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    Differences in autonomic activity in individuals with optimal, normal, and high-normal blood pressure levels
    (2010) Doğru M.T.; Şimşek V.; Şahin Ö.; Özer N.
    Objectives: We investigated differences in autonomic activity in normotensive individuals having optimal, normal and high-normal blood pressure (BP) levels according to the guidelines of the European Society of Hypertension and European Society of Cardiology (ESH/ESC). Study design: The study included 294 normotensive subjects (135 males, 159 females; age range 16 to 75 years) with similar clinical, morphometric, biochemical, electrocardiographic, and echocardiographic features. The subjects were classified into the following BP groups: group 1 (n=113) with optimal BP (<120/80 mmHg); group 2 (n=104) with normal BP (120-129/80-84 mmHg), and group 3 (n=77) with high-normal BP (130-139/85-89 mmHg). All the subjects underwent 24-hour Holter monitoring to obtain heart rate variability (HRV) parameters of 24-hour, daytime, and nighttime periods. Normalized low (LF n) and high (HF n) frequency powers, and logarithmic (Log) values of HRV parameters were also calculated. Results: On 24-hour Holter monitoring, heart rates were similar in three groups. Compared to group 1 and 2, group 3 exhibited significantly higher LF/HF (p<0.001) and LF n (p=0.001) values, and significantly lower HF n (p=0.001), pNN50 (p=0.001), and rMSSD (p=0.005) values. There were no significant differences between the groups with respect to daytime HRV parameters; however, nighttime LF/HF, LF n, and HF n values were significantly different between the groups. Log LF/HF values obtained during the 24-hour and nighttime periods showed significant differences between group 1 and group 3 (for 24 hours, p<0.001; for night, p=0.001) and between group 2 and group 3 (for 24 hours, p<0.001; for night, p=0.009), but group 1 and group 2 did not differ significantly in this respect (p>0.05). Conclusion: These findings suggest that subjects with high-normal BP have increased sympathetic activity and decreased parasympathetic activity, possibly making them more liable to hypertension.
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    The relationship between orthostatic differences in arterial blood pressure and autonomic tone: Gender variability
    (2007) Doğru T.; Günaydin S.; Şimşek V.; Tulmaç M.; Tireli E.
    Objectives: The differences in orthostatic blood pressure result from dynamic changes in the sympathovagal balance. We studied sex-related variations in autonomic tone regulation. Study design: The study included 237 individuals (114 males, 123 females) who were asymptomatic and had no abnormal laboratory or physical findings. The mean age was 47 years (range 20 to 79 years) for men, and 39 years (range 20 to 71 years) for women. All the participants were subjected to a careful history taking, physical examination, routine biochemical examinations, electrocardiographic recording, 24-hour Holter monitoring, and orthostatic tests. Results: In heart rate variability analysis, parasympathetic tone parameters, in particular the high frequency (HF) component was significantly high in females, whereas sympathetic tone parameters, in particular the low frequency (LF)/HF ratio was significantly high in males (p<0.001). The normalized LF component in males showed positive correlations with systolic (r=0.308, p=0.001) and diastolic (r=0.301, p=0.002) blood pressures during the rapid stand test; this correlation was not seen in females. Blood pressures obtained in the second minute of the rapid supine test following the stand test were in positive correlation with the LF/HF ratio in both sexes. In males, variations in systolic and diastolic blood pressures during rest, stand, and supine positions were primarily influenced by the LF component and HF component, respectively. In females, variations in systolic blood pressure during the three positions were not correlated with autonomic tone components, but variations in diastolic blood pressure were primarily affected by the LF/HF ratio. Conclusion: Autonomic system works through varying priorities in both sexes and this causes sex-related differences in orthostatic tolerance.
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    The relationship between serum sex steroid levels and heart rate variability parameters in males and the effect of age
    (2010) Doğru M.T.; Başar M.M.; Yuvanç E.; Şimşek V.; Şahin Ö.
    Objectives: We evaluated the relationships between sex steroid levels and heart rate variability (HRV) parameters. Study design: The study included 114 male subjects (mean age 46.6±11.3 years) presenting to our department for cardiologic evaluation. Hormonal analysis included serum levels of luteinizing hormone, prolactin, total testosterone (TT), free testosterone, estradiol (E2), and dehydroepiandrosterone sulfate (DHEA-S). Parameters of HRV were derived from 24-hour Holter monitoring. The associations between serum sex steroid levels and HRV parameters were investigated in three age groups (20-39 years; 40-59 years; >60 years). Results: All the participants had normal biochemical results. The three age groups were similar in terms of anthropometric measurements. Among sex steroids analyzed, only serum DHEA-S level was significantly different among the groups (p=0.026), showing a decreasing trend with age. In the evaluation of HRV, all parasympathetic activities decreased (for HFn, pNN50, and rMSDD: p=0.001, p=0.000, and p=0.000, respectively), while only LF/HF among sympathetic activities increased (p=0.000) with age. Partial correlation analysis with control of age and waist circumference showed that TT and DHEA-S were positively correlated with HF n (parasympathetic parameter), and were in negative correlation with LF/HF24 hours and global sympathetic index (GSI) (sympathetic parameters). Serum E2 level was negatively correlated with the parasympathetic parameter of rMSSD, and positively correlated with LF/HF24 hours and GSI. Among serum sex steroids, DHEA-S was the most correlated parameter with autonomic functions. Conclusion: Our results showed positive correlations between androgens and parasympathetic activity and between estradiol and sympathetic activity in men, independent from anthropometric factors.