Method of vagal stimulation to treat patients suffering from congestive heart failure
First Claim
1. A method of evaluating the cardio-circulatory and ventilatory condition of a human patient suffering from congestive heart failure disorder for delivery of therapy to alleviate the disorder, which comprises the steps of:
- sensing cardiac signals emanating from electrical energy generated by the patient'"'"'s heart as the heart undergoes its cardiac cycle,applying the sensed electrical signals with a dynamic impedance as the sole input to signal detection circuitry to determine the patient'"'"'s thoracic impedance and ventilation therefrom, andstimulating the patient'"'"'s vagus nerve with stimulation pulses in a pattern and at a rate controlled by the determined impedance and ventilation.
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Abstract
An improved method is presented for evaluating the physiological status of a patient diagnosed with congestive heart failure and treating the patient accordingly to alleviate the congestive heart failure. As part of the method, the thoracic or cardiac impedance and ventilation of the particular patient are derived solely from an input consisting of cardiac signals (EKG) generated by electrical energy of the patient'"'"'s heart as the heart is undergoing its cardiac cycle with a dynamic impedance obtained by subjecting the EKG to alternately high and low input impedances. The derived thoracic impedance and ventilation are used to control the pattern and rate at which stimulating electrical pulses are applied to the patient'"'"'s vagus nerve by an implanted stimulator, in a manner to deliver therapy to the patient'"'"'s heart by adjusting the heart rate to a prescribed target rate for alleviating the congestive heart failure. A change in state of the patient from one of rest to one of physical exercise and vice versa detected from the derived impedance and ventilation is accommodated by modifying the vagal stimulation therapy to adjust the patient'"'"'s heart rate to a new target rate accordingly, while continuing to deliver the therapy for alleviating the congestive heart failure. A closed loop system is preferably employed for the control and adjustment functions.
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Citations
22 Claims
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1. A method of evaluating the cardio-circulatory and ventilatory condition of a human patient suffering from congestive heart failure disorder for delivery of therapy to alleviate the disorder, which comprises the steps of:
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sensing cardiac signals emanating from electrical energy generated by the patient'"'"'s heart as the heart undergoes its cardiac cycle, applying the sensed electrical signals with a dynamic impedance as the sole input to signal detection circuitry to determine the patient'"'"'s thoracic impedance and ventilation therefrom, and stimulating the patient'"'"'s vagus nerve with stimulation pulses in a pattern and at a rate controlled by the determined impedance and ventilation. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8)
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9. A method of delivering therapy to a patient suffering from chronic heart failure, said method comprising the steps of:
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applying vagal stimulation to the patient to provide a therapeutic heart rate for said patient, controlling the pattern, timing and frequency of said vagal stimulation according to thoracic impedance and ventilation of the patient, whereby to provide said therapeutic heart rate, and deriving said thoracic impedance and ventilation solely from EKG signals produced by electrical energy generated by the patient'"'"'s heart with intervening dynamic impedance. - View Dependent Claims (10, 11, 12, 13, 14, 15, 16)
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17. A method of evaluating the status of congestion of a patient diagnosed with congestive heart failure and applying vagal stimulation therapy to alleviate the congestive heart failure, said method comprising the steps of:
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deriving the patient'"'"'s thoracic impedance and ventilation solely by processing cardiac signals generated by electrical energy of the patient'"'"'s heart as the heart is undergoing its cardiac cycle while subjecting said cardiac signals to a dynamic input impedance, to assess said status of congestion, and controlling the pattern and frequency of said applied vagal stimulation therapy according to the derived impedance and ventilation to adjust the patient'"'"'s heart rate to a prescribed therapeutic rate. - View Dependent Claims (18, 19, 20, 21, 22)
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Specification