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Method and apparatus for preventing heart rhythm disturbances by recording cardiac electrical activity, measuring beat-to-beat variability in the morphology of electrocardiographic waveforms, and using the measured beat-to-beat variability to control the delivery of electrical impulses to the heart

Method and apparatus for preventing heart rhythm disturbances by recording cardiac electrical activity, measuring beat-to-beat variability in the morphology of electrocardiographic waveforms, and using the measured beat-to-beat variability to control the delivery of electrical impulses to the heart during the absolute refractory period.

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1. A method of preventing a heart rhythm disturbance comprising: detecting cardiac electrical activity;analyzing the cardiac electrical activity to measure beat-to-beat variability in the morphology of the electrocardiographic waveforms;determining whether the measured beat-to-beat variability excee

1. A method of preventing a heart rhythm disturbance comprising: detecting cardiac electrical activity;analyzing the cardiac electrical activity to measure beat-to-beat variability in the morphology of the electrocardiographic waveforms;determining whether the measured beat-to-beat variability exceeds a threshold used to trigger therapy; anddelivering electrical impulses during the refractory period when the threshold is exceeded. 2. The method of claim 1 wherein the beat-to-beat variability is repolarization alternans. 3. The method of claim 1 further comprising the step of using one or more threshold values in the analyzing step to determine when to initiate the delivering step. 4. The method of claim 1 further comprising the step of detecting and analyzing beat-to-beat variability in arterial blood pressure. 5. The method of claim 1 further comprising the step of detecting and analyzing beat-to-beat variability in instantaneous lung volume. 6. The method of claim 1, wherein the heart rhythm disturbance is a tachyarrhythmia. 7. The method of claim 1, wherein the heart rhythm disturbance is a bradyarrhythmia. 8. The method of claim 1, wherein the detecting step utilizes at least one passive electrode inside the body in the vicinity of the heart. 9. The method of claim 1, wherein the detecting step utilizes at least one passive electrode within the heart. 10. The method of claim 1 further comprising the use of an implanted device in the detecting, analyzing and/or delivering steps. 11. The method of claim 10, wherein the implanted device serves as a cardiac pacemaker or a cardiac cardioverter/defibrillator. 12. The method of claim 10, wherein the implanted device has means for generating electrical stimulating pulses of specified energies and applying the pulses to body tissue at specified times. 13. The method of claim 10, wherein the implanted device has means for generating electrical stimulating pulses of specified amplitudes and durations and applying the pulses to body tissue at specified times. 14. The apparatus of claim 1, wherein the delivered electrical impulses reduce repolarization alternans. 15. The method of claim 1, wherein the electrical impulses are delivered during absolute refractory period on alternate beats. 16. The method of claim 1, wherein the electrical impulses are delivered during absolute refractory period of each beat. 17. The method of claim 1, wherein the delivered electrical impulses alternate in polarity in successive beats. 18. The method of claim 1 wherein the refractory period is the absolute refractory period.