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Diastolic filling characteristics in the stage 12 to 27 chick embryo ventricle
N Hu1, D M Connuck, B B Keller
1Cook Research Laboratory, Department of Pediatrics, University of Rochester School of Medicine and Dentistry, New York 14642.
Insights
Cardiac output relies on ventricular filling. This study shows passive filling dominates early heart development, shifting to active filling as the chick embryo heart matures into a four-chamber structure.
Area of Science:
- Cardiovascular Physiology
- Developmental Biology
- Embryology
Background:
- Cardiac output is significantly influenced by ventricular diastolic filling characteristics.
- The developing heart transitions from a simple tube to a complex four-chambered structure.
- Understanding these developmental changes in filling dynamics is crucial for comprehending cardiac function.
Purpose of the Study:
- To investigate the changing contributions of passive and active ventricular filling during embryonic heart development.
- To correlate these filling dynamics with structural maturation from a tube to a trabeculated heart.
Main Methods:
- Simultaneous measurement of ventricular pressure and blood velocities (atrioventricular and dorsal aortic) in chick embryos (stages 12-27).
- Utilized a servo-null micropressure system and a 20-MHz pulsed-Doppler velocity meter.
- Partitioned diastole into passive and active filling phases for quantitative analysis.
Main Results:
- End-diastolic pressure increased significantly from stage 12 to stage 27.
- At stage 12, passive filling constituted 92% of diastolic volume, with active filling at 8%.
- By stage 27, passive filling decreased to 24%, while active filling increased to 76%, with the passive to active filling ratio decreasing from 7.89 to 0.35.
Conclusions:
- The relative contribution of passive and active ventricular filling undergoes a significant shift during embryonic development.
- Active filling becomes the predominant mechanism as the embryonic heart matures structurally.
- These findings highlight the dynamic adaptation of cardiac filling mechanisms during vertebrate heart development.
Abstract:
Cardiac output is affected by the diastolic filling characteristics of the ventricle. We hypothesized that the relative contributions of passive and active filling change as the ventricle develops from a smooth-walled tube to a trabeculated four-chamber heart. In stage 12 to 27 white Leghorn chick embryos, we simultaneously measured ventricular pressure with a servo-null micropressure system and dorsal aortic and atrioventricular velocities with a 20-MHz pulsed-Doppler velocity meter. The analog waveforms were sampled at 500 Hz and converted to digital format via an analog/digital board. We partitioned diastole into passive and active components. The passive phase began with the return of the pressure curve to baseline and extended to the onset of the a-wave. The active phase began with the upstroke of the atrial velocity curve and extended to the upstroke of the ventricular pressure curve at end-diastole. Data are presented as mean +/- SEM (n greater than or equal to 6 at each stage) and analyzed by analysis of variance and regression analysis. At similar cycle lengths ranging from 480 to 600 ms (p greater than 0.05), end-diastolic pressure increased from 0.24 +/- 0.02 mm Hg at stage 12 to 0.55 +/- 0.01 mm Hg at stage 27. Passive and active filling volumes were 92 (0.0038 +/- 0.0005 mm3) and 8% (0.0004 +/- 0.0002 mm3), respectively, at stage 12 and changed to 24 (0.23 +/- 0.08 mm3) and 76% (0.62 +/- 0.08 mm3), respectively, at stage 27. The ratio of passive to active filling volume decreased from 7.89 to 0.35.(ABSTRACT TRUNCATED AT 250 WORDS)