Introduction to Pediatric ECGs

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Introduction to Pediatric ECGs

  1. 1. Introduction to Pediatric ECGs Thomas R. Burklow, MD Asst C, Pediatric Cardiology Walter Reed Army Medical Center
  2. 2. Electrophysiology and Anatomy SA Node 
  3. 3. Mechanics of tracing <ul><li>Small box = 1 x 1 mm </li></ul><ul><li>Large box = 5 x 5 mm </li></ul><ul><li>Paper speed (horizontal boxes) </li></ul><ul><ul><li>Standard = 25 mm/sec </li></ul></ul><ul><li>Voltage calibration (vertical boxes) </li></ul><ul><ul><li>Standard = 10 mm/mV (2 big boxes) </li></ul></ul><ul><ul><li>Half standard = 5 mm/mV (1 big box) </li></ul></ul><ul><ul><li>May have 10/5: standard for chest leads, half-standard for precordial leads </li></ul></ul><ul><ul><li>NOTE THE CALIBRATION!! </li></ul></ul>
  4. 4. ECG basics: grid paper
  5. 5. Basic electrocardiogram
  6. 6. Interpretation <ul><li>Be systematic!! </li></ul><ul><ul><li>Rhythm </li></ul></ul><ul><ul><li>Rate </li></ul></ul><ul><ul><li>Axis </li></ul></ul><ul><ul><li>Intervals </li></ul></ul><ul><ul><li>Atrial enlargement </li></ul></ul><ul><ul><li>Ventricular hypertrophy </li></ul></ul><ul><ul><li>ST/T wave evaluation </li></ul></ul>
  7. 7. Rhythm <ul><li>Sinus rhythm </li></ul><ul><li>Subsidiary pacemaker </li></ul><ul><li>Tachyarrhythmia </li></ul><ul><li>Bradyarrhythmia </li></ul><ul><li>Atrioventricular block </li></ul>
  8. 8. Normal sinus rhythm <ul><li>P wave before every QRS </li></ul><ul><li>QRS following every P wave </li></ul><ul><li>Normal P wave axis </li></ul><ul><li>Normal PR interval is NOT required </li></ul>
  9. 9. P wave axis <ul><li>Atrial depolarization occurs from SA node </li></ul><ul><ul><li>Wave passes right to left, top to bottom </li></ul></ul><ul><ul><li>Positive deflections in leads I (right to left) and aVF (top to bottom) </li></ul></ul><ul><ul><li>Normal P wave axis = 0-90 degrees </li></ul></ul><ul><li>Abnormal axis implies ectopic pacemaker </li></ul><ul><ul><li>Coronary sinus or “low right atrial” rhythm is common benign finding, especially in teens </li></ul></ul><ul><ul><li>Positive in lead I, negative in aVF </li></ul></ul>
  10. 10. Rate <ul><li>Measured in beats per minute </li></ul><ul><li>60 / RR interval (in seconds) </li></ul><ul><li>300 / number of “big boxes” between consecutive QRS complexes </li></ul><ul><li>1500 / number of “little boxes” between consecutive QRS complexes </li></ul>
  11. 11. Heart rate <ul><li>Known time interval </li></ul><ul><ul><li>Beats in 6 seconds (30 “big boxes”) x 10 </li></ul></ul><ul><ul><li>Beats in 3 seconds (15 “big boxes”) x 20 </li></ul></ul>
  12. 12. Heart rate <ul><li>Rate approximation </li></ul><ul><ul><li>Rate estimate: 300 - 150 - 75 - 60 - 50 </li></ul></ul><ul><ul><li>Easy to memorize </li></ul></ul><ul><ul><li>No calculator needed </li></ul></ul>
  13. 13. Normal resting heart rates <ul><li>Newborn: 110 - 150 bpm </li></ul><ul><li>2 years: 85 - 125 bpm </li></ul><ul><li>4 years: 75 - 115 bpm </li></ul><ul><li>> 6 years: 60 - 100 bpm </li></ul><ul><li>Adult: 50 - 100 bpm </li></ul>
  14. 14. Axis <ul><li>Hexaxial reference system </li></ul><ul><ul><li>Bipolar limb leads </li></ul></ul><ul><ul><ul><li>I, II, III </li></ul></ul></ul><ul><ul><li>Augmented unipolar leads </li></ul></ul><ul><ul><ul><li>aVR, aVL, aVF </li></ul></ul></ul><ul><li>Horizontal reference system </li></ul><ul><ul><li>Precordial leads </li></ul></ul><ul><ul><ul><li>V1 - V7 </li></ul></ul></ul><ul><ul><ul><li>Right sided leads (e.g. rV3) </li></ul></ul></ul>
