This invention is generally in the field of medical devices, and relates to methods and systems for use in the determination of a patient's heart condition.
Monitoring of the heart condition is important for timely detection of various abnormalities such as cardiac arrhythmias, conduction abnormalities, ventricular hypertrophy, myocardial infarction, electrolyte derangements, etc.
Assessment of left ventricular (LV) function plays a central role in diagnosis and treatment of heart disease. Cardiac resynchronization therapy (CRT) improves quality of life, reduces hospitalizations due to heart failure, and reduces mortality
The heart condition is generally characterized by various measurable parameters, including among others an ejection fraction and a cardiac synchrony. The ejection fraction can directly be calculated using echocardiology, cardiac MRI, CT, etc. On the other hand, an effect of reduction in the ejection fraction can be detected via ECG-QRS based measurements: increase in the QRS is indicative of a reduction of the ejection fraction. As for the cardiac synchrony, it is typically detected by echocardiography.
The present invention provides novel methods and systems for monitoring a patient's heart conditions, such as ejection fraction and cardiac synchrony conditions.
According to one broad aspect of the invention, a monitoring method comprises extracting information about the subject's ejection fraction from ECG-based measured data. The inventors have found that a relation between a measurement taken from a diagonal pair of electrodes and a measurement taken from a planar pair of electrodes appropriately applied to the subject is indicative of the ejection fraction.
It should be understood that the expression “a diagonal pair of electrodes” relates to electrodes applied to patient's arm and leg (according to existing standards these are electrodes applied to the right arm and left leg); and the expression “a planar pair of electrodes” relates to electrodes applied to either two arms or two legs (according to existing standards these are electrodes applied to two arms).
Generally, such two pairs of electrodes, diagonal pair of electrodes and planar pair of electrodes, can be obtained using three electrodes: two applied to the patient's arm and one to his/her leg; or two electrodes applied to the legs and one to the arm.
The present invention may be used with standard ECG equipment including 6 leads interconnecting 4 electrodes. For the purposes of the present invention, signals measured from any two leads can be used.
Thus, a first data portion, indicative of a first time profile of an electrical signal measured on a planar pair of electrodes applied to a subject during a measurement session, and a second data portion, indicative a second time profile of an electrical signal measured on a diagonal pair of electrodes applied to said subject during the same measurement session, are processed. The processing comprises determining a relation between the first and second data portions, e.g. comparing the first and second data portions and upon identifying a time shift between a certain event in the first and second time profiles, generating output data indicative of the ejection fraction for said subject.
The event to be identified is typically a peak R of the QRS complex.
A time delay of the appearance of such peak R in the second time profile (diagonal pair of electrodes—Lead II in
In some embodiments of the invention, a combination of ECG measured data and acoustic measurements is used, namely substantially simultaneously obtained data corresponding to measurements by the ECG assembly and acoustic data corresponding to measurements by an array of transducers (acoustic receivers) from a planar region of the chest or back skin surface of the patient overlying a heart chamber. The processed ECG and acoustic measured data is used for determination of ejection fraction, based on the determination of the cardiac cycle events (E1, E2, E3, E4). The use of acoustic data for determining the ejection fraction is disclosed in PCT/IL2007/001533, assigned to the assignee of the present application, which application is incorporated herein by reference.
In an embodiment of the present invention, the acoustic data is indicative of acoustic signals recorded by an array of transducers during the measurement session. It should be understood that according to the invention the acoustic data is indicative of acoustic signal(s) recorded by one or more transducers (e.g. microphones) during the measurement session, and may comprise the time profile of an electrical output of one or more transducers, and/or a certain functional of an electrical output of one or more transducers.
According to another broad aspect of the invention, there is provided a method for use in monitoring a subject's cardiac synchrony. The method comprises processing first and second measured data portions corresponding to respectively an ECG measurement and an acoustic measurement, both obtained from a subject during the same measurement session of a duration including at least two cardiovascular cycles. The processing comprises identifying certain first and second events in each of these at least two cycles in the first and second measured data, and determining a relation between them for each cycle. Then, a degree of fluctuation of this relation in the at least two cycles is determined being indicative of cardiac synchrony for said subject.
In a preferred embodiment of the invention, the two events to be identified include an initial point of the QRS complex in the first measured data and a first event (E1) in the second measured data. The first event (E1) in the acoustic measured data is a first acoustic signal peak occurring after the initial points of the QRS complex during the measurement session. The relation to be identified is a time delay between such two events, e.g. between the initial points of the QRS complex and the corresponding first acoustic signal peak (E1). When the fluctuation is well identifiable, i.e. a time delay value fluctuates from cycle to cycle, the existence of abnormality in the heart condition is considered.
Preferably, the method comprises selecting one or more acoustic signals from one or more locations, respectively, with respect to a region of interest in the subject's body. Data indicative of the so-selected acoustic signal(s) is included in the second measured data for further processing. The selected acoustic signals may be those corresponding to the output of transducers located at a certain distance from a location on the body aligned with the heart region.
