Faculty Collaboration Database

Aortic Wave Reflection During Orthostatic Challenges: Influence of Body Position and Venous Pooling. Am J Hypertens 2017 Feb;30(2):166-172

Date

01/13/2017

Pubmed ID

28077421

DOI

10.1093/ajh/hpw138

Scopus ID

2-s2.0-85016029331 (requires institutional sign-in at Scopus site)   6 Citations

Abstract

BACKGROUND: Aortic wave reflection (augmentation index; AIx) decreases during orthostatic challenges despite increased peripheral resistance, which is thought to be due to venous pooling. The purpose of this study was to examine if the decrease in AIx during an orthostatic challenge is due to venous pooling alone or body position manipulation.

METHODS: Twenty-three young, healthy adults (11F/12M) participated in 3 separate orthostatic challenges (5 minutes each); 60° head-up tilt (HUT), 60° HUT with bilateral rhythmic blood pressure (BP) cuff inflation on calves (75 mm Hg) to minimize venous pooling, and lower body negative pressure (LBNP; -30 mm Hg) for venous pooling independent of body position. High-fidelity radial artery pressure waveforms using applanation tonometry were recorded at minutes 2:30 and 5:00 during each condition. Aortic BP and wave reflection were analyzed from a synthesized aortic BP waveform.

RESULTS: Compared to resting (baseline) measurements, AIx did not significantly decrease at minutes 2:30 or 5:00 of HUT conditions (HUT 0 ± 2% vs. -3 ± 3%, 0 ± 2%; HUT w/cuffs 0 ± 2% vs. -4 ± 2%, 0 ± 2%). Conversely, LBNP substantially reduced AIx at minutes 2:30 and 5:00 (1 ± 2% vs. -15 ± 2% and -12 ± 2%; P < 0.01). When standardized to heart rate (AIx@75), AIx@75 increased relative to baseline during HUT conditions (P < 0.05).

CONCLUSIONS: In contrast to previous studies, AIx did not decrease during passive HUT, yet decreased substantially during LBNP. Despite being well matched for peripheral hemodynamics, it appears that LBNP elicits a greater effect on central hemodynamics, relative to passive HUT. Collectively, changes in body position alone do not explain differences in AIx during orthostatic conditions.

Author List

Hughes WE, Casey DP

Author

William E. Hughes Postdoctoral Fellow in the Medicine department at Medical College of Wisconsin

MESH terms used to index this publication - Major topics in bold

Adult
Aorta
Arterial Pressure
Electrocardiography
Exercise
Female
Follow-Up Studies
Healthy Volunteers
Heart Rate
Humans
Hydroxyethylrutoside
Hypertension
Lower Body Negative Pressure
Male
Posture
Pulse Wave Analysis
Rest
Vascular Stiffness
Young Adult