Apparatus and method for analyzing patient tolerance to a stimulation mode favoring a spontaneous atrioventricular conduction

1. An active implantable medical device for stimulation, resynchronization and/or defibrillation of a patient, comprising:

means for detecting spontaneous atrial and ventricular events;

means for delivering ventricular and atrial stimulation;

means for detecting spontaneous ventricular depolarization after an atrial pacing;

means for measuring an atrioventricular delay between the atrial pacing and the corresponding ventricular depolarization;

means for operating the device in a dual chamber mode with ventricular sensing and ventricular pacing in the absence of spontaneous ventricular depolarization detected after an atrioventricular delay;

means for mode switching, to control conditionally, according to a predetermined criteria, the switching of the device between a dual chamber mode and a pacing mode favoring a spontaneous atrioventricular conduction;

a hemodynamic sensor having an output signal;

means for deriving from the output signal a hemodynamic index representative of a patient's tolerance to the atrioventricular delay, wherein the means for deriving utilizes output data from the hemodynamic sensor associated with a single cardiac cycle to derive the hemodynamic index, wherein the means for deriving the hemodynamic index is configured to derive the hemodynamic index when the atrioventricular delay exceeds a threshold value; and

means for inhibiting or forcing said conditional switching of the device to the dual chamber mode based on said hemodynamic index derived from the output data from the hemodynamic sensor associated with the single cardiac cycle.

2. The device of claim 1 , wherein the pacing mode favoring the spontaneous atrioventricular conduction to the dual chamber mode comprises an AAI mode having a ventricular detection.

3. The device of claim 1 , wherein the pacing mode favoring the spontaneous atrioventricular conduction to the dual chamber mode is one of a DDD mode and a biventricular mode having hysteresis of the atrioventricular delay.

4. The device of claim 1 , further comprising means for diagnosing an occurrence of an atrioventricular block, wherein the means for inhibiting or forcing said conditional switching of the device to the dual chamber mode is selectively activated in the absence of atrioventricular block proved by the means for diagnosing.

5. The device of claim 1 , further comprising:

means for evaluating a current value of an interval between the atrial pacing and the consecutive spontaneous ventricular depolarization; and means for comparing said current value of the interval to the threshold value, wherein the means for inhibiting or forcing the conditional switching of the device to the dual chamber mode is selectively activated in response to the current value of the interval being greater than the threshold value.

6. The device of claim 5 , wherein the threshold value comprises a variable threshold, depending on the heart rate of the patient, and the device further comprising means for dynamically reducing the value of the variable threshold when the current heart rate is increased.

7. The device of claim 1 , further comprising means for detecting of a state of patient effort, wherein the means for inhibiting or forcing of the conditional switching of the device to the dual chamber mode further comprises means for forcing a switch to the dual chamber mode, and inhibiting a return back to the pacing mode favoring the spontaneous atrioventricular conduction until the device detects a state of patient effort.

8. The device of claim 1 , wherein the means for inhibiting or forcing the conditional switching of the device to the dual chamber mode further comprises means for comparing the current value of the hemodynamic index to a reference hemodynamic index, wherein the means for forcing switches the device to the dual chamber mode when the current value of the hemodynamic index is less than the reference hemodynamic index.

9. The device of claim 8 , wherein the value of the reference hemodynamic index is a variable value depending on the heart rate of the patient, and the device further comprises means for dynamically increasing the value of the reference hemodynamic index when the current heart rate is increased.

10. The device of claim 9 , wherein the value of the reference hemodynamic index is a variable value between a minimum limit and a maximum limit, and the device further comprises means for dynamically updating said minimum and maximum limits.

11. The device of claim 8 , further comprising:

means for determining an occurrence of a permanent atrioventricular block, and

means for forcing the reference hemodynamic index to a value independent of the heart rate in the presence of a determined permanent atrioventricular block.

12. The device of claim 1 , wherein the hemodynamic sensor further comprises a sensor selected from among the group consisting of an endocardial acceleration sensor, an epicardial acceleration sensor, a myocardium wall motion sensor, an intracardiac pressure sensor, an intracardiac bioimpedance sensor, an optical sensor measuring oxygen saturation, and a sensor for measuring a change in volume by ultrasounds.

