Electrical and Mechanical Properties of Chick Embryo Heart Chambers

Electrical and mechanical events of the atrium, ventricle and conus of the 72-hour chick embryo heart were recorded by a specially designed instrument. The electrical-mechanical delay and the time of muscular contraction differed among the chambers, the atrium being the most rapid and the conus, the slowest. Muscular relaxation times of the atrium and ventricle were approximately one-half that of the conus. Mechanical performance, gaged by the approximations of work and power, was greatest for the ventricle, but based on the muscle mass (protein), values for the ventricle and conus were similar. Electrical activation of the ventricle followed a consistent pathway, suggesting the existence of a preferential conduction system prior to the development of the His bundle.