Dual-chamber implantable pacemaker and method of operating same for automatically setting the pacemaker's AV interval as a function of a natural measured conduction time

Claim 3

The method of claim 1 wherein step (a) comprises determining an average AR interval over k cardiac cycles, where k is an integer between 2 and 1024, and wherein step (b) comprises setting the AV interval to be equal to the average AR interval ±Δ.

Claim 4

The method of claim 1 wherein step (c) comprises (1) defining a cardiac cycle; (2) sensing whether an R-wave occurs in the defined cardiac cycle; (3) using as the determined AR interval the AR interval of the defined cardiac cycle when an R-wave occurs therein, (4) in the event an R-wave does not occur in the defined cardiac cycle, defining a subsequent cardiac cycle as one wherein an R-wave does occur, and (5) measuring an AR interval of the subsequent cardiac cycle as the determined AR interval.

Claim 5

The method of claim 3 wherein the step of defining the subsequent cardiac cycle comprises sensing whether an R-wave occurs during each defined cardiac cycle, waiting for at least x consecutive cardiac cycles without an R-wave having been sensed, and then monitoring each cardiac cycle thereafter until an R-wave is sensed, where x is an integer from 4 to 512, the first cardiac cycle during which an R-wave is sensed after waiting at least x cardiac cycles comprising the subsequent cardiac cycle.

Claim 6

The method of claim 1 wherein the pacemaker further has a VA interval that, in sequential combination with the AV interval defines the duration of an A-to-A interval, or pacing cycle, and wherein variations in the determined AR interval cause corresponding variations in the AV interval, and wherein the method further comprises: (e) setting a VA interval of the pacemaker to a value that compensates for the variations in the AV interval in order to assure that the A-to-A interval does not change.

Claim 9

The method of claim 6 further including determining the natural conduction time as set forth in step (b) pursuant to a prescribed schedule that comprises determining the natural conduction time after x cardiac cycles have elapsed, wherein x is an integer of from 4 to 512.

Claim 10

The method of claim 7 wherein step (b) comprises determining whether an R-wave is sensed or not; and, if an R-wave is sensed, measuring the duration of an AR interval that begins with an atrial event and ends with the sensed R-wave, and using the AR interval thus measured as the determined natural conduction time; and; if an R-wave is not sensed, using the duration of a previously measured AR interval of an immediately-preceding cardiac cycle during which an R-wave was sensed as the determined natural conduction time.

Claim 11

The method of claim 8, further including measuring the duration of the AR interval of an immediately preceding cardiac cycle during which an R-wave was sensed as the determined natural conduction time only when x consecutive cardiac cycles have elapsed without sensing an R-wave, where x is an integer between 4 and 512.

Claim 12

The method of claim 6, comprising generating and delivering the V-pulse at a delivery time within the cardiac cycle that is a prescribed amount Δ less than the natural conduction time determined in step (b).

Claim 13

The method of claim 6, wherein the pacemaker further includes means for defining a VA interval and means for generating an atrial stimulation pulse (A-pulse) at the conclusion of the VA interval, wherein the VA interval begins upon the occurrence of a ventricular event and terminates upon the occurrence of an atrial event, and wherein the method also includes: changing the VA interval by an appropriate amount so that the duration between successive A-pulses, comprising an A-to-A interval made up of the interval between an atrial event and the generation of the V-pulse as determined in step (c) plus the VA interval, remains unchanged.

Claim 14

The method of claim 11, wherein the appropriate amount by which the VA interval is changed comprises 1 to 100 msec.

Claim 15

The method of claim 6 wherein the step of determining the natural conduction time comprises measuring the natural conduction time for at least y cardiac cycles, where y is an integer, and computing an average of the natural conduction time measurements thus made, and using such average natural conduction time as the determined natural conduction time.

Claim 16

A dual-chamber pacemaker for controlling ventricular pacing as a function of a natural conduction time of a patient's heart, comprising: an atrial channel comprising means for sensing a natural atrial depolarization (P-wave) and means for generating an atrial stimulation pulse (A-pulse) and delivering the A-pulse to an atrium of the patient's heart; a ventricular channel comprising means for sensing a natural ventricular depolarization (R-wave) and means for generating a ventricular stimulation pulse (V-pulse) and delivering the V-pulse to a ventricle of the patient's heart at the conclusion of an AV interval unless an R-wave is sensed during the AV interval; means for sensing a natural conduction time interval of the patient's heart through the atrial and ventricular channels, the natural conduction time interval comprising the time interval within a given cardiac cycle that commences with atrial activity, where atrial activity comprises either a sensed P-wave or a paced A-pulse, whichever occurs first within the given cardiac cycle, and that terminates upon a sensed R-wave; and timing means for defining the AV interval so that the AV interval commences with atrial activity and terminates at a time within the cardiac cycle that is a function of the natural conduction time.

Claim 17

A dual-chamber pacemaker for controlling ventricular pacing as a function of a natural conduction time of a patient's heart, comprising: an atrial channel comprising means for sensing a natural atrial depolarization (P-wave) and means for generating an atrial stimulation pulse (A-pulse) and delivering the A-pulse to an atrium of the patient's heart; a ventricular channel comprising means for sensing a natural ventricular depolarization (R-wave) and means for generating a ventricular stimulation pulse (V-pulse) and delivering the V-pulse to a ventricle of the patient's heart at the conclusion of an AV interval unless an R-wave is sensed during the AV interval; means for sensing a natural conduction time interval of the patient's heart through the atrial and ventricular channels, the natural conduction time interval comprising the time interval within a given cardiac cycle that commences with atrial activity, where atrial activity comprises either a sensed P-wave or a paced A-pulse, whichever occurs first within the given cardiac cycle, and that terminates upon a sensed R-wave; and timing means for defining the AV interval so that the AV interval commences with atrial activity and terminates at a time within the cardiac cycle that is a function of the natural conduction time.

Claim 18

The dual-chamber pacemaker of claim 14, wherein the timing means includes means for defining said AV interval to be equal to the natural conduction time interval ±Δ, where Δ is a specified amount.

Claim 19

The dual-chamber pacemaker of claim 15, wherein said timing means further includes: means for defining a VA time interval that commences with a V-pulse and terminates with atrial activity, and wherein the AV interval plus the VA interval defines a pacing interval for the pacemaker; and means for altering the VA time interval by an appropriate amount so that the pacing interval remains unchanged.