System and method for hemodynamic pacing in ventricular tachycardia

• US 5,741,310 A
• Filed: 10/26/1995
• Issued: 04/21/1998
• Est. Priority Date: 10/26/1995
• Status: Expired due to Term

• Current Assignee: Meotronic, Inc.
• Original Assignee: Medtronic Incorporated (Medtronic Plc)
• Inventors: Wittkampf, Frederik H. M.
• Primary Examiner(s): Kamm, William E.
• Assistant Examiner(s): LAYNO, CARL HERNANDZ
• Application Number:
  US08/548,541
• Time in Patent Office: 908 Days
• Field of Search: 607/13, 607/14, 607/9
• US Class Current: 607/14
• CPC Class Codes: A61N 1/3621 for treating or preventing abnormally high heart rate

Abstract

A system and method for providing a 1:2 pacing therapy in response to a sensed ventricular tachycardia, which results in an improved hemodynamic response while limiting the potential for interrupting the tachycardia in a way that can cause a more dangerous tachycardia, or even VF. The pacing therapy involves obtaining a measure of the time interval between ventricular beats, and using this information to time out and deliver alternate stimulus pulses which occur just a short time interval (Δ) before the next expected natural ventricular beat. By delivering the alternate cycle stimulus at a predetermined time interval before the expected ventricular beat, the advantage of increased arterial pressure on alternate spontaneous beats is obtained, while avoiding the danger of evoking a more dangerous arrhythmia. The system further monitors change in rate while therapy is being applied, and either adjusts the timing or exits the routine whenever significant rate change is detected.

Claims

1. An implantable cardiac pacing system, having a controllable pulse generator for generating pacing pulses and a lead for delivering pacing pulses to a patient'"'"'s ventricle and for sensing natural heartbeats in said patient'"'"'s ventricle, VT means for detecting when said patient is in ventricular tachycardia, response means for responding to detected VT by controlling said pulse generator to deliver pace pulses in a 1:

2 relation to the patient'"'"'s natural cardiac rhythm during said VT, said response means having;

measure means for determining a measure of the patient'"'"'s natural rhythmic interval (T) during said VT;

determining means operative after a sensed natural heartbeat for determining, based on said measure of T, a time of expected occurrence of the patient'"'"'s next natural heartbeat; and

control means for controlling said pulse generator to generate a pacing pulse following a ventricular sense and before the said next expected natural heartbeat, said pacing pulse to precede said next expected heartbeat by a predetermined time greater than 30 ms and less than 150 ms.

2. The pacing system as described in claim 1, wherein said predetermined time is in the range of 40-60 ms.

3. The pacing system as described in claim 1, wherein said predetermined time is greater than 50 ms.

4. The pacing system as described in claim 1, wherein said measure means comprises means for determining the time interval between the natural beat preceding a delivered pacing pulse and the natural beat following said delivered pacing pulse.

5. The pacing system as described in claim 1, comprising means for adjusting said predetermined time.

6. The pacing system as described in claim 1, comprising tachy change means for determining when the patient VT has changed by more than a predetermined tolerance, and adjust means for adjusting the response of said response means when VT is determined to have changed by more than said tolerance.

7. A device for treatment of cardiac arrhythmias, said device having a controllable pulse generator for generating stimulus pulses, lead means for delivering stimulus pulses to a patient'"'"'s heart, sense means connected to said lead means for sensing ventricular beats, tachy means for determining when the patient is in VT, and 1:

2 response means for responding to VT, said 1;

2 response means having timing means for timing out an early escape interval following a sensed ventricular beat, said timing means having determining means for determining the time of the next expected ventricular beat, and escape interval means for setting an escape interval calculated to time out a predetermined Δ

interval before said time of the next expected beat, and control means for controlling said pulse generator to deliver an early stimulus pulse at the time out of said early escape interval in the absence of an intervening ventricular beat.

8. The device as described in claim 7, comprising tachy change means for determining when the patient VT changes by more than a predetermined tolerance, and wherein said 1:

2 response means has disable means for disabling said 1;

2 response means when there is a said determined VT change.

9. The device as described in claim 7, comprising tachy change means for determining when the patient VT changes by more than a predetermined tolerance, and comprising response adjust means for adjusting said response when there is a said predetermined VT change.

