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Heart rate perturbation in the stage 17-27 chick embryo: effect on stroke volume and aortic flow
B Cuneo1, S Hughes, D W Benson
1Division of Cardiology, Children's Memorial Hospital, Chicago, Illinois 60611.
Insights
Embryonic heart rate (HR) control is vital for maximizing blood flow during development. Changes in HR significantly impact stroke volume (SV) and flow, with effects varying by developmental stage.
Area of Science:
- Developmental biology
- Cardiovascular physiology
- Embryology
Background:
- Embryonic heart development involves significant structural and functional changes.
- Heart rate (HR), stroke volume (SV), and aortic flow increase linearly from developmental stages 17 to 27.
- The embryonic heart transitions from a simple tube to a four-chambered structure with increased cardiac mass.
Purpose of the Study:
- To investigate the hypothesis that HR perturbation has a developmentally dependent effect on flow and SV.
- To understand the relationship between intrinsic HR and cardiovascular parameters during embryonic development.
- To determine how HR control influences blood flow maximization in the developing embryo.
Main Methods:
- Transiently perturbed HR in 81 chick embryos (stages 17-27) to 40-250% of intrinsic rate using thermal probes on the sinus venosus.
- Calculated aortic blood flow and SV using measurements of aortic blood velocity and cross-sectional area.
- Analyzed the relationship between %HR and SV across different developmental stages.
Main Results:
- Aortic blood flow was maximal at the intrinsic HR for each developmental stage.
- The relationship between %HR and SV was linear, inverse, and dependent on developmental stage.
- Despite significant changes in heart structure, HR control optimizes blood flow.
Conclusions:
- Embryonic heart rate control is a critical mechanism for maximizing blood flow to the developing embryo.
- The preinnervated embryonic heart demonstrates a sophisticated regulation of cardiovascular function.
- Understanding these developmental dynamics is key to comprehending normal and abnormal cardiac development.
Abstract:
Heart rate (HR), stroke volume (SV), and aortic flow increase linearly between developmental stages 17 and 27, as the embryonic chick heart progresses from a bent tube to a rudimentary four-chambered structure and cardiac mass increases fourfold. We hypothesized that HR perturbation, expressed as percent of intrinsic HR (%HR), would have a developmentally dependent effect on flow and SV. HR was transiently perturbed to 40-250% of intrinsic rate with a 1-mm cooled or heated steel probe applied to the sinus venosus of 81 embryos. Aortic blood velocity, cross-sectional area, and HR were used to calculate flow and SV. At each stage, flow was maximal at intrinsic HR. The %HR vs. SV relationship was linear, inverse, and developmentally dependent. In spite of a tremendous change in ventricular shape, mass, and volume, HR control during development of the preinnervated heart maximizes blood flow to the developing embryo.