Pacemaker system and method for measuring and monitoring cardiac activity and for determining and maintaining capture

• US 4,817,605 A
• Filed: 03/19/1987
• Issued: 04/04/1989
• Est. Priority Date: 10/19/1984
• Status: Expired due to Term

• Current Assignee: Pacesetter Incorporated (Abbott Laboratories Incorporated)
• Original Assignee: Siemens Pacesetter, Inc. (Abbott Laboratories Incorporated)
• Inventors: Sholder, Jason A.
• Primary Examiner(s): Kamm, William E.
• Application Number:
  US07/027,715
• Time in Patent Office: 747 Days
• Field of Search: 128/419 PG, 128/419 PT
• US Class Current: 607/28
• CPC Class Codes: A61N 1/368 comprising more than one electrode co-operating with different heart regions A61N1/3622, A61N1/3627 take precedence
• CPC Class Codes: A61N 1/3712 Auto-capture, i.e. automatic adjustment of the stimulation threshold
• CPC Class Codes: A61N 1/3714 Atrial capture

Abstract

A system for determining P-wave or R-wave capture in response to pacemaker supplied electrical stimuli. One embodiment includes a conventional bipolar atrial lead having a tip electrode, connected to an atrial pulse generator circuit within an implantable pacemaker, and a ring electrode, spaced apart from the tip electrode, connected to a P-wave sensing EGM amplifier within the pacemaker. The bandpass characteristics of the P-wave sensing EGM amplifier allow detection of all electrical frequencies in the atrium within the bandpass chosen. The output signal from this amplifier is selectively telemetered to an external receiver, as is a signal indicating the generation of an atrial stimulation pulse, where the occurrence of atrial stimulation pulses and P-waves can be monitored. In operation, if constant time intervals between the monitored atrial stimulation pulses and P-wave occurrences are present, P-wave capture has occurred. In the event of variable time intervals, capture has not occurred and the magnitude of the atrial stimulation pulses can be increased until P-wave capture does occur. An alternative embodiment measures this time differential and makes the stimulation pulse adjustment automatically. Other embodiments use the same manual or automatic systems to determin R-wave capture.

Claims

1. A system for determining atrial capture comprising:

heart pacing means for generating stimulation pulses;

electrically conductive lead means for sending electrical stimulation pulses to and receiving electrical signals from a desired atrial location, said lead means including

a first electrically conductive electrode connected to said heart pacing means, and

a second electrically conductive electrode spaced apart from said first electrode;

an amplifier connected to receive signals sensed by said second electrically conductive electrode, said amplifier including receiving means for receiving signals indicative of any atrial P-wave sensed by said second electrode, whether said atrial P-wave is a naturally occurring P-wave or a P-wave resulting from the application of a stimulation pulse applied to said first electrode, said amplifier further having means for generating an output signal indicative of the sensing of said atrial P-wave; and

means responsive to the presence of said output signal for determining whether atrial capture has occurred, said means for determining atrial capture comprising means for measuring successive time intervals between application of an atrial stimulation pulse through said first electrode and the generation of the output signal by said amplifier, atrial capture being indicative if said measured time interval remains constant and corresponds approximately to a predetermined time interval.

2. The system recited in claim 1 wherein said first and second electrodes are spaced apart at least one-half inch.

3. The system recited in claim 1 wherein the amplifier includes means for amplifying frequencies within the range of 3 to 125 Hz.

4. The system recited in claim 1 wherein said lead means further includes a third electrode electrically coupled to said heart pacing means through which stimulating pulses can be provided for stimulating the ventricle, and a second amplifier coupled to said third electrode that senses R-wave signals originating in the ventricle, said second amplifier generating a second output signal indicative of the sensing of an R-wave at said second amplifier, said second output signal being provided to said heart pacing means to signal that an R-wave has occurred.