In order to understand the invention and to see how it may be carried out in practice, embodiments will now be described, by way of non-limiting example only, with reference to the accompanying drawings, in which:
Reference is made to
In the present example, the ECG assembly 16 includes the standard ECG equipment including 6 leads (I, II, III, aVR, aVL and aVF) connecting four electrodes LA, RA, LL and RL (by reference or NULL). Thus, the lead I connects electrodes LA-RA, lead II-electrodes LL-RA, lead III-electrodes LL-LA, and so on. Generally, the ECG assembly includes an electrodes' arrangement formed by at least three electrodes LA, RA, LL involved in the measurements and a reference electrode RL (not shown), and includes a voltage supply/read unit (not shown). It should be noted that typically each electrode is formed by an electrode pair for applying and reading the voltages, respectively. The construction and operation of an ECG measurement unit are known per se and need not be described in details, except to note that for the purposes of the present invention the ECG unit, which collects measured data to be processed by the monitoring system, utilizes a planar pair of electrodes LA-RA and a diagonal pair of electrodes LL-RA.
The monitoring system 10 receives and processes measured data, where the latter includes a first data portion MD1 indicative of a first time profile of an electrical signal measured on planar pair of electrodes LA-RA and a second data portion MD2 indicative of a second time profile of an electrical signal measured on a diagonal pair of electrodes LL-RA. The measurements by the first and second pairs of electrodes LA-RA and LL-RA are applied to the patient during the same measurement session. The processing of the so-obtained measured data portions MD1 and MD2 includes comparing these first and second data portions to determine whether there exists a time shift between a certain event (e.g. signal peak) appearing in the first and second time profiles. Upon identifying the time shift, the system generates and displays output data indicative of the ejection fraction condition for the patient.
As shown more specifically in
Generally, such parameters as duration, amplitude, and morphology of the QRS complex are useful in diagnosing of cardiac arrhythmias, conduction abnormalities, ventricular hypertrophy, myocardial infarction, electrolyte derangements, and other disease states. Considering the ejection fraction determination, a condition of the ejection fraction reduction can be detected via ECG-QRS: an increase in the QRS-width corresponds to a reduction of the ejection fraction. Such ECG-QRS based measurements are insensitive to the selection of electrode-pair. In other words, all the electrode-pairs show the same results with regard to the QRS-width.
The inventors have found that although the QRS-width remains unchanged when measured on planar or diagonal electrode pairs, the QRS complexes measured by planar and diagonal electrode pairs are shifted in time. Moreover, this shift in the QRS complex at different electrode pairs is more sensitive to a change in the ejection fraction condition, than a change in the QRS-width.
Turning back to
Reference is made to
Referring to
The present invention, according to yet another aspect relates to a method and system for monitoring a condition of a subject's heart synchrony/asynchrony, by determining the so-called “Vibration Systolic Desynchrony Index”. According to this technique, as shown in
Referring to
The inventors have found that the ECG measured data and the acoustic measured data are characterized by certain first and second events appearing in each cardiovascular cycle. In the normal cardiac synchrony condition, a relation between these is maintained for all the cardiovascular cycles, while a condition of desynchrony can be identified by a certain degree of fluctuation of this relation in the cardiovascular cycles.
Turning back to
As shown in
Reference is made to
It should be noted that the acoustic data included in the respective measured data potion and further processed may be data obtained from the single microphone or from the matrix of microphones. In the latter case, this may be the entire matrix applied to the patient, or a group (sub-matrix) of the entire matrix. It should also be noted that such acoustic data may include the output of the microphone(s) itself, or a certain functional of this output signal (e.g., standard deviations for all the microphones).
Referring to
The inventors have found that acoustic data associated with microphones located far away from the heart-region is more sensitive with regard to fluctuations in said relation between the events in ECG- and acoustic-signals caused by abnormality on the cardiac synchrony. In this connection, turning back to
The following is an example of processing the output of the microphones to create the acoustic measured data:
For each microphone, a distance between the beginning of QRS complex (ECG) and E1 peak cardiac cycle event is calculated (presenting an acoustic signal envelope), for all cardiac cycles of the recording, as follows:
D
i,j
=B
i,j
QRS
−E1i,j
Here, i is the microphone number which varies from 1 to N; N is the number of the microphones, and j is the cycle number which varies form 1 to n, where n is the number of cycles in a record.
For each microphone, median of the distances is calculated for all cardiac cycles of the recording, as follows:
D
i
m=median(Di,j=1:n)
For each microphone, normalize standard deviations is calculated as follows:
For all microphones, median of the standard deviations of the all microphones is calculated, as follows:
σm=median(σin)
Thirty four subjects were examined including 24 healthy controls and 40 subjects from cardiology clinics. A matrix of 5×5 transducers was applied to the chest, and the vibrations were mapped and recorded digitally. For each transducer, the interval between the onset of Q-wave and the peak of the amplitude vibration (E1 peak) was measured. VSDI for each subject was determined as the standard deviation of the difference between the median and each transducer interval. VSDI for normal controls (12.6±6.2 msec) was found to be lower than that for subjects with right ventricular pacing (30.3±9.9 msec), p<0.05. Variation of VSDI was observed in subjects with wider QRS implied various degrees of desynchrony. Thus, a simple new vibration systolic desynchrony index can differentiate between various degrees of cardiac desynchrony.
Thus, the present invention provides novel techniques for monitoring various parameters characterizing the heart condition. The ejection fraction parameter can be determined from a relation (time shift) between the respective signal peaks (QRS-complexes) in the ECG signals measured on planar and diagonal electrode pairs. The cardiac synchrony parameter can be determined from a behavior (degree of fluctuation) of a relation between corresponding events (e.g. QRS and E1) in the ECG and acoustic data during at least two cardiovascular cycles.
Filing Document | Filing Date | Country | Kind | 371c Date |
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PCT/IL09/00326 | 3/29/2009 | WO | 00 | 9/19/2010 |
Number | Date | Country | |
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61064739 | Mar 2008 | US |