  15. 15. Reference systems
  16. 16. Axis determination <ul><li>Successive approximation </li></ul><ul><ul><li>Locate quadrant with leads I and aVF </li></ul></ul><ul><ul><li>Narrow down by using leads within quadrant </li></ul></ul><ul><ul><ul><li>Use most equiphasic lead </li></ul></ul></ul><ul><ul><ul><li>Axis is perpendicular to that lead, in the quadrant previously identified </li></ul></ul></ul><ul><li>Equal amplitudes </li></ul><ul><ul><li>If two leads with equal net QRS amplitudes exist, the mean axis lies midway between the axis of these two leads </li></ul></ul>
  17. 17. Quadrant determination Normal axis Left axis “ Boston” Right axis Extreme R/L axis “ Seattle”
  18. 18. Successive approximation
  19. 19. Axis determination <ul><li>Amplitude vector </li></ul><ul><ul><li>Add net R-S in lead I, R-S in aVF </li></ul></ul><ul><ul><li>Plot in mm on grid (lead I horizontal, lead aVF vertical) </li></ul></ul><ul><ul><li>Draw vector from origin to net amplitude </li></ul></ul><ul><ul><li>Angle of vector = axis </li></ul></ul>
  20. 20. Right axis deviation <ul><li>Axis > 100 degrees </li></ul><ul><li>“Normal for age”: rightward axis > 100 degrees, but within normal limits for age (e.g. 2 week old with axis of +140) </li></ul><ul><li>Suggestive of RVH </li></ul>
  21. 21. Left axis deviation <ul><li>Axis < -5 degrees </li></ul><ul><li>Q waves in leads I and aVL </li></ul><ul><li>Conduction abnormality </li></ul><ul><li>Associated with atrioventricular septal defect </li></ul><ul><li>No correlation with LVH </li></ul><ul><li>Occurs in 5% of normal population </li></ul>
  22. 22. Causes of left axis deviation <ul><li>Normal variant </li></ul><ul><li>AV septal defect (including primum ASD) </li></ul><ul><li>Perimembranous inlet VSD </li></ul><ul><li>Tricuspid atresia </li></ul><ul><li>Single ventricle </li></ul><ul><li>Double outlet right ventricle </li></ul><ul><li>Noonan syndrome </li></ul><ul><li>Left anterior hemiblock after MI </li></ul>
  23. 23. PR Interval <ul><li>Onset of atrial contraction to onset of ventricular contraction (measures cumulative time of depolarization through atria, AV node, and His-Purkinje system) </li></ul><ul><li>Varies between leads </li></ul><ul><li>Increases with age </li></ul><ul><li>Decreases with heart rate </li></ul>
  24. 24. Long PR interval <ul><li>= First degree AV block </li></ul><ul><ul><li>Drugs </li></ul></ul><ul><ul><li>Atrial surgery (scar tissue) </li></ul></ul><ul><ul><li>Acute rheumatic fever (minor Jones criteria) </li></ul></ul><ul><ul><li>Kawasaki disease </li></ul></ul>
  25. 25. Short PR interval <ul><li>Etiologies </li></ul><ul><ul><li>Wolff-Parkinson-White </li></ul></ul><ul><ul><li>Glycogen storage disease type IIa (Pompe’s) </li></ul></ul><ul><ul><li>Fabry disease </li></ul></ul><ul><ul><li>GM1 gangliosidosis </li></ul></ul><ul><ul><li>Friedrich’s ataxia </li></ul></ul><ul><ul><li>Duchenne’s muscular dystrophy </li></ul></ul>
  26. 26. QRS Duration <ul><li>Beginning of Q wave to end of S wave </li></ul><ul><li>Use a lead where a Q wave is visible </li></ul><ul><li>Normal = 0.04 - 0.08 (may be up to 0.09 in adolescents) </li></ul><ul><li>> 0.12 = bundle branch block </li></ul><ul><li>0.10-0.12: evaluate morphology </li></ul>
