Ultra Low Frequency Band Research Articles

24 HOUR HEART RATE AND EMG MONITORING DURING REST AND NORMAL DAILY ACTIVITY1020

Recently, 24 h heart rate variability (HRV) monitoring has gained popularity as a clinical tool that might provide indications of morbidity and mortality in patient populations. However, interpretation has been performed in the absence of information about the effect of different activity patterns on long-term HRV. We monitored 5 healthy young subjects while they were normally active, and while they remained in bed with minimal activity for 24 h. A new 24 h HR monitor (Polar, RR-Recorder) was first evaluated by simultaneous collection with a standard ECG while subjects performed a range of activities for 1 h. A tight one-to-one relationship existed between the methods. Physical activity was quantified over 24 h by a portable EMG unit(MEGA, ME-3000). As anticipated, there was a dramatic reduction in EMG activity in the resting tests. The mean RR-interval over 24 h was significantly less during activity (846±60 ms) than rest (971±66 ms, P<0.05). Total spectral power was markedly greater, especially in the ultra-low frequency range, during activity (26,015±9,262 vs. 16,100±7,111 ms2/Hz, P<0.05). These results indicate that interpretation of HRV data, especially the ultra-low frequency band (e.g. Bigger et al. Circulation 91: 1936-43, 1995), where prognostic value has been implied, must be made with caution in the absence of information on physical activity patterns. Simply resting in bed caused HRV of healthy subjects to be more similar to the pattern of patients with cardiac disease.

Changes in cardiac autonomic activities in patients with syndrome X. A study of spectral analysis of heart rate variability.

The present study was designed to assess cardiac autonomic activities, coronary microvascular function, and their relationship in patients with syndrome X. Control of coronary blood flow is complex, and impaired coronary flow reserve has been attributed as the cause of myocardial ischemia in patients with syndrome X. It is unknown whether cardiac autonomic activities are altered in the presence of coronary microvascular dysfunction in patients with syndrome X. Eighteen patients with syndrome X were studied. Great cardiac vein flow was measured by the thermodilution method and the coronary flow reserve was determined by intravenous dipyridamole (0.56 mg/kg) infusion. Twenty-four-hour ambulatory electrocardiograms were obtained in a drug-free state. Another 14 age- and sex-matched normal subjects served as a control group. The amplitude (in ms) of ultralow (ULF), very-low (VLF), low (LF), and high (HF) frequency bands and total spectra of heart rate variability were measured for twenty-four-hour and every four-hour interval of the day.

Report from the IUGG Assembly: IAGA session on pulsations

Geomagnetic pulsations are small oscillatory changes in the earth's magnetic field. Their periods fall in the ULF (ultra low frequency) band and range from a second up to 600 seconds. First reported in the last century, significant progress in understanding the origin of these surprisingly sinusoidal signals only followed J. W. Dungey's suggestion, in the early 1950's, that they might be due to hydromagnetic waves in the earth's magnetosphere. The 1960's saw an accumulation of evidence, but in the 1970's the field blossomed.A variety of factors were responsible. Most important was that theories of large‐scale structure of signals were developed just as the first arrays of magnetometers were measuring the north‐south signal structure along lines of longitude. Theory and experiment agreed probably better than theorists or experimenters had expected; thus began a healthy mix of collaboration between theorists and experimenters.

The expanding horizon of phonocardiography

(1) Phonocardiography is defined and the various bands of the vibratory spectrum are described, both from a physical standpoint and in relation to clinical methods of observation. Methods employed by various authors for recording phonocardiograms are compared. A new calibrated phonocardiograph is described. (2) International attempts at standardization of phonocardiography are summarized. Symbols for describing the vibrations of a phonocardiogram are discussed. (3) The advantages and disadvantages of various types of filters and the methods of calibrated and spectral phonocardiography are analyzed. (4) The vibrations created by the heart are separately described in the ultra-low, low, medium, and high frequency bands. A special discussion presents the author's viewpoints in regard to the two main components of the first sound and the so-called ejection sound. (5) The mechanism of production of the heart tones is described. (6) The value of the various tracings from a clinical standpoint is briefly analyzed.