TY - JOUR
T1 - Cardiovascular dynamics in healthy subjects with differing heart rate responses to tilt
AU - Ramirez-Marrero, Farah A.
AU - Charkoudian, Nisha
AU - Hart, Emma C.
AU - Schroeder, Darrell
AU - Zhong, Liu
AU - Eisenach, John H.
AU - Joyner, Michael J.
PY - 2008/11
Y1 - 2008/11
N2 - Orthostatic stress such as head-up tilt (HUT) elicits a wide range of heart rate (HR) and arterial pressure (AP) responses among healthy individuals. In this study, we evaluated cardiovascular dynamics in healthy subjects with different HR responses to HUT, but without autonomic dysfunction. We measured AP (brachial artery) and HR (ECG) during 5 min of 60° HUT in 76 healthy normotensive individuals. We then chose individuals on the basis of the extremes of HR responses to HUT (high = ΔHR ≥ 20 beats/min, and low = ΔHR ≤ 10 beats/min; n = 15 per group). Peak HR during HUT was 87 ± 10 beats/min in the high and 69 ± 14 beats/min in the low group (P < 0.05). High HR responders had lower systolic pressure at baseline (121 ± 9 vs. 129 ± 11 mmHg, P < 0.05) and during HUT (120 ± 10 vs. 131 ± 13 mmHg, P < 0.05), and higher plasma norepinephrine (NE) response to HUT (ΔNE: 156.9 ± 17.8 vs. 89.0 ± 17.2 pg/ml; P < 0.05). ΔNE during HUT was also significantly correlated with ΔHR when all 76 subjects were included in a regression analysis (r = 0.39; P < 0.001). Pulse pressure was lower during HUT in high HR responders compared with low HR responders (45 ± 1 vs. 55 ± 2 mmHg, P < 0.05). High HR responders also had larger fluctuations in systolic and pulse pressure during HUT (coefficient of variation = 10.7 ± 0.7 vs. 5.7 ± 0.3%; 7.9 ± 0.5 vs. 4.1 ± 0.4%, respectively, P < 0.05). Sex distribution was different between groups (high: 5 women, 10 men; low: 10 women, 5 men). Higher HR with lower AP during HUT is consistent with normal baroreflex mechanisms of integration. Although interindividual variability appears to be a fundamental part of cardiovascular regulation, the mechanisms of these differences and the sex discrepancy requires further investigation.
AB - Orthostatic stress such as head-up tilt (HUT) elicits a wide range of heart rate (HR) and arterial pressure (AP) responses among healthy individuals. In this study, we evaluated cardiovascular dynamics in healthy subjects with different HR responses to HUT, but without autonomic dysfunction. We measured AP (brachial artery) and HR (ECG) during 5 min of 60° HUT in 76 healthy normotensive individuals. We then chose individuals on the basis of the extremes of HR responses to HUT (high = ΔHR ≥ 20 beats/min, and low = ΔHR ≤ 10 beats/min; n = 15 per group). Peak HR during HUT was 87 ± 10 beats/min in the high and 69 ± 14 beats/min in the low group (P < 0.05). High HR responders had lower systolic pressure at baseline (121 ± 9 vs. 129 ± 11 mmHg, P < 0.05) and during HUT (120 ± 10 vs. 131 ± 13 mmHg, P < 0.05), and higher plasma norepinephrine (NE) response to HUT (ΔNE: 156.9 ± 17.8 vs. 89.0 ± 17.2 pg/ml; P < 0.05). ΔNE during HUT was also significantly correlated with ΔHR when all 76 subjects were included in a regression analysis (r = 0.39; P < 0.001). Pulse pressure was lower during HUT in high HR responders compared with low HR responders (45 ± 1 vs. 55 ± 2 mmHg, P < 0.05). High HR responders also had larger fluctuations in systolic and pulse pressure during HUT (coefficient of variation = 10.7 ± 0.7 vs. 5.7 ± 0.3%; 7.9 ± 0.5 vs. 4.1 ± 0.4%, respectively, P < 0.05). Sex distribution was different between groups (high: 5 women, 10 men; low: 10 women, 5 men). Higher HR with lower AP during HUT is consistent with normal baroreflex mechanisms of integration. Although interindividual variability appears to be a fundamental part of cardiovascular regulation, the mechanisms of these differences and the sex discrepancy requires further investigation.
KW - Arterial pressure
KW - Baroreflex
KW - Norepinephrine
KW - Orthostasis
KW - Sympathetic nervous system
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U2 - 10.1152/japplphysiol.90796.2008
DO - 10.1152/japplphysiol.90796.2008
M3 - Article
C2 - 18756006
AN - SCOPUS:57349130984
SN - 8750-7587
VL - 105
SP - 1448
EP - 1453
JO - Journal of applied physiology
JF - Journal of applied physiology
IS - 5
ER -