  27. 27. RSR’ Morphology <ul><li>Seen in right precordial leads: V1, rV3 </li></ul><ul><li>Common: occurs in 7% of kids </li></ul><ul><li>R and R’ both small and of short duration </li></ul><ul><li>S wave larger than R and R’ </li></ul><ul><li>R’ is less than 10 mm (15 mm in infants) </li></ul><ul><li>Abnormal RSR’ may reflect RBBB or RVH (volume overload type) </li></ul>
  28. 28. QT Interval <ul><li>Onset of ventricular depolarization (Q wave) to end of ventricular repolarization (T wave) </li></ul><ul><li>Do NOT include U waves </li></ul><ul><li>Varies inversely with heart rate </li></ul><ul><li>Best leads: II, V5, V6 </li></ul><ul><li>QTC (Bazett’s formula) = QT/square root RR </li></ul><ul><ul><li>Normal < 0.44 sec </li></ul></ul><ul><ul><li>May be as high as 0.45 sec in adol/adult females </li></ul></ul><ul><ul><li>May be as high as 0.49 sec in newborns (to 6 mo.) </li></ul></ul><ul><li>QT ruler </li></ul>
  29. 29. QT Abnormalities <ul><li>Short QT </li></ul><ul><ul><li>Digoxin </li></ul></ul><ul><ul><li>Hypercalcemia </li></ul></ul><ul><li>Long QT - Congenital </li></ul><ul><ul><li>Jervell-Lange-Nielsen </li></ul></ul><ul><ul><ul><li>AR, deafness </li></ul></ul></ul><ul><ul><li>Romano-Ward </li></ul></ul><ul><ul><ul><li>AD, normal hearing </li></ul></ul></ul><ul><li>Long QT - Acquired </li></ul><ul><ul><li>Metabolic </li></ul></ul><ul><ul><ul><li>Hypocalcemia </li></ul></ul></ul><ul><ul><ul><li>Hypomagnesemia </li></ul></ul></ul><ul><ul><ul><li>Malnutrition (anorexia) </li></ul></ul></ul><ul><ul><li>Drugs </li></ul></ul><ul><ul><ul><li>Ia and III antiarrhythmics </li></ul></ul></ul><ul><ul><ul><li>Phenothiazines </li></ul></ul></ul><ul><ul><ul><li>TCA </li></ul></ul></ul><ul><ul><li>CNS trauma </li></ul></ul><ul><ul><li>Myocardial </li></ul></ul><ul><ul><ul><li>Ischemia </li></ul></ul></ul><ul><ul><ul><li>Myocarditis </li></ul></ul></ul>
  30. 30. Atrial enlargement <ul><li>Right atrial enlargement </li></ul><ul><ul><li>P wave amplitude > 2.5 mm in II </li></ul></ul><ul><ul><li>Deep negative deflection in first 0.04 seconds in chest leads </li></ul></ul><ul><li>Left atrial enlargement </li></ul><ul><ul><li>Terminal portion of P wave </li></ul></ul><ul><ul><li>Negative deflection in V1 beyond 0.04 sec </li></ul></ul><ul><ul><li>Duration of negative deflection > 0.04 sec </li></ul></ul><ul><ul><li>Total duration > 0.10 sec </li></ul></ul>
  31. 31. Atrial enlargement
  32. 32. Right ventricular hypertrophy <ul><li>Mild </li></ul><ul><ul><li>R’ > 15 mm (< 1 year) or > 10 mm (> 1 year) </li></ul></ul><ul><ul><li>Abnormal RSR’ of normal to slightly prolonged duration in right chest leads </li></ul></ul><ul><li>Moderate </li></ul><ul><ul><li>Definite right axis deviation (non-RBBB) </li></ul></ul><ul><ul><li>rR’ or pure R in right chest leads </li></ul></ul><ul><ul><li>Significant S in left chest leads </li></ul></ul>
  33. 33. Right ventricular hypertrophy <ul><li>Severe </li></ul><ul><ul><li>Marked RAD </li></ul></ul><ul><ul><li>qR pattern V3R or V1 </li></ul></ul><ul><ul><li>Tall pure R wave > 15 mm (any age) in right chest </li></ul></ul><ul><ul><li>Upright T wave > 3-5 days of age </li></ul></ul><ul><ul><li>Very tall R wave with ST depression and T wave inversion in V1 (“strain”) </li></ul></ul><ul><ul><li>Deep S wave V6 </li></ul></ul>
