suMMARY Twenty-four-hour electrocardiograms were recorded in the first 10 days of life on 134 healthy full-term infants with birthweights greater than 2-5 kg. The highest heart rate a minute, measured over nine beats, was 175±19 (SD). The This study shows that normal infants have variations in heart rate and rhythm hitherto considered to be abnormal.The range of heart rate and nature of heart rhythms are poorly documented in normal healthy infants. Twenty-four-hour recordings of the electrocardiogram provide an accurate means of measuring heart rate and rhythm over long periods. The technique does not seriously interfere with normal behaviour and therefore documentation of changes in rhythm and rate is possible during activities such as sleeping, feeding, or crying. This report describes the results of single 24-hour recordings of the electrocardiogram on 134 healthy full-term neonates who weighed over 2-5 kg at birth. Patients and methodsStudies were made between birth and 10 days of age (the normal period of postnatal hospitalisation in this area) on 134 randomly selected infants born in West Dorset between January 1977 and June 1978. They were all healthy and recordings were performed in the maternity ward before discharge home. All infants studied had normal standard 12 lead electrocardiograms with a 10-second rhythm strip. They were studied under standard maternity ward environmental conditions and were fed and handled normally by their mothers during the recording period.Received for publication 5 July 1979 The recordings were made onto a Medilog cassette recorder* and the tapes were analysed for the presence of arrhythmias using a playback system* and arrhythmia detector*, by a trained technician. The Medilog recorder and analyser incorporated a synclock mechanism which, by providing and processing a reference time signal, ensured that possible variations in tape speed did not produce artefactual rhythm or rate disorders. Mothers were encouraged to handle their babies in the normal way while recordings were taken.Heart rates during activity and rest were measured by a histogram module in the analyser*. Histograms of the distribution of different heart rates (as obtained by continuous measurement of all intervals) were made on 79 babies during approximately two hours each of activity and rest.The maximum heart rates, measured by direct electrocardiographic analysis, over nine consecutive beats were recorded. The minimum rates found over three, five, and nine consecutive beats were also measured in this way and the heart rhythm at this time (whether sinus or junctional) was noted.

SUMMARY The fetal heart beat, detected by ultrasound, was recorded for five minutes from 934 antenatal women-266 at 30 to 35 weeks' gestation and 718 at 36 to 41 weeks. Episodes of bradycardia <100/minute ranging from 5-30 seconds' duration occurred in 3 (1 1 %) of the former and in 9 (1.3%) of the latter group. Tachycardia >180/minute ranging from 30-90 seconds' duration o curred in 1 (0.4%) of the former and in 4 (0.6%) of the latter. Premature beats were not detected between 30 and 35 weeks, but occurred in 12 (1 7%) of 720 at 36 to 41 weeks' gestation. 50 subjects were monitored at both 30 to 35 weeks and 36 to 41 weeks' gestation and in one woman premature beats were present in the latter but not in the former recording. The incidence (1 .7%) of premature beats in the fetus at 36 to 41 weeks' gestation was similar to that in the healthy neonate (0.8%). Recordings of arrhythmias or rates outside the range 100-180/minute were replayed through a standard antepartum fetal heart rate monitor. The monitor failed to detect premature beats, 2 of 4 episodes of tachycardia >180/minute, and 9 of 12 episodes of bradycardia <100/minute, stressing its unreliability for detecting rapidly changing rates.DiMorders of cardiac rhythm and conduction have b_en shown by standard electrocardiograms (ECG) in 1% of a population of over 3000 newborn infants.'-3 24-hour ECGs also show a wide variation in normal heart rates and rhythms at this age.4 Although there are many reports of fetal arrhythmias-for example, Silber and Durnin,5 Hedvall,6 Eibschitz et al.7 and Armstrong et al.8-the incidence of these disorders in a healthy fetal population is unknown. We have therefore investigated the incidence of fetal heart rate or rhythm disorders in 934 antenatal patients; none had any complication of pregnancy at the time of recording. The findings were compared with those in the healthy newborn infant. Patients and methodsBetween 1 June 1977 and June 30 1978, 5-minute Doppler recordings of the fetal heart beat were taken from 934 women attending an antenatal clinic in west Dorset. 266 were monitored at 30 to 35 weeks' gestation and 718 were monitored at 36 to 41 weeks' gestation; 50 of them were monitored at both times. Women with complications of pregnancy requiring admission to hospital were excluded. Six mothcrs had twin pregnancies without other complications.Recordings were performed using an undirectional, single crystal ultrasound detector (Sonic Aid) with a direct connection to a high fidelity cassette recorder (Sony TC 207). Recordings were taken from mothers in the supine position and therefore the possible effects of superior vena caval compression would not have been avoided. Braxton Hicks's contractions were not monitored. The maternal pulse rate was measured during each recording to ensure that the signal received was not from a maternal vessel. Episodes of tachycardia, bradycardia, or rhythm disturbance detected by listening to the tape recordings were replayed on to paper using a fibreoptic recorder (Medilec) from which hig...

