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Time courses of central hemodynamics during rapid changes in posture
Patrik Sundblad1, Jonas Spaak, Lennart Kaijser
1Section of Environmental Physiology, Department of Physiology and Pharmacology, Karolinska Institutet, Sweden;
Journal of Applied Physiology (Bethesda, Md. : 1985)
|March 15, 2014
Summary
Posture changes rapidly alter blood volume, affecting heart filling. This study shows right atrial pressure changes faster than pulmonary capillary wedge pressure, transiently impacting left ventricular stroke volume due to ventricular interdependence.
Area of Science:
- Cardiovascular Physiology
- Human Physiology
- Hemodynamics
Background:
- Posture changes induce significant blood volume redistribution, impacting cardiac filling and stroke volume (SV).
- Understanding the dynamic interplay between right and left ventricular filling is crucial for comprehending cardiovascular responses to postural shifts.
Purpose of the Study:
- To investigate the differential time courses of right and left ventricular filling during rapid postural changes.
- To examine the influence of transient imbalances in ventricular filling pressures on left ventricular stroke volume.
- To explore the role of ventricular interdependence in mediating these hemodynamic adjustments.
Main Methods:
- Beat-by-beat recording of right atrial pressure (RAP), pulmonary capillary wedge pressure (PCWP), left ventricular stroke volume, heart rate, and arterial pressure.
- Subjects underwent rapid tilts between supine and upright positions during rest and dynamic leg exercise.
- Analysis focused on the time course of pressure changes and their correlation with stroke volume variations.
Main Results:
- Right atrial pressure changes exhibited a significantly faster time course than pulmonary capillary wedge pressure during down-tilts, both at rest and during exercise.
- This discrepancy led to a transient decrease in the diastolic pressure difference between the ventricles, impeding left ventricular filling and causing a temporary fall in SV.
- Ventricular interdependence mechanisms were also observed to maintain SV during up-tilts despite falling PCWP.
Conclusions:
- Rapid postural changes create transient pressure imbalances between the right and left ventricles, primarily driven by faster right atrial pressure adjustments.
- Ventricular interdependence plays a significant role in modulating left ventricular stroke volume during postural transitions, affecting filling dynamics.
- The findings highlight the complex, rapid compensatory mechanisms of the cardiovascular system in response to acute hemodynamic challenges.
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