  34. 34. Left ventricular hypertrophy <ul><li>Criteria </li></ul><ul><ul><li>LAD for age (more useful in neonates/infants) </li></ul></ul><ul><ul><li>R in V5/V6 or I, II, III, aVF, aVL above normal </li></ul></ul><ul><ul><li>S in V1/V2 above normal </li></ul></ul><ul><ul><li>Abnormal R/S ratio (R/S in V1/V2 below normal) </li></ul></ul><ul><ul><li>Deep/wide q wave in V5/V6 above fmm </li></ul></ul><ul><ul><ul><li>Tall symmetric T waves = “LV diastolic overload” </li></ul></ul></ul><ul><ul><li>With LVH, inverted T waves in I/aVF = “strain” </li></ul></ul>
  35. 35. Combined ventricular hypertrophy <ul><li>Criteria </li></ul><ul><ul><li>Positive voltage criteria for LVH and RVH </li></ul></ul><ul><ul><ul><li>In absence of BBB, preexcitation </li></ul></ul></ul><ul><ul><li>Positive voltage criteria for LVH or RVH with relatively large voltages for the other ventricle </li></ul></ul><ul><ul><li>Large equiphasic QRS complexes in > 2 limb leads and midprecordial (V2 - V5) leads </li></ul></ul><ul><ul><ul><li>“ Katz-Wachtel” phenomenon </li></ul></ul></ul>
  36. 36. QRS morphologies Normal RBBB Preexcitation (“delta wave”) IV block
  37. 37. Conduction disturbances: RBBB <ul><li>Prolongation in terminal phase of QRS (“terminal slurring” </li></ul><ul><li>Delayed conduction through RBB prolongs depolarization of RV </li></ul><ul><li>Slurring is to the right and anterior </li></ul><ul><ul><li>RAD </li></ul></ul><ul><ul><li>QRS above ULN for age </li></ul></ul><ul><ul><li>Wide/slurred S in I, V5, V6 </li></ul></ul><ul><ul><li>Terminal slurred R’ in aVR and V1, V2, V3r </li></ul></ul><ul><ul><li>ST segment shift, T wave inversion (in adults) </li></ul></ul>
  38. 38. RBBB
  39. 39. Bundle branch block <ul><li>RBBB: Etiologies </li></ul><ul><ul><li>ASD/PAPVR </li></ul></ul><ul><ul><li>Right ventriculotomy </li></ul></ul><ul><ul><li>Ebstein’s </li></ul></ul><ul><ul><li>Coarctation (< 6 months) </li></ul></ul><ul><li>LBBB </li></ul><ul><ul><li>Rare in children </li></ul></ul><ul><ul><li>Seen in adults with ischemic and hypertensive heart disease </li></ul></ul>
  40. 40. Intraventricular block <ul><li>Slowing throughout QRS complex </li></ul><ul><li>Etiologies </li></ul><ul><ul><li>Metabolic disorders (hyperkalemia) </li></ul></ul><ul><ul><li>Myocardial ischemia (CPR, quinidine toxicity) </li></ul></ul><ul><ul><li>Diffuse myocardial disease </li></ul></ul>
  41. 41. Wolff-Parkinson-White <ul><li>“ Preexcitation”: initial slurring of QRS </li></ul><ul><li>Accessory conduction pathway </li></ul><ul><ul><li>Premature depolarization of part of the myocardium </li></ul></ul><ul><ul><li>Slow conduction  delta wave </li></ul></ul><ul><li>Criteria: </li></ul><ul><ul><li>Short PR interval for age </li></ul></ul><ul><ul><li>Delta wave </li></ul></ul><ul><ul><li>Wide QRS for age </li></ul></ul>
  42. 42. Preexcitation syndromes <ul><li>Lown-Ganong-Levine </li></ul><ul><ul><li>Short PR interval </li></ul></ul><ul><ul><li>Normal QRS duration </li></ul></ul><ul><ul><li>Fibers bypass upper AV node, but conduct normally </li></ul></ul><ul><li>Mahaim fiber </li></ul><ul><ul><li>Normal PR interval </li></ul></ul><ul><ul><li>Long QRS duration </li></ul></ul><ul><ul><li>Delta wave </li></ul></ul><ul><ul><li>Fiber bypasses His bundle, enters RV myocardium </li></ul></ul>

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