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Via the delivery of blood, heart transfers oxygen and nutrients to various organs and is thus a highly influential for circulatory system. To adapt to the variation of physiological conditions, the intensity and frequency of heart beats change with time. Careful observation finds that the time intervals between heartbeats are often different even if the body is at rest. Such heart rate variability (HRV) has been used to estimate the activity of the autonomic nervous system which can be divided into sympathetic and parasympathetic subsystems both of which can significantly affect the physiology of the human body. As a result, HRV has been used as a physiological indicator to assist doctors in making diagnostic decisions. Many studies have used HRV to analyze the ECG signal via studying the QRS complex waveform to determine the time intervals between R-peaks and analyze the R-R intervals from time and frequency domains. Different from the conventional R-R Interval based approach, this work introduces new HRV feature variables by computing spectrogram of the ECG signal waveform. In particular, based on the harmonics of the spectrum, we introduce the concepts of modes. By find the relative amount of energy associated with each mode and degree-of-energy-concentration associated with each mode, this work introduces two sets of new HRV features. In addition, we also investigate how these variables change with time and the correlations between these features. To demonstrate the potential of the proposed features, the differences of the values of the proposed features are compared for healthy individuals versus OSA patients, young versus old and male versus female. The experimental results show the differences between many of the tested features are statistically significant.

The present study addressed cognitive biases in anxiety and depression using the emotional Stroop task, and explored both the affective space and autonomic underpinnings of these disorders. In previous studies, anxiety has been associated with both an attentional bias toward threat information and low cardiac vagal control, as reflected in heart rate variability (HRV) indices. Depression has been linked to a memory bias for negative information; however, findings of low HRV for depression are mixed. The high comorbidity of these disorders renders such findings as difficult to interpret. In the present study, it was hypothesized that the negative affect groups (anxious, depressed, comorbid anxious/depressed) would have lower vagally mediated HRV across tasks compared to the control group and that the anxiety and depression groups would show biases for group specific words on the Stroop task. Results for the Stroop tasks generally support previous findings of an attention bias in anxiety. The comorbid anxiety/depression group generally showed lower vagal control across tasks compared to the other groups, although comparisons between the "pure" anxiety and depression groups and the controls were not significant. It is suggested that this is because the comorbid group had higher depression and anxiety than either of the "pure" groups. / Master of Science

Indiana University-Purdue University Indianapolis (IUPUI) / Autonomic control of the heart results in variations in the intervals between heart beats, known as heart rate variability. One of the defining components of autonomic control is the baroreflex, a negative feedback controller that balances heart rate and blood pressure. The baroreflex is under constant command from the branches of the autonomic nervous system. To better understand how the autonomic nervous system commands the baroreflex, a baroreflex reflexogenic animal protocol was carried out. Heart rate variability analysis and baroreflex sensitivity were used to quantify the neural control of the heart. This thesis reconfirmed the existence of sexually dimorphic properties in the baroreflex through the use of heart rate variability analysis and baroreflex sensitivity. It was discovered that there are many caveats to utilizing heart rate variability analysis, which have to be addressed both in the experimental protocol and the signal processing technique. Furthermore, it was suggested that the slope method for quantifying baroreflex sensitivity also has many caveats, and that other baroreflex sensitivity methods are likely more optimal for quantifying sustained activation of the baroreflex. By utilizing various heart rate variability signal processing algorithms to assess autonomic tone in Sprague-Dawley rats during rest and sustained electrical activation of the baroreflex, the null hypothesis was rejected.

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In patients with normal hearts, increased vagal tone is associated with the onset of paroxysmal atrial fibrillation (AF). Vagal denervation of the atria renders AF less inducible. Circumferential pulmonary vein ablation (CPVA), with or without isolation (CPVI), is effective for treating paroxysmal AF, and has been shown to impact HRV indices, in turn reflecting vagal denervation. We examined the impact of CPVI on HRV indices over time, and evaluated the relationship between vagal modification and rate of recurrence of AF. High resolution ECG recordings were collected from 64 patients (49 male, 15 female, mean age 57.1±9.7) undergoing CPVI for paroxysmal (n=46) or persistent (n=18) AF. Recordings were made pre-procedure, and at intervals up to 12 months. Success was defined as no recurrence. After CPVI, 27 patients presented recurrence. Pre-procedure HRV variables did not differ from controls in patients with a subsequent successful procedure. However, patients with recurrence demonstrated significantly-reduced pre-procedure HRV compared both with controls, and with patients having successful procedures (39.6±23.4 & 33.7±19.2 vs 21.8±11.8, P =0.01 & P=0.04). Following the procedure, HRV was reduced vs pre-procedure in patients with successful procedures (33.7±19.2 vs 18.6±15.8, P=0.01), and did not differ from unsuccessful procedures over a 12 month FU. Both groups were reduced compared with a control value. There was no significant difference in HRV between patients who experienced recurring AF (n=9), and those who experienced AT or flutter (n=18). Our data suggests that patients experiencing recurrence after one procedure have reduced HRV that is not changed by CPVI; whereas patients with a successful single procedure experience a change in HRV variables that is sustained over a long period, but is no different post-procedure from patients experiencing recurrence. These data suggest that denervation associated with CPVI may benefit patients with normal vagal tone prior to the procedure, but that sustained denervation is not a critical factor in successful outcome after CPVI. / Thesis (Master, Computing) -- Queen's University, 2010-12-07 08:32:15.066

