IMPLANTABLE MEDICAL DEVICE FOR MONITORING CONGESTIVE HEART FAILURE
First Claim
1. In an implantable medical device, a system for monitoring the state of heart failure of the heart of a heart failure patient comprising:
- pulse generating means for selectively generating and applying a pacing pulse to at least one heart chamber to effect a contraction of the heart chamber commencing a heart cycle and for selectively generating and applying an extrasystolic electrical stimulus to the at least one heart chamber at the time out of an extrasystolic escape interval to induce post-extrasystolic potentiation increasing the strength of contraction of the heart chamber;
electrical signal sense means for sensing the electrical signals of the heart in said at least one heart chamber and providing a sense event signal signifying the contraction of the heart commencing a heart cycle;
heart chamber volume measuring means for measuring the volume of a heart chamber over at least a portion of a heart cycle and providing a chamber volume value;
blood pressure measuring means for measuring blood pressure within a heart chamber over at least a portion of a heart cycle and providing a blood pressure value;
parameter deriving means for selectively enabling operation of said pulse generating means, said electrical signal sense means, said heart chamber volume measuring means, and said blood pressure measuring means for periodically deriving a plurality of heart failure parameters signifying the state of heart failure from selected measured values of chamber volume and blood pressure, the heart failure parameters including;
a tau parameter representing one of a relaxation and contraction time constant of the heart chamber, a mechanical restitution parameter representing the mechanical response of a heart chamber to electrical stimuli applied to the heart chamber prematurely at differing times during a plurality of heart cycles, a recirculation fraction parameter representing the increase in strength of a contraction of the heart chamber in response to an electrical stimuli applied to the heart chamber during a heart cycle and the rate of decay of the increase in strength of successive contractions of the heart chamber over a series of heart cycles; and
an elastance parameter representing the slope of plotted sets of end systolic blood pressure versus end systolic chamber volume over a plurality of heart cycles;
means for storing the derived heart failure parameters; and
means for retrieving the stored heart failure parameters to enable a determination of the state of heart failure of the patient'"'"'s heart.
1 Assignment
0 Petitions
Accused Products
Abstract
An implantable stimulator and monitor measures a group of heart failure parameters indicative of the state of heart failure employing EGM signals, measures of blood pressure including absolute pressure P, developed pressure (DP=systolic P−diastolic P), and/or dP/dt, and measures of heart chamber volume (V) over one or more cardiac cycles. These parameters include: (1) relaxation or contraction time constant tau (τ); (2) mechanical restitution (MR), i.e., the mechanical response of a heart chamber to premature stimuli applied to the heart chamber; (3) recirculation fraction (RF), i.e., the rate of decay of PESP effects over a series of heart cycles; and (4) end systolic elastance (EES), i.e., the ratios of end systolic blood pressure P to volume V. These heart failure parameters are determined periodically regardless of patient posture and activity level. However, certain of the parameters are only measured or certain of the data are only stored when the patient heart rate is regular and within a normal sinus range between programmed lower and upper heart rates. The parameter data is associated with a date and time stamp and with other patient data, e.g., patient activity level, and the associated parameter data is stored in IMD memory for retrieval at a later date employing conventional telemetry systems. Incremental changes in the parameter data over time, taking any associated time of day and patient data into account, provide a measure of the degree of change in the heart failure state of the heart.
