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Left ventricular contractile state in preterm infants: relation between wall stress and velocity of circumferential
H Igarashi1, H Shiraishi, H Endoh
1Department of Pediatrics, Jichi Medical School, Tochigi, Japan.
Insights
Preterm infants exhibit a robust left ventricular contractile state, indicated by high velocity of circumferential fiber shortening (VCF) and low wall stress. However, their hearts may struggle with increased afterload.
Area of Science:
- Neonatal cardiology
- Pediatric cardiovascular physiology
Background:
- Fetal and newborn lambs demonstrate limited adaptation to increased afterload.
- Left ventricular pump function in human preterm infants under increased afterload remains understudied.
Purpose of the Study:
- To ascertain the normal left ventricular resting contractile state in preterm infants.
- To investigate the relationship between end-systolic wall stress and VCF in preterm neonates.
Main Methods:
- Studied 11 preterm infants (28-36 weeks gestational age) at two postnatal age intervals.
- Assessed left ventricular function by measuring end-systolic wall stress and rate-corrected velocity of circumferential fiber shortening (VCF).
Main Results:
- A significant inverse linear correlation was observed between wall stress and VCF in both examinations.
- Preterm infants showed high VCF values and low-wall stress values.
- Regression line slopes were steeper than in older age groups, suggesting a higher contractile state.
Conclusions:
- Preterm infants possess a high resting left ventricular contractile state.
- Left ventricular performance in preterm infants may be compromised when faced with elevated afterload.
Abstract:
Fetal and newborn lambs' hearts have limited capacity to adapt to increased afterload. In human preterm infants, however, this limited left ventricular pump function has not been investigated. To determine the normal left ventricular resting contractile state in preterm infants, we studied the relation of end-systolic wall stress to the rate-corrected velocity of circumferential fiber shortening (VCF) in 11 preterm infants of gestational ages 28 to 36 weeks. We performed the first (7 to 14 days of postnatal age) and the second (29 to 39 days of postnatal age) examinations. There was a significant inverse linear correlation between wall stress and VCF in the first and the second examinations (r = -0.616 and r = -0.715, respectively). Both regression lines had slopes that were steeper than those previously reported for older age groups. The preterm infants had high VCF values (mean 1.05 and 1.09 cir/sec, respectively) and low-wall stress values (mean 36.0 and 36.9 gm/cm2, respectively) in the first and the second examinations. We therefore suggest that the preterm infants have a high resting contractile state, but left ventricular performance may deteriorate in the face of increased afterload.