Blood pressure, sympathovagal tone, exercise capacity and metabolic status are linked in Turner syndrome

Abstract

Objectives: We studied cardiac autonomic changes in relation to metabolic factors, body composition and 24-hour ambulatory blood pressure measurements in Turner syndrome patients without known hypertension.

Design: Cross sectional.

Patients: Participants were 48 TS women and 24 healthy female controls aged over 18 years.

Methods: Short-term power spectral analysis was obtained in supine-standing-supine position. Bedside tests included three conventional cardiovascular reflex tests of heart rate response to standing up, heart rate response to deep breathing and blood pressure response to standing up. Mean heart rate during the last 2 minutes of work was used to calculate the maximal aerobic power (VO_2max ).

Results: We found a significantly higher mean reciprocal of the heart rate per second (RR) in TS. Testing for interaction between position and status (TS or control), there were highly significant differences between TS and controls in high-frequency (HF) power, the coefficient of component variation (square root of HF power/mean RR) and low-frequency (LF): HF ratio, with a dampened decline in vagal activity among TS during standing. Bedside test showed TS had a significantly higher diastolic BP in the supine position compared to controls, and the adaptive rise in BP, when changing to upright position was reduced. VO_2max and self-reported level of physical activity were significantly correlated to systolic ambulatory blood pressure both 24-hour and night diastolic ambulatory blood pressure.

Conclusion: Vagal tone and modulation of the sympathovagal balance during alteration in body position are impaired in TS. These changes can be risk factors for cardiovascular disease.

Keywords: autonomic nervous system; biomarkers; blood pressure; heart rate; human; physical conditioning.