Techniques for prevention of atrial fibrillation

• US 20070179543A1
• Filed: 01/24/2007
• Published: 08/02/2007
• Est. Priority Date: 05/23/2002
• Status: Active Grant

• Current Assignee: Medtronic Incorporated (Medtronic Plc)
• Original Assignee: BioControl Medical (B.C.M) Ltd.
• Inventors: Cohen, Ehud, Ben-David, Tamir, Ben-Ezra, Omry
• Granted Patent: US 8,204,591 B2
• Time in Patent Office: Days
• US Class Current: 607/14
• CPC Class Codes: A61N 1/0556 Cuff electrodes
• CPC Class Codes: A61N 1/36114 Cardiac control, e.g. by vagal stimulation stimulating the heart A61N1/362
• CPC Class Codes: A61N 1/36117 for treating hypertension
• CPC Class Codes: A61N 1/3621 for treating or preventing abnormally high heart rate
• CPC Class Codes: A61N 1/395 for treating atrial fibrillation
• CPC Class Codes: A61N 1/3962 in combination with another heart therapy
• CPC Class Codes: A61N 1/39622 Pacing therapy

Abstract

A method is provided, including identifying that a subject is at risk of suffering from atrial fibrillation (AF). Responsively to the identifying, a risk of an occurrence of an episode of the AF is reduced by applying an electrical current to a site of the subject selected from the group consisting of: a vagus nerve, a sinoatrial (SA) node fat pad, a pulmonary vein, a carotid artery, a carotid sinus, a coronary sinus, a vena cava vein, a jugular vein, an azygos vein, an innominate vein, and a subclavian vein, and configuring the current to stimulate autonomic nervous tissue in the site. Other embodiments are also described.

Claims

1. A method comprising:

identifying that a subject is at risk of suffering from atrial fibrillation (AF); and

responsively to the identifying, reducing a risk of an occurrence of an episode of the AF by;

applying an electrical current to a site of the subject selected from the group consisting of;

a vagus nerve, a sinoatrial (SA) node fat pad, a pulmonary vein, a carotid artery, a carotid sinus, a coronary sinus, a vena cava vein, a jugular vein, an azygos vein, an innominate vein, and a subclavian vein, and

configuring the current to stimulate autonomic nervous tissue in the site.

2. The method according to claim 1, wherein applying the current comprises applying the current even in the absence of a prediction of an imminent episode of the AF.

3. The method according to claim 1, wherein applying the current comprises applying the current in the absence of a prediction of an imminent episode of the AF.

4. The method according to claim 1, wherein applying the current comprises detecting normal sinus rhythm (NSR) of the subject, and applying the current during the detected NSR.

8. The method according to claim 1, wherein identifying comprises identifying, after the subject has suffered from at least one episode of the AF, that the subject is at risk.

11. The method according to claim 1, wherein applying the current comprises configuring the current to delay electrical remodeling of an atrium of the subject.

13. The method according to claim 1, wherein applying the current comprises configuring the current to induce rhythmic vagal activity.

15. The method according to claim 1, wherein applying the current comprises:

applying, during stimulation periods that alternate with rest periods, the current during “

on”

periods that alternate with low stimulation periods, the “

on”

periods having on average an “

on”

duration equal to at least 1 second, and the low stimulation periods having on average a low stimulation duration equal to at least 50% of the “

on”

duration;

setting the current applied on average during the low stimulation periods to be less than 20% of the current applied on average during the “

on”

periods;

setting the current applied on average during the rest periods to be less than 20% of the current applied on average during the “

on”

periods; and

setting the rest periods to have on average a rest period duration equal to at least a cycle duration that equals a duration of a single “

on”

period plus a duration of a single low stimulation period, and the stimulation periods to have on average a stimulation period duration equal to at least five times the rest period duration.

19. The method according to claim 1, wherein applying the current comprises detecting whether applying the current causes one or more cardiac contractions, and responsively to finding that applying the current causes the contractions, reducing a strength of the current to a level insufficient to cause the contractions.

20. The method according to claim 1, wherein applying the current comprises applying the current at least once during each of seven consecutive 48-hour periods.

24. The method according to claim 1, wherein the site includes the vagus nerve, and wherein applying the current comprises applying the current to the vagus nerve, and configuring the current to induce propagation of efferent action potentials traveling towards a heart of the subject, and to suppress artificially-induced afferent action potentials traveling towards a brain of the subject.

27. The method according to claim 1, wherein applying the current comprises configuring the current so as to minimize an effect of the applying of the current on a heart rate of the subject.