210 Citations
62 Claims
-
1. In an implantable medical device, a system for monitoring the state of heart failure of the heart of a heart failure patient comprising:
-
pulse generating means for selectively generating and applying a pacing pulse to at least one heart chamber to effect a contraction of the heart chamber commencing a heart cycle and for selectively generating and applying an extrasystolic electrical stimulus to the at least one heart chamber at the time out of an extrasystolic escape interval to induce post-extrasystolic potentiation increasing the strength of contraction of the heart chamber;
electrical signal sense means for sensing the electrical signals of the heart in said at least one heart chamber and providing a sense event signal signifying the contraction of the heart commencing a heart cycle;
heart chamber volume measuring means for measuring the volume of a heart chamber over at least a portion of a heart cycle and providing a chamber volume value;
blood pressure measuring means for measuring blood pressure within a heart chamber over at least a portion of a heart cycle and providing a blood pressure value;
parameter deriving means for selectively enabling operation of said pulse generating means, said electrical signal sense means, said heart chamber volume measuring means, and said blood pressure measuring means for periodically deriving a plurality of heart failure parameters signifying the state of heart failure from selected measured values of chamber volume and blood pressure, the heart failure parameters including;
a tau parameter representing one of a relaxation and contraction time constant of the heart chamber, a mechanical restitution parameter representing the mechanical response of a heart chamber to electrical stimuli applied to the heart chamber prematurely at differing times during a plurality of heart cycles, a recirculation fraction parameter representing the increase in strength of a contraction of the heart chamber in response to an electrical stimuli applied to the heart chamber during a heart cycle and the rate of decay of the increase in strength of successive contractions of the heart chamber over a series of heart cycles; and
an elastance parameter representing the slope of plotted sets of end systolic blood pressure versus end systolic chamber volume over a plurality of heart cycles;
means for storing the derived heart failure parameters; and
means for retrieving the stored heart failure parameters to enable a determination of the state of heart failure of the patient'"'"'s heart. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8)
-
-
9. In an implantable medical device, a system for monitoring the state of heart failure as a function of the mechanical restitution of the heart of a heart failure patient comprising:
-
means for determining a stable cardiac cycle of a heart chamber having a heart cycle escape interval;
means for timing out an extrasystolic escape interval during the heart cycle escape interval;
pulse generating means for selectively generating and applying an extrasystolic electrical stimulus to the heart chamber at the time out of the extrasystolic escape interval to induce post-extrasystolic potentiation increasing the strength of contraction of the heart chamber;
blood pressure measuring means for measuring blood pressure within a heart chamber over at least a portion of a heart cycle and providing a blood pressure value;
mechanical restitution parameter deriving means for selectively enabling operation of said pulse generating means and said blood pressure measuring means for periodically deriving a mechanical restitution parameter representing the mechanical response of a heart chamber to the electrical stimuli applied to the heart chamber prematurely at differing extrasystolic escape intervals during a plurality of heart cycles;
means for storing the derived mechanical restitution parameter; and
means for retrieving the stored mechanical restitution parameter to enable a determination of the state of heart failure of the patient'"'"'s heart. - View Dependent Claims (10)
-
-
11. In an implantable medical device, a system for monitoring the state of heart failure as a function of the mechanical restitution of the heart of a heart failure patient comprising:
-
pacing pulse generating means for selectively generating and applying a pacing pulse to at least one heart chamber to effect a contraction of the heart chamber commencing a paced heart cycle;
extrasystolic escape interval timing means for timing an extrasystolic escape interval from a previously generated and applied pacing pulse;
extrasystolic stimuli generating means for selectively generating and applying electrical stimuli to the at least one heart chamber at the time out of the extrasystolic escape interval to induce post-extrasystolic potentiation increasing the strength of contraction of the heart chamber;
blood pressure measuring means for measuring blood pressure within a heart chamber over at least a portion of a heart cycle and providing a blood pressure value;
mechanical restitution parameter deriving means for selectively enabling operation of said pacing pulse generating means to generate and apply pacing pulses to the heart chamber, said extrasystolic escape interval timing means to time out a predetermined extrasystolic escape interval following predetermined applied pacing pulses, said extrasystolic stimuli generating means to generate and apply extrasystolic stimuli to the heart chamber at the time out of each extrasystolic escape interval, and said blood pressure measuring means to determine a blood pressure value representing the force of contraction of the heart chamber following each applied extrasystolic stimuli, whereby a data set of such determined blood pressure values correlated to the extrasystolic escape intervals is derived and represents the mechanical restitution parameter of the heart chamber;
means for storing the derived mechanical restitution parameter; and
