Overview:
- S wave: 1st negative deflection after R wave
S waves in precordial leads: [1]
- Right precordial leads (V1-V2):
- Term newborn: S waves prominent (up to 23 mm in V1) despite RV dominance
- 1 week to 1 month of age: S waves ↓ to minimum
- S waves gradually ↑ with age & ↑ LV mass
- Mid-precordial leads (V3-V4):
- Birth: S waves prominent (up to 28 mm)
- Gradual ↓ with age (but remains more prominent than V5-V6)
- Left-lateral precordial leads (V5-V6):
- Birth: often prominent (up to 10 mm in V6)
- Gradual ↓ with age & ↑ LV mass
REFERENCES
1. Davignon A, Rautaharju P, Boisselle E, et al. Normal ECG standards for infants and children. Ped Cardiol 1:123, 1979.