Faculty Collaboration Database

Effect of acute nitrate ingestion on central hemodynamic load in hypoxia. Nitric Oxide 2016 Jan 30;52:49-55

Date

12/19/2015

Pubmed ID

26679695

DOI

10.1016/j.niox.2015.12.001

Scopus ID

2-s2.0-84951853987 (requires institutional sign-in at Scopus site)   5 Citations

Abstract

UNLABELLED: Acute hypoxia results in local vasodilation that may temporarily unload the left ventricle (LV) through nitric oxide (NO)-mediated mechanisms. Whether increasing NO levels augments LV unloading and improves ventricular-vascular coupling in hypoxia remains unknown.

PURPOSE: Investigate the effect of acute nitrate ingestion on central hemodynamic load in hypoxia.

METHODS: 20 Healthy men (23 ± 3 yrs, BMI 24.6 ± 2.8 kg m(-2)) consumed 70 mL of either a) 0.45 g nitrate (NIT) or b) an inert placebo (PLA) prior to 105 min of normobaric hypoxia (11.6 ± 0.1%) in this randomized, double-blind, crossover-design study. Wave reflection index (RIX; ratio of forward to reflected wave pressure), augmentation index (AIX75) and pulse wave velocity were calculated as measures of wave reflection magnitude and aortic stiffness, respectively, from the aortic blood pressure (BP) waveform. LV wasted pressure effort (WPE) was calculated as an index of LV work due to wave reflections. Subendocardial viability ratio (SEVR) was assessed a measure of myocardial O2 supply/demand ratio.

RESULTS: Aortic diastolic BP decreased in hypoxia compared to normoxia (p < 0.05). Aortic RIX, AIX75, and LV WPE significantly decreased in hypoxia compared to normoxia (p < 0.05). Aortic systolic BP, SEVR, and PWV were unaffected by hypoxia (p > 0.05). Compared to placebo, nitrate ingestion did not significantly alter central hemodynamics in hypoxia (p > 0.05).

CONCLUSIONS: Acute hypoxic exposure unloads the LV (WPE, AIX75, and RIX) without disturbing myocardial O2 supply-demand ratio (SEVR). Reductions in LV work with hypoxia are likely due to reductions in pressure from wave reflections as hypoxia had negligible effects on aortic stiffness. Nitrate ingestion did not affect the central hemodynamic response to acute systemic hypoxia.

Author List

Lefferts WK, Hughes WE, Heffernan KS

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

Administration, Oral
Adult
Arterial Pressure
Cross-Over Studies
Double-Blind Method
Heart Ventricles
Hemodynamics
Humans
Hypoxia
Male
Nitrates
Ventricular Function, Left
Young Adult