AN ABSTRACT OF THE THESIS OF DAGONG RAN, for the MASTER OF ARTS degree in PSYCHOLOGY, presented on JULY 5, 2016, at Southern Illinois University Carbondale. TITLE: HEART RATE VARIABILITY IN CHILDREN: TONIC CHARACTERISTICS AND REACTIVITY MAJOR PROFESSOR: Dr. Sarah Kertz This study investigated tonic heart rate variability (HRV) and heart rate variability reactivity in response to stress in children with anxiety and worry symptoms. Twenty-nine children age 8 to 12 from a rural Midwestern region completed the study and were included in the data analyses. Participants completed an artificial auditioning task in which they were asked to sing in front of a video camera. Electrocardiogram were recorded prior, during, and after the task. Frequency and time domain analyses of HRV were conducted. Neither parent-report or child self-report anxiety/worry symptom levels were associated with baseline frequency domain and time domain HRV. All participants showed similar HRV reactivity in response to the stress task. Specifically, high frequency HRV was higher during baseline than during stress task, and low frequency HRV was higher during baseline than both during stress task and recovery. These findings contradicted with previous literature results. More studies are needed to examine the association between anxiety and HRV in children.

Abstract The traditional methods of analysing heart rate variability based on means and variance are unable to detect subtle but potentially important changes in interbeat heart rate behaviour. This research was designed to evaluate the clinical applicability and prognostic significance of new dynamical methods of analysing heart rate behaviour derived from nonlinear mathematics. The study covered four different patient populations, their controls and one general population of elderly people. The first patient group consisted of 38 patients with coronary artery disease without previous myocardial infarction, the second of 40 coronary artery disease patients with a prior Q-wave myocardial infarction, and the third of 45 patients with a history of ventricular tachyarrhythmia. The fourth group comprised 10 patients with a previous myocardial infarction who had experienced ventricular fibrillation during electrocardiographic recordings. The fifth group comprised a random sample of 347 community-living elderly people invited for a follow-up of 10 years after electrocardiographic recordings. Heart rate variability was analysed by traditional time and frequency domain methods. The new dynamical measures derived from nonlinear dynamics were: 1) approximate entropy, which reflects the complexity of the data, 2) detrended fluctuation analysis, which describes the presence or absence of fractal correlation properties of time series data, and 3) power-law relationship analysis, which demonstrates the distribution of spectral characteristics of RR intervals, but does not reflect the magnitude of spectral power in different spectral bands. Approximate entropy was higher in postinfarction patients (1.17 ± 0.22), but lower in coronary artery disease patients without myocardial infarction (0.93 ± 0.17) than in healthy controls (1.03 ± 014, p < 0.01, p < 0.05 respectively). It did not differ between patients with and without ventricular arrhythmia. The short term fractal-like scaling exponent of the detrended fluctuation analysis was higher in coronary artery disease patients without myocardial infarction (1.34 ± 0.15, p < 0.001), but not in postinfarction patients without arrhythmia (1.06 ± 0.13) compared with healthy controls (1.09 ± 0.13). The short term exponent was markedly reduced in patients with life-threatening arrhythmia (0.85 ± 0.25 ventricular tachycardia patients, 0.68 ± 0.18 ventricular fibrillation patients, p < 0.001 for both). The long term power-law slope of the power-law scaling analysis was lower in the ventricular fibrillation group than in postinfarction controls without arrhythmia risk (-1.63 ± 0.24 vs. -1.33 ± 0.23, p < 0.01) and predicted mortality in a general elderly population with an adjusted relative risk of 1.74 (95% CI 1.42–2.13). The present observations demonstrate that dynamic analysis of heart rate behaviour gives new insight into analysis of heart rate dynamics in various cardiovascular disorders. The breakdown of the normal fractal-like organising principle of heart rate variability is associated with an increased risk of mortality and vulnerability to life-threatening arrhythmias.