Browsing by Subject "Active standing test"

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    Skin sympathetic nerve activity and nocturnal blood pressure non-dipping in patients with postural orthostatic tachycardia syndrome
    (Wolters Kluwer, 2023) Liu, Xiao; Rosenberg, Carine; Reaso, Jewel N.; Lee, Andrew M.; Ricafrente, Joselyn; Ebinger, Joseph E.; Chen, Lan S.; Li, Xiaochun; Merz, C. Noel Bairey; Rader, Florian; Chen, Peng-Sheng; Biostatistics and Health Data Science, Richard M. Fairbanks School of Public Health
    Objective: Postural orthostatic tachycardia syndrome (POTS) is associated with abnormal blood pressure (BP) regulation and increased prevalence of nocturnal nondipping. We hypothesized that nocturnal nondipping of BP is associated with elevated skin sympathetic nerve activity (SKNA) in POTS. Method: We used an ambulatory monitor to record SKNA and electrocardiogram from 79 participants with POTS (36 ± 11 years, 72 women), including 67 with simultaneous 24-h ambulatory BP monitoring. Results: Nocturnal nondipping of BP was present in 19 of 67 (28%) participants. The nondipping group had a higher average SKNA (aSKNA) from midnight of day 1 to 0100 h on day 2 than the dipping group ( P = 0.016, P = 0.030, respectively). The differences (Δ) of aSKNA and mean BP between daytime and night-time were more significant in the dipping group compared with the nondipping group (ΔaSKNA 0.160 ± 0.103 vs. 0.095 ± 0.099 μV, P = 0.021, and Δmean BP 15.0 ± 5.2 vs. 4.9 ± 4.2 mmHg, P < 0.001, respectively). There were positive correlations between ΔaSKNA and standing norepinephrine (NE) (r = 0.421, P = 0.013) and the differences between standing and supine NE levels ( r = 0.411, P = 0.016). There were 53 (79%) patients with SBP less than 90 mmHg and 61 patients (91%) with DBP less than 60 mmHg. These hypotensive episodes were associated with aSKNA of 0.936 ± 0.081 and 0.936 ± 0.080 μV, respectively, which were both significantly lower than the nonhypotensive aSKNA (1.034 ± 0.087 μV, P < 0.001 for both) in the same patient. Conclusion: POTS patients with nocturnal nondipping have elevated nocturnal sympathetic tone and blunted reduction of SKNA between day and night. Hypotensive episodes were associated with reduced aSKNA.
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    Skin sympathetic nerve activity in patients with chronic orthostatic intolerance
    (Elsevier, 2022) Lee, Andrew; Liu, Xiao; Rosenberg, Carine; Borle, Sanjana; Hwang, Daerin; Chen, Lan S.; Li, Xiaochun; Merz, Noel Bairey; Chen, C. Peng-Sheng; Biostatistics and Health Data Science, School of Medicine
    Background: Chronic orthostatic intolerance (OI) is characterized by the development of tachycardia and other symptoms when assuming an upright body position. Objective: The purpose of this study was to test the hypothesis that skin sympathetic nerve activity (SKNA) bursts are specific symptomatic biomarkers in patients with chronic OI. Methods: We used an electrocardiogram monitor with a built-in triaxial accelerometer to simultaneously record SKNA and posture in ambulatory participants. Study 1 compared chronic OI (14 women and 2 men; mean age 35 ± 10 years) with reference control participants (14 women; mean age 31 ± 6 years). Study 2 included 17 participants with chronic OI (15 women and 2 men; mean age 39 ± 12 years) not yet treated with ivabradine, pyridostigmine, or β-blockers. Results: In study 1, there were 124 episodes (8 ± 4 per participant) of postural changes, with 11 episodes (8.9%) associated with symptoms. In comparison, 0 of 104 postural changes (7 ± 3 per participant) in controls were symptomatic (P = .0011). In participants with chronic OI, the SKNA bursts associated with symptoms had higher burst frequencies, longer burst durations, and larger mean burst areas than did bursts during asymptomatic periods. However, SKNA bursts and tachycardia were asymptomatic in controls. We analyzed 110 symptomatic episodes in study 2 (6 ± 5 per participant). Among them, 98 (89.1%) followed at least 1 SKNA burst. In comparison, only 41 (37.3%) had heart rate exceed 100 beats/min 1 minute before symptom onset (P < .0001). Conclusion: SKNA bursts are a highly specific, albeit insensitive, symptomatic biomarker for chronic OI.
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    Using an ambulatory electrocardiogram monitor to record skin sympathetic nerve activity
    (Elsevier, 2022) Liu, Xiao; Rosenberg, Carine; Ricafrente, Joselyn; Leier, Mary E.; Dinh, Harrison; Everett, Thomas H., IV; Chen, Peng-Sheng; Medicine, School of Medicine