David Gordon

An Efficient Algorithm for Spectral Analysis of Heart Rate Variability

We present a simple efficient algorithm for the derivation of a heart rate signal from the electrocardiogram. We demonstrate that the amplitude spectrum of this heart rate signal more closely matches that of the input signal to an integral pulse frequency modulation (IPFM) model of the hearts pacemaker than do the spectra of other ECG-derived heart rate signals. The applicability of this algorithm in cross-spectral analysis between heart rate and other physiologic signals is also discussed.

Sudden infant death syndrome: abnormalities in short term fluctuations in heart rate and respiratory activity.

Summary: In order to test the hypothesis that a defect in cardiorespiratory regulation contributes to death of infants from sudden infant death syndrome (SIDS), we analyzed the power spectra of heart rate and respiratory activity during 256-sec epochs of quiet sleep. Data were obtained from pneumogram recordings performed for 12 h at night on eight infants who subsequently died from SIDS and 22 age-matched control infants. We computed the heart rate and respiratory power spectra from a single epoch on each infant using an algorithm developed for an 8085 microprocessor system dedicated to this investigation. There was no statistically significant difference between SIDS and controls based on mean respiratory and heart rates. Spectral analysis revealed enhancement of low frequency power in the 0.02 to 0.1 Hz band in the heart rate power spectrum in the SIDS group compared to control (p < 0.002) and dispersion in respiratory frequency as determined by the respiratory band width (p < 0.00001). These data suggest that a predisposition to SIDS manifests itself in an abnormal pattern of fluctuations in heart rate and respiratory activity.

Isolation and complete nucleotide sequence of the gene for bovine parathyroid hormone

The structure of the bovine parathyroid hormone (PTH) gene has been analyzed by Southern blot hybridization of genomic DNA and by nucleotide sequence analysis of a cloned PTH gene. In the Southern analysis, several restriction enzymes produced single fragments that hybridized to PTH cDNA suggesting that there is a single bovine PTH gene. The restriction map of the cloned gene is the same as that determined by Southern blot analysis of bovine DNA. The sequence of 3154 bp of the cloned gene has been determined including 510 bp and 139 bp in the 5 and 3 flanking regions, respectively. The gene contains two introns which separate three exons that code primarily for: (i) the 5 untranslated region, (ii) the pre-sequence of preProPTH, and (iii) PTH and the 3 untranslated region. The gene contains 68% A + T and unusually long stretches of 100- to 150-bp sequences containing alternating A and T nucleotides in the 5 flanking region and intron A. The 5 flanking region contains two TATA sequences, both of which appear to be functional as determined by S1 nuclease mapping. Compared to the rat and human genes, the locations of the introns are identical but the sizes differ. Comparable human and bovine sequences in the flanking regions and introns are about 80% homologous.

Analysis of heart rate and respiratory patterns in sudden infant death syndrome victims and control infants

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.

Assessment of Quality of Life in Young Patients with Single Ventricle after the Fontan Operation

OBJECTIVESnTo assess self-reported quality of life (QOL) in a large multicenter cohort of adolescent and young adults surviving Fontan.nnnSTUDY DESIGNnCross-sectional. The Pediatric Quality of Life Inventory (PedsQL) was administered to 408 survivors of Fontan ages 13-25 years enrolled in the Pediatric Heart Network Fontan Follow-up Study. Subjects also completed either the Child Health Questionnaire (age <19 years) or Short Form Health Survey (age ≥ 19 years). PedsQL data were compared with matched controls without a chronic health condition. Correlations between the measures were examined.nnnRESULTSnMean PedsQL scores for subjects receiving Fontan were significantly lower than those for the control group for physical and psychosocial QOL (P < .001). Overall, 45% of subjects receiving Fontan had scores in the clinically significant impaired range for physical QOL with 30% in the impaired range for psychosocial QOL. For each 1 year increase in age, the physical functioning score decreased by an average of 0.76 points (P = .004) and the emotional functioning score decreased by an average of 0.64 points (P = .03). Among subjects ≥19 years of age, the physical functioning score decreased by an average of 2 points for each year increase in age (P = .02). PedsQL scale scores were significantly correlated with conceptually related Child Health Questionnaire (P < .001) and Short Form Health Survey scores (P < .001).nnnCONCLUSIONSnSurvivors of Fontan are at risk for significantly impaired QOL which may decline with advancing age. Routine assessment of QOL is essential to inform interventions to improve health outcomes. The PedsQL allowed QOL assessment from pediatrics to young adulthood.nnnTRIAL REGISTRATIONnClinicalTrials.gov: NCT00132782.

