Rate-responsive pacing method and system employing minimum blood oxygen saturation as a control parameter and as a physical activity indicator
First Claim
1. A method of automatically controlling the rate at which a rate-responsive pacemaker delivers pacing pulses to a patient'"'"'s heart, said method comprising the steps of:
- (a) measuring the oxygen content of blood returning to the right atrium of the patient'"'"'s heart as the blood enters the right atrium before the blood has an opportunity to become thoroughly mixed;
(b) determining the minimum value of blood oxygen content measured in step (a) during a prescribed time period, said prescribed time period including at least a portion of a plurality of consecutive cardiac cycles; and
(c) using the minimum value blood oxygen content determined in step (b) as a direct indicator of the blood oxygen content of the blood returning from body tissue of the patient, undergoing the highest oxygen demand, and hence as an indicator of the need to adjust the pacing rate of said rate-responsive packmaker.
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Accused Products
Abstract
A rate-responsive pacing method and system senses the minimum blood oxygen saturation in the right atrium of a patient'"'"'s heart and uses such minimum blood oxygen saturation as a control parameter for indicating the muscular activity of a patient. Because the oxygen content of the venous blood in the right atrium varies significantly as venous blood from all parts of the body is introduced therein, evidencing differing levels of oxygen demand throughout the patient'"'"'s body, the minimum oxygen content of the venous blood provides an accurate and reliable measure of those portions of the patient'"'"'s body experiencing the greatest oxygen demand, i.e., experiencing muscular activity. A rate-responsive pacing system includes means for sensing the minimum oxygen content in the right atrium over a prescribed time interval, and using such minimum oxygen content as a control parameter for adjusting the rate of the pacemaker.
61 Citations
18 Claims
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1. A method of automatically controlling the rate at which a rate-responsive pacemaker delivers pacing pulses to a patient'"'"'s heart, said method comprising the steps of:
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(a) measuring the oxygen content of blood returning to the right atrium of the patient'"'"'s heart as the blood enters the right atrium before the blood has an opportunity to become thoroughly mixed; (b) determining the minimum value of blood oxygen content measured in step (a) during a prescribed time period, said prescribed time period including at least a portion of a plurality of consecutive cardiac cycles; and (c) using the minimum value blood oxygen content determined in step (b) as a direct indicator of the blood oxygen content of the blood returning from body tissue of the patient, undergoing the highest oxygen demand, and hence as an indicator of the need to adjust the pacing rate of said rate-responsive packmaker. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9)
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10. A method of determining the physical activity level of a patient comprising:
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(a) repeatedly measuring the oxygen content of blood in the right atrium of the patient'"'"'s heart as the blood enters the right atrium before the blood has an opportunity to become thoroughly mixed; (b) monitoring the measurements made in step (a) over a prescribed interval, said prescribed interval including at least a portion of a plurality of consecutive cardiac cycles; (c) ascertaining the minimum blood oxygen content measured during the monitoring interval of step (b); and (d) using the minimum blood oxygen content ascertained in step (c) as a direct indicator of the blood oxygen content of the blood returning from body tissue of the patient undergoing the greatest oxygen demand, and hence as a direct indicator of the body tissue experiencing the most physical exercise, the lower the minimum blood oxygen content the greater the physical activity. - View Dependent Claims (11, 12, 13)
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14. A system for reliably determining the physical activity level of a patient comprising:
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measurement means for repeatedly measuring the oxygen content of blood in the right atrium of the patient'"'"'s heart before the blood has an opportunity to become thoroughly mixed; monitoring means for monitoring the blood oxygen measurements made with said measurement means over a prescribed interval, said prescribed interval including at least a portion of a plurality of consecutive cardiac cycles; and determining means for determining the minimum blood oxygen content measured during said prescribed interval, said minimum blood oxygen content measurement providing a direct indicator of the blood oxygen content of the blood returning from body tissue of the patient undergoing the greatest oxygen demand, and hence a direct indicator of the body tissue experiencing the most physical exercise, the lower the minimum blood oxygen content the greater the physical activity. - View Dependent Claims (15, 16)
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17. A rate-responsive pacing system comprising:
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a blood oxygen sensor, said sensor including light emitting means for emitting light energy from said blood oxygen sensor, and light sensing means for sensing light energy directed to said blood oxygen sensor; a sensor drive circuit for selectively energizing said light energy emitting means and causing said light emitting means to emit light energy; a sensor process circuit for determining the amount of light energy sensed by said light sensing means corresponding to a given amount of light emitted by said light emitting means, and for converting said determined amount of light energy into a first measurement representative of the minimum amount of said light energy sensed during a prescribed interval, said prescribed interval comprising at least a portion of a plurality of consecutive cardiac cycles; rate-responsive pacing means for generating stimulation pulses on demand at a rate controlled by said first measurement; and lead means for delivering said stimulation pulses to a desired heart chamber; said blood oxygen sensor being positioned for emitting and sensing light in the vicinity of venous blood in the right atrium of the heart before said venous blood has an opportunity to become thoroughly mixed; whereby the rate at which said pacing pulses arm provided to said desired heart chamber on demand is determined by the minimum amount of light energy sensed by said blood oxygen sensor during said prescribed interval, which minimum amount of light energy corresponds to the minimum amount of oxygen present in said venous blood during said prescribed interval, and which minimum amount of oxygen provides a direct indication of the blood oxygen in the venous blood returning from the body tissue of the patient undergoing the greatest oxygen demand. - View Dependent Claims (18)
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Specification