Hemodynamics of orthostatic intolerance: Implications for gender differences

Qi Fu, Armin Arbab-Zadeh, Merja A. Perhonen, Rong Zhang, Julie H. Zuckerman, Benjamin D Levine

Research output: Contribution to journalArticle

136 Scopus citations

Abstract

Women have a greater incidence of orthostatic intolerance than men. We hypothesized that this difference is related to hemodynamic effects on regulation of cardiac filling rather than to reduced responsiveness of vascular resistance during orthostatic stress. We constructed Frank-Starling curves from pulmonary capillary wedge pressure (PCWP), stroke volume (SV), and stroke index (SI) during lower body negative pressure (LBNP) and saline infusion in 10 healthy young women and 13 men. Orthostatic tolerance was determined by progressive LBNP to presyncope. LBNP tolerance was significantly lower in women than in men (626.8 ± 55.0 vs. 927.7 ± 53.0 mmHg ± min, P < 0.01). Women had steeper maximal slopes of Starling curves than men whether expressed as SV (12.5 ± 2.0 vs. 7.1 1.5 ml/mmHg, P ± 0.05) or normalized as SI (6.31 ± 0.8 vs. 4.29 ± 0.6 mI·m -2·mmHg-1, P < 0.05). During progressive LBNP, PCWP dropped quickly at low levels, and reached a plateau at high levels of LBNP near presyncope in all subjects. SV was 35% and SI was 29% lower in women at presyncope (both P < 0.05). Coincident with the smaller SV, women had higher heart rates but similar mean arterial pressures compared with men at presyncope. Vascular resistance and plasma norepinephrine concentration were similar between genders. We conclude that lower orthostatic tolerance in women is associated with decreased cardiac filling rather than reduced responsiveness of vascular resistance during orthostatic challenges. Thus cardiac mechanics and Frank-Starling relationship may be important mechanisms underlying the gender difference in orthostatic tolerance.

Original languageEnglish (US)
Pages (from-to)H449-H457
JournalAmerican Journal of Physiology - Heart and Circulatory Physiology
Volume286
Issue number1 55-1
DOIs
StatePublished - Jan 2004

Keywords

  • Lower body negative pressure
  • Orthostatic hypotension
  • Pulmonary capillary wedge pressure
  • Stroke volume
  • Vascular resistance

ASJC Scopus subject areas

  • Physiology
  • Cardiology and Cardiovascular Medicine
  • Physiology (medical)

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