Surgery: light – thermal – and electrical application – Light – thermal – and electrical application – Electrical therapeutic systems
Reexamination Certificate
1999-06-22
2001-09-18
Kamm, William E. (Department: 3762)
Surgery: light, thermal, and electrical application
Light, thermal, and electrical application
Electrical therapeutic systems
Reexamination Certificate
active
06292694
ABSTRACT:
FIELD OF THE INVENTION
The present invention is generally directed to an implantable medical device. The present invention is more particularly directed to an implantable medical device which provides atrial fibrillation prevention pacing therapy to a heart upon detecting an interatrial conduction disturbance predictive of a pathological atrial tachyarrhythmia.
BACKGROUND OF THE INVENTION
Atrial fibrillation is a common cardiac arrhythmia. Although not life-threatening, it is associated with stroke and congestive heart failure. Further, patients with atrial fibrillation can experience palpitations of the heart and even dizziness. In short, atrial fibrillation can substantially reduce quality of life.
While drug therapy for atrial fibrillation is available, many patients either are, or become, refractory to such therapy. Drug therapy can also cause undesirable side effects.
Intemal cardioversion of atrial fibrillation is also known. This therapy, however, is not widely or commercially available.
Extemal cardioversion of atrial fibrillation is often the last resort for atrial fibrillation patients. However, this therapy generally requires a hospital stay and can be traumatic.
Atrial fibrillation is a progressive disease. In early stages it can be paroxysmal in nature. Many patients with sick sinus syndrome also experience or may develop paroxysmal atrial fibrillation. Research has been conducted to determine if there are predictors of paroxysmal atrial fibrillation. For example, Liu et al (PACE, Vol. 21:79-86) reported that prolongation of P-wave duration is an indicator of interatrial conduction disturbance. They also reported that prolongation of P-wave duration is an indication of sick sinus syndrome and that in those patients, the prolongation of P-wave is associated with an increased incidence of paroxysmal atrial fibrillation. Further, Jordaens et al (JCE 1998:530-534) concluded that it is possible to recognize patients with paroxysmal atrial fibrillation using P-wave signal averaging. They also concluded, however, that its role in the clinical management of patients remained unclear.
Further, Montereggi et al (AJC 1996:266-269) evaluated the correlation between the signal-averaged P-wave duration and the occurrence of paroxysmal atrial fibrillation in hyperthyroid patients with and without a history of atrial fibrillation. They concluded that a P-wave duration cut-off value of 130 ms held specificity, sensitivity, and positive predictive accuracy values of 79%, 85%, and 83%, respectively.
Still further, Cecchi et al (Heart 1997: 44-99) assessed the relationships between P-wave duration and the occurrence of atrial fibrillation in hypertrophic cardiomyopathy. In assessing risk for atrial fibrillation, they reported that P-wave duration greater than 140 ms was associated with sensitivity, specificity, and positive predictive accuracy values of 56%, 83%, and 66%.
While P-wave duration has been found to indicate an interatrial conduction disturbance and provide a predictive tool with respect to paroxysmal atrial fibrillation, other work was also conducted. For example, Stafford et al. (BrHeartJ 1995: 413-418) used spectral analysis.
Spectral analysis was performed on the entire P-wave. The P-wave signals were filtered with a high pass of 15 Hz before Fourier transformation to attenuate large low frequency components. P-wave energy was estimated by summating the energies contained in frequency bands extending from 20, 30, 40, 60 and 80 to 150 Hz. Each was expressed as an absolute value and in an energy percentage ratio. They found that paroxysmal atrial fibrillation patients had more energy in the higher frequency bands of the P-wave and greater spatial velocity.
While the foregoing evidences new diagnostic tools for paroxysmal atrial fibrillation, the use of these tools in an implanted device to trigger atrial arrhythmia prevention therapy has not been addressed. More specifically, as these patients are generally already being treated with an implantable cardiac rhythm management device, it would be advantageous if such a device could also detect an interatrial conduction disturbance and provide atrial arrhythmia prevention therapy responsive thereto in addition to the traditional therapies for sick sinus syndrome. More particularly, it would be advantageous to have an implantable medical device capable of employing additional methods of identifying disease progress towards paroxysmal atrial fibrillation prior to its actual start and then applying pacing therapies to prevent the start of an atrial arrhythmia such as atrial fibrillation. The present invention provides such an implantable medical device.
SUMMARY OF THE INVENTION
The present invention provides an implantable medical device for detecting an interatrial conduction disturbance and provides atrial tachyarrhythmia prevention stimulation in response thereto. In a preferred embodiment, the present invention provides an implantable medical device including a sensing system that senses atrial activity of a heart and a discriminator, coupled to the sensing system, that determines if a selected characteristic of the detected atrial activity satisfies a predetermined criteria indicative of an interatrial conduction disturbance. The implantable medical device further includes a pulse generator circuit, coupled to the discriminator, that delivers atrial arrhythmia prevention pacing pulses to the heart responsive to the discriminator determining that the selected characteristic of the sensed atrial activity satisfies a predetermined criterion.
In accordance with one aspect of the present invention, the interatrial conduction disturbance is a P-wave duration in excess of predetermined criterion. A signal processor including a P-wave duration timer determines durations of detected P-waves. The selected characteristic of the sensed atrial activity indicative of an interatrial conduction disturbance may further be an average P-wave duration in excess of a predetermined criterion wherein the signal processor includes a duration averager coupled to the P-wave duration timer that averages determined P-wave durations.
In accordance with further aspects of the present invention, the selected characteristic of the sensed atrial activity indicative of an interatrial conduction disturbance is an interatrial delay time exceeding a predetermined criterion, wherein a first detector detects right atrial activations and a second detector detects left atrial activations. The signal processor includes an interatrial delay timer coupled to the first and second detectors that determines if interatrial delay times between activations detected by the first detector and the second detector exceed the predetermined criterion.
In accordance with further aspects of the present invention, the atrial arrhythmia prevention pacing pulses are atrial overdrive pacing pulses and the pulse generator circuit includes an atrial overdrive pulse generator that provides atrial overdrive pacing pulses to the heart when the interatrial conduction disturbance is detected.
In accordance with a further aspect of the present invention, a detector detects P-waves of the heart and the pulse generator circuit includes an atrial pulse generator that delivers an atrial pacing pulse a delay time after each detected P-wave. The implantable medical device may further include a P-wave duration timer coupled to the detector that determines durations of detected P-waves and a pacing control that varies the delay time responsive to determined P-wave durations.
In accordance with a further aspect of the present invention, the implantable medical device may include a P-wave alternans analyzer that analyzes a selected characteristic of detected odd and even P-waves and wherein the discriminator determines if the difference between the selected characteristic of odd and even P-waves exceeds a predetermined criterion indicative of an interatrial conduction disturbance.
In accordance with a further aspect of the present invention, the interatrial conduction disturbance is a predetermined
Kroll Mark W.
Levine Paul A.
Schloss Harold C.
Kamm William E.
Pacesetter Inc.
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