Automatic detection and reporting of cardiac asystole

Details Automatic detection and reporting of cardiac asystole Automatic detection and reporting of cardiac asystole

1999-05-21

2001-10-16

Schaetzle, Kennedy (Department: 3762)

Surgery

Diagnostic testing

Cardiovascular

C600S518000, C607S005000

Reexamination Certificate

active

06304773

ABSTRACT:

FIELD OF THE INVENTION
The present invention relates generally to the monitoring and analysis of cardiac activity, and more particularly, to the analysis of non-invasive signals indicative of cardiac condition to enhance triage and patient treatment decisions.
BACKGROUND OF THE INVENTION
Automated external defibrillators (AEDs) are generally able to monitor and analyze electrocardiogram (ECG) data obtained from a patient and determine whether the patient's ECG indicates a “shockable” or “non-shockable” cardiac rhythm (i.e., a cardiac rhythm that may be treated with a defibrillation pulse). Commonly accepted medical protocol recommends treating certain cardiac rhythms, such as ventricular fibrillation (VF) and pulseless ventricular tachycardia (VT), with rapid application of a defibrillation pulse. On the other hand, potentially perfusing cardiac rhythms are generally not treated by application of a defibrillation pulse. These “non-shockable” rhythms include those with QRS complexes being present, such as supraventricular tachycardia and bradycardia. Cardiac asystole (i.e., a lack of cardiac activity) is also considered to be “non-shockable,” since a shock provides no benefit during asystole.
An AED typically obtains ECG data from a patient through electrodes placed on the patient. The AED evaluates the ECG data and makes a binary shock
o-shock decision based on the ECG evaluation. The AED then reports the shock
o-shock decision to the operator of the AED. If the AED detects a VF or VT cardiac rhythm in the patient, for example, the AED typically reports “Shock Advised” on a display, charges a defibrillation capacitor inside the defibrillator, and when instructed by the operator of the AED, delivers a defibrillation pulse from the capacitor to the patient. If, on the other hand, the AED detects a non-shockable cardiac rhythm (e.g., asystole or a rhythm with QRS complexes), the AED simply reports “No Shock Advised.” As noted, cardiac asystole represents the absence of electrical activity in the heart. Cardiac asystole may be found initially in a patient, it may develop over time during a resuscitation effort, or it may occur for some time after a defibrillation shock. Defibrillation therapy is generally neither effective nor indicated in the treatment of asystole. Chest compressions and artificial respirations (i.e., cardiopulmonary resuscitation, or CPR) may be performed on the patient, but normally are not effective in treating asystole when it is the initial rhythm. As noted by the American Heart Association (AHA) in its
Textbook of Advanced Cardiac Life Support
(1994), asystole unfortunately “most often represents a confirmation of death rather than a rhythm to be treated.”
The AHA encourages medical directors of pre-hospital care to establish criteria for those providing basic life support in the field to determine when to cease providing treatment, including defibrillation, to a patient, particularly in circumstances where a lack of resources and/or risk to rescuers from continuing to treat the patient outweigh the likelihood of successful resuscitation. Such risks include the risk of vehicular accidents during high-speed emergency transport and the risk of withholding basic life support from another patient needing medical assistance in favor of continuing to attempt to resuscitate the patient in an asystolic condition.
A caregiver providing basic life support to a patient may not recognize when the patient's heart is in an asystolic condition. At the present time, AEDs are intended for use by minimally-trained responders and indicate whether delivery of a defibrillation pulse is advised, but do not identify specific ECG rhythms. Without knowing when a patient's heart is in an asystolic condition, a caregiver may continue to apply basic life support techniques, such as defibrillation and CPR, to a patient for a time longer than is medically useful and perhaps to the risk of self and others. In addition, without the ability to recognize cardiac asystole, a caregiver is also not able to perform meaningful triage.
SUMMARY OF THE INVENTION
The present invention provides methods and an apparatus for evaluating ECG data to automatically detect and report a cardiac condition, such as cardiac asystole. In one exemplary embodiment, the invention is implemented in a defibrillator which obtains ECG data and calculates one or more ECG measures from the ECG data. The defibrillator classifies ECG data in multiple classifiers using the one or more ECG measures. Each classifier of the multiple classifiers classifies the ECG data into a class indicative of cardiac condition. One class indicative of cardiac condition is indicative of cardiac asystole. If the defibrillator classifies the ECG data in the class indicative of cardiac asystole, the defibrillator reports the detection of asystole on its display.
The defibrillator may obtain and classify a single segment of ECG data multiple segments of ECG data. Alternatively, the defibrillator may obtain ECG data continuously and classify the ECG data at one or more instances in time. If classifying multiple segments of ECG data, the defibrillator determines and reports an overall ECG classification based on a consensus (e.g., two out of three) of the classification of each segment.
In one aspect, the defibrillator may use a statistical binary classification and regression tree to classify the ECG data. The classification and regression tree implements a series of binary decision rules to systematically classify the ECG into a particular class. For instance, the defibrillator may classify the ECG data into a rhythm class associated with a cardiac rhythm. The binary decision rules of the classification and regression tree systematically classify ECG data of unknown rhythm type into a particular rhythm class.
In implementations where the defibrillator classifies the ECG data according to cardiac rhythm, the defibrillator may report the rhythm class into which the ECG data is classified. The defibrillator may also automatically prompt on its display a procedure to undertake based on the rhythm class into which the ECG data is classified. The procedure to be undertaken may be a therapy associated with the rhythm class of the ECG data, such as a defibrillation pulse for ECG data classified as a shockable cardiac rhythm. The procedure may also be determining and displaying an instruction providing guidance for prioritizing the delivery of a therapy.
In another aspect of the invention, the outcome of an ECG evaluation (i.e., the overall ECG classification) is recorded in a history of ECG evaluations stored in memory. When cardiac asystole is detected, the history of ECG evaluations is reviewed to determine whether a predetermined number of ECG evaluations over a predetermined period of time resulted in detection of asystole. If so, cardiac asystole is reported. If not, a no-shock advisory may be prompted on the display without reporting cardiac asystole. In this manner, asystole is reported only when the asystolic condition is persistent. Identifying persistent asystole is particularly useful to first-responding caregivers performing triage in emergency situations.
In still another aspect of the invention, if the ECG data is classified as cardiac asystole, the defibrillator determines whether a defibrillation pulse has been delivered to the patient within a predetermined time period. Since a period of asystole may occur following the delivery of a defibrillation pulse, the defibrillator reports cardiac asystole only if asystole is detected outside the predetermined time period following delivery of a defibrillation pulse.
As an alternative to classifying ECG data using multiple classifiers, a medical device configured according to the invention may use a single classifier, such as a statistical binary classification and regression tree, to directly classify the ECG as shockable, asystole, or non-asystole. If the classifier classifies the ECG data into one of a plurality of rhythm classes, the rhythm classes associated with shockabl

Affiliated with

Also associated with

Rating

Automatic detection and reporting of cardiac asystole does not yet have a rating. At this time, there are no reviews or comments for this patent.

If you have personal experience with Automatic detection and reporting of cardiac asystole, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Automatic detection and reporting of cardiac asystole will most certainly appreciate the feedback.

Rate now

Comments { 0 }

Profile ID: LFUS-PAI-O-2610442