Maximilian Moser

Increased heart rate in depressed subjects in spite of unchanged autonomic balance

A clinical study was conducted to examine the effects of depression on cardiac autonomic control. Cardiac autonomic control was measured in 26 nonmedicated patients (19 females) suffering from Major Depression, melancholic type, and in 26 age- and sex-matched normal controls. We measured heart rate and high frequency heart rate variability (respiratory sinus arrhythmia), pulsewave velocity and blood pressure, during 10 min of supine rest under controlled conditions. Using a log transformed time domain measure of respiratory sinus arrhythmia (logRSA), we found an inverse linear dependence between cardiac vagal tone and age in the healthy subjects as well as the depressed patients. logRSA was 0.22+/-0.25 in the patients and 0.25+/-0.16 in the control group. While this difference was not significant (P > 0.1), the deviations from the regression line were significantly (P < 0.0005) greater in the patients (0.21+/-0.12) than in the control group (0.09+/-0.07), indicating a more heterogeneous vagal tone in the depressed patients. Heart rate was also significantly (P < 0.03) greater in the depressed patients (76.6+/-12.4) than in the control group (69.5+/-6.9). No between-group differences were found in pulsewave velocity or systolic blood pressure, but diastolic blood pressure was lower in depressed patients (73.5+/-8.7 vs. 80.8+/-9.1). We discuss the possibility that the increased heart rate seen in the absence of vagal tone changes may not be due to altered vagal or sympathetic tone, as measured in this study. Other factors, including altered autonomous heart rate, may be responsible for the higher heart rate in the depressed group.

Major depression and cardiac autonomic control.

We investigated autonomic control of heart rate in patients with major depression, melancholic type. Twenty-three depressed inpatients who were being treated with tricyclic antidepressants and 23 depressed patients who were taking no medications were compared with age- and sex-matched control groups on resting cardiac vagal tone and heart rate. In unmedicated depressed patients, cardiac vagal tone was comparable to that of control subjects, but heart rate was significantly higher. This increase in heart rate may have been due to sympathetic activation caused by anxiety, since the depressed patients were significantly more anxious than the control subjects. Medicated patients exhibited diminished cardiac vagal tone and higher heart rate than unmedicated patients and controls. This was probably due to the anticholinergic effects of the antidepressants. Our findings suggest that cardiac vagal tone is not lower than normal in patients with depression, melancholic type.

Heart rate variability as a prognostic tool in cardiology. A contribution to the problem from a theoretical point of view.

BackgroundRecent clinical studies have proposed standard deviation of heart rate as a diagnostic tool for the outcome of cardiac infarction. Mathematical analysis of heart rate variability shows that heart rate is influenced by different frequency components derived from different parts of the autonomous nervous system. In the experimental part of this study, we investigated the possibility of calculating a variable describing the parasympathetic branch of the autonomous nervous system exclusively. Methods and ResultsIn 60 healthy volunteers, heart rate was measured to 1 millisecond during two different conditions: 5 minutes of rest, and 5 minutes of intermittent handgrip dynamometry; the latter is known to increase sympathetic arousal selectively. Heart rate was found to be lower at rest (65.9±9.7 beats per minute) than during dynamometry (72.8±10.4 beats per minute, P<.001). Respiratory sinus arrhythmia (RSA) calculated from the mean absolute differences between successive heart beats showed no significant change (3.01± 1.62 beats per minute at rest versus 2.97±1.30 beats per minute during dynamometry). In contrast, standard deviation increased from 5.19±1.98 to 9.22±3.56 beats per minute (P<.001). ConclusionsIt can be concluded from these data as well as from other plots presented in this article that RSA is a measure of the parasympathetic vagal tone, whereas standard deviation is increased by both sympathetic and parasympathetic arousal. Clinical evidence and data from physiological experiments are presented to show that a selective measure of vagal tone like RSA may offer advantages over standard deviation as a prognostic tool in cardiology.

Relative Timing Of Inspiration And Expiration Affects Respiratory Sinus Arrhythmia

1. The effect of a variation in inspiration and expiration times on heart rate variability was studied in 12 healthy subjects (mean age 30±6 years; five females).

In vivo cardiac phase response curve elucidates human respiratory heart rate variability

Recovering interaction of endogenous rhythms from observations is challenging, especially if a mathematical model explaining the behaviour of the system is unknown. The decisive information for successful reconstruction of the dynamics is the sensitivity of an oscillator to external influences, which is quantified by its phase response curve. Here we present a technique that allows the extraction of the phase response curve from a non-invasive observation of a system consisting of two interacting oscillators--in this case heartbeat and respiration--in its natural environment and under free-running conditions. We use this method to obtain the phase-coupling functions describing cardiorespiratory interactions and the phase response curve of 17 healthy humans. We show for the first time the phase at which the cardiac beat is susceptible to respiratory drive and extract the respiratory-related component of heart rate variability. This non-invasive method for the determination of phase response curves of coupled oscillators may find application in many scientific disciplines.

