Cardiac sensing by implantable medical devices during magnetic resonance imaging
First Claim
1. A method of determining a heart rate from a physiological electrical signal received in an implantable medical device, the method comprising:
- (i) receiving an input associated with the presence of an environment that tends to cause corruption of a physiological electrical signal; and
(ii) initiating a mode of operation for reducing corruption of the physiological electrical signal, the mode of operation comprising(a) providing a high and a low bandwidth amplifier in an implantable medical device, wherein the high bandwidth amplifier has a bandwidth of at least 4 kHz and the low bandwidth amplifier has a bandwidth equal no greater than 1 kHz;
(b) providing a switch configured to select between the high bandwidth and low bandwidth amplifiers, wherein the switch is switched to utilize the high bandwidth amplifier if corruption of the physiological electrical signal is detected;
(c) amplifying the physiological electrical signal with the selected amplifier;
(d) sampling the amplified physiological electrical signal at a sampling frequency of at least 8 kHz to obtain a first sequence of samples;
(e) processing the first sequence of samples to identify a superposed signal artifact characteristic of MRI interference;
(f) reducing the superposed signal artifact from the first sequence of samples to form a second sequence of samples; and
(g) processing the second sequence of samples to identify the timing of heart contractions.
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Accused Products
Abstract
Embodiments of the invention can include a method for reducing MRI interference from a physiological electrical signal received in an implantable medical device. The method can include the steps of amplifying the physiological electrical signal with a high bandwidth amplifier and sampling the amplified physiological electrical signal at a sampling frequency of at least 8 kHz to obtain a first high-frequency sequence of samples. The method can further includes the steps of processing the first high-frequency sequence of samples to identify a signal artifact that is characteristic of MRI interference and creating a second high-frequency sequence of samples by reducing the signal artifact characteristic of MRI interference from the first sequence of samples. Embodiments can also include a method of determining a heart rate from a physiological electrical signal received in an implantable medical device. Embodiments can also includes an implantable medical device that receives and processes a physiological electrical signal. Other embodiments are also described herein.
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Citations
22 Claims
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1. A method of determining a heart rate from a physiological electrical signal received in an implantable medical device, the method comprising:
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(i) receiving an input associated with the presence of an environment that tends to cause corruption of a physiological electrical signal; and (ii) initiating a mode of operation for reducing corruption of the physiological electrical signal, the mode of operation comprising (a) providing a high and a low bandwidth amplifier in an implantable medical device, wherein the high bandwidth amplifier has a bandwidth of at least 4 kHz and the low bandwidth amplifier has a bandwidth equal no greater than 1 kHz; (b) providing a switch configured to select between the high bandwidth and low bandwidth amplifiers, wherein the switch is switched to utilize the high bandwidth amplifier if corruption of the physiological electrical signal is detected; (c) amplifying the physiological electrical signal with the selected amplifier; (d) sampling the amplified physiological electrical signal at a sampling frequency of at least 8 kHz to obtain a first sequence of samples; (e) processing the first sequence of samples to identify a superposed signal artifact characteristic of MRI interference; (f) reducing the superposed signal artifact from the first sequence of samples to form a second sequence of samples; and (g) processing the second sequence of samples to identify the timing of heart contractions. - View Dependent Claims (2, 3, 4, 5, 6)
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7. A method for reducing MRI interference from a physiological electrical signal received in an implantable medical device, the method comprising:
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providing a high and a low bandwidth amplifier in an implantable medical device, wherein the high bandwidth amplifier has a bandwidth of at least 4 kHz and the low bandwidth amplifier has a bandwidth equal no greater than 1 kHz; providing a switch configured to select between the high bandwidth and low bandwidth amplifiers, wherein the switch is switched to utilize the high bandwidth amplifier if corruption of the physiological electrical signal is detected; amplifying the physiological electrical signal with the selected amplifier; sampling the amplified physiological electrical signal at a sampling frequency of at least 8 kHz to obtain a first sequence of samples; processing the first sequence of samples to identify a signal artifact characteristic of MRI interference; and creating a second sequence of samples by reducing the signal artifact characteristic of MRI interference from the first sequence of samples, the second sequence continuous in time. - View Dependent Claims (8, 9, 10, 11, 12, 13, 14)
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15. A method of calculating a heart rate from a physiological electrical signal received in an implantable medical device, the method comprising:
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providing a high and a low bandwidth amplifier in an implantable medical device, wherein the high bandwidth amplifier has a bandwidth of at least 4 kHz and the low bandwidth amplifier has a bandwidth equal no greater than 1 kHz; providing a switch configured to select between the high bandwidth and low bandwidth amplifiers, wherein the switch is switched to utilize the high bandwidth amplifier if corruption of the physiological electrical signal is detected; amplifying the physiological electrical signal with the selected amplifier; sampling the amplified physiological electrical signal at a sampling frequency of at least 8 kHz to obtain a first sequence of samples; processing the first sequence of samples to identify a superposed signal artifact characteristic of MRI interference; reducing the superposed signal artifact from the first sequence of samples to form a second sequence of samples; and processing the second sequence of samples to identify the timing of heart contractions. - View Dependent Claims (16, 17, 18, 19, 20, 21)
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22. An implantable medical device that receives and processes a physiological electrical signal, the implantable medical device comprising:
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(i) a conductor for transmitting the physiological electrical signal from body tissue to the implantable medical device; (ii) physiological signal processing circuitry for identifying heart contractions from the physiological electrical signal, the signal processing circuitry including; (a) a first amplifier for amplifying the physiological electrical signal received from the conductor having a bandwidth of at least 4 kHz; (b) a first analog to digital converter for sampling the amplified physiological electrical signal at a sampling frequency of at least 8 kHz to obtain a first sequence of samples; (c) a digital signal processor configured to process the first sequence of samples to identify a superposed signal artifact characteristic of MRI interference and further configured to reduce the superposed signal artifact from the first sequence of samples to form a second sequence of samples; and (d) cardiac activity detection circuitry configured to process the second sequence of samples to identify heart contractions; (iii) a sensor configured to detect the presence of an environment that tends to cause corruption of a physiological electrical signal; (iv) a second amplifier for amplifying the physiological electrical signal received from the conductor; (v) a second analog to digital converter for sampling the amplified physiological electrical signal from the second amplifier at a sampling frequency less than about 1 kHz; and (vi) a switch to selectively couple either the first analog to digital converter or the second analog to digital converter to the digital signal processor, where the switch is configured to couple the first analog to digital converter to the digital signal processor in response to the detection of the presence of an environment that tends to cause corruption of a physiological electrical signal.
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Specification