Introduction to Pediatric ECGs Thomas R Burklow MD

Introduction to Pediatric ECGs Thomas R. Burklow, MD Asst C, Pediatric Cardiology Walter Reed Army Medical Center Pediatric ECGs

Electrophysiology and Anatomy SA Node Pediatric ECGs

Mechanics of tracing Small box = 1 x 1 mm ª Large box = 5 x 5 mm ª Paper speed (horizontal boxes) ª ã ª Standard = 25 mm/sec Voltage calibration (vertical boxes) ã ã Standard = 10 mm/m. V (2 big boxes) Half standard = 5 mm/m. V (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 ª Be systematic!! Rhythm ã Rate ã Axis ã Intervals ã Atrial enlargement ã Ventricular hypertrophy ã ST/T wave evaluation ã Pediatric ECGs

Rhythm Sinus rhythm ª Subsidiary pacemaker ª Tachyarrhythmia ª Bradyarrhythmia ª Atrioventricular block ª Pediatric ECGs

Normal sinus rhythm P wave before every QRS ª QRS following every P wave ª Normal P wave axis ª Normal PR interval is NOT required ª Pediatric ECGs

P wave axis ª Atrial depolarization occurs from SA node ã ã ã ª Wave passes right to left, top to bottom Positive deflections in leads I (right to left) and a. VF (top to bottom) Normal P wave axis = 0 -90 degrees Abnormal axis implies ectopic pacemaker ã ã Coronary sinus or “low right atrial” rhythm is common benign finding, especially in teens Positive in lead I, negative in a. VF Pediatric ECGs

Rate Measured in beats per minute ª 60 / RR interval (in seconds) ª 300 / number of “big boxes” between consecutive QRS complexes ª 1500 / number of “little boxes” between consecutive QRS complexes ª Pediatric ECGs

Heart rate ª Known ã ã time interval Beats in 6 seconds (30 “big boxes”) x 10 Beats in 3 seconds (15 “big boxes”) x 20 Pediatric ECGs

Heart rate ª Rate ã ã ã approximation Rate estimate: 300 - 150 - 75 - 60 - 50 Easy to memorize No calculator needed Pediatric ECGs

Normal resting heart rates Newborn: ª 2 years: ª 4 years: ª > 6 years: ª Adult: ª 110 - 150 bpm 85 - 125 bpm 75 - 115 bpm 60 - 100 bpm 50 - 100 bpm Pediatric ECGs

Axis ª Hexaxial reference system ã Bipolar limb leads ã ã Augmented unipolar leads ã ª I, III a. VR, a. VL, a. VF Horizontal reference system ã Precordial leads ã ã V 1 - V 7 Right sided leads (e. g. r. V 3) Pediatric ECGs

Reference systems Pediatric ECGs

Axis determination ª Successive approximation ã ã ª Locate quadrant with leads I and a. VF Narrow down by using leads within quadrant ã Use most equiphasic lead ã Axis is perpendicular to that lead, in the quadrant previously identified Equal amplitudes ã 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 ª Amplitude vector ã ã Add net R-S in lead I, R-S in a. VF Plot in mm on grid (lead I horizontal, lead a. VF vertical) Draw vector from origin to net amplitude Angle of vector = axis Pediatric ECGs

Right axis deviation Axis > 100 degrees ª “Normal for age”: rightward axis > 100 degrees, but within normal limits for age (e. g. 2 week old with axis of +140) ª Suggestive of RVH ª Pediatric ECGs

Left axis deviation Axis < -5 degrees ª Q waves in leads I and a. VL ª Conduction abnormality ª Associated with atrioventricular septal defect ª No correlation with LVH ª Occurs in 5% of normal population ª Pediatric ECGs

Causes of left axis deviation ª ª ª ª 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) ª Varies between leads ª Increases with age ª Decreases with heart rate ª Pediatric ECGs

Long PR interval ª = First degree AV block ã ã Drugs Atrial surgery (scar tissue) Acute rheumatic fever (minor Jones criteria) Kawasaki disease Pediatric ECGs

Short PR interval ª Etiologies ã ã ã Wolff-Parkinson-White Glycogen storage disease type IIa (Pompe’s) Fabry disease GM 1 gangliosidosis Friedrich’s ataxia Duchenne’s muscular dystrophy Pediatric ECGs

QRS Duration Beginning of Q wave to end of S wave ª Use a lead where a Q wave is visible ª Normal = 0. 04 - 0. 08 (may be up to 0. 09 in adolescents) ª > 0. 12 = bundle branch block ª 0. 10 -0. 12: evaluate morphology ª Pediatric ECGs