Why life oscillates : from a topographical towards a functional chronobiology

Chronobiology has identified a multitude of rhythms within our body as well as within each living cell. Some of these rhythms, such as the circadian and circannual, interact with our environment, while others run on their own, but are often coupled to the circadian or to other body rhythms. Recent evidence shows that these rhythms might be more important for our health than expected: Disturbance of the circadian rhythms by jet lag or shift work not only evokes autonomic disturbances but also increases the incidence of cancer, as shown in this issue of Cancer Causes and Control. The occurrence of rhythms in the organism obviously bears several advantages: (1) It increases organismic stability by calibrating the system’s characteristics: Regulation curves in time and space are crucial for controlling physiological long-term stability. To determine its properties continuously the system varies its parameters slightly over several time scales at different frequencies—akin to what our body does, e.g. in heart-rate variability. (2) Tuning and synchronization of rhythms saves energy: It was Huygens who observed that clocks on a wall tend to synchronize their beats. It turned out later that synchronisation is a very common phenomenon observed in bodies’ rhythms and can be found, for example, when we relax or sleep. At such times energy consumption is minimal, our body working most efficiently. (3) Temporal compartmentalization allows polar events to occur in the same space unit: there are polarities in the universe of our body, which cannot happen simultaneously. Systole and diastole, inspiration and expiration, work and relaxation, wakefulness and sleep, reductive and oxidative states cannot be performed efficiently at the same time and place. Temporal compartmentalization is probably the most efficient way to mediate between these polarities. Chronobiology and chronomedicine are opening a new and very exciting understanding of our bodies’ regulation. The biological time and its oscillations gain more attention and importance as these interrelations are understood.

Effects of speech therapy with poetry on heart rate rhythmicity and cardiorespiratory coordination

Our objective was to study the effects of guided rhythmic speech with poetry, referred to as anthroposophical therapeutic speech (ATS), on binary differential heart rate dynamics (also called musical heart rate rhythmicity or HRR) as well as on classical spectral parameters during the 15 min after a speech exercise had ended. A total of 105 1-h sessions with speech or control exercises were performed in seven healthy subjects, with 15 sessions each. Heart rate was recorded with ambulatory solid state recorders. Sessions were divided into a 15-min baseline measurement (S1), 30 min of exercise and a 15-min effect measurement (S2). The overall binary pattern predominance (PP) as well as the frequency of predominant and cyclically recurrent cardiorespiratory phase locking patterns were calculated from HRR and their changes from S1 to S2 were compared with the changes in low and high frequency heart rate variability. The results showed that: (i) ATS provokes alterations in heart rate dynamics which are different from those after control exercises and which persist at least for 15 min following exercise; (ii) in comparison to spectral parameters of heart rate variability, pattern predominance discloses the effects of rhythmic speech exercises best; and (iii) cardiorespiratory phase locking patterns, which contribute most to the rhythm pattern predominance, are more prominent after ATS.

Cancer and Rhythm

In a recent editorial comment, Denise Duboule [1] emphasized that ‘‘animal development is, in fact, nothing but time.’’ In this issue of Cancer Causes and Control, several papers will substantiate that not only developmental, but also neoplastic processes may be linked to what Duboule [1] and Halberg [2] referred to as ‘chronomics’: timing and rhythm. Moreover, there is reason to believe that timing and rhythm may have been underappreciated in current therapeutic settings [3]. The papers in this issue of Cancer Causes and Control are from leading researchers in the field of cancer and body rhythms. Each one addresses a specific aspect of the topic, and their work is cited below in this overview editorial. Evidence from observational studies is growing [4] that the disturbance of body rhythms, in particular, circadian disruption e.g., shift work [5–8] or chronic jet-lag [9–12] contribute significantly to the development of breast cancer. Figure 1 compares the relative impact of rhythm disturbances to other exposures of significance in breast tumor development [13]. Reproductive risk factors such as parity and age at first birth, age at menarche, and age at menopause each confer a change in risk of roughly 20–30%. Only family history in a first degree confers a relative risk comparable in magnitude to that of female flight attendants. Unlike for other cancers for which primary risk factors have been identified (e.g., smoking and lung cancer risk), to date, no single environmental risk factor has been identified that can account for a major proportion of breast cancers, the incidence of which is still rising. Thus, there is a need for continued, vigorous search of breast cancer risk factors. Disruption of circadian rhythms, which can be caused by a wide variety of factors, may play an important role, not only for breast—but also other cancers, but results are still premature. Disruption of clock gene function may increase cancer risk: In mice, clock genes stabilize the genome and help maintain important repair mechanisms such as the apoptosis of damaged cells [14]. Per-2 gene deprived mice lack a circadian rhythm [15] and have been shown to develop cancer rapidly and spontaneously. The difference between wild type and rhythm-deprived mice was found to be most striking after exposure to ionizing radiation. In suprachiasmatic nuclei (SCN) ablated mice, disruption of circadian rhythms was associated with accelerated growth of Dedication This special issue of CCC is dedicated to Gunther Hildebrandt (Marburg, Germany) and Franz Halberg (Minnesota, USA), two great pioneers of Chronobiology.

Phase‐ and frequency coordination of cardiac and respiratory function

Abstract ECG and respiration (by nose thermistor sensor) were measured in 160 healthy volunteers under resting conditions. Frequency analysis allowed to distinguish fast (center frequency ≈ 0,25 Hertz), medium (center frequency ≈ 0,1 Hertz) and slow waves (center frequency = 0,05 Hertz) of heart rate variability. The fast waves are related to respiratory sinus arrhythmia, which mirrors parasympathetic tone and the slow waves are mainly connected with the sympathetic nervous activities, whereas medium waves are influenced by both the sympathetic and the parasympathetic nervous system. Simultaneously we calculated the heart ‐ respiration coupling by recording a total of ≈ 18.000 respiratory cycles as well as the time from the R‐peak to the onset of the next inspiration. Three distinct peaks of coincidence are related to afferents discharging in the isometric systolic phase (peak I ), to the baroreceptor afferents in the great arterial vessels (peak 2) and afferents excited in the relaxation or diastolic fil...

The Symphony of Life [Chronobiological Investigations]

Biological rhythms in a wide range of frequencies are present in the whole organism as well as within each living cell. Some of these rhythms reflect adaptations to cosmic cycles and help to anticipate changes in the environment. Others integrate and coordinate body. Importance, interaction, and visualization of biological rhythms is presented in this article. Chronobiology observes notable amount of rhythms at all organismic levels and over several orders of time magnitude.