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Cardiac Autonomic Tone (cardiac + autonomic_tone)
Selected AbstractsCardiac autonomic function and baroreflex changes following 4 weeks of resistance versus aerobic training in individuals with pre-hypertensionACTA PHYSIOLOGICA, Issue 3 2009S. R. Collier Abstract Aim:, Cardiac autonomic modulation and baroreflex sensitivity (BRS) are altered in individuals with hypertension. Aerobic exercise (AE) training has been shown to improve both measures, yet little is known about the effects of resistance exercise (RE). The purpose of this study was to examine the heart rate variability (HRV) and BRS following 4 weeks of resistance or aerobic training in a population with borderline high blood pressure (BP). Methods:, Twenty-nine mild hypertensives were recruited and randomly assigned to 4 weeks of RE or AE training. Before and after training, resting measures of HRV frequencies and BRS were obtained. Results:, There was a significant decrease in resting systolic BP for both exercise training modes (RE 136 ± 3.0 pre- to 132 ± 3.4 post-training vs. AE 142 ± 4.0 pre- to 137 ± 3.6 mmHg post-training, P = 0.019). Diastolic BP decreased significantly following both exercise training modes (RE 78 ± 1.31 pre to 74 ± 1.1 post vs. AE 80 ± 1.7 pre to 77 ± 1.6 mmHg post, P = 0.002). A significant time by training mode interaction for low frequency : high frequency (HF) ratio (P = 0.017) with AE decreasing the ratio (275.21 ± 67.28 to 161.26 ± 61.49) and RE increasing this ratio (143.73 ± 65.00 to 227.83 ± 59.41). Natural log-transformed (ln) HRV values showed a time-by-training mode interaction for ln HF (P = 0.05) as ln HF increased (4.7 ± 0.38 to 5.4 ± 0.35 ms2) following AE and decreased (5.98 ± 0.37 to 5.76 ± 0.42 ms2) following RE. BRS increased following aerobic training and decreased after resistance training (6.74 ± 1.2 to 7.94 ± 1.3 and 10.44 ± 1.2 to 9.1 ± 1.2 ms mmHg,1 respectively, P = 0.021). Conclusions:, Aerobic exercise improved the autonomic nervous system (increasing vagal tone, reducing sympathovagal balance while increasing BRS) while RE showed no improvements in cardiac autonomic tone and decreased BRS. [source] The Impact of the Components of Metabolic Syndrome on Heart Rate Variability: Using the NCEP-ATP III and IDF DefinitionsPACING AND CLINICAL ELECTROPHYSIOLOGY, Issue 5 2008KYOUNG-BOK MIN M.D., Ph.D. Background: This study examined the relationship between metabolic syndrome (MetS) and heart rate variability (HRV) in Korean adults. Methods: Data were collected from family health examinations performed from December 2003 through January 2004, and 1,041 subjects consisting of males and females aged 20,87 years were included in this study. Measurement of the 5-minute HRV and several examinations for MetS were completed. The HRV was analyzed in both the time domain with the standard deviation of NN (SDNN) intervals and the frequency domain with the low frequency (LF) and high frequency (HF) components. MetS was defined by the criteria of the National Cholesterol Education Program's Adult Treatment Panel III (NCEP-ATP III) and the International Diabetes Federation (IDF). Results: There were significant differences in the MetS components and HRV indices between the two groups (with vs without MetS). The adjusted means of the HRV indices in the group with MetS were significantly lower than those in the group without MetS (P < 0.05). Furthermore, a significant negative correlation was found between all components of MetS and the HRV indices; additionally, as the number of MetS components increased, the HRV indices gradually decreased. Conclusions: Decreased cardiac autonomic tone was strongly associated with an increased cardiovascular risk, and HRV measurement could become an indispensable part of evaluating one's risk of cardiovascular disease, though we currently do not have sufficient information to identify the cutoff values for the HRV indices. [source] The effects of 12 months of growth hormone replacement therapy on cardiac autonomic tone in adults with growth hormone deficiencyCLINICAL ENDOCRINOLOGY, Issue 6 2005F. Tanriverdi Summary Objectives, Growth hormone deficiency (GHD) in adults is associated with a cluster of cardiovascular risk factors. Some abnormalities of cardiac structure and function have been reported in adult patients with GHD, but there are few data related to cardiac autonomic tone. Non-invasive assessment of cardiac autonomic status can be achieved by heart rate variability (HRV), which can be measured by using time-domain or frequency-domain variables. To our knowledge, short-term (6 months) effects of GH replacement therapy (GHRT) on HRV in a limited number of patients have been evaluated prospectively in only two previous studies. The present study was therefore designed to investigate the effects of GHD and 12 months of GHRT on cardiac autonomic tone in a larger number of adult patients with severe GHD. Patients and methods, HRV measurement, by using time-domain variables, was performed in 22 patients with GHD (eight men, 14 women; mean age 45·4 ± 2·4 years) and 22 healthy controls (nine men, 13 women; mean age 40·8 ± 1·8 years) at baseline. The time-domain variables (sympathetically influenced parameters SDNN and SDANN and parasympathetically influenced parameters RMSSD and PNN50) were derived from 24-h electrocardiogram (ECG) recordings. In the patient group, cardiac autonomic tone was re-evaluated after 6 and 12 months of GHRT. Results, Mean baseline values of SDNN and SDANN were significantly higher (higher values mean lower sympathetic activity) in GHD patients than in healthy controls (P < 0·05), but mean baseline values of RMSSD and PNN50 did not differ significantly in healthy controls and patients. After 6 and 12 months of GHRT, mean SDNN and SDANN were decreased significantly when compared with the baseline values before GHRT (P < 0·05). However, mean RMSSD and PNN50 did not differ significantly from baseline. When SDNN and SDANN measurements were evaluated individually for each patient, after 12 months of GHRT both of the sympathetically influenced parameters decreased in 90% of the patients. Conclusions, These data indicate that sympathetic tone is decreased in adult patients with severe GHD. Additionally, an increment in sympathetic activity and normalization of sympathovagal balance have been demonstrated after 6 and 12 months of GHRT. This result suggests that, at least at the doses used in this study, GHRT improves sympathetic tone, without an obvious arrhythmogenic effect. [source] | ||||||||||