Pediatric ECGs

Introduction to Pediatric ECGs

Thomas R. Burklow, MDAsst C, Pediatric CardiologyWalter Reed Army Medical Center

Pediatric ECGs

Electrophysiology and Anatomy

SA Node

Pediatric ECGs

Mechanics of tracing

Small box = 1 x 1 mm Large box = 5 x 5 mm Paper speed (horizontal boxes)

Standard = 25 mm/sec

Voltage calibration (vertical boxes) Standard = 10 mm/mV (2 big boxes) Half standard = 5 mm/mV (1 big box) May have 10/5: standard for chest leads, half-standard for

precordial leads NOTE THE CALIBRATION!!

Pediatric ECGs

ECG basics: grid paper

Pediatric ECGs

Basic electrocardiogram

Pediatric ECGs

Interpretation

Be systematic!! Rhythm Rate Axis Intervals Atrial enlargement Ventricular hypertrophy ST/T wave evaluation

Pediatric ECGs

Rhythm

Sinus rhythm Subsidiary pacemaker Tachyarrhythmia Bradyarrhythmia Atrioventricular block

Pediatric ECGs

Normal sinus rhythm

P wave before every QRS QRS following every P wave Normal P wave axis Normal PR interval is NOT required

Pediatric ECGs

P wave axis

Atrial depolarization occurs from SA node Wave passes right to left, top to bottom Positive deflections in leads I (right to left) and

aVF (top to bottom) Normal P wave axis = 0-90 degrees

Abnormal axis implies ectopic pacemaker Coronary sinus or “low right atrial” rhythm is

common benign finding, especially in teens Positive in lead I, negative in aVF

Pediatric ECGs

Rate

Measured in beats per minute 60 / RR interval (in seconds) 300 / number of “big boxes”

between consecutive QRS complexes 1500 / number of “little boxes”

between consecutive QRS complexes

Pediatric ECGs

Heart rate

Known time interval Beats in 6 seconds (30 “big boxes”) x

10 Beats in 3 seconds (15 “big boxes”) x

20

Pediatric ECGs

Heart rate

Rate approximation Rate estimate: 300 - 150 - 75 - 60 - 50 Easy to memorize No calculator needed

Pediatric ECGs

Normal resting heart rates

Newborn: 110 - 150 bpm 2 years: 85 - 125 bpm 4 years: 75 - 115 bpm > 6 years: 60 - 100 bpm Adult: 50 - 100 bpm

Pediatric ECGs

Axis

Hexaxial reference system Bipolar limb leads

I, II, III Augmented unipolar leads

aVR, aVL, aVF Horizontal reference system

Precordial leads V1 - V7 Right sided leads (e.g. rV3)

Pediatric ECGs

Reference systems

Pediatric ECGs

Axis determination

Successive approximation Locate quadrant with leads I and aVF Narrow down by using leads within quadrant

Use most equiphasic lead Axis is perpendicular to that lead, in the quadrant

previously identified

Equal amplitudes If two leads with equal net QRS amplitudes exist, the

mean axis lies midway between the axis of these two leads

Pediatric ECGs

Quadrant determination

Normal axis

Left axis“Boston”

Right axis

Extreme R/L axis“Seattle”

Pediatric ECGs

Successive approximation

Pediatric ECGs

Axis determination

Amplitude vector Add net R-S in lead I, R-S in aVF Plot in mm on grid (lead I horizontal,

lead aVF vertical) Draw vector from origin to net

amplitude Angle of vector = axis

Pediatric ECGs

Right axis deviation

Axis > 100 degrees “Normal for age”: rightward axis >

100 degrees, but within normal limits for age (e.g. 2 week old with axis of +140)

Suggestive of RVH

Pediatric ECGs

Left axis deviation

Axis < -5 degrees Q waves in leads I and aVL Conduction abnormality Associated with atrioventricular

septal defect No correlation with LVH Occurs in 5% of normal population

Pediatric ECGs

Causes of left axis deviation

Normal variant AV septal defect (including primum ASD) Perimembranous inlet VSD Tricuspid atresia Single ventricle Double outlet right ventricle Noonan syndrome Left anterior hemiblock after MI

Pediatric ECGs

PR Interval

Onset of atrial contraction to onset of ventricular contraction (measures cumulative time of depolarization through atria, AV node, and His-Purkinje system)

Varies between leads Increases with age Decreases with heart rate

Pediatric ECGs

Long PR interval

= First degree AV block Drugs Atrial surgery (scar tissue) Acute rheumatic fever (minor Jones

criteria) Kawasaki disease

Pediatric ECGs

Short PR interval

Etiologies Wolff-Parkinson-White Glycogen storage disease type IIa

(Pompe’s) Fabry disease GM1 gangliosidosis Friedrich’s ataxia Duchenne’s muscular dystrophy

