Elevated resting blood pressure augments autonomic imbalance in posttraumatic stress disorder

Abstract

Posttraumatic stress disorder (PTSD) is characterized by increased sympathetic nervous system (SNS) activity, blunted parasympathetic nervous system (PNS) activity, and impaired baroreflex sensitivity (BRS), which contribute to accelerated cardiovascular disease. Patients with PTSD also have chronic stress-related elevations in resting blood pressure (BP), often in the prehypertensive range; yet, it is unclear if elevated resting blood pressure (ERBP) augments these autonomic derangements in PTSD. We hypothesized that compared with normotensive PTSD (N-PTSD), those with ERBP (E-PTSD) have further increased SNS, decreased PNS activity, and impaired BRS at rest and exaggerated SNS reactivity, PNS withdrawal, and pressor responses during stress. In 16 E-PTSD and 17 matched N-PTSD, we measured continuous BP, ECG, muscle sympathetic nerve activity (MSNA), and heart rate variability (HRV) markers reflecting cardiac PNS activity [standard deviation of R-R intervals (SDNN), root mean square of differences in successive R-R intervals (RMSSD), and high frequency power (HF)] during 5 min of rest and 3 min of mental arithmetic. Resting MSNA ( P = 0.943), sympathetic BRS ( P = 0.189), and cardiovagal BRS ( P = 0.332) were similar between groups. However, baseline SDNN (56 ± 6 vs. 78 ± 8 ms, P = 0.019), RMSSD (39 ± 6 vs. 63 ± 9 ms, P = 0.018), and HF (378 ± 103 vs. 693 ± 92 ms², P = 0.015) were lower in E-PTSD versus N-PTSD. During mental stress, the systolic blood pressure response ( P = 0.011) was augmented in E-PTSD. Although MSNA reactivity was not different ( P > 0.05), the E-PTSD group had an exaggerated reduction in HRV during mental stress ( P < 0.05). PTSD with ERBP have attenuated resting cardiac PNS activity, coupled with exaggerated BP reactivity and PNS withdrawal during stress.

Keywords: baroreflex; heart rate variability; mental stress; muscle sympathetic nerve activity; parasympathetic nervous system; traumatic stress disorder.

Fig. 1.

Heart rate variability (HRV) measures at rest in 17 participants who are normotensive (N-PTSD) and 16 participants with elevated resting blood pressure (E-PTSD) with posttraumatic stress disorder (PTSD). Baseline standard deviation of normal R-R intervals (SDNN), root mean square of the successive differences (RMSSD), and high-frequency power (HF) were significantly lower in E-PTSD compared with N-PTSD. An independent t-test was used to compare HRV measures between the groups. *P < 0.05.

Fig. 2.

Changes in systolic arterial pressure (SAP), diastolic arterial pressure (DAP), and heart rate (HR) during 3 min of mental stress in 17 participants who are normotensive (N-PTSD) and 16 participants with elevated resting blood pressure (ERBP) (E-PTSD) participants with posttraumatic stress disorder (PTSD). SAP reactivity to mental stress was significantly higher in E-PTSD compared with N-PTSD. DAP reactivity and HR reactivity to mental stress were not different between the groups. A linear mixed-model analysis was used to assess the within-group and between-group differences in SAP, DAP, and HR. *P < 0.05 between groups at that time point; SAP (P = 0.004, 0.003, 0.002), DAP (P = 0.129, 0.135, 0.146), and HR (P = 0.280, 0.245, 0.247) at minutes 1, 2, and 3, respectively.

Fig. 3.

Changes in mean muscle sympathetic nerve activity (MSNA) burst frequency (bursts/min) and burst incidence (bursts/100 heartbeat) during 3 min of mental stress in 16 participants who are normotensive (N-PTSD) and 16 participants with elevated resting blood pressure (ERBP) (E-PTSD) with posttraumatic stress disorder (PTSD). MSNA frequency reactivity and MSNA incidence reactivity to mental stress were not different between the groups. A linear mixed-model analysis was used to assess the within-group and between-group differences in MSNA.

Fig. 4.

Changes in heart rate variability (HRV) measures during 3 min of mental stress in 17 participants who are normotensive (N-PTSD) and 16 participants with elevated resting blood pressure (ERBP) (E-PTSD) participants with posttraumatic stress disorder (PTSD). There was a significantly greater reduction in the standard deviation of normal R-R intervals (SDNN) during mental stress in E-PTSD compared with N-PTSD. There was a trend toward greater reduction in the root mean square of the successive differences (RMSSD) to mental stress in E-PTSD compared with N-PTSD. Change in high frequency power (HF) was not different between the groups. A linear mixed model analysis was used to assess the within-group and between-group differences in HRV measures. *P value < 0.05 between groups at that time point; SDNN (P = 0.303, 0.102, 0.024), RMSSD (P = 0.284, 0.190, 0.121), and HF (P = 0.215, 0.151, 0.124) at minutes 1, 2, and 3, respectively.