Changes in pericardial pressure during the perinatal period

Area of Science:

• Cardiology
• Perinatal Physiology
• Fetal Development

Background:

• The perinatal period involves significant physiological changes in cardiac function.
• Understanding the influence of surrounding tissues on fetal heart function is critical.

Purpose of the Study:

• To investigate how the tissues surrounding the fetal heart impact its diastolic and systolic function.
• To analyze the pressure-diameter relationship of the fetal left ventricle during the perinatal transition.

Main Methods:

• Utilized partially delivered fetal lambs, instrumented for left ventricular diameter, pericardial pressure, and left ventricular pressure.
• Recorded pressure-diameter relations under conditions of closed chest, after ventilation, and with pericardial retraction.
• Assessed left ventricular diastolic compliance and contractility using end-diastolic pressure and transmural end-diastolic pressure.

Main Results:

• Ventilation led to a significant decrease in pericardial pressure (48%).
• Left ventricular diameters increased at each end-diastolic pressure after ventilation, suggesting improved diastolic compliance.
• Left ventricular systolic function improved due to increased preload, not altered contractility.

Conclusions:

• Pericardial tissues elevate pressure and restrict fetal left ventricular preload.
• Initiation of ventilation decreases pericardial pressure, augmenting preload and systolic function.
• Postnatal reduction in pericardial pressure may enhance cardiac output via the Frank-Starling mechanism.