WO2003103487A1

WO2003103487A1 - Method of and apparatus for detecting arrhythmia and fibrillation

Info

Publication number: WO2003103487A1
Application number: PCT/US2002/018044
Authority: WO
Inventors: Joseph Wiesel
Original assignee: Joseph Wiesel
Priority date: 1999-12-20
Filing date: 2002-06-06
Publication date: 2003-12-18
Also published as: US7020514B1; US20030055351A1; US6519490B1

Abstract

The presence of an irregular heartbeat pattern and/or possible atrial fibrillation is determined by analyzing a measured pulse rate pattern or heart rate pattern. The standard deviation and mean of time intervals each corresponding to a respective heartbeat are determined and compared to a threshold value. When quotient formed by dividing the standard deviation by the mean has a value greater than or equal to the threshold value, the rhythm is irregular. When quotient formed by dividing the standard deviation by the mean has a value less than the threshold value the rhythm is regular.

Description

TITLE OF THE INVENTION

Method of and Apparatus for Detecting Arrhythmia and Fibrillation

BACKGROUND OF THE INVENTION

Field of the Invention

[0001] The present invention generally relates to a method of and an apparatus for detecting irregular heartbeats and, more particularly, to monitoring and analyzing pulse rates for detecting possible atrial fibrillation.

Discussion of the Related Art

[0002] The heart is the major muscle that functions as the primary pump for blood flow throughout the body. The heart contains two upper chambers called atria and two lower chambers called ventricles. The right atrium receives oxygen-depleted blood while the left atrium receives blood enriched with oxygen from the lungs. When the atria are full, the outlet valves within the heart open and the atria squeeze blood into the ventricles. The right ventricle then pumps oxygen-depleted blood to the lungs while the left ventricle pumps oxygen-enriched blood to all parts of the body. In this fashion, the heart functions primarily as a double sided pump.

[0003] The heart's internal pacemaker, known as the sinus node, signals the start of each heart beat. This signal originates in the right atrium in the sinoatrial node and travels simultaneously to the left atrium and down to the interatrial septum to the atrioventricular node. The cycle of electrical stimulation that normally occurs is referred to as normal sinus rhythm.

[0004] When a rhythm abnormality is present, however, there may exist an abnormal condition known as fibrillation. Fibrillation may occur as a result of an abnormality with either the ventricle and/or the atria. Atrial fibrillation is an abnormal heart condition in which the atria of the heart provide irregular impulses to the atrioventricular node so that an irregular heartbeat pattern results.

[0005] Atrial fibrillation is one of the most common arrhythmias requiring medical attention. Atrial fibrillation may be caused by a number of heart conditions, such as angina, myocardial infarction, heart valve abnormalities, and high blood pressure. These conditions may stretch or scar the atria, thereby causing irregularities in the heart system. Atrial fibrillation may also accompany lung problems or thyroid gland disorders and is also associated with significant morbidity and possible mortality. All persons, young and old, female or male, including the visually and/or sight impaired, may experience atrial fibrillation.

[0006] Atrial fibrillation may occur intermittently or chronically. The most serious complication of atrial fibrillation is formation of a blood clot in the left atrium which may result in a stroke. Many people who develop atrial fibrillation, however, are unaware of their abnormal rhythm. Some in the medical profession have, therefore, advocated self screening of the pulse rate to detect for the possible occurrence of atrial fibrillation. The literature, however, is generally limited to disclosing instructions for manually taking one's pulse rate accompanied with additional descriptive information. [0007] The reason for taking the pulse rate to detect at rate corresponds to the heart rate. The pumping action of the heart displaces blood in the rest of the body. The pulse is the movement of blood caused by the heart's pumping, and the pulse rate is the number of times that the blood is displaced during a fixed period, conventionally an interval of one minute.

[0008] Because of the correspondence between the heartbeat rate and pulse rate, atrial fibrillation causes an irregular detected pulse wherever a pulse can be palpated. Normal sinus rhythm produces a heartbeat pattern of a fixed number of beats per minute with equal interval between beats. Fibrillation is detected when the time between the beats is irregular, that is the time between beats changes irregularly.