means for retrieving the stored mechanical restitution parameter to enable a determination of the state of heart failure of the patient'"'"'s heart. - View Dependent Claims (12, 13, 14, 15, 17, 18, 19, 20, 21)
-
-
16. In an implantable medical device, a method of monitoring the state of heart failure as a function of the mechanical restitution of the heart of a heart failure patient and deriving a mechanical restitution parameter comprising the steps of:
-
(a) timing out a pacing escape interval;
(b) selectively generating and applying a pacing pulse to at least one heart chamber to effect a contraction of the heart chamber upon time out of the pacing escape interval to commence a paced heart cycle;
(c) measuring blood pressure within the heart chamber during a paced heart cycle and providing a reference blood pressure value;
(d) establishing an extrasystolic escape interval;
(e) timing the extrasystolic escape interval from a previously generated and applied pacing pulse;
(f) selectively generating and applying electrical stimuli to the at least one heart chamber at the time out of the extrasystolic escape interval to induce post-extrasystolic potentiation increasing the strength of contraction of the heart chamber;
(g) measuring blood pressure within the heart chamber during the heart cycle in which the electrical stimuli is applied and providing an extrasystolic blood pressure value;
(h) processing the extrasystolic blood pressure value with said reference systolic blood pressure value to determine a data point of mechanical restitution parameter of the heart chamber correlated to the extrasystolic interval;
(i) incrementing the extrasystolic escape interval;
(j) repeating steps (e) through (i) a predetermined number of times to obtain a plurality of data points from the extrasystolic blood pressure values at the plurality of extrasystolic escape intervals comprising the mechanical restitution parameter; and
(k) storing the derived mechanical restitution parameter.
-
-
22. In an implantable medical device, a method of monitoring the state of heart failure as a function of the mechanical restitution of the heart of a heart failure patient and deriving a mechanical restitution parameter comprising the steps of:
-
(a) timing out a pacing escape interval;
(b) selectively generating and applying a pacing pulse to at least one heart chamber to effect a contraction of the heart chamber upon time out of the pacing escape interval to commence a paced heart cycle;
(c) measuring blood pressure within the heart chamber during a paced heart cycle and providing a reference systolic blood pressure value and diastolic blood pressure value;
(d) establishing an extrasystolic escape interval;
(e) timing the extrasystolic escape interval from a previously generated and applied pacing pulse;
(f) generating and applying electrical stimuli to the at least one heart chamber at the time out of the extrasystolic escape interval to induce post-extrasystolic potentiation increasing the strength of contraction of the heart chamber;
(g) measuring blood pressure within the heart chamber during the heart cycle in which the electrical stimuli is applied and providing an extrasystolic systolic blood pressure value and diastolic blood pressure value;
(h) processing each post-extrasystolic systolic blood pressure value with said reference systolic blood pressure value and each post-extrasystolic diastolic blood pressure value with said reference diastolic blood pressure value to determine systolic and diastolic data points referenced to the extrasystolic interval;
(i) incrementing the extrasystolic escape interval;
(j) repeating steps (e) through (i) a predetermined number of times to obtain a plurality of sets of post-extrasystolic systolic blood pressure value and diastolic blood pressure values at a plurality of extrasystolic escape intervals; and
(k) storing the derived mechanical restitution parameter. - View Dependent Claims (23, 24, 25, 26, 28, 29, 30, 31)
-
-
27. In an implantable medical device, apparatus for monitoring the state of heart failure as a function of the mechanical restitution of the heart of a heart failure patient and deriving a mechanical restitution parameter comprising:
-
means for timing out a pacing escape interval;
pulse generating means for selectively generating and applying a pacing pulse to at least one heart chamber to effect a contraction of the heart chamber upon time out of the pacing escape interval to commence a paced heart cycle;
means for measuring blood pressure within the heart chamber during a paced heart cycle and providing a reference blood pressure value;
means for establishing an extrasystolic escape interval;
means operable following provision of the reference blood pressure value for (I) timing the extrasystolic escape interval from a previously generated and applied pacing pulse;
(ii) selectively generating and applying electrical stimuli to the at least one heart chamber at the time out of the extrasystolic escape interval to induce post-extrasystolic potentiation increasing the strength of contraction of the heart chamber;
(iii) measuring blood pressure within the heart chamber during the heart cycle in which the electrical stimuli is applied and providing an extrasystolic blood pressure value;
(iv) processing the extrasystolic blood pressure value with said reference systolic blood pressure value to determine a plotted data point of the mechanical restitution parameter of the heart chamber correlated to the extrasystolic interval;
(v) incrementing the extrasystolic escape interval; and
(vi) repeating operations (i) through (v) a predetermined number of times to obtain a plurality of plotted data points from the extrasystolic blood pressure values at the plurality of extrasystolic escape intervals comprising the mechanical restitution parameter;
means for storing the derived mechanical restitution parameter; and
means for retrieving the stored mechanical restitution parameter to enable a determination of the state of heart failure of the patient'"'"'s heart.
