Heart rate correction system and methods for the detection of cardiac events

摘要

A device for detecting a cardiac event is disclosed. Detection of an event is based on a test applied to a parameter whose value varies according to heart rate. Both the parameter value and heart rate (RR interval) are filtered with an exponential average filter. From these filtered values, the average change in the parameter and the RR interval are also computed with an exponential average filter. Before computing the average change in the parameter, large changes in the parameter over short times, which may be caused by body position shifts, are attenuated are removed, so that the average change represents an average of small/smooth changes in the parameter's value that are characteristic of acute ischemia, one of the cardiac events that may be detected. The test to detect the cardiac event depends on the heart rate, the difference between the parameter's value and its upper and lower normal values, and its average change over time, adjusted for heart rate changes. The upper and lower normal parameter values as a function of heart rate are determined from long term stored data of the filtered RR values and parameter values. Hysteeresis related data and transitory deviations from normal (e.g. vasospasm related data) are excluded from the computation of normal upper and lower parameter bounds.

主权项

1. A cardiac event detection system for detecting a cardiac event in a patient comprising:
(a) at least two sensors for sensing an analog signal from said patient's heart; (b) a device coupled to said sensors, said device having an analog-to-digital circuit system contained therein for digitizing said electrical signal to produce a digitized waveform of a heart rate of said patient over a plurality of heart beats, said heart rate defining a first parameter; (c) a processor electrically coupled to said analog-to-digital circuit system, said processor configured for:
(i) computing a digitized heart rate time series data from said digitized waveform over said plurality of heart beats;(ii) low pass filtering and averaging of the digitized heart rate time series data, thereby producing a filtered and averaged heart rate time series signal;(iii) performing a test to detect the cardiac event, wherein the test is based on the filtered and averaged heart rate time series signal, said test comparing a second parameter value of at least one beat with a heart rate dependent threshold, wherein the threshold is selected as a function of according to the filtered and averaged heart rate time series signal.