 1st degree | Prolonged PR, all P's conducted |
| 2nd degree Mobitz I | Progressive PR prolongation, dropped QRS |
| 2nd degree Mobitz II | Constant PR, sudden dropped QRS |
| 3rd degree (complete) | AV dissociation, escape rhythm |
Quick Reference Card¶
Normal Values by Age¶
| Parameter | Newborn | 1-6 mo | 6-12 mo | 1-3 yr | 3-8 yr | 8-16 yr |
|---|---|---|---|---|---|---|
| HR (bpm) | 100-180 | 100-180 | 80-160 | 70-150 | 70-130 | 60-120 |
| PR (sec) | 0.08-0.14 | 0.08-0.14 | 0.08-0.14 | 0.08-0.16 | 0.09-0.17 | 0.09-0.18 |
| QRS (sec) | <0.08 | <0.08 | <0.08 | <0.08 | <0.09 | <0.10 |
| Axis (°) | +60-180 | +30-110 | +10-110 | +10-100 | 0-90 | 0-90 |
Red Flags on Pediatric ECG¶
- QTc >470 ms - LQTS evaluation
- Delta wave - WPW, risk of sudden death
- Deep Q waves in I, aVL - ALCAPA in infant
- Complete heart block - Urgent cardiology consult
- Brugada pattern - Fever workup, family screening
- Extreme axis deviation - Complex CHD
- Low voltage with tachycardia - Pericardial effusion
Practical Tips¶
Common Mistakes¶
- Not using age-appropriate normals
- Forgetting RV dominance is normal in neonates
- Missing subtle delta waves
- Not measuring QTc on every ECG
- Forgetting to compare to prior ECGs
When to Get Urgent Cardiology Consult¶
- Wide complex tachycardia
- Complete heart block
- Suspected ALCAPA (Q waves I, aVL in infant with heart failure)
- QTc >500 ms with symptoms
- Brugada type 1 pattern
Always interpret pediatric ECGs with age-appropriate normal values When in doubt, compare to prior ECGs and consult cardiology