-
-
32. In an implantable medical device, a method of monitoring the state of heart failure as a function of the mechanical restitution of the heart of a heart failure patient and delivering a therapy comprising the steps of:
-
(a) determining a stable heart rate of a heart chamber having a heart cycle escape interval;
(b) determining an extrasystolic escape interval;
(c) timing out the extrasystolic escape interval during the heart cycle escape interval;
(d) selectively generating and applying an extrasystolic electrical stimulus to the heart chamber at the time out of the extrasystolic escape interval to induce post-extrasystolic potentiation increasing the strength of contraction of the heart chamber;
(e) measuring blood pressure within a heart chamber over at least a portion of a heart cycle and providing a blood pressure value;
(f) repeating steps (b)-(e) for a predetermined series of heart cycles, each time changing the extrasystolic escape interval in step (b), to accumulate a series of blood pressure measurements in step (e);
(g) determining a mechanical restitution parameter of the heart chamber from the accumulated series of blood pressure measurements representing the mechanical response of the heart chamber to the electrical stimuli applied to the heart chamber prematurely at differing extrasystolic escape intervals during the plurality of heart cycles; and
(h) storing the derived mechanical restitution parameter. - View Dependent Claims (33, 34, 35, 36, 37, 39)
-
-
38. In an implantable medical device, a method of monitoring the state of heart failure as a function of the recirculation fraction of the heart of a heart failure patient comprising the steps of:
-
determining a stable heart rate of a heart chamber having a heart cycle escape interval;
determining an extrasystolic escape interval;
timing out the extrasystolic escape interval during the heart cycle escape interval;
selectively generating and applying an extrasystolic electrical stimulus to the heart chamber at the time out of the extrasystolic escape interval to induce post-extrasystolic potentiation increasing the strength of contraction of the heart chamber;
during a series of heart cycles following the application of the extrasystolic electrical stimulus to the heart chamber, measuring an index of the strength of contraction of the heart chamber over at least a portion of a heart cycle and providing a strength of contraction value;
determining a recirculation fraction parameter of the heart chamber from the accumulated series of strength of contraction values representing the mechanical response of the heart chamber to the electrical stimuli applied to the heart chamber prematurely at expiration of the extrasystolic escape interval; and
storing the derived mechanical recirculation fraction parameter.
-
-
40. In an implantable medical device, apparatus for monitoring the state of heart failure as a function of the recirculation fraction of the heart of a heart failure patient comprising:
-
means for determining a stable heart rate of a heart chamber having a heart cycle escape interval;
means for determining an extrasystolic escape interval;
means for timing out the extrasystolic escape interval during the heart cycle escape interval;
means for selectively generating and applying an extrasystolic electrical stimulus to the heart chamber at the time out of the extrasystolic escape interval to induce post-extrasystolic potentiation increasing the strength of contraction of the heart chamber;
means operable during a series of heart cycles following the application of the extrasystolic electrical stimulus to the heart chamber for measuring an index of the strength of contraction of the heart chamber over at least a portion of a heart cycle and providing a strength of contraction value;
means for determining a recirculation fraction parameter of the heart chamber from the accumulated series of strength of contraction values representing the mechanical response of the heart chamber to the electrical stimuli applied to the heart chamber prematurely at expiration of the extrasystolic escape interval;
means for storing the derived recirculation fraction parameter; and
means for retrieving the stored mechanical restitution parameter to enable a determination of the state of heart failure of the patient'"'"'s heart.
