Rate responsive pacemaker controlled by isovolumic contraction time

• US 5,168,869 A
• Filed: 06/17/1991
• Issued: 12/08/1992
• Est. Priority Date: 06/17/1991
• Status: Expired due to Term

• Current Assignee: Dr. Raul Chirife
• Original Assignee: Dr. Raul Chirife
• Inventors: Chirife, Raul
• Primary Examiner(s): Cohen, Lee S.
• Assistant Examiner(s): Jastrzab, Jeffrey R.
• Application Number:
  US07/716,405
• Time in Patent Office: 540 Days
• Field of Search: 128/419 PL
• US Class Current: 607/25
• CPC Class Codes: A61N 1/36585 controlled by two or more physical parameters

Abstract

A rate responsive pacemaker uses isovolumic contraction time (IVCT) as a control signal responsive to metabolic demands. This control signal is injected into the timing circuit of a standard rate adaptive pacemaker to enhance the pacer'"'"'s ability to respond in direct relation to the patient'"'"'s changing metabolic needs as he performs his daily activities. A typical configuration, uses the duration of either right or left heart IVCT for rate control. The device has two inputs to measure IVCT: one, signaling the onset of mechanical activation of the ventricle, and another, signaling the onset of ejection. The time interval between these two signals is the duration of IVCT, which is processed by the pacemaker to determine the escape interval.

Claims

1. In a cardiac pacemaker of the type including a pulse generating means for applying stimulating pulses to tissue, said pulse generating means including rate control means for controlling timing of delivery of said stimulating pulses, the improvement comprising:

(a) means for detecting a first IVCT event using the timing of the onset of mechanical contraction of the ventricle of a heart as an indicator of the start of the physiological isovolumic contraction period;

(b) means for detecting a second IVCT event using the timing of the onset of ejection of blood from the ventricle as an indicator of the end of the physiological isovolumic contraction period;

(c) control signal generating means for developing a control signal proportional to the time difference between said first and second IVCT events as an indicator of duration of isovolumic contraction time; and

(d) means for injecting said control signal into said rate control means for altering the timing of the delivery of said stimulating pulses as a function of IVCT.

2. The cardiac pacemaker as in claim 1, wherein the means for detecting said first and second IVCT events further comprises an impedance sensor for indicating the start of the physiological isovolumic contraction period and the timing of the onset of ejection of blood from the ventricle.

3. The cardiac pacemaker as in claim 1, wherein the means for detecting said first and second IVCT events further comprises a pressure sensor for indicating the start of the physiological isovolumic contraction period and an impedance sensor for determining the timing of the onset of ejection of blood from the ventricle.

4. The cardiac pacemaker as in claim 1, wherein the means for detecting said first and second IVCT events further comprises a sound sensor for indicating the start of the physiological isovolumic contraction period and an impedance sensor for determining the timing of the onset of ejection of blood from the ventricle.

5. The cardiac pacemaker as in claim 1, wherein the means for detecting said first and second IVCT events further comprises an impedance sensor for indicating the start of the physiological isovolumic contraction period and a pressure sensor for determining the timing of the onset of ejection of blood from the ventricle.

6. The cardiac pacemaker as in claim 1, wherein the means for detecting said first and second IVCT events further comprises a pressure sensor for indicating the start of the physiological isovolumic contraction period and means for determining maximal rate of change of pressure for indicating the end of the physiological isovolumic contraction period.

7. The cardiac pacemaker as in claim 1, wherein the means for detecting said first and second IVCT events further comprises a sound sensor for indicating the start of the physiological isovolumic contraction period and a pressure sensor having differentiating means for determining the timing of the onset of ejecting of blood from the ventricle.

8. In a cardiac pacemaker of the type including a pulse generating means for applying stimulating pulses to tissue, said pulse generating means including rate control means for controlling timing of said stimulating pulses, the improvement comprising:

(a) impedance detecting means for sensing instantaneous impedance values and comparator means coupled to the impedance detecting means for comparing said instantaneous impedance values with a reference vale for determining a first timing value indicating the timing of the onset of change in instantaneous impedance value from said reference value as an indicator of the onset of contraction of the ventricle of the heart;

(b) means coupled to the impedance detecting means for determining a second timing value indicating the onset of abrupt rise in impedance within the ventricular cavity of the heart as an indicator of the onset of ventricular ejection;

(c) control signal generating means for developing a control signal related to the difference between said first and second timing values as an indicator of duration of isovolumic contraction time; and

(d) means for injecting said control signal into said rate control means for altering the timing of the delivery of said stimulating pulses in proportion to said control signal and as a function of IVCT.