[0009] There are several devices available that measure both blood pressure and pulse rate, but none of these devices is capable of monitoring, detecting and/or communicating whether or not an irregular heartbeat pattern is present to indicate possible atrial fibrillation. The commercially available devices measure the number of pulse beats over a preset time interval, usually ten (10) seconds, but these devices neither analyze nor determine the presence of irregular heartbeat rhythms.

[0010] Commercially available devices for determining pulse rates use several methods including: i) measuring a pulse beat when systolic pressure peaks are detected such as by using an inflated cuff that is wrapped around the upper arm, ii) utilizing electrodes to determine pulse rates in the same manner used while taking an EKG, and iii) detecting pulse beats from changes in light transmission through body appendages, such as through the fingers, where a pulse is recorded whenever the difference in 1 between one point of the appendage and another point on the appendage changes. The change in transmission results from the pulse moveably changing the volume of blood flowing through the appendage, which changes, in turn, the amount of light absorbed in the appendage.

[0011] What is needed is a method and apparatus to detect the presence of irregular heartbeats and communicate this condition to the user so that the user is alerted to consult a medical practitioner for further testing and/or treatment.

[0012] What is also needed is a method that can differentiate an irregular pulse rate pattern from a normal pulse rate pattern and from common heart rhythm patterns that are not of significant risk, such as regular sinus rhythm, sinus arrhythmia, atrial premature beats and ventricular premature beats.

[0013] What also is a needed is a home monitoring method and apparatus that analyzes pulse rates for the presence of irregular pulse rhythms and that communicates this information to the user.

[0014] What further is needed is a method of and an apparatus for detecting irregular pulse rhythms during a time period and storing this information so that comparisons may be made with the pulse rate rhythms at later times.

[0015] What is further needed is a noninvasive and relatively simple method and apparatus that monitors pulse rate irregularities to detect fibrillations, including the possibility of atrial fibrillation, and that is suitable for use of all ages, and impaired and that is relatively easy to use.

[0016] What is still further needed is a monitoring method and apparatus that detects the presence of irregular heartbeats and then displays and stores: i) the number of irregular pulse beats during a pre-selected time interval; and ii) the duration of time between beats during selected intervals.

[0017] Yet another need is for a monitoring method and apparatus that determine whether or not a heartbeat is irregular based on algorithmic or heuristic operations performed on selected pulse rate or heartbeat data.

BRIEF SUMMARY OF THE INVENTION

[0018] The present invention provides a method and apparatus that (i) detects the presence of irregular heartbeats by analyzing a pulse rate pattern, that is, by analyzing the pulse beat rhythm during a time interval; (ii) determines whether this pulse rate pattern indicates a possible atrial fibrillation or other irregularity; and then (iii) communicates this information to the user so that a medical practitioner may be consulted for further testing and/or treatment. The present invention also provides a method of and an apparatus for detecting irregular pulse rhythms during a time period and storing this information for comparison with the pulse rate rhythm at later time periods. The present invention may also detect irregular pulse rhythms over multiple time periods and capture the similarities and/or differences in the pulse rate for selected intervals over various time periods. [0019] The present invention fiirther provides a noninv apparatus for monitoring pulse rate irregularities to detect atrial fibrillation. The invention may store and display information such as the number of irregular pulse beats during preselected time intervals and the duration of time between beats during the selected intervals. The invention also determines the presence of an irregular heartbeat via algorithmic or heuristic operations performed on the relevant data.

[0020] For patients with a baseline rhythm abnormality, or for those who want improved accuracy for detecting atrial fibrillation, a device comprised of electrodes may be placed on the skin. This device uses the actual electrocardiogram, in contrast to the pulse, to determine whether an atrial fibrillation warning should be indicated. The electrodes may be wrist straps that are placed on the arms or which are removably secured to various areas on the torso, arms or legs. This device may be used in conjunction with an electrocardiogram (EKG) recording device. The device may record the electrocardiogram, analyze the heartbeats, and display the appropriate warnings when pre-selected criteria for fibrillation are met. The present invention also works using either the heartbeat rate or the pulse rate.

[0021] Pulse rates may also be monitored by tracking the systolic peak that coincides with each heartbeat. Typically, an inflatable cuff is wrapped around the upper arm of a person and is inflated to a pressure greater than the person's blood pressure. Each heartbeat causes a rise in the blood pressure up to a systolic peak, which corresponds to a pulse beat.

