Method for low-voltage termination of cardiac arrhythmias by effectively unpinning anatomical reentries
A method for extinguishing a cardiac arrhythmia utilizes destructive interference of the passing of the reentry wave tip of an anatomical reentry through a depolarized region created by a relatively low voltage electric field in such a way as to effectively unpin the anatomical reentry. Preferably, the relatively low voltage electric field is defined by at least one unpinning shock(s) that are lower than an expected lower limit of vulnerability as established, for example, by a defibrillation threshold test. By understanding the physics of the electric field distribution between cardiac cells, the method permits the delivery of an electric field sufficient to unpin the core of the anatomical reentry, whether the precise or estimated location of the reentry is known or unknown and without the risk of inducting ventricular fibrillation. A number of embodiments for performing the method are disclosed.
1. An apparatus for treating a cardiac arrhythmia, the apparatus including programmably operable circuitry to detect a ventricular tachycardia event in a heart of a patient and to generate electrical shocks to be delivered to a plurality of electrodes, the improvement comprising:
in response to detecting a ventricular tachycardia event, the apparatus is configured to automatically deliver at least one pulse to the patient to generate a relatively low voltage field that creates a depolarized region in the heart which extinguishes the cardiac arrhythmia by destructive interference with a reentry wave tip of an anatomical reentry associated with the cardiac arrhythmia that is passing through the depolarized region so as to effectively unpin the anatomical reentry and/or destructively destabilize a functional reentry,
wherein the at least one pulse has an energy that is substantially the same as conventional anti-tachy pacing pulses or lower than an expected lower limit of vulnerability of the patient such that the relatively low voltage field created by the at least one pulse is sufficient to unpin the anatomical reentry from a location in the heart at a core of the anatomical reentry and/or destructively destabilize a functional reentry without creating a risk of inducing ventricular fibrillation.
2. The apparatus of claim 1 , wherein the at least one pulse terminates a ventricular tachycardia without inducing the ventricular fibrillation.
3. The apparatus of claim 1 , wherein the low voltage field has a voltage gradient within the heart of the patient of less than 4.5 V/cm and more than 0.25 V/cm.
4. The apparatus of claim 1 , wherein the apparatus is further configured to deliver an anti-repinning pulse (ARP) after the at least one pulse.
5. The apparatus of claim 4 , wherein the ARP is delivered immediately following the at least one pulse.
6. The apparatus of claim 4 , wherein the ARP is delivered as near-field electrical stimulation.
7. The apparatus of claim 4 , wherein the ARP is delivered as far-field electrical stimulation pulses.
8. The apparatus of claim 1 , wherein the apparatus is further configured to:
detect an electrical waveform;
record a maximum negative derivative of the electrical waveform; and
determine a threshold voltage based on the maximum negative derivative.
9. The apparatus of claim 8 , wherein the apparatus is further configured to deliver the pulse during a period of reentry when the maximum negative derivative exceeds the threshold voltage.
10. The apparatus of claim 1 , wherein the apparatus is further configured to establish a termination window.
11. The apparatus of claim 10 , wherein the at least one pulse is delivered within the termination window.
12. The apparatus of claim 1 , wherein the at least one pulse includes multiple shocks delivered to present alternative wave fronts to the anatomical reentry.
13. The apparatus of claim 12 , wherein the multiple shocks are delivered over different electrode paths to produce an equivalent of a vector rotating field to the anatomical reentry.
14. The apparatus of claim 12 , wherein the apparatus is further configured to establish a termination window.
15. The apparatus of claim 14 , wherein the multiple shocks are delivered over the termination window.
16. The apparatus of claim 14 , wherein the termination window is about 100-150 ms.
17. The apparatus of claim 1 , wherein the apparatus is further configured to determine whether the at least one pulse was delivered within a pre-set safety time period.
18. The apparatus of claim 17 , wherein the apparatus is further configured to deliver a defibrillation shock at the time of expiration of the pre-set safety time period if the at least one pulse was not delivered within the pre-set safety time period.
19. The apparatus of claim 1 , wherein the apparatus is further configured to determine whether the anatomical reentry was terminated.
20. The apparatus of claim 19 , wherein the apparatus is further configured to deliver a defibrillation shock at the time of expiration of the pre-set safety time period if the anatomical reentry was not terminated.