The purpose of this investigation was to examine the potential differences in autonomic nervous system adaptations, as assessed by heart rate variability techniques, between a group of stabilized CHF patients randomized to either a training group (aerobic+resistance) or a control group (usual care). In a single-blind, randomized controlled trial of 3-months of supervised exercise training and a further 3-months of home-based exercise, 28 stabilized CHF patients (NYHA 1-111) were randomized to either a training (AERWT) (n=16;11M,5F; age, 64.9±2.3; LVEF, 29.4±1.7%) or usual care (UC) (n=12; 10M,2F; age, 58.0±2.8; LVEF, 24.4±2.0%) group. Upon completion of the supervised exercise program, the AERWT group increased peak oxygen uptake (V02) (13.2±0.5 to 15.5±0.84 ml/kg/min, p<0.05), and single-arm curl scores (16.2±2.8 to 19.2±3.3 kg, p<0.05) significantly compared to the UC group, without any deleterious effect upon clinical status or left-ventricular function (LVEF: 31.3±1.7 to 33.2±1.9%, p=0.99). Physical training reduced expired ventilation and carbon dioxide based on successive workloads during symptom-limited incremental cycle ergometry in the AERWT group; however, this was found to be non-significant, in addition to changes in resting heart rate, anaerobic threshold, maximal exercise duration, maximal power output, and double product following training. Supine, resting power spectral indices remained unchanged from baseline to 6-months in both groups, as did the recovery of power spectral indices during supine rest following a symptom-limited incremental cycle ergometry test. A qualitative comparison of the power spectral changes from supine to standing revealed no significant differences between groups with respect to improvements in the baroreceptor response to orthostatic stress. Time domain parameters, derived from 24-hour ambulatory bolter monitoring, were also obtained at baseline, 3-months, and 6-months. The indices believed to be largely representative of vagal modulation, SDNN-Index, r-MSSD, and pNN50, tended to increase in the AERWT group with increased participation in the training program; however, the results did not obtain statistical significance (p=0.07). In addition, there were no significant changes in mean 24-hour heart rate or NN-interval, SDNN, or SDANN in the AERWT group (p=0.21). The present investigation revealed some evidence to suggest that exercise training in selected populations of CHF patients results in favourable changes in vagal modulation and baroreceptor sensitivity; however, unlike Coats et al. (1992), the present investigation failed to note any significant alterations in HRV frequency domain indices as a result of exercise training despite identical improvements in peak V02. The lack of significant findings in both the frequency and time domain HRV data could indicate that the autonomic dysfunction is so widespread and rampant in CHF that we cannot induce alterations through training as would be demonstrated in normal, healthy controls. In effect, these findings reinforce the hypothesis that in CHF the heart is the 'slave' of the periphery, and that due to the progressive lack of neural control of both the heart and circulation, in addition to an impairment in pump function, that the only effective means of improving physiological variables is through changes at the peripheral level. / Thesis / Master of Science (MS)
| Identifer | oai:union.ndltd.org:mcmaster.ca/oai:macsphere.mcmaster.ca:11375/24485 |
| Date | 09 1900 |
| Creators | Bentley, Todd |
| Contributors | McCartney, Neil, Kinesiology |
| Source Sets | McMaster University |
| Language | English |
| Detected Language | English |
| Type | Thesis |
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