Introduction to Pediatric ECGs Thomas R. Burklow, MD Asst C, Pediatric Cardiology
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 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: 2 years: 4 years: > 6 years: Adult: 110 - 150 bpm 85 - 125 bpm 75 - 115 bpm 60 - 100 bpm 50 - 100 bpm Pediatric ECGs Axis Hexaxial reference system Bipolar limb leads Augmented unipolar leads I, II, III 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 Long QT - Acquired Digoxin Hypercalcemia Metabolic Long QT - Congenital AR, deafness Romano-Ward Drugs Jervell-Lange-Nielsen AD, normal hearing Ia and III antiarrhythmics Phenothiazines TCA CNS trauma Myocardial Pediatric ECGs Hypocalcemia Hypomagnesemia Malnutrition (anorexia) Ischemia Myocarditis 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 Pediatric ECGs 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 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 IV block (“delta wave”) 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) Pediatric ECGs RBBB 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 Pediatric ECGs
© Copyright 2024