29. The method according to claim 1, wherein applying the current comprises:

applying the current at a first strength on average;

sensing the occurrence of the episode of the AF; and

responsively to the sensing, applying the current at a second strength on average during a strength reduction period having a duration of at least one minute, which second strength is less than the first strength.

30. The method according to claim 29, wherein applying the current at the second strength comprises withholding applying the current.

37. The method according to claim 1, wherein applying the current comprises applying the current in a series of bursts, each of which bursts includes one or more pulses.

38. The method according to claim 37, wherein the series of bursts includes at least first and second bursts, the first burst including a plurality of the pulses, and the second burst including at least one of the pulses, and wherein applying the current comprises setting (a) a pulse repetition interval (PRI) of the first burst to be on average at least 20 ms, (b) an interburst interval between initiation of the first burst and initiation of the second burst to be less than 10 seconds, (c) an interburst gap between a conclusion of the first burst and the initiation of the second burst to have a duration greater than the average PRI, and (d) a burst duration of the first burst to be less than a percentage of the interburst interval, the percentage being less than 67%.

40. The method according to claim 37, wherein applying the current comprises synchronizing at least a portion of the bursts with a feature of a cardiac cycle of the subject.

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47. Apparatus comprising:

an electrode device, configured to be coupled to a site of the subject at risk of suffering from atrial fibrillation (AF), the site selected from the group consisting of;

a vagus nerve, a sinoatrial (SA) node fat pad, a pulmonary vein, a carotid artery, a carotid sinus, a coronary sinus, a vena cava vein, a jugular vein, an azygos vein, an innominate vein, and a subclavian vein; and

a control unit, configured to reduce a risk of an occurrence of an episode of the AF by;

driving the electrode device to apply an electrical current to the site, and

configuring the current to stimulate autonomic nervous tissue in the site.

48. The apparatus according to claim 47, wherein the control unit is configured to apply the current even in the absence of a prediction by the control unit of an imminent episode of the AF.

49. The apparatus according to claim 47, wherein the control unit is configured to apply the current in the absence of a prediction by the control unit of an imminent episode of the AF.

50. The apparatus according to claim 47, wherein the control unit is configured to detect normal sinus rhythm (NSR) of the subject, and to drive the electrode device to apply the current during the detected NSR.

52. The apparatus according to claim 47, wherein the control unit is configured to configure the current to delay electrical remodeling of an atrium of the subject.

54. The apparatus according to claim 47, wherein the control unit is configured to configure the current to induce rhythmic vagal activity.

55. The apparatus according to claim 47, wherein the control unit is configured to:

drive the electrode device, during stimulation periods that alternate with rest periods, to apply the current during “

on”

periods that alternate with low stimulation periods, the “

on”

periods having on average an “

on”

duration equal to at least 1 second, and the low stimulation periods having on average a low stimulation duration equal to at least 50% of the “

on”

duration,

set the current applied on average during the low stimulation periods to be less than 20% of the current applied on average during the “

on”

periods,

set the current applied on average during the rest periods to be less than 20% of the current applied on average during the “

on”

periods, and

set the rest periods to have on average a rest period duration equal to at least a cycle duration that equals a duration of a single “

on”

period plus a duration of a single low stimulation period, and the stimulation periods to have on average a stimulation period duration equal to at least five times the rest period duration.

58. The apparatus according to claim 47, comprising a sensing unit configured to detect whether applying the current causes one or more cardiac contractions, and wherein the control unit is configured, responsively to finding that applying the current causes the contractions, to reduce a strength of the current to a level insufficient to cause the contractions.

59. The apparatus according to claim 47, wherein the control unit is configured to drive the electrode device to apply the current at least once during each of seven consecutive 48-hour periods.

63. The apparatus according to claim 47, wherein the site includes the vagus nerve, wherein the electrode device is configured to be coupled to the vagus nerve, and wherein the control unit is configured to configure the current to induce propagation of efferent action potentials traveling towards a heart of the subject, and suppress artificially-induced afferent action potentials traveling towards a brain of the subject.

66. The apparatus according to claim 47, wherein the control unit is configured to configure the current so as to minimize an effect of the applying of the current on a heart rate of the subject.

68. The apparatus according to claim 47, wherein the control unit is configured to:

apply the current at a first strength on average,

sense the occurrence of the episode of the AF, and

responsively to the sensing, apply the current at a second strength on average during a strength reduction period having a duration of at least one minute, which second strength is less than the first strength.

69. The apparatus according to claim 68, wherein the control unit is configured to apply the current at the second strength by withholding applying the current.

73. The apparatus according to claim 47, wherein the control unit is configured to apply the current in a series of bursts, each of which bursts includes one or more pulses.

