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Cardiovascular dynamics in healthy subjects with differing heart rate responses to tilt
Author(s) -
RamirezMarrero Farah A,
Charkoudian Nisha,
Zhong Liu,
Eisenach John H,
Joyner Michael J
Publication year - 2008
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fasebj.22.1_supplement.970.6
Subject(s) - heart rate , baroreflex , medicine , blood pressure , orthostatic vital signs , heart rate variability , autonomic nervous system , brachial artery , cardiology , hemodynamics , sympathetic nervous system , endocrinology
Orthostatic stress such as head‐up tilt (HUT) elicits a wide range of HR and BP responses among healthy individuals. In this study, we evaluated cardiovascular dynamics of subjects with different HR responses to HUT but without autonomic dysfunction. We measured BP (brachial artery) and HR (ECG) during 5 min of 60° HUT in 76 healthy young individuals, while norepinephrine (NE) was assayed during the final 30 s. We then chose 30 individuals based on the extremes of HR responses to HUT: 15 with the highest (ΔHR≥ 20 bpm) and 15 with the lowest response (ΔHR ≤10 bpm). Age and BMI were not different between groups; however, gender distribution was different (high: 5F, 10 M; low: 10F, 5M). Peak HR during HUT was 87.2±10.4 bpm in the high and 69.1±14.1 bpm in the low group (P< 0.05). Baseline HR was not different between groups. High HR responders had lower SBP at baseline (120.9±9.4 vs. 129.4±11.0 mmHg) and during HUT (119.9±9.7 vs. 131.4±13.1 mmHg). High HR responders also had higher plasma NE response to HUT (ΔNE: 156.9±82.1 vs. 89.0±48.0 pg/ml; P< 0.05). Higher HR with lower BP during HUT is consistent with normal baroreflex mechanisms of integration. Although inter‐individual variability appears to be a fundamental part of cardiovascular regulation, the mechanisms of these differences and the gender discrepancy requires further investigation. Supported by K23 RR17520, HL46493, NS32352, KL2 RR024151 ‐01.