Background & Rationale: Heart rate variability analysis has provided scholars and clinicians with a powerful non-invasive tool for the assessment of cardiac autonomic function in health and disease. However, the interpretation of the information provided by this technique would be greatly facilitated by a more precise definition of 'normality'. The purpose of this investigation was to examine the alterations in cardiac autonomic function across a broad spectrum of ages in healthy males and females. Methods: Heart rate variability data during 20 min supine rest and orthostatic stress (10 min free standing) as well as 24-hour ambulatory Holter ECG recordings were obtained on 123 healthy volunteers (72 female/51 male). Subjects were arbitrarily classified into five categories: pediatric (PED; 5-12 yrs, n=22, 12 female:10 male), adolescent (ADO; 13-17 yrs, n=21, 13 female:8 male), adult (ADU; 18-30 yrs, n=26, 13 female:13 male), middle aged (MDA; 31-60 yrs, n=24, 15 female:9 male) and elderly (ELD; 61+ yrs, n=30, 19 female:11 male) age groups. Power spectral analysis (autoregressive) was determined from supine and standing acute data sets as well as six evenly spaced one hour periods during the Holter recording. Time domain variables (pNN50, R-MSSD, SDNN, SDANN & SDNN index) were derived from the 24-hour data sets. Results: Heart rate in the supine position declined progressively from age 5 years to 30 years but showed no further changes thereafter. In contrast, power spectral measures remained relatively stable in the younger age groups but subsequently exhibited a significant shift toward a higher LF:HF area signifying sympathetic dominance (or vagal withdrawal) in the MDA and ELD subjects. The heart rate and spectral response to orthostasis was most dramatic in the ADO subjects and exhibited a progressive decline in the three older age groups. With respect to the time domain variables, those parameters characterizing short term variability (pNN5O & R-MSSD) were stable in the PED, ADO and ADU subjects but significantly diminished in the two older age groups. In contrast, time domain variables encompassing long term (SDNN & SDANN) and intermediate (SDNN index) oscillations exhibited age-related increases reaching peak values in the ADU subjects and declining progressively thereafter. Power spectral analysis of the six evenly spaced one hour periods of the 24-hour holter recording revealed a diminished circadian rhythm for the majority of the frequency domain indices in the two oldest age groups. Conclusions: The present investigation revealed substantial evidence supporting the existence of an age dependent change in cardiac autonomic function. However, this process appeared to act homogeneously across gender. The similarity of these age dependent changes to those previously observed in pathological conditions commonly associated with autonomic neuropathy serves to emphasize the importance of HRV research aimed at the establishment of reference standards in healthy populations and a more precise definition of 'normal' autonomic neurocardiac function. / Thesis / Master of Science (MSc)

There have been many attempts at answering the question of whether the cardiovascular adaptations resulting from aerobic exercise training of a particular muscle group are transferable when exercise is performed with the untrained muscles? Through the use of power spectral analysis (PSA) of heart rate variability (HRV) and blood pressure variability (BPV) the present study investigated this question in terms of a training induced modification of neurocardiac control. Fifteen healthy subjects (7 arm trainers & 8 leg trainers) aerobically exercise trained for 9 weeks, 3 sessions/week for 45 minutes/session. Training workload intensities were selected individually to obtain a target training heart rate (HR) between 75-80% HR maximum as determined from the initial pre-training V0₂ₘₐₓ. of the respective limbs. The exercise training program had no effect on supine rest HR, HR V or BPV, or standing HR and HRV. Following training, the arm group demonstrated a significant increase in V0₂ₚₑₐₖ (30.0 ± 1.4 to 34.2 ± 1.8 ml/kg/min.; p<0.05) during arm exercise and a significant reduction in leg exercise V0₂ₚₑₐₖ ( 44.8 ± 2.1 to 41.2 ± 1.6 ml/kg/min.; p<0.05). The leg training group demonstrated a slight post-training increase in leg exercise V0₂ₚₑₐₖ (43.5 ± 1.7 to 44.2 ± 2.4 ml/kg/min.; N.S.) and no change in arm exercise V0₂ₚₑₐₖ. Post-training changes in the maximum power produced during the respective limb group exercise tests corresponded to those of V0₂ₚₑₐₖ results. Mean HR values obtained from the arm trained group during the progressive maximal arm exercise test demonstrated significant post-training reductions at 50 percent (Δ-13 ±3.0 b.p.m.;p<0.05) and 75 percent (Δ-16 ± 5.8 b.p.m.;p<0.05) of the pre-training maximum workload. No change in mean HR was observed during progressive leg exercise in the arm trained group. The leg training group demonstrated non-significant HR reductions in both arm (Δ-3 ± 3.1 b.p.m. at 50% & Δ-6 ± 2.8 b.p.m. at 75%; N.S.) and leg (Δ -6 ± 4.5 b.p.m. at 50% & Δ -9 ± 3.5 b.p.m. at 75%; N.S.) progressive exercise tests. Mean HR and indices of HRV and BPV measured over 15 minutes of recovery following maximal exercise of both limb groups, were unaffected as a result of either training modality. The leg trained group demonstrated non-significant reductions in mean HR during both arm and leg steady-state submaximal exercise tests following training. No significant changes in any HRV components were observed in concordance with these non-significant mean HR reductions. Similarly, the arm trained group failed to demonstrate any significant changes in mean HR or HRV indices during either arm or leg submaximal exercise. Results from the present investigation indicated that a positive exercise training effect had occurred in the arm trained group, while the leg training group demonstrated smaller improvements in exercise performance compared to the arm trainers. Findings from the incremental exercise test further demonstrated the post-training improvements in the arm training group, and negligible improvements within the leg trained group. These improvements, or lack of, were all demonstrated in the mean HR measure with no significant changes in HRV patterns. This would suggest that non-neural factors contributed to most of the post-training adaptations. The discrepancies in results between the two training groups may be attributed firstly to the arm muscles greater potential for peripheral adaptations. Secondly, an inadequate training stimulus for the leg training group probably resulted in their poor post-training improvements. Lastly, the low submaximal exercise test intensities may have limited a clear observation in training improvements of either limb training group. The examination of post-maximal arm and leg exercise recovery failed to disclose any new information on the neurocardiac influences during exercise recovery subsequent to upper or lower limb training. The question of whether training induced neurocardiac control modifications may be transferable between the trained and untrained limbs may still be relevant, but requires more vigorous training of either muscle group. / Thesis / Master of Science (MSc)

