Dynamic Analysis of Cardiac R-R Intervals in Normal Infants and in Infants Who Subsequently Succumbed to the Sudden Infant Death Syndrome

Abstract

ABSTRACT. Infants who subsequently succumb to the sudden infant death syndrome (SIDS) have higher heart rates and reduced heart rate variation com~ared with other infants. We examined dynamic changes in cardiac interbeat intervals to explore these differences in cardiac control. Recordings of electrocardiographic activity and respiratory movement were acquired from 13 SIDS victims before their deaths. Moment-to-moment changes in R-R intervals during quiet sleep, rapid eye movement sleep, and waking were compared with values of 13 matched control infants. For each sleep-waking state, every R-R interval was plotted against the previous interval (PoincarC plots), and each change in interbeat interval was plotted against the previous change. Dispersion of interbeat intervals at different heart rates was reduced in SIDS victims, resulting in Poincare plots markedly different from those of controls. The dispersion, sampled at the 10th and 90th percentiles of heart rates, was reduced across all sleep-waking states in SIDS victims. At high heart rates, the difference between groups disappeared after correcting for basal rate; however, the reduced range at low heart rates was independent of basal rate. SIDS victims also showed smaller beat-to-beat changes in heart rate and fewer sustained runs of consistent heart rate changes during waking relative to controls. The differences in cardiac rate dynamics suggest altered autonomic control in infants who succumb to SIDS. We speculate that the autonomic disturbance may lead to cardiac instability or may indicate CNS alterations with the potential to affect other vital functions. (Pediatr Res 31: 606-612,1992) Abbreviations AW, waking QS, quiet sleep REM, rapid eye movement SIDS, sudden infant death syndrome ANOVA, analysis of variance Infants who subsequently succumb to SIDS demonstrate higher heart rates, diminished heart rate variation associated with respiration, and disturbed long-term coordination of cardiac and Supported by HD22695 from the National Institute of Child Health and Human Development, U.S. Public Health Service.respiratory measures relative to age-matched controls (1-5). Some of these differences are apparent only in particular sleepwaking states (2, 4, 6). We examined respiratory patterning to determine the factors underlying the differences in heart rate variation and found fewer respiratory pauses in the SIDS victims (7); however, respiratory rate and its overall variability did not differ significantly from those of control infants (2). Despite the similarities on summary respiratory measures (respiratory rate and overall variability) between a group of infants who succumbed to SIDS and a group of infants who survived, some modulator of cardiac interbeat intervals must be responsible for the diminished cardiac variation observed in infants who later succumb to SIDS. Although summary measures of cardiac activity failed to distinguish those aspects, examination of momentto-moment dynamics of cardiac patterning may reveal the mechanisms influencing cardi...

Mice Lacking Brain-Derived Neurotrophic Factor Exhibit Visceral Sensory Neuron Losses Distinct from Mice Lacking NT4 and Display a Severe Developmental Deficit in Control of Breathing

“…For example, increased incidence of periodic breathing and apnea (Steinschneider, 1972;Guilleminault et al, 1979;Kelly et al, 1986), impaired regulation of alveolar ventilation (Shannon and Kelly, 1977), abnormal fluctuations in heart rate and respiratory patterns (Gordon et al, 1984;Schechtman et al, 1988Schechtman et al, , 1990Schechtman et al, , 1992, and abnormal development of vagal nerve fibers (Becker et al, 1993) have all been implicated as factors contributing to the Sudden Infant Death Syndrome. Impaired hypoxic ventilatory responsiveness may also contribute to some forms of congenital chronic hypoventilation syndrome (Marcus et al, 1991;Weese-Mayer et al, 1992;Ogawa et al, 1993).…”

Cardiorespiratory Behavior during Sleep in Full-Term and Preterm Neonates at Comparable Postconceptional Term Ages

“…SIDS victims show reduced dispersion of interbeat intervals across all sleep-waking states with smaller beat-tobeat changes in heart rate relative to controls (26).…”

Correlations between the Poincaré Plot and Conventional Heart Rate Variability Parameters Assessed during Paced Breathing

“…This method has also been used in other clinical settings, such as stroke, diabetes, chronic renal failure, in patients after coronary artery bypass grafting or with sleep apnea syndrome (27-29, 33, 34). The Poincaré plot method also provides prognostic information about mortality in post myocardial infarction, chronic heart failure, and sudden infant death syndrome and about the risk of life threatening ventricular arrhythmias in patients subjected to cardiac surgery (4,7,12,(35)(36)(37).…”