Because of renewed clinical interest in the Q-T interval and because of a need of normal values for an accompanying investigation in rheumatic fever, the Q-T was studied in 517 normal infants and children from birth to 13 years of age. A mean
K
of 0.404 for Bazett's formula and of 0.378 for Ashman and Hull's formula was obtained. With Bazett's curve approximating the data more closely, a Bazett's scattergram of the normal Q-T at varying heart rates was constructed. Although no difference in
K
value was noted between the sexes, significant differences were observed in certain age groups.
The value of the P-R interval in the study and evaluation of treatment of rheumatic carditis, a disease predominantly of the younger ages, has prompted a re-examination of the normal P-R standards for infants and children. This study reports these data as obtained from 506 normal infants and children. The data reveal that both age and heart rate exert a significant influence on the P-R interval. The minimum, average, and maximum values are given as related to different ages and different heart rates.
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