CET Pediatric ECG Considerations 3 — Questions and Answers
Question 1: What electrode placement modification is used for small infants when standard chest electrode spacing is too large?
- Skip precordial leads V3 and V5
- Use pediatric (smaller) electrode pads and reposition to fit the chest (Correct answer)
- Place all precordial leads in the left hemithorax only
- Use limb leads only and omit chest leads
Correct answer: Use pediatric (smaller) electrode pads and reposition to fit the chest
Pediatric-sized electrode pads are used on small infants and repositioned proportionally across the smaller chest wall to maintain anatomically correct lead placement.
Question 2: Which ECG finding is characteristic of right ventricular hypertrophy (RVH) in a 3-year-old?
- Tall R wave in lead V1 with R/S ratio > 1 (Correct answer)
- Deep S wave in lead V1 and tall R wave in V5
- Tall R wave in aVL exceeding 11 mm
- Prolonged QRS duration > 120 ms with left axis deviation
Correct answer: Tall R wave in lead V1 with R/S ratio > 1
A tall R wave in V1 with an R/S ratio greater than 1 is the hallmark of right ventricular hypertrophy in children, reflecting right ventricular dominance or pathological RV enlargement.
Question 3: A 7-year-old's ECG shows a QRS axis of +110 degrees. How should this be interpreted?
- Normal finding for this age
- Left axis deviation
- Right axis deviation, potentially abnormal at this age (Correct answer)
- Extreme axis deviation
Correct answer: Right axis deviation, potentially abnormal at this age
By age 7, the QRS axis should fall between 0° and +90°; an axis of +110° represents right axis deviation and may indicate right ventricular hypertrophy or other pathology.
Question 4: The ECG of a child with Down syndrome and an atrioventricular septal defect (AVSD) typically shows:
- Right bundle branch block and left axis deviation (Correct answer)
- Left bundle branch block and right axis deviation
- Wolff-Parkinson-White pattern
- Normal sinus rhythm with no axis abnormality
Correct answer: Right bundle branch block and left axis deviation
AVSD classically produces left axis deviation (often superior axis, -30° to -90°) along with right bundle branch block due to the abnormal conduction through the defective AV junction.
Question 5: When measuring the QT interval in a child with a heart rate of 120 bpm, which formula corrects for heart rate?
- QTc = QT / √RR (Bazett's formula) (Correct answer)
- QTc = QT × √RR
- QTc = QT + 0.154 × (1 − RR)
- QTc = QT / RR²
Correct answer: QTc = QT / √RR (Bazett's formula)
Bazett's formula (QTc = QT ÷ √RR) is the most widely used method to correct the QT interval for heart rate, though it tends to overcorrect at very fast rates common in children.
Question 6: A child's ECG shows delta waves, a short PR interval, and wide QRS complexes. This pattern indicates:
- Complete heart block
- Wolff-Parkinson-White (WPW) syndrome (Correct answer)
- Left bundle branch block
- Brugada syndrome
Correct answer: Wolff-Parkinson-White (WPW) syndrome
WPW syndrome is characterized by ventricular pre-excitation via an accessory pathway, producing a delta wave, shortened PR interval, and widened QRS on the ECG.
Question 7: In pediatric ECG interpretation, T-wave inversion in leads V1–V3 in a 5-year-old is considered:
- Strongly suggestive of myocardial ischemia
- Normal persistent juvenile T-wave pattern (Correct answer)
- Diagnostic of hypertrophic cardiomyopathy
- Indicative of hyperkalemia
Correct answer: Normal persistent juvenile T-wave pattern
Persistent T-wave inversions in V1–V3 (juvenile T-wave pattern) are normal in children and may persist into adolescence, particularly in females, and do not indicate ischemia.
CET Pediatric ECG Considerations 3
What electrode placement modification is used for small infants when standard chest electrode spacing is too large?