13. The device of claim 12 , wherein the hemodynamic sensor is a hemodynamic endocardial acceleration sensor, delivering the output signal representative of the movements produced by the cyclical contractions of the myocardium.

14. The device of claim 13 , further comprising:

means for recognizing and isolating in the output signal a component corresponding to a peak endocardial acceleration associated with a ventricular contraction, and means for deriving said hemodynamic index from said component.

15. The device of claim 13 , further comprising:

means for recognizing and isolating in the output signal delivered by the hemodynamic sensor at least two components corresponding to two respective peaks of endocardial acceleration associated with the ventricular contraction, and

means for deriving said hemodynamic index from a time interval separating the at least two components.

16. The device of claim 1 , wherein said dual chamber mode comprises a DDD mode.

17. The device of claim 1 , wherein said dual chamber mode comprises a biventricular mode.

18. The device of claim 1 , wherein:

said hemodynamic sensor comprises a hemodynamic endocardial acceleration sensor;

said output signal is representative of movements produced by cyclical contractions of a myocardium;

said means for deriving from the output signal a hemodynamic index is configured to derive said hemodynamic index from a component in the output signal corresponding to a peak endocardial acceleration associated with a ventricular contraction; and

said means for inhibiting or forcing said conditional switching of the device to the dual chamber mode is configured to determine whether to place the device in the dual chamber mode based on the hemodynamic index derived from the component in the output signal corresponding to the peak endocardial acceleration associated with the ventricular contraction.

19. An implantable medical device comprising:

a hemodynamic sensor configured to generate an output signal, wherein the hemodynamic sensor comprises an electronic sensor configured to measure a value representative of a property of at least one of heart tissue and blood flowing through a heart or blood vessels proximate to the heart; and

one or more circuits configured to:

switch the implantable medical device between a single chamber mode and a dual chamber mode, wherein, in the single chamber mode, the one or more circuits are configured to stimulate the atrium and prompt spontaneous atrioventricular conduction, and wherein, in the dual chamber mode, the one or more circuits are configured to stimulate the ventricle in the absence of spontaneous ventricular depolarization detected after an atrioventricular delay,

measure the atrioventricular delay between an atrial pacing event and a spontaneous ventricular depolarization after the atrial pacing event,

determine whether the atrioventricular delay exceeds a threshold atrioventricular delay,

in response to the atrioventricular delay exceeding the threshold atrioventricular delay:

derive from the output signal of the hemodynamic sensor a hemodynamic index representative of a patient's tolerance to the atrioventricular delay that exceeds the threshold atrioventricular delay, and

determine whether to activate or deactivate the dual chamber mode based on the hemodynamic index.

20. The device of claim 19 , wherein the single chamber mode comprises an AAI mode having a ventricular detection.

21. The device of claim 19 , wherein the hemodynamic sensor is configured to measure one or more of an endocardial acceleration value, an epicardial acceleration value, a myocardium wall motion value, an intracardiac pressure value, an intracardiac bioimpedance value, an oxygen saturation value, or a volume change value.

22. An implantable medical device comprising:

a hemodynamic sensor configured to generate an output signal; and

one or more circuits configured to:

switch the implantable medical device between a single chamber mode and a dual chamber mode, wherein, in the single chamber mode, the one or more circuits are configured to stimulate the atrium and prompt spontaneous atrioventricular conduction, and wherein, in the dual chamber mode, the one or more circuits are configured to stimulate the ventricle in the absence of spontaneous ventricular depolarization detected after an atrioventricular delay,

determine, over a plurality of atrial events, whether an amount of atrial events that are not followed by a detected ventricular event exceeds a threshold,

in response to the number of atrial events that are not followed by a detected ventricular event exceeding the threshold, activate the dual chamber mode,

in response to the number of atrial events that are not followed by a detected ventricular event not exceeding the threshold, determine whether to activate or deactivate the dual chamber mode using the hemodynamic sensor by:

deriving from the output signal of the hemodynamic sensor a hemodynamic index representative of a patient's tolerance to the atrioventricular delay when the atrioventricular delay exceeds a threshold value, and

determining whether to activate or deactivate the dual chamber mode based on the hemodynamic index.