[0022] Pulse rates may also be monitored through changes in light transmitted through various body appendages. Each pulse beat changes the light transmission through a location on the appendage. The change in the light transmission over a time interval yields a pulse rate or an average pulse rate.

[0023] A monitoring method of the present invention includes detecting irregular pulse beats, analyzing the irregularity based on one or more predetermined factors, and communicating this information to a user such as via a screen display, a paper printout, a tone, or auditory, vibratory or other sensory communication.

[0024] The invention may utilize algorithmic or heuristic techniques to determine whether the irregular pulse beat(s) signals the possible presence of atrial fibrillation.

[0025] Other features and advantages of the present invention will become apparent from the following detailed description of the invention with reference to the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

[0026] The invention will now be described in greater detail in the following detailed description with the reference to the drawings in which:

[0027] Figure 1 is a diagram showing an arrangement for detecting possible atrial fibrillation using an inflated cuff in accordance with the invention.

[0028] Figure 2 is a diagram showing an arrangement for detecting possible atrial fibrillation by detecting changes in the amount of blood that is absorbed in an appendage area in accordance with the invention. [0029] Figure 3 is a diagram showing an arrangement detecting possible atrial fibrillation using electrodes placed on the skin of an individual in accordance with the invention.

DETAILED DESCRIPTION OF THE INVENTION

[0030] Figure 1 shows an embodiment of the invention in which heartbeat irregularities and possible atrial fibrillation are detected using an inflated-cuff device 202. The inflated-cuff device may be a known apparatus, which monitors pulse rates by tracking the systolic peak that coincides with a heartbeat. An inflatable cuff is wrapped around the upper arm of an individual and is inflated to a pressure that is greater than the individual's blood pressure. Each heartbeat creates a rise in the individual's blood pressure, which corresponds to a pulse beat. The time of each pulse beat is delivered to a processor 204, which includes instructions that carry out the method described above. Further, the processor 204 stores the time of each pulse beat, the intervals between pulse beats, and other information in a memory 206. The memory 206 may include RAM or other device memory or include a hard disk, a floppy disk or other memory devices. The processor 204 may comprise a microprocessor, and applications specific integrated circuit (ASIC), a programmable logic array (PLA) or reduced instruction set chip (RISC).

[0031] The processor 204 determines that the heartbeat pattern is regular or irregular.

The processor then delivers the results to a printer 208 a display 210 a vibration generator, and/or an auditory generator, etc. which may include an indication that the heartbeat is regular, irregular, in possible atrial fibrillation, or that a physician should be contacted. Other information, such as the heart rate or pulse rate, may also be di

[0032] Figure 2 shows another embodiment of the invention in which the pulse rate is monitored through changes in light transmitted through a body appendage, such as a finger. Light is transmitted by a light source 300 through the finger, or other appendage of an individual, and is received by a detector 302, which measures the change in light transmitted through the appendage to detect a pulse beat. The detector 302 may comprise a known pulse measurement device. The detector 302 delivers the time of each measured pulse to the processor 204, which carries out the operations described above regarding Figure 1.

[0033] Figure 3 shows a further embodiment of the invention in which heartbeats are detected by measuring cardiac electrical activity using an electrode device 402 in which electrodes are placed on various locations of an individual. The electrodes may include wrist straps that are placed on the arms or other contacts, which are removably secured to various areas on the individual including the torso, arms and legs. The electrode device 402, which may operate in a manner similar to a known EKG device, delivers the time of each measured heartbeat to the processor 204. The processor 204 then carries out the operations described above.

[0034] Advantageously, the invention provides a method and apparatus that easily detect the presence of irregular heartbeats from a plurality of heartbeats, pulses or other measurements.

[0035] As a further advantage, the invention differentiates a normal heartbeat pattern from an irregular heartbeat pattern.

[0036] A still further advantage is that the invention provides relatively simple, non- invasive home monitoring.

[0037] Although the present invention has been described in relation to particular embodiments thereof, many other variations and modifications and other uses may become apparent to those skilled in the art. It is preferred, therefore, that the present invention be limited not by this specific disclosure herein, but only by the appended claims.

