Screening Procedure for Identifying Risk of Arrhythmia

• US 20150223760A1
• Filed: 09/12/2013
• Published: 08/13/2015
• Est. Priority Date: 09/12/2012
• Status: Abandoned Application

• Current Assignee: To Health Limited
• Original Assignee: To Health Limited
• Inventors: Greifer, Joshua David
• Application Number:
  US14/427,938
• Publication Number:
  US 20150223760A1
• Time in Patent Office: Days
• US Class Current: 1/1
• CPC Class Codes: A61B 2562/0238 Optical sensor arrangements for performing transmission measurements on body tissue
• CPC Class Codes: A61B 5/02405 Determining heart rate variability
• CPC Class Codes: A61B 5/02416 using photoplethysmograph signals, e.g. generated by infrared radiation A61B5/14552 takes precedence
• CPC Class Codes: A61B 5/0261 using optical means, e.g. infrared light
• CPC Class Codes: A61B 5/0295 using plethysmography, i.e. measuring the variations in the volume of a body part as modified by the circulation of blood therethrough, e.g. impedance plethysmography
• CPC Class Codes: A61B 5/7203 for noise prevention, reduction or removal
• CPC Class Codes: A61B 5/7275 Determining trends in physiological measurement data; Predicting development of a medical condition based on physiological measurements, e.g. determining a risk factor
• CPC Class Codes: A61B 5/7278 Artificial waveform generation or derivation, e.g. synthesising signals from measured signals A61B5/327 takes precedence

Abstract

A screening procedure and apparatus enables those at risk of cardiac arrhythmia to be identified. The procedure utilises a blood flow detector (12) in conjunction with a signal analysis unit (18) to monitor a sequence of multiple heart pulses, hence to deduce the values of a sequence of multiple heart pulse intervals, and to analyse the sequence of multiple heart pulse intervals to deduce a risk parameter whose value enables those at risk of cardiac arrhythmia to be identified. The risk parameter may be calculated from a first measure, or alternatively by combining the first measure with a second measure, where the first measure is calculated from the ratio between the variability between successive intervals in the sequence, and the mean interval value, while the second measure relates to the proportion of cases in which a long interval is followed by another long interval in the sequence.

Claims

1. A screening procedure to identify those at risk of cardiac arrhythmia, the procedure utilising a blood flow detector in conjunction with a signal analysis unit, the procedure comprising using the blood flow detector to monitor a sequence of multiple heart pulses, hence deducing the values of a sequence of multiple heart pulse intervals, and analysing the sequence of multiple heart pulse intervals by means of the signal analysis unit to deduce a risk parameter whose value enables those at risk of cardiac arrhythmia to be identified.

2. A procedure as claimed in claim 1 wherein the blood flow detector is a photoplethysmograph, or a pulse oximeter which incorporates a photoplethysmograph.

3. A procedure as claimed in claim 1 wherein the signal analysis unit calculates a first measure from the ratio between the variability between successive intervals in the sequence, and the mean interval value.

4. A procedure as claimed in claim 3 wherein the variability between successive intervals in the sequence is calculated from the standard deviation of the differences between successive intervals.

5. A procedure as claimed in claim 3 wherein, before performing the calculations, any interval values that deviate from the mean by more than three times the standard deviation are discarded, and wherein any interval values that are within 5% of twice the modal interval are also discarded.

6. A procedure as claimed in claim 3 wherein the signal analysis unit calculates a second measure related to the proportion of cases in which a long interval is followed by another long interval in the sequence.

7. A procedure as claimed in claim 6 wherein an interval is taken as a long interval if it is equal to or longer than the modal interval.

8. A procedure as claimed in claim 1 wherein the signal analysis unit calculates the first measure as claimed in claim 3 and calculates the second measure as claimed in claim 6, and wherein the risk parameter combines the first measure with the second measure.

9. A procedure as claimed in claim 8 wherein the risk parameter is the product of the first measure and the second measure.

10. A procedure as claimed in claim 6 wherein the signal analysis unit calculates at least one of:

(a) a third measure related to the variability of the intervals, in comparison to the mean interval value;

(b) a fourth measure, which combines the variability between successive intervals, and the third measure;

(c) a fifth measure providing an indication of the extent to which successive intervals differ from the mean in terms of both the variability between successive intervals and the variability of the intervals.

11. A procedure as claimed in claim 10 wherein the third measure is calculated from the standard deviation of the sum of the differences from the mean interval value, for successive intervals in the sequence.

12. A procedure as claimed in claim 10, wherein the fifth measure is calculated by giving less weight to those pairs of successive intervals in a Poincaré

plot that are within an elliptical region, E, centred on the point (mean interval, mean interval) with major and minor semi-axes oriented at 45° and

of lengths equivalent to the variability between successive intervals in the sequence, and to the third measure, respectively.

13. A procedure as claimed in claim 6 wherein the sequence of heart pulse intervals that is analysed in this way is a continuous sequence.

14. A screening apparatus to identify those at risk of cardiac arrhythmia, the apparatus comprising a blood flow detector and a signal analysis unit, such that the blood flow detector may be used to monitor a sequence of multiple heart pulses, wherein the signal analysis unit is arranged to deduce the values of a sequence of multiple heart pulse intervals, and to analyse the sequence of multiple heart pulse intervals to deduce a risk parameter whose value enables those at risk of cardiac arrhythmia to be identified.

15. A screening apparatus as claimed in claim 14 wherein the signal analysis unit is adapted to perform a procedure as claimed in claim 6.