Investigation of beat-to-beat cardiovascular activity of rats by radio telemetry

This paper was aimed to apply telemetry technology to investigate the cardiovascular activity of rats. A subminiature radio transducer was implanted in the body of rat to measure beat to beat blood pressure, ECG, body temperature, as well as the activity of rat continuously. Mathematic tools were developed to extract beat to beat cardiovascular parameters. Accordingly, spectral analysis of blood pressure variability and heart rate variability was performed to analyze cardiovascular activity in both normotensive and hypertensive rats. New indices were also established to assess the fluctuation of blood pressure of hypertensive rats and thus the effect of anti-hypertensive medication. The ratio of low frequency power to high frequency power in heart rate variability of normotensive rats was much lower than that of hypertensive rats. In hypertensive rats, the blood pressure variability demonstrated significant increase. Furthermore, the circadian rhythm of blood pressure and heart rate variability also altered in hypertensive rats. After the treatment, the blood pressure of hypertensive rats dropped significantly. Meanwhile, the developed indices, such as 24h smoothness index were consistent with the behavior of blood pressure satisfactorily. The results suggest that the developed methods are powerful in studying cardiovascular system as well as evaluating the effects of antihypertensive medication objectively.