Surgery: light – thermal – and electrical application – Light – thermal – and electrical application – Electrical therapeutic systems
Reexamination Certificate
1999-03-17
2001-08-07
Schaetzle, Kennedy (Department: 3762)
Surgery: light, thermal, and electrical application
Light, thermal, and electrical application
Electrical therapeutic systems
C607S009000, C607S063000, C600S517000, C600S515000
Reexamination Certificate
active
06272379
ABSTRACT:
FIELD OF USE
This invention is in the field of devices implanted within a person for the purpose of automatically detecting the onset of myocardial infarction and promptly warning that person to immediately seek medical care.
BACKGROUND OF THE INVENTION
Heart disease is the leading cause of death in the United States. The most prevalent form of heart disease is myocardial infarction resulting from a thrombus that obstructs blood flow in one or more coronary arteries. The sooner thrombolytic medication such as tissue plasminogen activator or urokinase is placed into the patient's bloodstream after the occurrence of a myocardial infarction, the sooner an obstructive thrombus will be dissolved and some perfusion of the myocardium can occur. The damage to the myocardium is strongly dependent on the length of time that occurs prior to restoration of some blood flow to the heart muscle. However, at this time, no implantable system exists that provides for early and automatic detection of myocardial infarction and for warning the patient that a myocardial infarction is occurring.
There are many patients who have implanted heart pacemakers or automatic defibrillators. The purpose of the pacemaker is to provide a low energy electrical stimulation pulse that causes the heart to beat at a prescribed rate. The purpose of the defibrillator is to shock the heart back into sinus rhythm after ventricular fibrillation has been detected. However, no existing implantable pacemaker or defibrillator is able to detect a partial or complete blockage of a coronary artery because of a thrombus in that artery and warn the patient that this potentially fatal event is occurring.
SUMMARY OF THE INVENTION
The present invention is a system for detecting a myocardial infarction (i.e., a heart attack) at the earliest possible time and promptly warning the patient that he should immediately seek medical care. Specifically, a first embodiment of the present invention has an implantable electronic system that can sense a change in the patient's electrogram that is indicative of a myocardial infarction. If a myocardial infarction is sensed, the device would then cause an implantable or externally located alarm means such as an audio sound source or a subcutaneous electrical tickle to be actuated in order to warn the patient of his condition. The patient could then promptly seek medical care, for example, at a hospital emergency room. Having been trained to recognize such an alarm, most patient would neither fail to recognize such an indication of a myocardial infarction nor would they ignore such an alarm signal if it were to occur.
Since an implantable heart pacemaker or defibrillator already has within its structure many of the elements required for the device to recognize a myocardial infarction, it would be expeditious to add a capability to these existing devices to detect a myocardial infarction and provide an alarm means to inform the patient to take appropriate action. Specifically, since an implantable pacemaker or defibrillator already has a long-lived battery and one or more electrodes connected by a lead wire to an electrogram amplifier within a hermetically sealed metal case. These same elements can be used for an implantable system to detect a myocardial infarction and alarm the patient accordingly.
It is well known that a myocardial infarction can be detected from a patient's ECG by noting an ST segment deviation (i.e., voltage change) as compared to the voltage of the patient's TP or PQ segments. Such an ST segment deviation can be even more clearly discerned with electrodes implanted within the body (especially within or in close proximity to the heart) as compared with detecting the elevated ST segment from chest and/or limb mounted electrodes. The electrical signal from the heart as measured from electrodes within the body is called an “electrogram”. Thus the early detection of a thrombus causing myocardial ischemia is clearly feasible by using an implantable system that notes a change in a patient's electrogram. The implanted portion of such a system is defined herein as a “cardiosaver” device.
One embodiment of the present invention is a cardiosaver that can detect the occurrence of a myocardial infarction, i.e., a heart attack, within less than a minute after it occurs and then automatically alarm the patient that this event is occurring. The patient's warning can come from an alarm means implanted in the patient's body and/or from an externally located alarm means that receives a radio message from the implanted portion of the system. The entire system including the implantable part (the cardiosaver) and the external equipment is defined herein as the “cardiosaver system”.
The implanted alarm means within the cardiosaver can be either an acoustic alarm or a subcutaneous electrical tickle. Either of these implanted signals could be applied periodically, for example at 30 second intervals, after the detection of a heart attack. The external alarm means would be accomplished by means of a radio receiving system that causes an audio alarm to occur when a radio signal is received from the cardiosaver. The external audio alarm would inform the patient that a myocardial infarction has been detected by his implanted system. It would also inform him that he should promptly take some predetermined medication such as aspirin, and he should promptly proceed to an emergency medical facility. The external equipment could also be programmed to call a rescue service to send an ambulance to bring the patient to an emergency facility. Still further, the external system could send the patient's electrogram to the rescue service so that they could be ready to provide medical treatment and advice based on the electrogram data.
It is believed that this system could be extremely valuable because many patients who have early symptoms of a myocardial infarction such as indigestion or left arm pain or even a chest discomfort very often tend to ignore these warning signs. If, for example, the patient experiences some indigestion that has an associated elevated ST segment that is indicative of a myocardial infarction, then promptly notifying the patient of this condition can significantly decrease the mortality and morbidity associated with acute myocardial infarction. Furthermore, as many as 20% of all patients who have a myocardial infarction have no detectable symptoms whatsoever. This is very often the case for elderly individuals who have had diabetes for many years. The invention described herein would be of particular value for such patients.
Thus it is an object of this invention to automatically sense that a myocardial infarction has occurred by means of an implantable device called a “cardiosaver”.
Another object of this invention is to use the cardiosaver to warn the patient that a myocardial infarction has occurred by means of a subcutaneous electrical tickle or audio signal.
Still another object of this invention is to have an implantable myocardial infarction detection device (a cardiosaver) that sends a radio signal to a warning system that is located in close proximity to where the patient spends most of his time. That close proximity alarm system would inform the patient that he may be undergoing a myocardial infarction and that an ambulance has been called to bring him to a hospital and that he should take certain actions such as immediately going to an emergency room and/or promptly taking certain medications.
Still another object of this invention is to provide a means for informing the patient that he is having a myocardial infarction when he might otherwise ignore some particular symptom or he may not have had any detectable symptom.
Still another object of this invention is to provide a patient who has either an implanted heart pacemaker or defibrillator with the additional capability for sensing the occurrence of a myocardial infarction and promptly warning the patient that a myocardial infarction is occurring.
Still another object of this invention is t
Fischell David R.
Fischell Robert E.
Fischell Tim A.
Cathco, Inc.
Schaetzle Kennedy
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