Research On Estimating Of The Postmortem Interval By The Magnitude Changes Of Myocardial Impedance In Swine Cadavers

Objective Using bioelectricity impedance measurement instrument measuring the hearts muscle tissue impedance of pigs dying at different time, discuss the change of correlation with PMI to find a simple and reliable method, so as to obtain a simple but reliable method in concluding the PMI for forensic clinical practice.Methods Obtain 12 pig hearts from pigs, randomly divided the pigs into 4 groups of three, punctured the hearts to release blood to cause the pigs to death, then immediately extract the heart tissues. Introduce electrode into the left ventricular wall of the pig cardiac muscle and first group fixed by 0.3 KHZ, second group use 2khz and take measurement, the third group use frequency with 10khz, forth group use frequency with 50khz to take measurement, use the bioelectricity frequency.Results From the four sets of data, we can know the pig myocardial impedance amplitude, the rise and decline, about 4 hours prior to death, myocardial tissue impedance amplitude, impedance rise rapidly after the maximum present slow decline, eventually tend to flat. Each point of impedance measurement, the mean and statistical analysis, to a certain extent has ineffectual instrument measurement error caused by the system. From the four groups of data, we can understand the bioelectricity impedance amplitude frequency by the incentive effects of rising, frequency, namely resistance drops. Four groups of testing the slope and decline resistance, the time of death correlation coefficient in the two groups was above 0.89, frequency decrease with high correlation between PMI can be used as a time of death index. Pig tissue in early death stage, the muscle, nucleus do not show obvious changes,4 hours later myocardial tissue will show visible muscle swelling of the beam, horizontal grain is not clear,12 hours later cardiac troponin beam particles, horizontal grain appearance. Conclusionâ‘ The measured data from myocardial tissue taken after death correlate with the death period shows the impedance values. Understanding from the rising and the drop down part of impedance, we can have the change plotted on the linear relationship between PMI.â‘¡The frequency of the measured data, and the impedance from its decline slope (i.e. impedance rate), and the correlation coefficient is greater than PMI 0.89, impedance frequency and the slope of the decline in relation to changes in different excitation frequency measurement, the decline of the slope and the correlation is higher, PMI dropped out of the starting point, the slope, the maximum impedance, the relationship between the decline, so it can be used as a linear relationship of early PMI basis. Therefore may be used as death in biological tissue to speculate bioelectricity impedance time of death.â‘¢Frequency is the important factors to influence impedance variations bioelectricity, experiment, with incentives frequency, impedance downward trend.â‘£From the microscopic observation myocardial tissue, discusses the bioelectric morphological changes of the time of death and pathological morphology, from this angle to explain the changes.â‘£From the current deduced technology with PMI biological resistance is simple and accurate. It has the advantage of reliability. Feasibility in the application needs further studies.