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Left ventricular output during postnatal circulatory adaptation in healthy infants born at full term

P Winberg1, M Jansson, L Marions

  • 1Department of Paediatrics, Karolinska Institute, Sachs' Children's Hospital, Stockholm, Sweden.

Archives of Disease in Childhood
|October 1, 1989
PubMed

Insights

In newborn infants, left ventricular output initially remains high but significantly decreases within 24 hours after birth. This reduction is primarily due to a fall in stroke volume, possibly adapting to ductal constriction.

Area of Science:

  • Neonatal Physiology
  • Pediatric Cardiology
  • Cardiovascular Adaptation

Background:

  • Understanding the cardiovascular adjustments in term infants immediately after birth is crucial for identifying potential issues.
  • The transition from fetal to neonatal circulation involves significant changes in hemodynamics.

Purpose of the Study:

  • To non-invasively measure left ventricular output in term infants during the first 72 hours of life.
  • To investigate the changes in left ventricular output, heart rate, and stroke volume post-birth.

Main Methods:

  • Non-invasive measurement of left ventricular output using range-gated Doppler and echocardiography.
  • Continuous monitoring of blood flow velocity in the ascending aorta and cardiac dimensions.
  • Data collected at predefined intervals from <15 minutes to 72 hours after birth in 16 term infants.

Main Results:

  • Left ventricular output remained high (235-243 ml/min/kg) in the first 2 hours post-birth, despite a 10% heart rate decrease.
  • Stroke volume increased by 15% to compensate for the reduced heart rate in the initial hours.
  • A significant fall in mean left ventricular output to 187 (35) ml/min/kg occurred between 2 and 24 hours, mainly due to reduced stroke volume.

Conclusions:

  • Left ventricular output in term infants decreases significantly after the first two hours of life.
  • The observed decline in output is primarily attributed to a reduction in stroke volume.
  • This hemodynamic shift may represent an adaptation to decreased left ventricular workload as the ductus arteriosus constricts.

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