Automatic implantable fibrillation preventer
First Claim
1. Apparatus for stimulating the heart through electrodes adapted to be in contact with heart tissue comprising:
- pulse generating means for generating stimulation pulses at output terminals adapted to be electrically coupled to heart tissue through electrodes;
first sensing means for measuring the current vectors of electrical depolarization signals of the heart and for producing a first electrical signal representative of the measured current vector;
means for establishing a threshold current vector signal;
second sensing means for measuring the concentration of certain extracellular ions in the blood and producing a second electrical signal representative of the measured ionic concentration; and
triggering means responsive to the measured first and second electrical signals and the threshold current vector signals for causing said pulse generating means to provide a stimulating pulse to the heart.
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Abstract
Apparatus and method for sensing the probable onset of ventricular fibrillation or other harmful tachyarrythmias and delivering electrical cardioverting stimulation pulses in response thereto. The sensing of the onset of the harmful tachyarrhythmia is accomplished using two different types of sensors. The first sensing technique utilizes an intracardiac ECG observed within three dimensional space. Directional changes of the current vector within the intracardiac ECG are used to predict the onset of harmful ventricular tachyarrhythmias. The second sensing technique employs a chemically sensitive semiconductor device which measures the level of ionic potassium found within the intracardiac blood. Rapid changes in ionic potassium level are used to predict the onset of detrimental ventricular tachyarrhythmias. An implantable device uses both types of sensors in a programmable fashion to deliver cardioverting electrical stimulation pulses based upon the predicted onset of ventricular fibrillation.
303 Citations
19 Claims
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1. Apparatus for stimulating the heart through electrodes adapted to be in contact with heart tissue comprising:
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pulse generating means for generating stimulation pulses at output terminals adapted to be electrically coupled to heart tissue through electrodes; first sensing means for measuring the current vectors of electrical depolarization signals of the heart and for producing a first electrical signal representative of the measured current vector; means for establishing a threshold current vector signal; second sensing means for measuring the concentration of certain extracellular ions in the blood and producing a second electrical signal representative of the measured ionic concentration; and triggering means responsive to the measured first and second electrical signals and the threshold current vector signals for causing said pulse generating means to provide a stimulating pulse to the heart. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13)
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14. A method of cardioverting the heart comprising the steps of:
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(a) sensing the intracardiac ECG in three dimensional space; (b) deriving a current vector signal for the sensed intracardiac ECG; (c) storing the current vector signal; (d) repeating steps (a) and (b) to derive a current vector rate of change signal; (e) storing a threshold rate of change value; (f) comparing the derived current vector rate of change signal to the threshold rate of change value; (g) generating stimulating pulses to cardiovert the heart whenever the comparison reveals that the derived current vector differs from the threshold rate of change value by a predetermined amount indicative of fibrillation; and (h) applying said pulses to the heart. - View Dependent Claims (15, 16)
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17. Apparatus for cardioverting the heart comprising:
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(a) means for sensing the intracardiac ECG in three dimensional space; (b) means for deriving a current vector signal for the sensed intracardiac ECG; (c) means for deriving a current vector rate of change signal; (d) means for storing a threshold rate of change value; (e) means for comparing the derived current vector rate of change signal to the threshold rate of change value; (f) means for generating stimulating pulses to cardiovert the heart whenever the comparison reveals that the derived current vector differs from the threshold rate of change value by a predetermined amount indicative of fibrillation; and (g) means for applying said pulses to the heart. - View Dependent Claims (18, 19)
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Specification