The influence of vagal activity on heart block

Messer, Addison L.; Donegan, Charles K.; Orgain, Edward S.

doi:10.1016/0002-8703(49)90529-3

Cited by 6 publications

(1 citation statement)

References 13 publications

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“…On the other hand, transient prolongation of auriculo-ventricular conduction is generally considered to be of vagal origin (Messer, Donegan, and Orgain, 1949), and is attributed to increased potassium permeability of conduction tissue (Lepeschkin, 1959). There is some evidence that vagal tone is active in the neonate, although the question is far from settled.…”

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P Wave Duration and P-R Interval During First Week of Life

Sz¹

1963

Heart

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Interpretation of the electrocardiogram in the neonate is complicated by the profound physiological changes occurring after birth, the pattern and normal variation of which are as yet inadequately documented. Serial examination permits analysis of individual differences that at times may prove more informative than group differences.In this investigation, electrocardiograms were recorded on 68 infants on their first, second, third, and fifth or sixth day of life, and measurements of the P wave, P-R intervals, and P-R segment in lead II were analysed. An attempt was made to include as many of the youngest infants as possible, since it was clear that most previous authors had either not examined this group (Maroney and Rantz, 1950;Coleman, 1961) or not measured these intervals (Datey and Bharucha, 1960) or had studied them only on their first day of life (Kessel, 1953) or had grouped them in such a manner that differences encountered immediately after birth were not noted (Ziegler, 1951; Datey and Bharucha, 1960; and Tudbury and Atkinson, 1950). METHOD All electrocardiograms were taken on a 4-channel Mingograph 42 direct writer by the author, with the help of a full-time assistant. A paper speed of 100 mm./sec. was employed throughout to increase the accuracy of measurement of intervals. The smallest unit of measurement was 0 005 sec. The machine was standardized to produce a deflection of 1 cm. with the introduction of 1 mV into the circuit. The heart rate was generally measured on strips of 30 cm. length. Measurements were made in lead II for purposes of comparison with most available data. All P waves and P-R intervals in a single strip were measured using a magnifying lens of 5 x and the maximum value was taken. The P-R segment was calculated by subtracting P duration from the P-R interval.Infants were either asleep or quietly sucking a pacifier at the time of examination. Every effort was made to disturb the infant as little as possible during the examination and many fell asleep. No records were taken when the infants became restless. Maternal aniesthesia at the time of delivery was little or none.All infants were carefully examined and the chest was X-rayed. None showed clinical evidence of heart disease. RESULTSThe infants were divided into two groups according to the time after birth of the initial examination, those 1 hour old or less, Group I (38 cases), and those 90 minutes or more, Group 11 (30 cases).The mean age and weight of the infants in Group I was 40 minutes and 3450 g. (7 lb. 9j oz.); and in Group II, 5 hours 54 minutes and 3555 g. (7 lb. 1Ij oz.). Forty-two of the 68 infants were female.Rate. A wide range in heart rate was noted with a slight increase in the mean from the first to

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confidence: 99%