Abstract
ECGs were taken on 68 healthy newborn infants on their first, second, third, and fifth or sixth day of life. P wave duration was not influenced by heart rate at any time during the first week of life. The P-R interval was related to the heart rate in infants only one hour old or less, but not subsequently. Significant prolongation of P wave duration and the P-R interval was encountered mainly in infants one hour old, or less, and possible mechanisms are discussed.