Surgery – Means for introducing or removing material from body for... – Treating material introduced into or removed from body...
Reexamination Certificate
1999-09-28
2001-08-28
Kamm, William E. (Department: 3737)
Surgery
Means for introducing or removing material from body for...
Treating material introduced into or removed from body...
Reexamination Certificate
active
06280409
ABSTRACT:
COPYRIGHT NOTICE
Except for the right to reproduce copies of this patent document, the use of all copyrightable material herein for any purpose whatever is expressly retained by the owners of this patent. Copyright Medtronic Inc., 1998, all other rights reserved.
This invention relates to the field of implantable medical devices for enabling enhanced medical monitoring of patients, most particularly for use with activity sensing, and has application to the field of monitoring patients generally and particularly those with conditions such as Cardiac Heart Failure (CHF).
BACKGROUND
There are numerous devices both implantable and external that have been used to monitor various medical patient conditions. Well known for heart patients is the Holter monitor which permits somewhat uncomfortable monitoring of an electrocardiogram for 24 hours which can then be read by a physician to find anamolies in the rhythm which were not susceptible to discovery or confirmation in a patient's office visit to the doctor. A number of other devices have improved on the ability to maintain records of electrocardiograms and numerous other health related patient parameters and even device performance parameters. Implantable medical devices such as pacemakers and cardioverter-defibrillators and even non-therapeutic monitoring devices are currently capable of maintaining some records and reporting out such data. An example of a non-therapy delivering monitoring implantable medical device can be seen in U.S. Pat. Nos. 5,313,953 and 5,411,031 issued to Yomtov et al., and in Holsbach et al. 5,312,446, and others. Nolan et al.'s U.S. Pat. No 5,404,877 teaches that such devices can even generate patient alarms. All these patents are incorporated herein by this reference in that they provide information about what can currently be done in the implantable device field.
Current generation pacemakers and implantable defibrillators/cardioverters have the ability to store different types of information in order to provide feedback to the clinician about the patient/device system. Examples of stored information include arrhythmia diagnostics, histograms of paced and sensed events, electrograms and trends of lead impedance. Such information is useful not only in optimizing device programming but also in the management of the patient's arrhythmias and other conditions. While out invention focuses on the monitoring of patient activity, which we use as a functional status monitor, the additional information available from implantable devices could be used as an adjunct.
However, to date the literature is devoid of a satisfactory description of how to use activity information. There has been considerable thinking in this area, but none have yet succeeded in producing a satisfactory measure to track patient functional status. Some examples of this thinking in the current literature include:
Walsh J. T., Charlesworth A., Andrews R., Hawkins M., and Cowley A. J.“Relation of daily activity levels in patients with chronic heart failure to long-term prognosis”, Am J Cardiol, 1997, 79: 1364-1369.
Rankin S. L., Brifa T. G., Mortan A. R., and Hung J., “A specific activity questionnaire to measure the functional capacity of cardiac patients”, Am J Cardiol 1996, 77: 1220-1223.
Davies S. W., Jordan S. L., and Lipkin D. P., “Use of limb movement sensors as indicators of the level of everyday physical activity in chronic congestive heart failure”, Am J Cardiol 1992, 67: 1581-1586.
Hoodless D. J., Stainer K., Savic N., Batin P., Hawkins M. and Cowley A. J., “Reduced customary activity in chronic heart failure: assessment with a new shoe-mounted pedometer”, International Journal of Cardiology, 1994, 43: 39-42.
Alt E., Matula M., Theres H., Heinz M. and Baker R., “The basis for activity controlled rate variable cardiac pacemakers: An analysis of mechanical forces on the human body induced by exercise and environment”, PACE, vol 12, Oct. 1989.
Lau C. P., Mehta D., Toff W. D., Stott R. J., Ward D. E. and Camm A. J., “Limitations of rate response of an activity sensing rate responsive pacemaker to different forms of activity”, PACE, vol. 11, Feb 1988, and
Lau C. P., Stott J. R. R., Zetlin M. B., Ward A. J., and Camm A. J., “Selective vibration sensing: a new concept for activity-sensing rate-responsive pacing”, PACE, vol. 11, September, 1988. Matula M., Schlegl M., and Alt E., “Activity controlled cardiac pacemakers during stairwalking: A comparison of accelerometer with vibration guided devices and with sinus rate”, PACE, 1996, vol 19, 1036:1041.
Specific Information Uses:
The ability to perform normal daily activities is an important indicator of a patient's functional status and is related to improved quality of life in patients. An increase in the ability to perform activities of daily living (ADL) is an indicator of improving health and functional status, while a decrease in the ability to perform daily activities may be an important indicator of worsening health. Activities of daily living are submaximal activities performed during daily life. Examples are going to work, cleaning the house, vacuuming the house, cooking and cleaning, working in the garden, short walk to grocery stores, cleaning the car, and slow paced evening walks.
In order the asses the amount of daily activities that patients can perform and the ease with which they can perform these activities, clinicians typically ask their patients during office visits the following questions:
How do you feel?
Are you as active today as you were 2 months ago?
Are you as active today as you were 6 months ago?
Are you able to climb stairs?
How far can you walk?
Do you do your own grocery shopping?
Do you perform chores around the house?
Are you able to complete your activities without resting?
They also employ other tools such as the symptom based treadmill exercise test, the 6 minute walk test, questions and answers (Q&A), and quality of life (QOL) questionnaires in order to learn about their patients' ability to perform exercise and normal activities, but these assessment tools have limitations. Q&A techniques are subjective and biased towards recent events(at least partly due to patient bias toward present recall, if not also due to patient memory impairment or insufficiency, or a patient's desire to provide positive data). Maximal treadmill exercise tests assesses the patient's ability to perform intense (maximal) exercises and do not reflect the ability to perform normal daily activities. The 6 minute walk test has to be administered very carefully and rigorously to achieve valid results.
Impairment of functional status can be seen in changes in the ability to perform exercises and ADL. This can be affected by many physiological factors such as progressive decompensation in the setting of left ventricular cardiac (LV) dysfunction, beta blocker treatment, symptomatic arrhythmias, and depression. These changes may take place over a long period of time and may be too subtle to be discerned by patients.
Physicians use answers to these questions and observation in clinic to determine what New York Heart Association “class” into which a patient falls, and on this basis, among others, they administer and alter treatment. Class I is defined as “Patients with cardiac disease but without resulting limitation of physical activity. Ordinary physical activity does not cause undue fatigue, palpitation, dyspnea or anginal pain.” NYHA Class II is “Patients with cardiac disease resulting in slight limitation of physical activity. They are comfortable at rest. Ordinary physical activity results in fatigue, palpitation, dyspnea or anginal pain.”, Class III is defined: “Patients with marked limitation of physical activity. They are comfortable at rest. Less than ordinary activity causes fatigue, palpitation, dyspnea, or anginal pain. And, Class IV is “Patients with cardiac disease resulting in inability to carry on any physical activity without discomfort. Symptoms of heart failure or of the anginal syndrome may
Padmanabhan Vasant
Stone Karen A.
Berry Thomas
Kamm William E.
McMahon Beth L.
Medtronic Inc.
Wolde-Michael Girma
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