10. The device as described in claim 7, comprising Δ

change means for changing said predetermined Δ

.

11. The device as described in claim 7, wherein said determining means comprises means for determining a running measure of the time interval corresponding to the rate of natural ventricular beats during VT.

12. The device as described in claim 7, comprising means for setting said Δ

at a value in the range of 30-150 ms.

13. The device as described in claim 11, wherein said control means further comprises means operative after delivery of a said early stimulus pulse for controlling said pulse generator to time out an escape interval which is greater than said time interval measure by at least said Δ

.

14. A method of responding to an episode of ventricular tachycardia (VT) in a patient, comprising

sensing the occurrence of a ventricular beats,

determining a measure of the beat to beat interval of said VT,

following a sensed ventricular beat, calculating an early escape interval which is less than said beat to beat interval by Δ

amount, where said Δ

amount is in the range of 30-150 ms, and initiating time out of said escape interval following said sensed beat, and

delivering an early stimulus pulse to the patient when said early escape interval times out without an intervening patient heartbeat further comprising limiting said Δ

_-- to 30-90 ms.

15. The method as described in claim 14, comprising determining when the rate of the patient'"'"'s VT changes by more than a predetermined tolerance, and adjusting the response to VT as a function of said determining.

16. A method of responding to an episode of ventricular tachycardia (VT) in a patient, comprising

sensing the occurrence of a ventricular beats,

determining a measure of the beat to beat interval of said VT,

following a sensed ventricular beat, calculating an early escape interval which is less than said beat to beat interval by a Δ

amount, where said Δ

amount is in the range of 30-150 ms, and initiating time out of said escape interval following said sensed beat, and

delivering an early stimulus pulse to the patient when said early escape interval times out without an intervening patient heartbeat further comprising determining when the patient VT is not stable, and terminating said responding when VT is determined not to be stable.

17. A method of responding to an episode of ventricular tachycardia (VT) in a patient, comprising

sensing the occurrence of a ventricular beats,

determining a measure of the beat to beat interval of said VT,

following a sensed ventricular beat, calculating an early escape interval which is less than said beat to beat interval by a Δ

amount, where said Δ

amount is in the range of 30-150 ms, and initiating time out of said escape interval following said sensed beat, and

delivering an early stimulus pulse to the patient when said early escape interval times out without an intervening patient heartbeat further comprising following delivery of a said early stimulus pulse, timing out an escape interval greater than said beat-to-beat interval by at least said amount.

18. An implantable cardiac pacing system, comprising:

a controllable pulse generator for generating pacing pulses;

a lead for delivering pacing pulses to a patient'"'"'s ventricle and for sensing natural heartbeats in the patient'"'"'s ventricle,

VT means for detecting when the patient'"'"'s heart is in VT; and

means for providing improved hemodynamic performance during VT in response to the detected VT through the deliver of a hemodynamic pacing therapy.

19. The pacing system as described in claim 18, wherein means for providing improved hemodynamic performance during VT in response to the detected VT through the deliver of a hemodynamic pacing therapy comprises means for responding to detected VT by controlling the pulse generator to deliver pace pulses in a 1:

2 relation to the patient'"'"'s natural cardiac rhythm during the VT, the means for responding to detected VT having;

measure means for determining a measure of the patient'"'"'s natural rhythmic interval (T) during the VT;

determining means operative after a sensed natural heartbeat for determining, based on the measure of T, a time of expected occurrence of the patient'"'"'s next natural heartbeat; and

control means for controlling the pulse generator to generate a pacing pulse following a ventricular sense and before the next expected natural heartbeat, the pacing pulse to precede the next expected heartbeat by a predetermined time greater than 30 ms and less than 150 ms.

20. The pacing system as described in claim 18, wherein the predetermined time comprises the range of 40-60 ms.

21. The pacing system as described in claim 18, wherein the predetermined time comprises a period greater than 50 ms.

22. The pacing system as described in claim 19, wherein the measure means comprises means for determining time interval between the natural beat preceding a delivered pacing pulse and the natural beat following the delivered pacing pulse.

23. The pacing system as described in claim 19, comprising means for adjusting the predetermined time.