Atrioventricular conduction guided His-bundle pacing

1. A medical-device system, comprising:

an atrioventricular (AV) conduction monitor circuit configured to detect an indication of a presence or absence of AV conduction abnormality of a heart of a subject; and

a control circuit configured to control an electrostimulation circuit configured to generate His-bundle pacing (HBP) pulses, and to provide a control signal to:

in response to a detected indication of presence of AV conduction abnormality of the heart, deliver HBP pulses at expiration of an atrio-Hisian delay (AHD) to stimulate a physiologic conduction pathway of the heart, sense a ventricular activation during a second atrioventricular delay (AVD), and time delivery of ventricular backup pacing (VBP) at expiration of the second AVD if no ventricular activation is sensed during the second AVD, wherein both the AHD and the second AVD begin at an atrial sensed event or an atrial paced event, and the second AVD is longer than the AHD; and

in response to a detected indication of absence of AV conduction abnormality of the heart, withhold delivery of HBP pulses.

2. The system of claim 1 , including the electrostimulation circuit, wherein, in response to the detected indication of absence of AV conduction abnormality:

the control circuit is configured to sense an intrinsic ventricular activation during a first atrioventricular delay (AVD) that begins at the atrial sensed event or the atrial paced event; and

the electrostimulation circuit is configured to deliver ventricular demand pacing (VDP) at expiration of the first AVD if no intrinsic ventricular activation is sensed during the first AVD.

3. The system of claim 1 , wherein the control circuit is configured to determine a frequency of VBP delivery over a specified time period, and to optimize an HBP configuration for stimulating the physiologic conduction pathway if the determined VBP frequency exceeds a threshold.

4. The system of claim 3 , wherein the control circuit is configured to optimize the HBP configuration including:

verifying a HBP capture status;

extending the second AVD if the HBP capture status is a selective or non-selective His bundle capture; and

adjusting an HBP parameter if the HBP capture status is a para-Hisian capture or a loss of capture.

5. The system of claim 4 , wherein the control circuit is configured to perform a threshold test to determine an HBP threshold, and to adjust the HBP parameter using the determined HBP threshold.

6. The system of claim 4 , wherein adjusting the HBP parameter includes altering a pacing site at the physiologic conduction pathway for delivering the HBP pulses if the HBP capture status is a para-Hisian capture or a loss of capture.

7. The system of claim 3 , wherein the AV conduction monitor circuit is configured to periodically assess AV conduction status if the frequency of VBP falls below the threshold, the assessment including detecting the indication of presence or absence of AV conduction abnormality.

8. The system of claim 1 , wherein:

the AV conduction monitor circuit is configured to detect the indication of presence or absence of AV conduction abnormality using a sensed AV interval (AVI S ) from an atrial sensed event, or a paced AV interval (AVI P ) from an atrial paced event; and

the control circuit is configured to control the electrostimulation circuit to:

in response to an indication of presence of AV conduction abnormality, deliver the HBP pulses at expiration of a sensed atrio-Hisian delay (AHD S ) that begins at the atrial sensed event, or at expiration of a paced atrio-Hisian delay (AHD P ) that begins at the atrial paced event; and

in response to an indication of absence of AV conduction abnormality, withhold delivery of the HBP pulses, and deliver ventricular demand pacing (VDP) at expiration of a sensed atrioventricular delay that begins at the atrial sensed event, or at expiration of a paced atrioventricular delay that begins at the atrial paced event.

9. The system of claim 1 , wherein the AV conduction monitor circuit is configured to detect an AV block pattern, and the control circuit is configured to time the delivery of HBP pulses in accordance with the detected AV block pattern.

10. The system of claim 9 , wherein:

the AV conduction monitor circuit is configured to determine a target AV interval (AVI) corresponding to the detected AV block pattern using a plurality of AV intervals prior to a conduction block to a ventricle of the heart; and

the control circuit is configured to determine an atrio-Hisian delay (AHD) using the target AVI and a His-to-ventricular interval (HVI), and to time the delivery of the HBP pulses at expiration of the determined AHD.

11. The system of claim 10 , wherein the AV block pattern is a Mobitz type I block, and the target AVI is a shortest interval among a plurality of progressively prolonged AV intervals prior to the conduction block to the ventricle.

12. The system of claim 10 , wherein the AV block pattern is a Mobitz type II block, and wherein:

the AV conduction monitor circuit is configured to generate a statistic of conducted beats prior to a conduction block to the ventricle; and

the control circuit is configured to control the electrostimulation circuit to deliver the HBP pulses for a first number of consecutive cardiac cycles followed by withholding the HBP delivery for a second number of cardiac cycles, the first and second numbers each determined using the generated statistic of conducted beats.

13. The system of claim 10 , wherein the control circuit is further configured to determine the second AVD using the target AVI.

14. A method for pacing a physiologic conduction pathway including a His bundle or a bundle branch of a heart, the method comprising:

detecting an indication of presence or absence of AV conduction abnormality;

in response to an indication of presence of AV conduction abnormality, delivering HBP pulses at expiration of an atrio-Hisian delay (AHD) to stimulate the physiologic conduction pathway, sensing a ventricular activation during a second atrioventricular delay (AVD), and delivering ventricular backup pacing (VBP) at expiration of the second AVD if no ventricular activation is sensed during the second AVD, wherein both the AHD and the second AVD begin at an atrial sensed event or an atrial paced event, and the second AVD is longer than the AHD; and

in response to an indication of absence of AV conduction abnormality, withholding delivery of the HBP pulses, and delivering ventricular demand pacing (VDP) at expiration of a first AVD if no intrinsic ventricular activation is sensed during the first AVD.

15. The method of claim 14 , comprising:

determining a frequency of VBP delivery over a specified time period; and

optimizing an HBP configuration for stimulating the physiologic conduction pathway if the determined VBP frequency exceeds a threshold.

16. The method of claim 15 , wherein optimizing the HBP configuration includes:

verifying a HBP capture status;

extending the second AVD if the HBP capture status is a selective or non-selective His bundle capture; and

adjusting an HBP parameter if the HBP capture status is a para-Hisian capture or a loss of capture.

17. The method of claim 16 , wherein adjusting the HBP parameter includes altering a pacing site at the physiologic conduction pathway for delivering the HBP pulses if the HBP capture status is a para-Hisian capture or a loss of capture.

18. The method of claim 14 , comprising:

detecting an AV block pattern; and

delivering the HBP pulses in accordance with the detected AV block pattern.

19. The method of claim 18 , wherein the AV block pattern is a Mobitz type I block, and the method comprising:

determining a target AV interval (AVI) corresponding to a shortest interval among a plurality of progressively prolonged AV intervals prior to a conduction block to a ventricle of the heart;

determining an atrio-Hisian delay (AHD) using the target AVI and a His-to-ventricular interval (HVI); and

delivering the HBP pulses at expiration of the determined AHD.

20. The method of claim 18 , wherein the AV block pattern is a Mobitz type II block, and the method comprising:

generating a statistic of conducted beats prior to a conduction block to a ventricle of the heart; and

delivering the HBP pulses for a first number of consecutive cardiac cycles followed by withholding the HBP delivery for a second number of cardiac cycles, the first and second numbers each determined using the generated statistic of conducted beats.