Matthias Frühwirth

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.

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.

Multimodal Therapy Concept and Aerobic Training in Breast Cancer Patients With Chronic Cancer-Related Fatigue

Hypothese: Cancer-related fatigue (CRF) and sleep disorders are some of the most wearing and common symptoms in disease-free breast cancer patients (BC). Aerobic training (AT) is the treatment with the best available evidence, even though it seems to be insufficient with regards to improvements in cognitive fatigue. We introduced a new multimodal therapy concept (MM) consisting of psycho-, sleep-education and new approaches based on anthroposophic medicine such as eurythmy and painting therapy. Study design: This pilot study will test the implementation of MM and yield first results of the MM and AE in our centres. Methods: 31 out of 34 patients suffering from BC and CRF were fully assessed in a ten-week intervention study. 21 patients chose MM and 10 decided on AT. CRF was measured with the help of the Cancer Fatigue Scale (CFS-D), and the global quality of sleep was measured with the Pittsburgh Sleep Quality Index (PSQI). We also captured autonomic regulation (aR) and patients’ satisfaction with questionnaires. Statistical analysis was done with SAS 9.1.3 for windows. Results: The new MM therapy can be implemented with high satisfaction among patients. Significant improvements were found in the MM group with regards to CFS-D, global quality of sleep, sleep efficiency (PSQI), aR and rest/activity regulation compared to baseline (all p<0.05). In the AT group aR orthostatic-circulatory and rest/activity regulation improved significantly (p<0.05), too. However, no improvement in cognitive fatigue was seen in either group. Conclusion: The multimodal therapy concept was feasible and improved cancer fatigue, sleep quality, autonomic and rest-/activity regulation in breast cancer patients. It may therefore constitute a valuable treatment option in addition to aerobic training for BC patients with CRF. A further study with larger sample size needs to be carried out to assess the efficacy of combined multimodal-aerobic therapy.

Wirkungen der Therapeutischen Sprachgestaltung auf Herzfrequenz-Variabilität und Befinden

Effects of Speech Therapy with Poetry on Heart Rate Variability and Well-Being Background: Anthroposophical Therapeutic Speech uses poems and exercises which typically induce rhythmical breathing. Speaking influences respiration and thus directly heart rate variability (HRV), in particular via respiratory sinus arrhythmia which, together with the slower rhythms of HRV, may be regarded as an indicator of sympathovagal balance. In chronomedicine numerous frequency ratios between physiological rhythms, especially in trophotropic phases, have been established. Integer ratios occur frequently and seem to be associated with the optimization of physiological processes. In larger groups the average pulse respiration quotient is about 4:1. Question: Can systematic effects on HRV, and thus on autonomic balance, be established through special speech therapy? Subjects and Methods: In two trained therapists and 7 untrained subjects the influence of different speech exercises and texts on HRV was investigated. With untrained subjects a total of 105 one-hour sessions, divided into speech and control exercises, was performed. The overall well-being and quality of well-being were assessed with questionnaires. Control evaluations were made in the same setting. Results: As a simultaneous effect, during speech exercises and texts typical intra- and inter-individually reproducible patterns in heart rate variability were observed. Reciting poems with a hexameter metric generates 2 oscillations with a 2:1 frequency ratio in the HRV spectrum. As immediate effects there were a significant drop in heart rate after speech sessions as well as a strengthening of vagus-related HRV parameters, especially after hexameter exercises. In comparison to control sessions the subjects felt significantly better, too. The different metric and poetic character of the texts was reflected clearly in the results.

Prolonged asystole provoked by head-up tilt testing.

SummaryWe describe a patient with a history of neurocardiogenic syncopes who had a positive headup tilt test that resulted in an lasting asystole lasting 34 seconds. However, the previously carried out Schellong test with a 30-min phase of standing showed a normal result. The patient showed typical orthostatic symptoms while tilted at the angle of 75°. Shortly before asystole occurred, heart rate variability showed high frequency bands, indicating vagal stimulation. The pathophysiology of neurocardiogenic syncope (NCS) in context with heart rate variability is discussed.This patient was successfully treated with propranolol. This case shows the utility of a provocative head-up tilt test in establishing the diagnosis of NCS. If the Schellong test is normal, still further examination by tilt-table test is indispensable.

Disentangling respiratory sinus arrhythmia in heart rate variability records

OBJECTIVE Several different measures of heart rate variability, and particularly of respiratory sinus arrhythmia, are widely used in research and clinical applications. For many purposes it is important to know which features of heart rate variability are directly related to respiration and which are caused by other aspects of cardiac dynamics. APPROACH Inspired by ideas from the theory of coupled oscillators, we use simultaneous measurements of respiratory and cardiac activity to perform a nonlinear disentanglement of the heart rate variability into the respiratory-related component and the rest. MAIN RESULTS The theoretical consideration is illustrated by the analysis of 25 data sets from healthy subjects. In all cases we show how the disentanglement is manifested in the different measures of heart rate variability. SIGNIFICANCE The suggested technique can be exploited as a universal preprocessing tool, both for the analysis of respiratory influence on the heart rate and in cases when effects of other factors on the heart rate variability are in focus.

Investigation of a Micro-test for Circulatory Autonomic Nervous System Responses

Aims and Objectives: The autonomic nervous system plays an important role in homeostasis and organismic recreation, control of immune function, inflammation, and bone growth. It also regulates blood pressure and orthostasis via vagal and sympathetic pathways. Besides recording of heart rate variability (HRV), which characterizes medium (1–5 min) and long term (circadian) autonomic tone or modulation, no gentle tests of short-term autonomic reactivity and control are available. In 1976 Nogier described a short time cardiovascular response (“Réflexe Auriculo Cardiaque”, RAC) which could be used to investigate short term autonomic reactions without changing system characteristics and thus being repeatable in short intervals. In this paper, we investigated the possible application of the Nogier reaction as a micro-test for the identification of a disturbed sensitivity or reactivity of the autonomic nervous system. Methods: We statistically analyzed cardiovascular signals derived during the application of small repeated stimuli utilizing methods of signal averaging to characterize the physiological background. Specifically, the Nogier reaction was investigated using simultaneous recordings of ECG, pulse waves, and respiration. Results: Significant fast (delay 1–5 s) and slower (delay 6–12 s) cardio-autonomic responses to different stimuli which characterize short term were observed. From time characteristics and type of signals where they occur we deduce that fast changes observed in heart rate are vagal reactions to the small stimuli whereas slower changes observed in pulse waves stem from sympathetic nervous system responses. Conclusions: The investigated autonomic micro-test opens the possibility to differentially investigate both limbs of the autonomic nervous system with minimal stimuli. It can be performed within seconds and does not change the set point of the system in opposition to less subtle tests such as Valsalva maneuver. Therefore, it is well-suited for quick, repeated measurements of autonomic nervous system reactivity.