PubMed · 4423760
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B V Agrawal, P N Somani, P K Srivastava. 1974. Interesting electrocardiogram.. https://pubmed.ncbi.nlm.nih.gov/4423760/
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Respiration is a powerful modulator of heart rate variability, and of baro- and chemoreflex sensitivity. Abnormal respiratory modulation of heart rate is often an early sign of autonomic dysfunction in a number of diseases. In addition, increase in venous return due to respiration may help in maintaining blood pressure during standing in critical situations. This review examines the possibility that manipulation of breathing pattern may provide beneficial effects in terms not only of ventilatory efficiency, but also of cardiovascular and respiratory control in physiologic and pathologic conditions, such as chronic heart failure. This opens a new area of future research in the better management of patients with cardiovascular autonomic dysfunction.
OBJECTIVE: Recent evidence in literature shows that the long QT syndrome accounts for a fraction of the sudden infant death syndrome. Newborn infants with prolongation of the Q-T interval often show sinus bradycardia, which led us to test whether children who were diagnosed with long QT syndrome also show sinus bradycardia in the cardiotocogram before birth. STUDY DESIGN: We identified 18 children who were born from singleton pregnancies at or near term in whom long QT syndrome (corrected QT interval, >0.440 second) was diagnosed after birth or in childhood. Cardiograms during pregnancy and delivery were available from 17 of the 18 children. RESULTS: The cardiotocogram showed persistent fetal sinus bradycardia (baseline heart rate permanently below 120 beats/min) in 12 of 17 fetuses (71%) with long QT syndrome. Two fetuses had additional intermittent tachyarrhythmias. CONCLUSION: Sinus bradycardia in the cardiotocogram during delivery or in pregnancy may indicate long QT syndrome in the fetus. Postnatal electrocardiography should be performed in these children to rule out or confirm a prolongation of the Q-T interval.
The frequency content of the heart rate (HR) series contains information regarding the state of the autonomic nervous system. Of particular importance is respiratory sinus arrhythmia (RSA), the high-frequency fluctuation in HR attributable to respiration. The unevenly sampled nature of heart rate data, however, presents a problem for the discrete Fourier transform. Interpolation of the HR series allows even sampling, but filters high-frequency content. The Lomb periodogram (LP) is a regression-based method that addresses these issues. To evaluate the efficacy of the LP and Fourier techniques in detecting RSA, we compared the spectrum of intervals, the spectrum of HR samples, and the LP of simulated and clinical neonatal time series. We found the LP was superior to the spectrum of intervals and the spectrum of HR samples in analysis near the critical frequency of one half the average sampling rate. Applying the LP to clinical data, we found (1) evidence of stochastic resonance, an enhancement of periodicity with the addition of small amounts of noise, and (2) reduced power at all frequencies prior to clinical diagnosis of neonatal sepsis.