Fibrillation and tachycardia detection
First Claim
1. An improved fibrillation and tachycardia detection system for a cardioversion-defibrillation system including means for detecting whether a patient'"'"'s heart is in a normal cardiac rhythm or an abnormal cardiac rhythm and, in response to detection of an abnormal cardiac rhythm, means for automatically delivering an electrical countershock therapy of greater than about 1.0 joules of electrical energy to treat the abnormal cardiac rhythm, the improvement comprising:
- local detection means for sensing a local electrical signal representing cardiac activity in one of a plurality of local areas of the patient'"'"'s heart, each local area having a local electrical signal;
global detection means for sensing a global electrical signal representing cardiac activity in a global area of the patient'"'"'s heart, the global area including the plurality of the local areas such that the global electrical signal represents an electrical average of the local electrical signals of the plurality of local areas;
means for successively measuring a delay value between a first time when the local electrical signal meets a predetermined trigger criteria and a second time when the global electrical signal meets the predetermined trigger criteria;
means for storing and comparing a series of the delay values to detect whether the patient'"'"'s heart is in the abnormal cardiac rhythm and should be treated by the cardioversion defibrillation system or whether the patient'"'"'s heart is in the normal cardiac rhythm and should not be treated by the cardioversion defibrillation system.
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Accused Products
Abstract
Providing a sensitive, prompt, and accurate indication of both ventricular fibrillation and monomorphic ventricular tachycardia is the aim of this invention. The invention employs electrical voltage-versus-time signals produced by the heart, these observed from two or more locations. By well-known signal-processing techniques, these signals are reduced to pulses of standardized height and duration, each derived from a prominent feature of the waveform for each heart period, such as its leading edge, in the process eliminating the irrelevant information in the waveform, but retaining the feature that is most relevant in the present context, namely, its precise time of occurrence. The invention then uses further standard electronic techniques to determine the amount of delay between the corresponding pulses in two such pulse trains, in the process distinguishing between monomorphic ventricular tachycardia and more benign conditions. It is a further straightforward matter of signal analysis to determine coincidence rate as a fraction of total pulse rate, which in the normal heart approaches unity (100%), while in the fibrillating heart is much lower, thus diagnosing ventricular fibrillation. The present invention is hence able to trigger a defibrillating-discharge decision, or a cardioversion-discharge in the prior case, much more reliably than has been possible in the prior art.
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Citations
13 Claims
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1. An improved fibrillation and tachycardia detection system for a cardioversion-defibrillation system including means for detecting whether a patient'"'"'s heart is in a normal cardiac rhythm or an abnormal cardiac rhythm and, in response to detection of an abnormal cardiac rhythm, means for automatically delivering an electrical countershock therapy of greater than about 1.0 joules of electrical energy to treat the abnormal cardiac rhythm, the improvement comprising:
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local detection means for sensing a local electrical signal representing cardiac activity in one of a plurality of local areas of the patient'"'"'s heart, each local area having a local electrical signal; global detection means for sensing a global electrical signal representing cardiac activity in a global area of the patient'"'"'s heart, the global area including the plurality of the local areas such that the global electrical signal represents an electrical average of the local electrical signals of the plurality of local areas; means for successively measuring a delay value between a first time when the local electrical signal meets a predetermined trigger criteria and a second time when the global electrical signal meets the predetermined trigger criteria; means for storing and comparing a series of the delay values to detect whether the patient'"'"'s heart is in the abnormal cardiac rhythm and should be treated by the cardioversion defibrillation system or whether the patient'"'"'s heart is in the normal cardiac rhythm and should not be treated by the cardioversion defibrillation system. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11)
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12. A method of fibrillation and tachycardia detection for a cardioversion-defibrillation device capable of automatically delivering an electrical countershock therapy of greater than 1.0 joules of electrical energy to treat a patient'"'"'s heart in response to detection of an abnormal cardiac rhythm, the method comprising the device-implemented steps of:
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(a) providing a local electrical signal representing cardiac activity in one of a plurality of local areas of the patient'"'"'s heart, each local area having a local electrical signal; (b) providing a global electrical signal representing cardiac activity in a global area of the patient'"'"'s heart including the plurality of local areas such that the global electrical signal represents an electrical average of the local electrical signals of the plurality of local areas; (c) detecting when either the local electrical signal or the global electrical signal meet a predetermined trigger condition and starting a delay timer; (d) detecting when the one of either the local electrical signal of the global electrical signal not detected in step (c) meets the predetermined trigger condition and stopping the delay timer; (e) storing a delay value from the delay timer for each of a series of trigger conditions; (f) comparing the series of delay values to detect whether the patient'"'"'s heart is in the abnormal cardiac rhythm and should be treated by the cardioversion defibrillation system or whether the patient'"'"'s heart is in the normal cardiac rhythm and should not be treated by the cardioversion defibrillation system. - View Dependent Claims (13)
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Specification