Claims

WHAT IS CLAIMED IS:

1. A method of determining the regularity of a cardiac rhythm, said method comprising the steps of:

(a) detecting differences in time intervals of a sequence of heartbeats; and

(b) determining the regularity of the cardiac rhythm from the differences, the regularity being indicative of atrial fibrillation when said sequence of heartbeats is irregular and being indicative of an absence of atrial fibrillation when said sequence of heartbeats is regular.

2. A method of Claim 1, wherein the determining includes ascertaining a mean and a standard deviation of a plurality of the time intervals, each of the time intervals corresponding to a respective one of the time intervals between successive ones of a sequence of heartbeats, the determining of the regularity being based upon a quotient formed by dividing said standard deviation by said mean and comparing the quotient with a threshold value.

3. A method of Claim 2, wherein the determining includes determining that the sequence of heartbeats is irregular in response to the quotient being greater than or equal to the threshold value.

4. The method of Claim 2, wherein the determining includes determining that the sequence of heartbeats is regular in response to the quotient being less than the threshold value.

5. The method of Claim 2, wherein said sequence ι taking a sequence of pulse rates.

6. The method of Claim 2, further comprising the step of storing at least one of said plurality of time intervals, said mean, said standard deviation, said quotient and said threshold value.

7. The method of Claim 2, wherein said sequence of heartbeats is determined by measuring a sequence of heartbeats.

8. The method of Claim 2 wherein said threshold value is within the range of .05 to .10.

9. The method of Claim 1, further comprising indicating the regularity.

10. An apparatus for detecting cardiac activity, said apparatus comprising: a detector for detecting cardiac activity related to heartbeats at measured times; and a processor for determining regularity of the cardiac activity from the sequence of heartbeats, the regularity being indicative of atrial fibrillation when said sequence of heartbeats is irregular and being indicative of an absence of atrial fibrillation when said sequence of heartbeats is regular.

11. An apparatus of Claim 10, wherein the detector is configured to detect differences in time intervals of a sequence of heartbeats as the c

12. An apparatus as in Claim 10, wherein the processor is configured to determine whether the cardiac activity is irregular or regular as a function of at least one of a standard deviation and mean of a plurality of time intervals of said cardiac activity.

13. The apparatus of Claim 10, wherein said detector is an inflatable-cuff device and said activity is a pulse beat.

14. The apparatus of Claim 10, wherein said detector is configured to detect changes in light transmitted through an appendage of an individual and the activity is a pulse rate.

15. The apparatus of Claim 10, wherein said detector is an electrode device and the activity is an actual heart rate.

16. The apparatus of Claim 10, further comprising a device for outputting an indication that is indicative of what the processor determined

17. The apparatus of Claim 16, wherein said device for outputting is selected from a group consisting of a printer, a display, an auditory signal generator, and a vibration signal generator.

18. The apparatus of Claim 10, wherein said processor comprises at least one of a microprocessor, and application specific integrated circuit (AS] array (PLA) and a reduced instruction set chip (RISC).

19. The apparatus of Claim 10, wherein said processor is configured to verify normal cardiac activity by carrying out the steps of: ascertaining a mean and a standard deviation of a plurality of the time intervals, each of the time intervals corresponding to a respective one of the time intervals between successive ones of a sequence of heartbeats, the determining of the regularity being based upon a quotient formed by dividing said standard deviation by said mean and comparing the quotient with a threshold value.

20. The apparatus of Claim 19, wherein said processor determines irregular cardiac activity in response to the quotient being greater than or equal to the threshold value.

21. The apparatus of Claim 19, wherein said processor determines regular, normal cardiac activity in response to the quotient being less than the threshold value.

22. The apparatus of Claim 19, wherein said threshold value is within the range of .05 to .10.

23. The apparatus of Claim 20, wherein said threshold value is within the range of .05 to .10.

24. The apparatus of Claim 21 , wherein said threshold value is within the range of

.05 to .10.

25. The apparatus of claim 10, wherein the detector is configured to detect the activity from a transmission of light.

26. The apparatus of claim 10, wherein the detector is configured to detect electrical cardiac activity.

27. The apparatus of claim 10, wherein the detector is a sphygmomanometer.