Low energy implantable atrial defibrillator using multiple electrodes and stimulation rates

• US 5,865,838 A
• Filed: 09/18/1997
• Issued: 02/02/1999
• Est. Priority Date: 08/16/1996
• Status: Expired due to Term

• Current Assignee: Pacesetter AB
• Original Assignee: Pacesetter AB
• Inventors: Hedberg, Sven-Erik, Obel, Martin
• Primary Examiner(s): Kamm, William E.
• Assistant Examiner(s): LAYNO, CARL HERNANDZ
• Application Number:
  US08/932,653
• Time in Patent Office: 502 Days
• Field of Search: 607/5, 607/9, 607/14, 607/15
• US Class Current: 607/5
• CPC Class Codes: A61N 1/3621 for treating or preventing abnormally high heart rate
• CPC Class Codes: A61N 1/3925 Monitoring; Protecting
• CPC Class Codes: A61N 1/395 for treating atrial fibrillation
• CPC Class Codes: A61N 1/39622 Pacing therapy

Abstract

In an apparatus for terminating atrial fibrillation using pulses having an energy content which is the same as the energy content of conventional pacing pulses, stimulation pulses are respectively emitted by a number of electrodes disposed at different sites in or on a heart experiencing atrial fibrillation. When atrial fibrillation is detected, waveforms are measured at each of the electrodes, and the electrode having the waveform exhibiting the shortest interval between successive identifiable, cyclical waveform characteristics, such as successive P-waves, is selected as a first electrode for beginning an atrial defibrillation attempt. Stimulation pulses are emitted from the first electrode at a stimulation rate which is slightly shorter than the aforementioned shortest interval and the other electrodes are stimulated at a rate which is slightly shorter than the rate for the first electrode. All of the stimulation pulses are delivered starting at the latest local detection point in time. Upon each of the other electrodes reaching a point at which emits a stimulation pulse which coincides with a stimulation pulse emitted by the first electrode, that other electrode is locked to the stimulation rate of the first electrode, until all of the electrodes are stimulating at a coincident rate. Detection is periodically undertaken to determine whether atrial fibrillation has been terminated, and if so the pacemaker resumes its normal pacing operation. If the atrial fibrillation has not been terminated, the procedure is continued (if not yet ended) or repeated.

Claims

1. In an implantable apparatus for terminating atrial fibrillation having at least one electrode cable, with at least two electrodes placeable in electrical contact with atrial tissue, and said electrodes being placed at respectively different locations relative to a heart atrium, a pulse generator connected to each of said electrodes for emitting stimulation pulses via said electrodes with an energy of 0.5 joules or less, a detector connected to each electrode for sensing a waveform representing atrial activity at the site of the electrode, a microprocessor connected to the pulse generators and to the detectors for controlling delivery of said stimulation pulses and for analyzing detected atrial activity to identify the occurrence of atrial fibrillation of said heart, the improvement comprising means in said microprocessor for controlling delivery of said stimulation pulses in an attempt to terminate said atrial fibrillation, comprising:

means, upon detection of atrial fibrillation, for identifying one of said electrodes having a detected waveform with a shortest interval between a repeated, identifiable waveform characteristic, said one of said electrodes being designated as a first electrode;

means for supplying said stimulation pulses having an energy of 0.5 joules or less to said heart via said first electrode at a first electrode stimulation interval which is shorter than said shortest interval and for supplying stimulation pulses to the other electrodes at a different stimulation rate which is shorter than said first electrode stimulation rate, the stimulation pulses emitted by said first electrode and by said other electrodes all being delivered at intervals starting with a latest local detection point in time;

means for identifying when a stimulation pulse emitted by any of said other electrodes coincides with a stimulation pulse emitted by said first electrode and thereafter locking the stimulation rate of that electrode to said first electrode stimulation rate, until all stimulation pulses emitted by all of said electrodes coincide; and

means for determining whether said atrial fibrillation has been terminated each time one of said other electrodes becomes locked to said first electrode and, if atrial fibrillation still exists for continuing said atrial defibrillation attempt until all electrodes are locked to said first electrode.

2. The implantable apparatus of claim 1 comprising means for setting said first electrode stimulation interval at a value which is the product of a constant multiplied by said shortest interval.

3. An implantable apparatus as claimed in claim 2 wherein said constant is in a range from 0.95 to 0.99.

4. An implantable apparatus as claimed in claim 1 comprising means for setting said other intervals at a value which is a product of a constant multiplied by said shortest interval.

5. An implantable apparatus as claimed in claim 1 comprising means for setting said first stimulation interval to a value which is a product of a first constant multiplied by said shortest interval, and means for setting said other intervals at a value which is a product of a second constant multiplied by said shortest interval.

6. An implantable apparatus as claimed in claim 5 wherein said second constant comprises a fraction of said first constant.

7. An implantable apparatus as claimed in claim 6 wherein said first constant is in a range from 0.95 to 0.99, and wherein said second constant is equal to a product of 0.95 multiplied by said first constant.

8. An implantable apparatus as claimed in claim 1 further comprising means for pacing said heart with said stimulation pulses having an energy of 0.5 joules or less at times when said atrial defibrillation attempt is not being executed.

9. An implantable apparatus as claimed in claim 1 wherein said means for identifying one of said electrodes having a shortest interval comprises means for identifying one of said electrodes having a shortest average P-wave interval in said waveform.