Refractoriless atrial sensing in dual chamber pacemakers

• US 4,799,486 A
• Filed: 03/13/1987
• Issued: 01/24/1989
• Est. Priority Date: 03/13/1987
• Status: Expired due to Term

• Current Assignee: Cardiac Pacemakers Incorporated (Boston Scientific Corporation)
• Original Assignee: Cardiac Pacemakers Incorporated (Boston Scientific Corporation)
• Inventors: DuFault, Robert A.
• Primary Examiner(s): Jaworski, Francis
• Assistant Examiner(s): MANUEL, GEORGE C
• Application Number:
  US07/025,571
• Time in Patent Office: 683 Days
• Field of Search: 128/696, 128/704, 128/705, 128/419 PG
• US Class Current: 607/9
• CPC Class Codes: A61N 1/368 comprising more than one electrode co-operating with different heart regions A61N1/3622, A61N1/3627 take precedence

Abstract

A method and apparatus for suppressing the ventricular component from an atrial sensing lead used with a dual chamber cardiac pacer, thus obviating the need for an atrial sense refractory period to prevent oversensing of the ventricular interference. The invention utilizes an adaptive filter embodying the Widrow-Hoff least mean square (LMS) algorithm which is connected to receive signals from an endocardial lead having a bipolar ventricular electrode and a unipolar atrial electrode. The bipolar electrodes disposed in the ventricle are connected as the "input" X_k signal to the LMS adaptive filter while the unipolar atrial electrode output is connected as the "desired" or reference signal d_k. In accordance with the LMS algorithm, the "error" signal is fed back and used to adjust the tap weights of the adaptive linear filter until the output thereof closely approximates the "desired" signal and then the "error" signal becomes a good approximation of the atrial signal alone, without the ventricular depolarization signal.

Claims

1. In a dual chamber cardiac pacer of the type having first electrode means disposed in the ventricle of the heart for detecting ventricular depolarization signals and second electrode means disposed in the atrium of the heart for primarily detecting atrial depolarization signals, atrial sensing means responsive to the signals on said second electrode means for suppressing those signals on said second electrode means due to said ventricular depolarizing signals comprising:

(a) an adaptive filter coupled to said first electrode means for receiving as an input signal said ventricular depolarizing signal;

(b) a summing circuit coupled to the output of said adaptive filter and to said second electrode means, said summing circuit producing an error signal proportional to the difference between the output of said adaptive filter and the signals on said second electrode means; and

(c) means coupling said error signal to said adaptive filter for continuously varying the parameters of said adaptive filter whereby said filter converges to the point where said error signal is minimized.

2. The dual chamber pacer as in claim 1 wherein said adaptive filter is a least means square (LMS) adaptive filter.

3. The dual chamber pacer as in claim 1 wherein said error signal indicates the occurrence of P-waves.

4. The dual chamber pacer as in claim 1 wherein said atrial sensing means remains operative throughout the entire cardiac cycle.

5. A method of operating a dual chamber pacemaker of the type including ventricular pacing means, ventricular sensing means and atrial sensing means such that natural or artificial electrical activity originating in the ventricle is not oversensed by said atrial sensing means, comprising the steps of:

(a) positioning a first electrode in the ventricle of the heart, said first electrode being coupled to said ventricular sensing means;

(b) positioning a second electrode in the atrium of the heart, said second electrode being coupled to said atrial sensing means;

(c) connecting the input of an LMS adaptive filter means to said ventricular sensing means;

(d) summing the output of said LMS adaptive filter means with the output from said atrial sensing means for generating an error signal proportional to the difference between said output of said LMS adaptive filter and the output of said atrial sensing means; and

(e) applying said error signal to said LMS filter for continuously adjusting the parameters of said LMS adaptive filter until said error signal is minimized.