Functional aspects in embryonic chick treated by —electrical shock-electrocardiographic and doppler findings—

Abstract

We have evaluated hemodynamic parameters of myocardial function and flow changes by electrocardiography and doppler in the developing chick embryo. Early on day 4 (Hamilton-Hamburger 24–27) of incubation, the eggs were prepared for electrical shock and functional analysis. At this stage, the great arteries are not completely divided. The divice used to apply the electrical shock to the heart was constructed using a 9 volt battery, a pushbutton switch, and a 100 ohm, ten-turn potentiometer with calibrated dial. Two different methods were chosen to apply the electrical shock at the conotruncal area of the heart. One method utilizes horizontal application and the other, vertical application of electrical shock to the conotruncus. The range of voltage applied to the conotruncal area of the heart was 2–4 volts for 1–2 seconds. For recording the low voltage electrocardiography of young embryos (10–100 μV) it is necessary to isolate the eggs from interfering electrical resources in Faraday's cage. In parallel studies, we also introduced a 10 MHz continuous wave Doppler probe to other embryos and assessed the flow pattern at the level of the conotruncus. Soon after electrical shock in embryonic chick heart, a heart rate of 210 beats per minute decreases to 120–100. The PR interval was lengthened to about 0.16-0.18 sec with decreasing heart rate. These slow cardiac rhythm follow a sudden onset of ventricular premature beats for a few seconds and become normalized. Usually, QRS voltage decreases after electrical shock to less than 10 percent. These electrocardiographic changes last for 30 minutes and return to normal. The most remarkable period is between 3 and 15 minutes after electrical shock. Doppler findings demonstrate that peak velocity initially increase 3 minutes after electrical stimulation. In control group, mean velocity is 3802 Hz. However, soon after electrical shock, peak velocity starts to increase with 4674 Hz. Thirty minutes after electrical shock, mean peak velocity starts to decrease. In normal control group, % window is 23 but soon after electrical shock, this turbulance rate is 30. However, 30 minutes after electrical shock, % window starts to decrease with a rate of 15. The present study revealed that the cardiovascular anomalies in chick embryos induced by electrical shock could be explained by the doppler findings and electrocardiographic changes. © 1987, The Showa University Society. All rights reserved.