Pediatric ECGs

QRS Duration

Beginning of Q wave to end of S wave

Use a lead where a Q wave is visible Normal = 0.04 - 0.08 (may be up to

0.09 in adolescents) > 0.12 = bundle branch block 0.10-0.12: evaluate morphology

Pediatric ECGs

RSR’ Morphology

Seen in right precordial leads: V1, rV3 Common: occurs in 7% of kids R and R’ both small and of short duration S wave larger than R and R’ R’ is less than 10 mm (15 mm in infants) Abnormal RSR’ may reflect RBBB or RVH

(volume overload type)

Pediatric ECGs

QT Interval

Onset of ventricular depolarization (Q wave) to end of ventricular repolarization (T wave)

Do NOT include U waves Varies inversely with heart rate Best leads: II, V5, V6 QTC (Bazett’s formula) = QT/square root RR

Normal < 0.44 sec May be as high as 0.45 sec in adol/adult females May be as high as 0.49 sec in newborns (to 6 mo.)

QT ruler

Pediatric ECGs

QT Abnormalities

Short QT Digoxin Hypercalcemia

Long QT - Congenital Jervell-Lange-Nielsen

AR, deafness Romano-Ward

AD, normal hearing

Long QT - Acquired Metabolic

Hypocalcemia Hypomagnesemia Malnutrition (anorexia)

Drugs Ia and III antiarrhythmics Phenothiazines TCA

CNS trauma Myocardial

Ischemia Myocarditis

Pediatric ECGs

Atrial enlargement

Right atrial enlargement

P wave amplitude > 2.5 mm in II

Deep negative deflection in first 0.04 seconds in chest leads

Left atrial enlargement

Terminal portion of P wave

Negative deflection in V1 beyond 0.04 sec

Duration of negative deflection > 0.04 sec

Total duration > 0.10 sec

Pediatric ECGs

Atrial enlargement

Pediatric ECGs

Right ventricular hypertrophy

Mild R’ > 15 mm (< 1 year) or > 10 mm (> 1

year) Abnormal RSR’ of normal to slightly

prolonged duration in right chest leads Moderate

Definite right axis deviation (non-RBBB) rR’ or pure R in right chest leads Significant S in left chest leads

Pediatric ECGs

Right ventricular hypertrophy

Severe Marked RAD qR pattern V3R or V1 Tall pure R wave > 15 mm (any age) in

right chest Upright T wave > 3-5 days of age Very tall R wave with ST depression and T

wave inversion in V1 (“strain”) Deep S wave V6

Pediatric ECGs

Left ventricular hypertrophy

Criteria LAD for age (more useful in neonates/infants) R in V5/V6 or I, II, III, aVF, aVL above normal S in V1/V2 above normal Abnormal R/S ratio (R/S in V1/V2 below

normal) Deep/wide q wave in V5/V6 above fmm

Tall symmetric T waves = “LV diastolic overload” With LVH, inverted T waves in I/aVF = “strain”

Pediatric ECGs

Combined ventricular hypertrophy

Criteria Positive voltage criteria for LVH and RVH

In absence of BBB, preexcitation Positive voltage criteria for LVH or RVH with

relatively large voltages for the other ventricle

Large equiphasic QRS complexes in > 2 limb leads and midprecordial (V2 - V5) leads

“Katz-Wachtel” phenomenon

Pediatric ECGs

QRS morphologies

Normal RBBB Preexcitation(“delta wave”)

IV block

Pediatric ECGs

Conduction disturbances: RBBB

Prolongation in terminal phase of QRS (“terminal slurring”

Delayed conduction through RBB prolongs depolarization of RV

Slurring is to the right and anterior RAD QRS above ULN for age Wide/slurred S in I, V5, V6 Terminal slurred R’ in aVR and V1, V2, V3r ST segment shift, T wave inversion (in adults)

RBBB

Pediatric ECGs

Bundle branch block

RBBB: Etiologies ASD/PAPVR Right ventriculotomy Ebstein’s Coarctation (< 6 months)

LBBB Rare in children Seen in adults with ischemic and hypertensive

heart disease

Pediatric ECGs

Intraventricular block

Slowing throughout QRS complex Etiologies

Metabolic disorders (hyperkalemia) Myocardial ischemia (CPR, quinidine

toxicity) Diffuse myocardial disease

Pediatric ECGs

Wolff-Parkinson-White

“Preexcitation”: initial slurring of QRS Accessory conduction pathway

Premature depolarization of part of the myocardium

Slow conduction delta wave Criteria:

Short PR interval for age Delta wave Wide QRS for age

Pediatric ECGs

Preexcitation syndromes

Lown-Ganong-Levine Short PR interval Normal QRS duration Fibers bypass upper AV node, but conduct normally

Mahaim fiber Normal PR interval Long QRS duration Delta wave Fiber bypasses His bundle, enters RV myocardium