9. In a cardiac pacemaker of the type including a pulse generating means for applying stimulating pulses to tissue, said pulse generating means including rate control means for controlling timing of said stimulating pulses, the improvement comprising:

(a) impedance detecting means for sensing instantaneous impedance values and comparator means coupled to the impedance detecting means for comparing said instantaneous impedance values with a reference value for determining a first timing value indicating the timing of the onset of change in impedance value from said reference value as an indicator of the onset of contraction of the ventricle of the heart;

(b) pressure sensing means coupled to said impedance detecting means for sensing instantaneous pressure values within the ventricular cavity of the heart and differentiator means coupled to said pressure sensing means for differentiating said instantaneous pressure values and for determining a second timing value indicating maximal rate of change of pressure as a measure of the onset of ventricular ejection;

(c) control signal generating means for developing a control signal related to the difference between said first timing value as an indicator of the timing of onset of contraction of the ventricle and said second timing value as an indicator of the timing of onset of ventricular ejection, said control signal being an indicator of duration of isovolumic contraction time; and

(d) means for injecting said control signal into said rate control means for altering the timing of the delivery of said stimulating pulses in proportion to said control signal and as a function of IVCT.

10. In a cardiac pacemaker of the type including a pulse generating means for applying stimulating pulses to tissue, said pulse generating means including rate control means for controlling timing of said stimulating pulses, the improvement comprising:

(a) pressure sensing means for sensing instantaneous pressure values within the ventricular cavity of the heart and comparator means coupled to the pressure sensing means for comparing said instantaneous pressure values and for determining a first timing value indicating when the rate of rise of the instantaneous pressure values exceeds a predetermined threshold value as a measure of the onset of contraction of the ventricle of the heart, and differentiator means for differentiating said instantaneous pressure values and for determining a second timing value indicating maximal rate of change of pressure as a measure of the onset of ventricular ejection;

(b) control signal generating means for developing a control signal related to the difference between said first and second timing values as an indicator of duration of isovolumic contraction time; and

(c) means for injecting said control signal into said rate control means for altering the timing of the delivery of said stimulating pulses in proportion to said control signal and as a function of IVCT.

11. In a cardiac pacemaker of the type including a pulse generating means for applying stimulating pulses to tissue, said pulse generating means including rate control means for controlling timing of said stimulating pulses, the improvement comprising:

(a) pressure sensing means for sensing instantaneous pressure values within a ventricular cavity of the heart and comparator means coupled to the pressure sensing means for comparing said instantaneous pressure values and for determining a first timing value indicating when the rate of rise of the instantaneous pressure values exceeds a predetermined threshold value as a measure of the onset of contraction of the ventricle of the heart;

(b) impedance means for determining a second timing value indicating the onset of abrupt rise in impedance within the ventricular cavity of the heart as an indicator of the onset of ventricular ejection;

(c) control signal generating means for developing a control signal related to the difference between said first timing value as an indicator of the timing of onset of contraction of the ventricle and said second timing value as an indicator of the timing of onset of ventricular ejection, said control signal being an indicator of duration of isovolumic contraction time; and

(d) means for injecting said control signal into said rate control means for altering the timing of the delivery of said stimulating pulses in proportion to said control signal and as a function of IVCT.

12. In a cardiac pacemaker of the type including a pulse generating means for applying stimulating pulses to tissue, said pulse generating means including rate control means for controlling timing of said stimulating pulses, the improvement comprising:

(a) sound detection means for developing a first timing value by sensing the timing of tricuspid valve closure, which indicates the onset of contraction of a ventricle of the heart, and impedance means for determining a second timing value indicating the onset of abrupt rise in impedance value within the ventricular cavity of the heart as an indicator of the onset of ventricular ejection;

(b) control signal generating means for developing a control signal related to the difference between said first timing value as an indicator of the timing of onset of contraction of the ventricle and said second timing value as an indicator of the timing of onset of ventricular ejection, said control signal being an indicator of duration of isovolumic contraction time; and

(c) means for injecting said control signal into said rate control means for altering the timing of the delivery of said stimulating pulses in proportion to said control signal and as a function of IVCT.

13. In a cardiac pacemaker of the type including a pulse generating means for applying stimulating pulses to tissue, said pulse generating means including rate control means for controlling timing of said stimulating pulses, the improvement comprising:

(a) sound detection means for developing a first timing value by sensing the timing of tricuspid valve closure, which indicates the onset of contraction of a ventricle of the heart, and pressure sensing means for sensing instantaneous pressure values within the ventricular cavity of the heart and differentiator means for differentiating said instantaneous pressure values and for determining a second timing value indicating maximal rate of change of pressure as a measure of the onset of ventricular ejection;

(b) control signal generating means for developing a control signal related to the difference between said first timing value as an indicator of the timing of onset of contraction of the ventricle and said second timing value as an indicator of the timing of onset of ventricular ejection, said control signal being an indicator of duration of isovolumic contraction time; and

(c) means for injecting said control signal into said rate control means for altering the timing of the delivery of said stimulating pulses in proportion to said control signal and as a function of IVCT.