PubMed · 5780413
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D W Bethune. 1969. Instantaneous pulse rate recording.. https://pubmed.ncbi.nlm.nih.gov/5780413/
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The aim of this investigation was to evaluate the role of autonomic nervous activity before and during transient ischemic events. Forty-one ischemic episodes detected on Holter recordings were analyzed for heart rate and heart rate variability (HRV). A time-dependent index of HRV the windowed median successive difference, which is a continuous measure of respiratory sinus arrhythmia and therefore a marker of vagal efferent activity was used. A small window consisting of five beats, which represented one respiratory cycle, was chosen. This method permitted continuous assessment of short-term alterations of vagal modulation. With two exceptions, all ischemic episodes were preceded by an acute almost complete suppression of respiratory sinus arrhythmia. During the entire ischemic episode, HRV stayed at this reduced level, and preceding the end of the ischemia, it increased again. This suppression of intrinsic heart period variations reflects an almost complete withdrawal of modulated vagal outflow immediately before and during ischemic episodes. In 26 cases (63%), Fast Fourier Transformations were carried out when the heart rate was almost constant in two segments around the onset of ischemia. In the other 15 cases we did not perform Fast Fourier Transformations because there was no stationary stage in the data. High-frequency power always decreased drastically at the onset of ischemia, confirming a significant loss of modulated vagal activity (P < .01). The low frequency/high frequency ratio did not increase, indicating that sympathetic activity did not increase significantly at the onset of ischemia in about two-thirds of our cases. The extent to which this suppression of modulated vagal activity reflects a similar suppression of vagal efferent activity is discussed, as well as whether this withdrawal of vagal outflow is cause or consequence of the ischemic event. The results suggest that a vagal depression may influence the onset of myocardial ischemia during daily life.
Current model internal cardioverter defibrillators (ICDs) have cardioversion, defibrillation, pacemaker, and telemetry function. Telemetry documents arrhythmia and facilitates therapeutic adjustments. We report two cases of pacing induced VF terminated by the defibrillator, with the device responsible for both initiation and correction of the arrhythmia.
OBJECTIVE: To determine the incidence of and risk factors for unexplained paroxysmal bradycardia in children treated with high-frequency oscillatory ventilation (HFOV). DESIGN: A nested case-control study. SETTING: A university-affiliated children's hospital. SUBJECTS: All children treated with HFOV for at least 3 days during a 2-year period and a randomly chosen comparison group of 50 children treated with only conventional mechanical ventilation (CMV) for at least 3 days during the same time period. INTERVENTIONS: None. MEASUREMENTS AND RESULTS: Unexplained paroxysmal sinus bradycardia occurred in six children (12%) receiving HFOV, and was significantly more common than in children treated with CMV (0%). The bradycardic events occurred after the lung disease started to improve, and the mean airway pressure (mPaw) at the time of the bradycardias was significantly decreased from the child's maximal mPaw. The bradycardic events were effectively treated acutely with manual ventilation or atropine sulfate, and resolved completely after the patient was changed to a regimen of CMV. CONCLUSION: Unexplained paroxysmal bradycardia associated with HFOV in children is not uncommon. It completely resolves with conversion to CMV and may be related to overdistention of alveoli as compliance improves.