5. The system recited in claim 1 wherein there is further included:

means for controlling the magnitude of the atrial stimulation pulses of said heart pacing means including means for reducing the magnitude of said atrial stimulation pulses until said atrial capture-determining means indicates lack of capture, and then increasing the magnitude of said stimulation pulses until said atrial capture-determining means indicates capture.

6. The system of claim 1 wherein there is further included means for controlling the magnitude of the atrill stimulation pulses generated by said heart pacing means in response to said atrial capture determining means.

7. A system for determining capture in response to pacemaker supplied electrical stimuli provided to a heart comprising:

a lead having proximal and distal ends, said lead having a first exposed electrically conductive electrode at said distal end, a second exposed electrically conductive electrode near said distal end, spaced apart and electrically isolated from said first electrode, first and second terminals near the proximal end of said of said lead, and first and second conductor means for electrically connecting said first and second electrodes, respectively, to said first and second terminals; and

pacemaker means comprising

pulse output means for generating stimulation pulses and applying said pulses to the first terminal of said lead, whereby said stimulation pulses are delivered to said first electrode of said lead,

a sensing amplifier connected to said second terminal of said lead, said sensing amplifier generating an output signal in response to sensed electrical signals applied thereto through said second terminal, said electrical signals being generated by spontaneous and stimulated cardiac activity, and

means for determining capture, said means for determining capture including means for monitoring the output signal of said sensing amplifier, said monitoring means including means for measuring successive time intervals between application of a stimulation pulse through said first electrode and the generation of the output signal by said sensing amplifier, said capture means providing an indication of capture if said measured time interval remains constant and corresponds approximately to a predetermined time interval.

8. A cardiac pacing system comprising:

lead means for providing electrical contact with a desired cardiac location, said lead means having first and second terminals at the lead proximal end, a first electrode at the lead distal end being electrically connected to said first terminal, a second electrode near the lead distla end being spaced apart and electrically insulated from said first electrode and being electrically connected to said second terminal; and

pacemaker means comprising

first connector means for electrically engaging said first terminal,

second connector means for electrically engaging said second terminal,

pulse generating means connected to said first connector means for providing a stimulation pulse,

sensing EGM amplifier means connected to said second connector means for sensing electrical signals representative of cardiac action and for generating an output signal in response thereto,

capture-determining means for determining if the stimulation pulse generated by said pulse generation means has produced capture, said capture-determining means including means for measuring the time interval between application of a stimulation pulse by said pulse generation means and the occurrence of the output signal from said sensing EGM amplifier means, capture being indicated if said measured time interval remains constant and corresponds approximately to a predetermined time interval, and

adjustment means coupled to said pulse generating means for increasing the energy of subsequent stimulation pulses in the event said capture-determining means indicates capture has not occured.

9. A method of determining capture of stimulation pulses comprising the steps of:

(a) generating a stimulation pulse and applying it to a prescribed location to be stimulated;

(b) sensing electrical activity at a location spaced apart from the stimulating location of step (a);

(c) measuring the time delay between the application of the stimulation pulse of step (a) and the sensing of electrical activity of step (b); and

(d) adjusting the magnitude of the stimulation pulses until the time delay measured in step (c) for successive measurements is substantially the same and within a prescribed tolerance of an expected propagation time delay, denoting captured stimulation pulses.

10. The method of determining capture of claim 9 wherein step (c) of adjusting the magnitude of the stimulation pulses comprises adjusting the stimulation pulse width.

11. The method determining capture of claim 9 wherein step (c) of adjusting the magnitude of the stimulation pulses comprises adjusting the stimulation pulse amplitude.

12. The method of determining capture of claim 9 wherein step (c) of adjusting the magnitude of the stimulation pulses comprises

decreasing the stimulation pulse magnitude until the time delay measured in step (b) for successive measurements is not substantially the same, indicating lack of capture, and

increasing the stimulation pulse magnitude in prescribed increments until the time delay measured in step (b) for successive measurements is substantially the same and within said prescribed tolerance of an expected propagation time delay, indicating captured stimulation pulses.