74. The apparatus according to claim 73, wherein the series of bursts includes at least first and second bursts, the first burst including a plurality of the pulses, and the second burst including at least one of the pulses, and wherein the control unit is configured to set (a) a pulse repetition interval (PRI) of the first burst to be on average at least 20 ms, (b) an interburst interval between initiation of the first burst and initiation of the second burst to be less than 10 seconds, (c) an interburst gap between a conclusion of the first burst and the initiation of the second burst to have a duration greater than the average PRI, and (d) a burst duration of the first burst to be less than a percentage of the interburst interval, the percentage being less than 67%.

76. The apparatus according to claim 73, wherein the control unit is configured to synchronize at least a portion of the bursts with a feature of a cardiac cycle of the subject.

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175. A method comprising:

applying an electrical current, at a first strength on average, to a site of a subject containing parasympathetic nervous tissue;

configuring the current to stimulate the nervous tissue in the site;

performing at least one action selected from the group consisting of;

sensing an occurrence of an episode of atrial fibrillation (AF), and predicting an imminent episode of the AF; and

responsively to the performing, applying the current at a second strength on average during a strength reduction period having a duration of at least one minute, which second strength is less than the first strength.

179. The method according to claim 175, comprising, upon a conclusion of the strength reduction period, configuring the current to reduce a heart rate of the subject, upon sensing that the episode of the AF has not terminated and that the subject has an elevated heart rate.

180. The method according to claim 175, wherein applying the current at the second strength comprises withholding applying the current.

183. The method according to claim 175, wherein applying the current at the first strength comprises applying the current at the first strength at least once during each of seven consecutive 48-hour periods.

191. The method according to claim 175, wherein applying the current at the first strength comprises:

applying, during stimulation periods that alternate with rest periods, the current during “

on”

periods that alternate with low stimulation periods, the “

on”

periods having on average an “

on”

duration equal to at least 1 second, and the low stimulation periods having on average a low stimulation duration equal to at least 50% of the “

on”

duration;

setting the current applied on average during the low stimulation periods to be less than 20% of the current applied on average during the “

on”

periods;

setting the current applied on average during the rest periods to be less than 20% of the current applied on average during the “

on”

periods; and

setting the rest periods to have on average a rest period duration equal to at least a cycle duration that equals a duration of a single “

on”

period plus a duration of a single low stimulation period, and the stimulation periods to have on average a stimulation period duration equal to at least five times the rest period duration.

195. The method according to claim 175, wherein applying the current at the first strength comprises configuring the current so as to minimize an effect of the applying of the current on a heart rate of the subject.

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203. Apparatus comprising:

an electrode device, configured to be coupled to a site of the subject at risk of suffering from atrial fibrillation (AF), the site containing parasympathetic nervous; and

a control unit, configured to;

drive the electrode device to apply an electrical current to the site at a first strength on average,

configure the current to stimulate the nervous tissue in the site,

perform at least one action selected from the group consisting of;

sensing an occurrence of an episode of atrial fibrillation (AF), and predicting an imminent episode of the AF, and

responsively to the performance, apply the current at a second strength on average during a strength reduction period having a duration of at least one minute, which second strength is less than the first strength.

207. The apparatus according to claim 203, wherein the control unit is configured to, upon a conclusion of the strength reduction period, configure the current to reduce a heart rate of the subject, upon sensing that the episode of the AF has not terminated and that the subject has an elevated heart rate.

208. The apparatus according to claim 203, wherein the control unit is configured to apply the current at the second strength by withholding applying the current.

211. The apparatus according to claim 203, wherein the control unit is configured to apply the current at the first strength at least once during each of seven consecutive 48-hour periods.

216. The apparatus according to claim 203, wherein the control unit is configured to:

drive the electrode device, during stimulation periods that alternate with rest periods, to apply the current at the first strength during “

on”

periods that alternate with low stimulation periods, the “

on”

periods having on average an “

on”

duration equal to at least 1 second, and the low stimulation periods having on average a low stimulation duration equal to at least 50% of the “

on”

duration,

set the current applied on average during the low stimulation periods to be less than 20% of the current applied on average during the “

on”

periods,

set the current applied on average during the rest periods to be less than 20% of the current applied on average during the “

on”

periods, and

set the rest periods to have on average a rest period duration equal to at least a cycle duration that equals a duration of a single “

on”

period plus a duration of a single low stimulation period, and the stimulation periods to have on average a stimulation period duration equal to at least five times the rest period duration.

220. The apparatus according to claim 203, wherein the control unit is configured to configure the current so as to minimize an effect of the applying of the current on a heart rate of the subject.

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