Introduction to Pediatric ECGs
Transcript of Introduction to Pediatric ECGs
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
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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
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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
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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