Related Experiment Videos
Heart rate-dependent characteristics of diastolic ventricular filling in the developing chick embryo
C M Phelan1, S F Hughes, D W Benson
1Children's Memorial Hospital, Division of Pediatric Cardiology, Chicago, Illinois, USA.
Insights
Ventricular filling in chick embryos changes with development and heart rate. Early filling decreases and late filling increases as heart rate rises, showing both developmental and cycle length dependence.
Area of Science:
- Cardiovascular Physiology
- Developmental Biology
- Embryology
Background:
- Ventricular filling comprises early (passive) and late (active) components.
- These components change during chick embryo cardiac development, with early filling decreasing and late filling increasing.
- Previous studies suggest these changes are linked to developmental alterations.
Purpose of the Study:
- To investigate the hypothesis that changes in ventricular filling during early cardiac development are driven by alterations in cardiac cycle length.
- To examine the independent and combined effects of embryonic development and cardiac cycle length on atrioventricular inflow patterns.
Main Methods:
- Studied 28 chick embryos at Hamilton-Hamburger stages 17, 24, and 26.
- Manipulated cardiac cycle length in ovo using controlled temperature changes.
- Measured atrioventricular inflow and dorsal aortic velocities using pulsed Doppler flowmetry.
Main Results:
- Both early and late ventricular filling components were significantly dependent on cardiac cycle length and developmental stage (p < 0.05).
- Older embryos exhibited larger early and late filling volumes.
- As cycle length decreased (heart rate increased), early filling volume decreased more significantly than late filling volume.
Conclusions:
- Ventricular filling dynamics in developing chick embryos are influenced by both intrinsic developmental programming and the prevailing cardiac cycle length.
- The relative contributions of early and late filling are adaptable to changes in heart rate, with implications for understanding cardiac adaptation during development.
Abstract:
The contributions of the early (passive) and late (active) components of ventricular filling have been reported to decrease and increase, respectively, during chick embryo cardiac development. We hypothesized that the observed changes in ventricular filling during early cardiac development results from a decrease in cycle length. We studied the effect of development and cycle length on atrioventricular inflow in 28 chick embryos, Hamilton-Hamburger stages 17, 24, and 26. Cycle length was perturbed (range 240-1040 ms) in ovo by transiently heating or cooling the sinus venosus. Atrioventricular inflow and dorsal aortic velocities were obtained by 20-MHz pulsed Doppler flow-meter and digitally recorded at 500 samples per second. Stroke volume was calculated from dorsal aortic velocity and cross-sectional area. The atrioventricular inflow wave form was integrated and partitioned by area and percentage of total into early (passive) and late (active) components using three methods. Regardless of method, the proportion of filling volume due to the early and late components was cycle length and stage dependent (p < 0.05). The early and late filling volumes were large in the older embryos, and during cycle length decrease (heart rate increase) the early filling volume decrease was greater than the late filling volume decrease. When compared with the percentage of intrinsic heart rate, the percentage of stroke volume due to early filling decreased as heart rate increased and was greater in younger embryos at all heart rates. That due to late filling increased as the percentage of intrinsic heart rate increased. Ventricular filling characteristics are both developmentally determined and cycle length dependent.