Cardiology - ECG Interpretation Flashcards
Normal HR for neonates
100-160bpm
Normal HR for infants
100-150bpm
Normal HR for children
70-140bpm
Normal HR for adolescents
60-120bpm
PR intervals
Shorter in younger patients due to smaller heart size and faster conduction.
- Neonates: 80-120ms
- Children: 100-140ms
QRS Complex
Narrow:
- Neonates: <80ms
- Children: 100-140ms
Poor R-wave progression due to RV dominance
QT Interval
QTc is used, upper limits:
- Neonates: <470ms
- Infants & Children: <440ms
- Adolescents: <460ms
Axis
RAD common in neonates due to physiological RVH - by 1 year the axis shifts to the left
Why is there RVH and RAD in neonates?
In utero, the lungs are not functional (collapsed, filled with air, relying on placenta instead) and so the heart is dependent on the ductus arteriosus.
- Some blood is shunted from the RA into the LA via the foramen ovale, most of it is shunted from the RV into the aorta via the ductus arteriosus (bypassing the PA and the lungs)
- Pulmonary vascular resistance is high and the RV does most of the work, it is thicker & stronger than the LV
- At birth, the lungs expand, the ductus closes, pulmonary vascular resistance drops, and normal circulation begins as the neonate takes its first breaths
- It takes time for the heart to remodel and adjust to this circulation, the right heart is still dominant for a short period (months to 1 year)
Other normal variants in children
- Sinus tachycardia or sinus arrhythmia
- Isolated PACs and PVCs
- Notched P-waves, particularly in V2-V3 in older children
- Juvenile T-wave inversion in V1-V3, needs analysis if persistent beyond adolescence
- 2:1 Wenkebach pattern in sleep
Consequences of right heart dominance
- RVH
- RAD
- Prominent R-waves in V1 (poor R-wave progression)
- T-wave inversions in V1-V3 (may also be biphasic)
- Prominent P-waves in lead II and V1, sometimes notched
