Simultaneous acquisition of ECG, BCG, and blood pressure from chick embryos in the egg

The applicability of the audiocartridge system to simultaneous measurements of the ballistic movements from multiple points of the egg was examined in late chick embryos. Despite direct contact between the cartridges and the egg, minute movements of the egg attributable to cardiac contractions of the embryo (ballistocardiogram, BCG) could be simultaneously detected from at least three points. The results showed that the amplitude of BCG waves was dependent on the site of detection, indicating that the BCG was a directional wave. The cartridge system for BCG measurement was incorporated in the electrocardiography and arterial catheterization to acquire simultaneously electrocardiogram (ECG), BCG, and blood pressure from the embryo confined in the egg. Isochronal comparison of these waves indicated that the ballistic movements of the embryo might be caused not only by the ventricular contraction but also by the atrial excitation, i.e., the BCG comprised waves appearing in the ventricular presystolic, contraction, and ejection periods. For wide changes in the heart rate, the approximate isometric ventricular contraction period remained almost constant.