Recent work has found that a frequency domain and time domain analysis of the heart rate variability signals can provide significant insights into function of the heart in healthy subjects and in patients with heart disease. Patients with congestive heart failure are an important clinical health issue and it is hoped that this work will contribute towards gaining knowledge of this debilitating pathological condition. Our laboratory has recently acquired more than three thousand 24-hour ECG tapes recorded during called Study of Left Ventricular Dysfunction (SOLVD). The SOL VD trial was conducted between 1987-1990 to test the efficacy of a medication called, Enalapril, to treat patients with heart failure. There were an equal number of patients with (group A) and without overt heart failure (group B). The work reported in this thesis describes the development of a hardware and software framework used to analyze the ECG signals recorded on these tapes. Primary objective of this work was to develop and test a system which would assist in analyzing the above tapes so as to examine if there are differences between two groups using the HRV parameters from both frequency and time domain. The research was conducted in three steps: Hardware design, software and algorithm development and finally the validation phase of the design, to test the usefulness of the overall system. The tapes were replayed on a tape recorder and the ECG was digitized at a rate corresponding to 500 samples/second. Labview software was invoked for this task. Secondly a set of algorithms were developed to perform QRS-detection and QT-interval identification. The detection algorithms involved placing critical ECG fiducials onto the ECG waveform through the use of a trained model. The model construction used patient specific pre-annotated data coupled with statistical and genetic algorithm techniques. The beat-to-beat HRV signal was thus generated using the annotation data from the ECG. Frequency domain indices were obtained using power spectral computation algorithms while time domain statistical indices were computed using standard methods. QT-interval algorithms were tested using a set of manually and automatically tagged set of beats from a sample of subjects. For the third part of this research, i.e. validation phase, we set up a test pool of 200 tapes each from patients with overt heart failure and with no heart failure, recorded at the baseline before the subjects entered the study. This phase of the study was conducted with the help of a statistician in a blinded fashion. Our results suggest that there is significant difference between frequency domain and time domain parameters computed from the HRV signals recorded from subjects belonging to group A and group B. The group A patients had a lot of ectopic beats and were challenging to analyze. These results provide a confirmation of our analytical procedures using real clinical data. The QT-analysis of the ECG signals suggest that automatic analysis of this interval is feasible using algorithms developed in this study. / Thesis / Master of Applied Science (MASc)

No description available.

Mental illness such as depression and anxiety as well as cerebrovascular disease are linked to impairment of neurocardiac function mediated by changes to the autonomic nervous system with increased sympathetic and decreased parasympathetic activity. Autonomic neurocardiac function can be evaluated by computing heart rate variability (HRV). Over the past decades, research has demonstrated the diagnostic value of HRV as independent predictor of cardiovascular mortality and as disease marker in progressive autonomic nervous system disorders such as Parkinson’s disease. Here we summarize our studies on HRV and its therapeutic modulation in the context of psychopharmacology as well as psychiatric and neurological disorders to honor the life of Professor Evgeny Vaschillo, the true pioneer of HRV research who sadly passed away on November 21st, 2020.