THE ELECTROCARDIOGRAM IN THE NORMAL INFANT

but the numbers of children under 1 year of age in these series are small.In Ziegler's monograph (1951), the numbers vary from 22 to 41 in different age-groups during the first year of life.Gros et al. (1951) include electrocardiograms from only nine infants in the age-group 1 week to 3 months and only six in the age-group 6 months to 1 year.The analysis of Bengtsson ( 1956) deals only with the terminal complex of the cardiogram and includes only nine children under 1 month of age; nine between 1 and 2 months; 15 between 3 and 5 months; and 22 between 6 and 11 months.Sodi-Pallares et a!.(1958) do not specify the number of infants.There have been few studies of the electrocardiograms of infants during the first week of life, and in only one series (Datey and Bharucha, 1960) have records been taken daily from the same 44 infants.Michaelsson (1959) obtained records from 37 infants on the first, second, third, fifth, and seventh days of life.Richman and Master (1951) obtained daily records for the first four days of life but the number of infants is not stated.We have seen 600 infants with congenital heart disease in this clinic.In some of these infants where right ventricular hypertrophy was diagnosed on other grounds, the measurements of the R waves in the precordial leads V3R and VI of the electrocardiogram were below the normal values given in published reports. SUBJECTS AND METHODSIt was therefore decided to carry out a study of the electrocardiogram in normal infants.Records were taken from the same 50 infants (29 girls and 21 boys) at 5 days, 1 month, 3 months, and 6 months: only 42 of these 50 infants attended for records at 1 year of age.In addition daily records for the first seven days of life were taken from 20 of these 50 infants.Q, R, and S waves were measured in all these records.The T waves were measured in 17 of the daily records, in 40 infants at 5 days, 1 month, 3 months, and 6 months, and in 25 infants at 1 year.The infants in this series were a random selection of normal babies born at Mill Road Maternity Hospital between August 1956 and April 1958.Most were from families of the lower income groups (3, 4, and 5 of the Registrar General's social classification).There were no abnormal signs in the cardiovascular system in any of these babies and chest radiographs taken at 5 days, 3 months, and 1 year were all normal.The electrocardiograms were recorded with the direct writer Cambridge 'Electrite' recorder, the infants being supine and unsedated.Leads I, II, III, AVR, AVL, and AVF were recorded in direct sequence using infant electrodes measuring 45 mm.x 20 mm.The prwcordial leads Vl, V3, V6, and V3R were taken at sites recommended by the British Cardiac Society (1949) using a Burger suction type electrode 1 -25 cm. in diameter.At least six complexes were taken in all leads; the paper speed was 25 mm.per second and the sensitivity was 1 mV to 1 cm.Q, R, S, and T waves were measured in all leads to an accuracy of 0*5 mm., and tables of mean, maximal, and minimal values for each wave were prepared.Histograms