Qualitative and quantitative analyses of the morphological-dynamics of early cardiac pump action using video densidometry and optical coherence tomography (OCT)

During the initial phase of its pump action, vertebrate embryonic hearts are seen as valveless tubular pumps. It was traditionally thought that these tubular hearts generate unidirectional blood flow via peristalsis. Recently, however, the pumping mechanism of early embryonic hearts has become a matter of dispute. Uncovering of the pumping mechanism of tubular embryonic hearts requires detailed information about the hemodynamics as well as morphological dynamics of their pump action. We have therefore analyzed the morphological dynamics of cardiac pump action in chick embryos (HH-stages 16-18) in shelless culture using densidometric analyses of high-speed video recordings and by M-mode optical coherence tomography (OCT). The high-speed video camera and the OCT probe were integrated into an environmental chamber, which provided stable physiological conditions during examination of the embryos. We have recorded striking differences in the contraction behavior (e.g. contraction speed, duration of systolic occlusion of heart lumen) of the embryonic heart segments (common atrium, AV-canal, embryonic ventricles, outflow tract). Moreover, we show, for the first time, the pump action of tubular embryonic chick hearts in frontal views, which provide a much better understanding of early cardiac pump action than the traditional right or left lateral views.