Demand cardiac pacer

• US 3,911,929 A
• Filed: 05/20/1974
• Issued: 10/14/1975
• Est. Priority Date: 05/20/1974
• Status: Expired due to Term

• Current Assignee: David H. Gobeli
• Original Assignee: David H. Gobeli
• Inventors: Gobeli, David H.
• Primary Examiner(s): Kamm, William E.
• Application Number:
  US05/471,564
• Time in Patent Office: 512 Days
• Field of Search: 128/419P,419PG,421,422
• US Class Current: 607/9
• CPC Class Codes: A61N 1/365 controlled by a physiological parameter, e.g. heart potential evoked response A61N1/371

Abstract

In a demand cardiac pacer including a resettable pulse generator and a sense amplifier adapted to be connected to the heart for generating a reset signal in response to a sensed heartbeat, the improved apparatus including a frequency detector for passing those reset signals whose interval is greater than a predetermined value and blocking those reset signals whose interval is less than the predetermined value. The frequency detector includes a timing circuit for establishing a predetermined period of time following each reset signal and circuitry for blocking all reset signals subsequent to a time period establishing signal. In a preferred embodiment, the blocking circuitry consists of a transistor switch for shunting the reset signals during the predetermined period of time and a delay element for allowing the passage of an initial time period establishing signal.

Claims

1. In a demand cardiac pacer of the type having a resettable pulse generator and having sense amplifier means adapted to be connected to the heart and responsive to heart activity for generating pulse generator reset signals, the improvement which comprises:

means for establishing a first predetermined period of time;

means responsive to said sense amplifier means and connected to said first time period establishing means for initiating the operation of said first time period establishing means On the occurrence of each reset signal;

means operative during said first predetermined period of time for blocking said reset signals from said pulse generator; and

means for delaying the operation of said blocking means for a second, shorter predetermined period of time following initiating the operation of said first time period establishing means.

2. The cardiac pacer of claim 1 wherein said blocking means comprises means for shunting said reset signals.

3. The cardiac pacer of claim 2 wherein said shunting means comprises transistor switch means.

4. The cardiac pacer of claim 3 wherein said first time period establishing means comprises resettable timing means.

5. The cardiac pacer of claim 4 wherein said delaying means comprises capacitive timing means.

6. The cardiac pacer of claim 1 wherein said first time period establishing means comprises first capacitive timing means and means for charging said first capacitive timing means in the interval between said reset signals, said initiating means comprising means for discharging said first capacitive timing means in response to said reset signals.

7. The cardiac pacer of claim 6 wherein said blocking means further comprises first switch means for switching from one state to another in response to the discharge of said first capacitive timing means.

8. The cardiac pacer of claim 7 wherein said blocking means further comprises normally-off switch means connecting said sense amplifier to ground and responsive to said first switch means for switching on and shunting said reset signals in response to the switching of said first switch means to said other state.

9. The cardiac pacer of claim 8 wherein said delaying means comprises second capacitive means interconnecting said first and normally-off switch means for delaying the response of said normally-off switch means to the switching of said first switch means to said other state.

10. The cardiac pacer of claim 9 wherein said first and normally-off switch means comprise transistor switch means.