ABSTRACT. Retrospective analyses of patterns of breathing and heart rate variability obtained by visual inspection and spectral analysis of ECG and respiratory activity have provided markers associated with subsequent death in a referred population of infants at high risk for sudden infant death syndrome (SIDS). Such markers include breathing patterns characterized by excessive apneic pauses and periodic breathing, heart rate spectra characterized by increased low frequency oscillations, and respiratory activity spectra characterized by a widened "bandwidth" during regular breathing. To test whether such measurements could distinguish SIDS cases and randomly selected controls from a population study the data from 10 cases and 100 age-matched control subjects were analyzed blind. The code was disclosed after completion of the analysis. We found that none of the markers served to distinguish the SIDS cases from the controls in the population at large. This observation may indicate important physiological differences between infants destined to die in the referred high risk population and infants who die of SIDS at large. The possible reasons for our inability to identify the group of SIDS in the general population, as compared to the group of deaths in the referred high risk group are: (1) different disease processes in the two groups, (2) difference responses to the same disease process in the two groups, (3) a response reflecting the psychosocial setting of the referred high risk population, (4) methodological differences between this and previous studies. We conclude that these markers are not of value in screening the population at large. (Pediatr Res 20: 680-684, 1986) Abbreviations HR, heart rate SIDS, sudden infant death syndrome Received August 14, 195; accepted February 18, 1986. Correspondence Dr. D. Gordon, Pediatric Cardiology, University of Illinois at Chicago, University of Illinois Hospital Box 6998, Chicago, IL 60680.Supported by the Reynolds Foundation, the Healthdyne Company, MESCO, the McGraw Foundation, the National Foundation for Sudden Infant Death, PhysioParameters, Inc., the Scholl Foundation, NSF Grant ECS8 12 157 1, Office of Naval Research Grant N00014-80-C-0520, USAF School of Aerospace Medicine Award F33615-84-C-0601, and NASA Grant NAG2-327. JMR was supported by the U.K. Foundation for the Study of Infant Death and DPS was supported by the British Heart Foundation.Several patterns of breathing and heart rate variation have been identified in infants referred for evaluation for high risk of SIDS which appear to distinguish them from infants not at risk ( 1-3). High levels of periodic breathing and apneic pauses ( 1, 3, 4) have been identified by visual inspection of respiratory activity recordings in the high risk infant referred for evaluation. Power spectrum analysis demonstrated two spectral variables that were increased in referred high risk babies who subsequently died suddenly, unexpectedly, and without explanation (2): the power of oscillation in heart rate with a period of a...

SUMMARY A system for simultaneous 24-hour tape recording of ECG and respiration has been developed and used in the study of 4 groups of newborn infants. In 50 randomly selected, healthy term infants, the mean lowest heart rate (>9 beats' duration; was 88 ± 13. 14 (28%) infants had junctional escape rhythms, 5 had supraventricular, and 2 ventricular premature beats. 34 (68%) subjects had apnoeic episodes >10 seconds' duration; the 95th centile for maximum duration of apnoea was 18 seconds, the longest episode being 28 seconds. Episodes of bradycardia <100/minute were associated with 50 of a total of 288 episodes of apnoea of 10-14 seconds, with all 4 episodes of 15-19 seconds, and with both episodes >20 seconds.In 100 randomly selected, healthy, preterm or low birthweight infants studied within 5 days oftheir discharge from hospital, the mean lowest heart rate was 91 + 18. 18 had junctional, one idioventricular, and 3 both junctional and idioventricular escape rhythms. Two had supraventricular and 6 had ventricular premature beats. 66 subjects had apnoeic episodes >10 seconds' duration; the 95th centile for maximum duration of apnoea was 20 seconds, the longest episode being 52 seconds. Episodes of bradycardia <100/min were associated with 84 of a total of 608 episodes of apnoea 10-14 seconds' duration, with 21 of 37 episodes of 15-19 seconds, and with 15 of 15>20 seconds. One preterm infant with a maximum apnoeic episode of 52 seconds had an associated bradycardia of 27/min.Three of 5 'near-miss' cot death infants and one preterm infant with a family history of cot death studied immediately before discharge showed prolonged apnoea >40 seconds, or extreme bradycardia <50/min, or both.Finally, 11 infants with arrhythmias on a standard ECG were studied. Of these, 6 with premature beats and 3 of 5 with episodes of bradycardia did not exhibit apnoea during arrhythmias. Two of the 5 babies with bradycardia however, demonstrated associated apnoea of 10-14 seconds.There may be a relationship between latent episodes of prolonged apnoea and bradycardia and hypoxaemic brain damage or sudden infant death.