Electrocardiograms on 167 average healthy infants and children

Abstract

1. 1. The P-wave showed higher and lower amplitudes than in the adult. Diphasic forms occurred in Leads II and III and notched forms in all leads. 2. 2. Q-waves were deeper in boys than in girls, and there was a more gradual decrease with age in girls than in boys. 3. 3. R-waves may be higher or lower than usual adult standards indicate. R-waves showed slurring in 457, or 35.8 per cent of the records, and notching in 56, or 4.38 per cent. R s alone presented M and W forms and inversion. It is difficult to classify portions of the QRS complex. 4. 4. S-waves decreased with age in all leads. 5. 5. Well-defined and frequently high T-waves were observed in Leads I and II. T 3 was usually of low voltage. Inversion was seen only in T 3. It occurred in 242, or 18.9 per cent, of the cases in this lead. 6. 6. Transmission time was shorter in hearts of children; as seen in the P-R and Q-S intervals. The S-T interval showed a definite lengthening with age. 7. 7. Heart rates decreased with age. 8. 8. Sinus arrhythmia was shown in 279, or 21.8 per cent, of our records and was seen most frequently in the tenth and eleventh years. 9. 9. The greatest number of instances of right axis deviation was found in the first three months of life, with a notable decrease in the period of from four to six months. Left axis deviation occasionally occurred in average healthy children. 10. 10. Our study indicates that normal standards must allow a wide range of individual variations in the electrocardiograms on healthy infants and children. 11. 11. This study indicates the need for similar statistical studies through later childhood and adult life and suggests a greater variation in the normal adult electrocardiogram than is indicated by present accepted standards.