Nucleotide sequence of bovine parathyroid hormone messenger RNA

The sequence of bovine parathyroid hormone mRNA has been determined by sequence analysis of near full-length cloned DNA complementary to the mRNA. Restriction fragments hybridized to the mRNA and extended toward the 5 terminus with reverse transcriptase were analyzed to derive the sequence not present in cDNA. The reverse transcripts were heterogeneous in length with three major stopping points within 8 nucleotides of each other and a minor stop about 30 bases further toward the 5 terminus of the mRNA. The sequence of the gene corresponding to the minor reverse transcript begins with the sequence 5 XXXATATATAAAA which contains the consensus sequence for a TATA box, a putative eukaryotic promoter sequence. Assuming that the major reverse transcriptase stop nearest the 5 terminus of the mRNA, which is 24 bases downstream from the TATA box, represents the beginning of bovine PTH mRNA, the mRNA contains 672 nucleotides, 100 in the 5 noncoding region, 348 in the coding region and 224 in the 3 noncoding region. Bovine PTH mRNA contains 38% G and C bases. The 3 noncoding region is particularly rich in A and U bases with the last 100 nucleotides of the molecules containing 46% U and 32% A. As with other mRNAs, the sequences CG and UAG occur much less than expected. The 5 noncoding region does not contain an AUG before the initiator codon and contains two potential regions that could base-pair with sequences near the 3 terminus of 18S ribosomal RNA. The sequence AAUAAA is present 14 nucleotides from the polyadenylic acid at the 3 terminus. Bovine PTH mRNA exhibits extensive homology with human PTH mRNA.

The Effect of Early Mother–Infant Separation on Later Maternal Performance

The care of premature infants in most nurseries entails prolonged physical separation of a mother from her baby. To determine whether this period of separation results in altered maternal behavior we measured feeding performance in a group of mothers who were permitted physical contact with their premature infants (mean b.w. 1,551 g) beginning in the first days of life (Early Contact). Their feeding behavior was compared at the time of discharge and one month later with another group of mothers who first handled their babies (mean b.w. 1,409 g) after 20 days of age (Late Contact). We made 34 time lapse movies of 24 mothers feeding their infants. Mothers and babies reactions were analyzed in detail at 1-sec intervals for 10 min of each 15 min filmed. Each frame was scored for twenty five activities ranging from caretaking skills such as the presence of milk in the tip of the nipple to measurements of maternal affection, such as the mothers body touching the infants trunk (cuddling). Although the amount of time the mothers were looking at their babies was the same in both groups, the Early Contact group had significantly greater ‘en face’ (mothers face rotated so that her eyes and those of the infant meet fully in the same vertical plane) 14.8% vs. 5.7% (p < 0.05) and also more cuddling 46.3% vs. 21.1% (p < 0.025) in the pre-discharge but not the one month feeding. Both of these reflect to some extent the active interest of the mother in her infant. There were no significant differences in measures of caretaking. it is intriguing to consider whether the differences in maternal behavior are dur to early initiation of physical contact.

PROSPECTIVE ANALYSIS OF HEART RATE AND BREATHING PATTERNS IN INFANTS SUCCUMBING TO SIDS AND IN CONTROLS

In studies of babies at high risk for SIDS (near-SIDS and siblings), we have identified among some who died excess periodic breathing (PB) excess variability (var) of respiratory frequency (f) and increased oscillation of heart rate (HR), at 4-7 cycles per min., (low frequency peak-LFP). The present study was planned to test the hypothesis that in an unselected prospectively studied population, these same variables might discriminate SIDS from controls. From 6914 term infants, we selected 24 hour pneumograms performed at 6 weeks on 11 SIDS and 101 random controls. One SIDS had one near-SIDS spell. Casettes were coded for blind analysis. From data recorded between 12MN and 6AM we transcribed ECG and respiratory signals onto hard copy for visual inspection and we transferred these signals during all 5 min epochs of quiet breathing (Q) onto FM tape for spectral analysis. We inspected hard copies for PB and apnea ⩾10s. Spectral analysis identified f and var, HR and var and power at f (resp. sinus arrhythmia) and at the LFP. We rank ordered results to test hypothesis 1) that PB and 2) that abnormal spectral var were markers for SIDS. We performed cluster analysis on each data set The code was then broken; neither hypothesis was correct. These results neither support nor negate the apnea hypothesis of SIDS.