newborns have a thick right ventricle resulting in a mean QRS axis which points anteriorly and to the right demonstrating a right axis deviation (70-180degress) and large R waves in the precordium
by 3 months of age, the QRS axis in the frontal plane shifts to the left with a mean of 65degress (0-125degress)
by older childhood, the normal mean QRS axis is -30-100degress)
thus, with age the R wave decreases in V1 and increases in V6
take home: right-axis deviation is often a normal finding in children and young adults when you see left-axis deviation in children consider tricuspid atresia, atrioventricularseptal defects, and LVH as the most associated conditions
References
MedStudyPedatrics Board Review, Core Curriculum, Book 3 2004
