Nocturnal hypertension and impaired sympathovagal tone in Turner syndrome

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Abstract
Increased blood pressure (BP), night: day BP ratio, and heart rate is seen in Turner syndrome (TS), and an increased risk of ischaemic heart disease and type 2 diabetes, as well as aortic dilatation and dissection. We hypothesized that altered heart rate variability is present in TS in comparison with controls, and can be influenced by hormonal replacement therapy (HRT). We examined the impact of HRT on sympathovagal control of heart rate variability. Patients (n = 8, aged 29.5 +/- 5.3 years; no treatment or HRT) and controls (n = 8, aged 28.5 +/- 4.2 years; no treatment) were examined by short-term spectral analysis (supine-standing), bedside neuropathy tests, and 24-h ambulatory BP. N-terminal pro-brain natriuretic peptide (BNP), renin, aldosterone and urinary albumin excretion was determined. The interaction between position and status (TS or control) was examined for data from spectral analysis. Low-frequency (LF) power, coefficient of component variation of LF (both measures of sympathetic and vagal activity), and the LF: high-frequency (HF) power ratio (a measure of sympathovagal balance) were diminished in TS compared with controls, especially during standing. Systolic and diastolic night ambulatory BP (both P = 0.03), and systolic and diastolic night: day ratio (P = 0.01; P = 0.004) was increased in TS. During HRT diastolic day (P = 0.05) and 24-h diastolic ambulatory BP (P = 0.08) decreased. N-terminal pro-BNP was elevated in TS. Decreased sympathovagal balance or tone and nocturnal hypertension is present in TS, and N-terminal pro-BNP is elevated. HRT did not modulate the sympathovagal tone, but decreased BP. These changes may be linked to the increased cardiovascular risk and possibly the increased risk of aortic dilatation in TS.