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【medical-news】Quantifying Arrhythmias using the HRV Modul
King's College postgraduate student Erika Kennington is using a PowerLab system with Chart 5 software to investigate the functional role of a small membrane protein, phospholemman, in isolated mouse hearts. Under the direction of Professor Mike Shattock, Erika is examining the role of this protein by examining the functional and electrophysiological characteristics of hearts isolated from mice in which the gene for this protein has been deleted.
"While recording contractile function from these hearts using intraventricular balloons, we realized that some of our interventions were causing an increase in the number of arrhythmias. Arrhythmias are by definition unpredictable and hence notoriously hard to quantify. We decided to see if we could use the statistical power of the HRV Module for Chart to provide us with a quantitative index of arrhythmias," said Erika.
Applying the Statistical Analyses
The HRV Module is primarily designed to measure natural variations in the beat-to-beat intervals of the heart in intact subjects. The variability is an indirect measure of health and a decreased HRV is strongly correlated with cardiac disease. The module measures intervals of each heart beat and calculates statistics accordingly.
One of the statistics is the standard deviation of changes in consecutive beat-to-beat intervals (SD of delta NN)/(mean NN). If the SD of delta NN is divided by mean NN, this provides an appropriate analysis of arrhythmias in isolated heats because it is independent of heart rate.
A New Method for Arrhythmia Screening
"The HRV analysis is usually applied to ECG traces; however, we applied it to left-ventricular pressure recordings. This almost instantaneous analysis can be applied to an entire experiment containing up to 10,000 heart beats." said Erika.
Top Panel: left-ventricular pressure trace from a heart exposed to isoprenaline (a synthetic form of noradrenaline) on a slow time-base. The aberrant 'spikes' show where the heart has had an arrhythmia.
Middle Panel: heart rate
Lower Panel: the 'arrhythmia score' generated by running the HRV Module and selectively plotting the SD of delta NN for different time periods.
"Using ADInstruments' HRV Module, we have been able to establish a novel quantitative method that allows rapid and retrospective assessment of arrhythmia incidence from a left-ventricular pressure trace. This analysis is simple, fast and much less subjective than previous methods of arrhythmia quantification. Whilst this analysis does not provide information about the type or origin of these arrhythmias (which requires ECG recordings) it does provide a simple and fast screening method for global arrhythmia incidence,” said Erika.
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作者:admin@医学,生命科学 2011-08-14 05:11
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