Arterial hemodynamics and mechanical properties after circulatory intervention in the chick embryo.

Altered blood pressure and flow impact cardiac function during morphogenesis. How the arterial system supports cardiac morphogenesis after circulatory disruptions is not well characterized. We manipulated arterial flow via left atrial ligation (LAL) or arterial load via right vitelline artery ligation (VAL) in Hamburger-Hamilton (HH) stage 21 chick embryos. Embryos were reincubated for 1 h (HH21), 14 h (HH24) or 30 h (HH27). At each stage we measured simultaneous dorsal aortic blood pressure and flow, and calculated arterial compliance, impedance and hydraulic power. LAL acutely reduced stroke volume (Vs), cardiac output (Q) and hydraulic power. Arterial pressure was preserved by a compensatory increase in characteristic impedance and decrease in compliance. Impedance parameters and compliance normalized by HH24 and all parameters normalized by HH27. VAL acutely increased arterial resistance. Embryos maintained arterial pressure by decreasing Vs and Q. These parameters remained altered through HH27. In summary, despite the intervention, compensatory alterations in Vs and arterial resistance maintained arterial pressure and fraction of oscillatory power within a narrow range. These results suggest that the maintenance of arterial pressure and circulatory energy efficiency, but not arterial flow, is critical to embryogenesis.