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Left ventricular systolic function, arterial elastance, and ventricular-vascular coupling: a developmental study in
S C Cassidy1, D P Chan, H D Allen
1Department of Pediatrics, The Ohio State University and Children's Hospital, Columbus 43205, USA.
Insights
Postnatal development reveals limited early left ventricular contractile reserve in piglets, with optimized ventricular-vascular coupling at one week. By six weeks, contractile reserve improves, but ventricular-vascular coupling is less optimized.
Area of Science:
- Cardiovascular Physiology
- Neonatal Physiology
- Pediatric Cardiology
Background:
- Perinatal circulatory changes enhance cardiac output and left ventricular contractile reserve.
- Understanding postnatal adaptations in cardiac function is crucial for pediatric cardiovascular health.
- Ventricular-vascular coupling plays a key role in efficient circulatory function.
Purpose of the Study:
- To investigate postnatal developmental changes in left ventricular systolic function.
- To analyze alterations in ventricular-vascular coupling during early postnatal life.
- To assess the impact of beta-adrenergic stimulation on cardiac performance across different ages.
Main Methods:
- Piglets underwent cardiac catheterization at 1, 2, 4, and 6 weeks of age.
- Measurements included end-systolic elastance (Ees), preload-recruitable stroke work, dP/dt(max), cardiac index, heart rate, and arterial elastance (Ea).
- Hemodynamic parameters were assessed at rest, during isoproterenol infusion, and after propranolol administration.
Main Results:
- Resting heart rate and cardiac index decreased from 1 to 6 weeks.
- At 1 week, Ees was maximal and unresponsive to isoproterenol; other contractility indices showed reserve.
- Ventricular-vascular coupling (Ea/Ees) was optimized at 1 week, improving with beta-adrenergic stimulation, while 6-week-olds showed increased contractility with stimulation.
Conclusions:
- Left ventricular contractile reserve, particularly Ees, is limited at 1 week in piglets.
- Ventricular-vascular coupling is optimized in early postnatal life, adapting efficiently to beta-adrenergic stimulation.
- Postnatal development leads to enhanced contractile reserve but a less optimized ventricular-vascular coupling by 6 weeks.
Abstract:
Circulatory changes occur during perinatal life that increase cardiac output and left ventricular contractile reserve. To examine postnatal changes in left ventricular systolic function and ventricular-vascular coupling, piglets underwent cardiac catheterization at 1, 2, 4, and 6 wk of age. We measured end-systolic elastance (Ees), preload-recruitable stroke work, dP/dt(max), the dP/dt(max) end-diastolic volume relation, cardiac index, heart rate, arterial elastance (Ea), and the ratio Ea/Ees, at rest, during isoproterenol infusions (0.05-1.0 microg/kg/min), and after propranolol (1 mg/kg i.v.). Resting heart rate and cardiac index decreased between 1 and 6 wk. In 1 wk olds, resting Ees was at maximum and was unchanged during isoproterenol infusion; isoproterenol increased other contractility indices. Two, 4, and 6 wk olds demonstrated reserve using all contractility indices. Contractile efficiency was not different between ages. In 1 wk olds, Ea decreased during isoproterenol infusion; isoproterenol did not change Ea at 6 wk. Ea/Ees was higher at rest at 6 wk than at 1 wk, and fell significantly on isoproterenol; isoproterenol did not change Ea/Ees at 1 wk. With beta-adrenergic stimulation, 1 wk olds increased cardiac index by increasing heart rate and decreasing afterload, 6 wk olds increased cardiac index by increasing heart rate and contractility; no change in contractile efficiency was found in either group. In summary, contractile reserve is limited at 1 wk when measured by Ees, but other indices demonstrated reserve. Indexed Ea falls in response to beta-adrenergic stimulation in all ages but 6 wk. Ventricular-vascular coupling is optimized at 1 wk even under baseline conditions.