Capture verification method and apparatus for implantable pacemaker utilizing heart rhythm stability measurements to minimize the likelihood of fusion
First Claim
1. A capture verification method for use with an implantable stimulation device, comprising the steps of:
- (a) operating the implantable stimulation device in a demand mode at a set stimulation pulse energy, the demand mode including sensing a patient'"'"'s cardiac rhythm and inhibiting a stimulation pulse in the presence of an intrinsic cardiac signal;
(b) measuring the stability of the cardiac rhythm;
(c) determining, based on the stability measuring step, a shortened cycle length that is likely to exceed the cardiac rhythm;
(d) adjusting a current pacing cycle length to the shortened cycle length for at least one cardiac cycle; and
(e) in the event the set stimulation pulse is delivered, determining capture threshold at the shortened cycle length.
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Abstract
An implantable pacemaker effectuates a capture verification method that minimizes the expenditure of battery current. A capture verification test is performed only occasionally, on a sampled basis, following delivery of a stimulation pulse. If capture is not verified, a loss of capture response mode is invoked that searches for an appropriate capture threshold, and when found, sets the stimulation energy at a level that is a prescribed safety factor above the capture threshold. All testing for capture is performed only after the heart rhythm has been measured, a short test pacing interval is selected that will be likely to overdrive the native rhythm, and the test pacing pulse delivered is delivered at the shortened interval so that the likelihood of fusion will be minimal.
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Citations
21 Claims
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1. A capture verification method for use with an implantable stimulation device, comprising the steps of:
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(a) operating the implantable stimulation device in a demand mode at a set stimulation pulse energy, the demand mode including sensing a patient'"'"'s cardiac rhythm and inhibiting a stimulation pulse in the presence of an intrinsic cardiac signal; (b) measuring the stability of the cardiac rhythm; (c) determining, based on the stability measuring step, a shortened cycle length that is likely to exceed the cardiac rhythm; (d) adjusting a current pacing cycle length to the shortened cycle length for at least one cardiac cycle; and (e) in the event the set stimulation pulse is delivered, determining capture threshold at the shortened cycle length. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11)
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12. A capture verification method comprising the steps of:
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(a) measuring the stability of a patient'"'"'s intrinsic cardiac rate to ascertain if the intrinsic cardiac rate is within a prescribed limit; (b) providing an electrical stimulation pulse to the heart at a shortened pacing cycle length only when the measuring step (a) indicates that the intrinsic cardiac rate has remained within the prescribed limit; and (c) sensing whether an evoked potential occurs following the electrical stimulation pulse at the shortened pacing cycle length provided in step (b), and if so, verifying that capture did occur. - View Dependent Claims (13, 14)
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15. A method of setting the pulse energy of a stimulation pulse generated by an implantable pacemaker that minimizes the expenditure of battery current, comprising the steps of:
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activating a capture verification test only occasionally, on a sampled basis, after verifying that a stable cardiac rhythm exists; and invoking a loss of capture response mode if the capture verification test determines that capture is lost, the loss of capture response mode including; searching for an appropriate capture threshold; and when capture threshold is found, setting a stimulation energy of a stimulation pulse of the implantable pacemaker at a level that is a prescribed safety factor above the capture threshold. - View Dependent Claims (16, 17, 18)
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19. An implantable stimulation device for maintaining a desired cardiac rhythm, comprising:
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timing means for defining a pacing interval, the pacing interval setting the lowest desired cardiac rhythm; pulse generating means for generating a stimulation pulse having a selectable pulse energy at the conclusion of the pacing interval; sensing means for sensing a cardiac depolarization corresponding to a contraction of cardiac muscle tissue; control means, coupled to the timing means, pulse generating means and sensing means, for inhibiting the pulse generating means and thereby preventing the stimulation pulse from being generated whenever the sensing means senses a natural cardiac depolarization before the end of the pacing interval, the control means further including; program means for operating the pacemaker at a set stimulation pulse energy for a first period of time so as to establish the desired cardiac rhythm, the first period of time including a multiplicity of cardiac cycles; verifying means for verifying, after the first period of time has elapsed, whether the cardiac rhythm is stable; capture verification means for verifying, once the cardiac rhythm is stable, whether the set stimulation pulse energy achieves capture; capture threshold measuring means for measuring the capture threshold in the event the capture verification means determines that the set stimulation pulse energy does not achieve capture; and pulse-energy setting means for automatically setting the pulse energy of the stimulation pulse at a level that is above the measured capture threshold by a prescribed safety factor; whereby capture is verified by the pacemaker only after the first period of time has elapsed, and thus only after a multiplicity of cardiac cycles have occurred, and then only when the cardiac rhythm is stable. - View Dependent Claims (20, 21)
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Specification