RSR’ Morphology Seen in right precordial leads: V 1, r. V 3 ª Common: occurs in 7% of kids ª R and R’ both small and of short duration ª S wave larger than R and R’ ª R’ is less than 10 mm (15 mm in infants) ª Abnormal RSR’ may reflect RBBB or RVH (volume overload type) ª Pediatric ECGs

QT Interval ª ª ª 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, V 5, V 6 QTC (Bazett’s formula) = QT/square root RR ã ã ã ª 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 ª Short QT ã ã ª Long QT - Acquired Digoxin Hypercalcemia ã Metabolic ã ã ã ª Long QT - Congenital ã ã AR, deafness ã Romano-Ward ã Drugs ã Jervell-Lange-Nielsen ã ã AD, normal hearing ã Ia and III antiarrhythmics Phenothiazines TCA CNS trauma Myocardial ã ã Pediatric ECGs Hypocalcemia Hypomagnesemia Malnutrition (anorexia) Ischemia Myocarditis

Atrial enlargement ª Right atrial enlargement ã ã P wave amplitude > 2. 5 mm in II Deep negative deflection in first 0. 04 seconds in chest leads ª Left atrial enlargement ã ã Pediatric ECGs Terminal portion of P wave Negative deflection in V 1 beyond 0. 04 sec Duration of negative deflection > 0. 04 sec Total duration > 0. 10 sec

Atrial enlargement Pediatric ECGs

Right ventricular hypertrophy ª Mild ã ã ª R’ > 15 mm (< 1 year) or > 10 mm (> 1 year) Abnormal RSR’ of normal to slightly prolonged duration in right chest leads Moderate ã ã ã Definite right axis deviation (non-RBBB) r. R’ or pure R in right chest leads Significant S in left chest leads Pediatric ECGs

Right ventricular hypertrophy ª Severe ã ã ã Marked RAD q. R pattern V 3 R or V 1 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 V 1 (“strain”) Deep S wave V 6 Pediatric ECGs

Left ventricular hypertrophy ª Criteria ã ã ã LAD for age (more useful in neonates/infants) R in V 5/V 6 or I, III, a. VF, a. VL above normal S in V 1/V 2 above normal Abnormal R/S ratio (R/S in V 1/V 2 below normal) Deep/wide q wave in V 5/V 6 above fmm ã ã Tall symmetric T waves = “LV diastolic overload” With LVH, inverted T waves in I/a. VF = “strain” Pediatric ECGs

Combined ventricular hypertrophy ª Criteria ã Positive voltage criteria for LVH and RVH ã ã ã 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 (V 2 - V 5) leads ã “Katz-Wachtel” phenomenon Pediatric ECGs

QRS morphologies Normal RBBB Preexcitation IV block (“delta wave”) Pediatric ECGs

Conduction disturbances: RBBB Prolongation in terminal phase of QRS (“terminal slurring” ª Delayed conduction through RBB prolongs depolarization of RV ª Slurring is to the right and anterior ª ã ã ã RAD QRS above ULN for age Wide/slurred S in I, V 5, V 6 Terminal slurred R’ in a. VR and V 1, V 2, V 3 r ST segment shift, T wave inversion (in adults) Pediatric ECGs

RBBB Pediatric ECGs

Bundle branch block ª RBBB: Etiologies ã ã ª ASD/PAPVR Right ventriculotomy Ebstein’s Coarctation (< 6 months) LBBB ã ã Rare in children Seen in adults with ischemic and hypertensive heart disease Pediatric ECGs

Intraventricular block ª Slowing throughout QRS complex ª Etiologies ã ã ã Metabolic disorders (hyperkalemia) Myocardial ischemia (CPR, quinidine toxicity) Diffuse myocardial disease Pediatric ECGs

Wolff-Parkinson-White ª “Preexcitation”: initial slurring of QRS ª Accessory conduction pathway ã ã Premature depolarization of part of the myocardium Slow conduction delta wave ª Criteria: ã ã ã Short PR interval for age Delta wave Wide QRS for age Pediatric ECGs

Preexcitation syndromes ª Lown-Ganong-Levine ã ã ã ª Short PR interval Normal QRS duration Fibers bypass upper AV node, but conduct normally Mahaim fiber ã ã Normal PR interval Long QRS duration Delta wave Fiber bypasses His bundle, enters RV myocardium Pediatric ECGs