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Southern Society for Clinical Investigation and Southern American Federation for Clinical Research, Plenary session, SSCI young investigator award finalists, SSCI poster award finalists, SAFMR/SSCI/ young faculty award, SAFMR/SSCI/ trainee research award, 8:00 AM, Friday, February 23, 2018
501 Impaired arterial baroreflex sensitivity in prehypertension
Purpose of study Prehypertension is associated with increased risk of hypertension and cardiovascular disease (CVD), the mechanisms of which remain unclear. Prior studies have shown increased resting sympathetic nerve activity (SNA), and augmented blood pressure (BP) responses during mental stress, suggesting autonomic dysregulation at rest and during stress. We hypothesized that compared to normotensives (<=120/80 mmHg), prehypertensives (120/80-139/89 mmHg) have impaired arterial baroreflex sensitivity (BRS) leading to autonomic dysregulation, and increased neurocardiovascular reactivity to mental stress.
Methods used 22 participants were studied: 12 otherwise healthy prehypertensives (35+-6 years) and 10 matched normotensive controls (32+-6 years). We recorded muscle SNA (MSNA) using microneurography, beat-to-beat BP, and continuous EKG during 5 minutes of supine rest and 3 minutes of stress via mental arithmetic. Arterial baroreflex sensitivity (BRS) was measured via modified oxford technique using IV boluses of nitroprusside and phenylephrine to manipulate arterial BP. The slope of the linear relationship between diastolic BP and MSNA (sympathetic BRS), and systolic BP and R-R interval (cardiovagal BRS) were assessed.
Summary of results As expected, baseline systolic BP (130+-7 vs 117+-8 mmHg) and diastolic BP (87+-7 vs 74+-8 mmHg) were significantly higher in prehypertensives (p<0.001). Resting MSNA (25+-12 vs 18+-10 bursts/min) tended to be higher in prehypertensives (p=0.08). Sympathetic BRS was comparable between the groups, but cardiovagal BRS (13+-10 vs 22+-10 ms/mmHg) was significantly lower in prehypertensives (p=0.03). During mental arithmetic, minute by minute increases in BP and MSNA did not differ between the groups. However, there was a significant correlation between diastolic BP reactivity to mental stress and resting cardiovagal BRS (r=0.703, p=0.016), as well as with resting sympathetic BRS (r=0.795, p=0.010) in the prehypertensive group. In contrast, in normotensive controls, there was no correlation between BP responses to stress and cardiovagal (r=0.126, p=0.766) or sympathetic BRS (r=0.287, p=0.581).
Conclusions These findings suggest that early impairment of arterial BRS may be present in prehypertension and may modulate BP responses to stress, contributing to increased hypertension and CVD risk.
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