-
-
41. In an implantable medical device, a system for monitoring the state of heart failure as a function of the recirculation fraction of the heart of a heart failure patient comprising:
-
pacing pulse generating means for selectively generating and applying a pacing pulse to at least one heart chamber to effect a contraction of the heart chamber commencing a paced heart cycle;
extrasystolic escape interval timing means for timing an extrasystolic escape interval from a previously generated and applied pacing pulse;
extrasystolic stimuli generating means for selectively generating and applying an electrical stimulus to the at least one heart chamber at the time out of the extrasystolic escape interval to induce post-extrasystolic potentiation increasing the strength of contraction of the heart chamber;
blood pressure measuring means for measuring blood pressure within a heart chamber over at least a portion of a heart cycle and providing measured blood pressure values;
recirculation fraction parameter deriving means for selectively enabling operation of said pacing pulse generating means to generate and apply pacing pulses to the heart chamber, said extrasystolic escape interval timing means to time out a predetermined extrasystolic escape interval following an applied pacing pulse, said extrasystolic stimuli generating means to generate and apply an extrasystolic stimulus to the heart chamber at the time out of the extrasystolic escape interval, and said blood pressure measuring means to determine a recirculation fraction blood pressure value representing the force of contraction of the heart chamber in the heart cycle in which the extrasystolic stimuli is applied and in a predetermined number of heart cycles following the heart cycle in which the extrasystolic stimuli is applied, whereby a data set of such determined blood pressure values is derived that represents the recirculation fraction parameter of the heart chamber;
means for storing the derived recirculation fraction parameter; and
means for retrieving the stored mechanical restitution parameter to enable a determination of the state of heart failure of the patient'"'"'s heart. - View Dependent Claims (42, 43)
-
-
44. In an implantable medical device, a method of monitoring the state of heart failure as a function of the recirculation fraction of the heart of a heart failure patient comprising the steps of:
-
generating and applying a pacing pulse to at least one heart chamber to effect a contraction of the heart chamber commencing a paced heart cycle;
timing an extrasystolic escape interval from a previously generated and applied pacing pulse;
generating and applying an extrasystolic electrical stimulus to the at least one heart chamber at the time out of the extrasystolic escape interval to induce post-extrasystolic potentiation increasing the strength of contraction of the heart chamber;
measuring blood pressure within a heart chamber over at least a portion of a heart cycle and providing measured blood pressure values to determine a recirculation fraction blood pressure value representing the force of contraction of the heart chamber in the heart cycle in which the extrasystolic stimuli is applied and in a predetermined number of heart cycles following the heart cycle in which the extrasystolic stimuli is applied, whereby a data set of such determined blood pressure values is derived that represents the recirculation fraction parameter of the heart chamber; and
storing the derived mechanical recirculation fraction parameter. - View Dependent Claims (45, 46, 47, 49)
-
-
48. In an implantable medical device, a system for monitoring the state of heart failure as a function of the relaxation time constant (tau) of the heart of a heart failure patient during a heart cycle comprising:
-
blood pressure measuring means for periodically measuring blood pressure within a heart chamber over at least a portion of a heart cycle and providing a set of measured blood pressure values including blood pressure (P) and rate of change of blood pressure (dP/dt);
means for determining the minimum value of the rate of change of blood pressure among the set of rate of change of blood pressure values;
means for determining the time in the measured heart cycle of the determined minimum value of the rate of change of blood pressure;
means for deriving a tau parameter as a function of a set of samples of blood pressure values within a time window measured from the determined time in the measured heart cycle of the determined minimum value of the rate of change of blood pressure;
means for storing the derived tau parameter; and
means for retrieving the stored tau parameter to enable a determination of the state of heart failure of the patient'"'"'s heart.
-
-
50. In an implantable medical device, a method of monitoring the state of heart failure as a function of the relaxation time constant (tau) of the heart of a heart failure patient over a heart cycle comprising the steps of:
-
periodically measuring blood pressure within a heart chamber over at least a portion of the heart cycle and providing a set of measured blood pressure values including blood pressure (P) and rate of change of blood pressure (dP/dt);
determining the minimum value of the rate of change of blood pressure among the set of rate of change of blood pressure values;
determining the time in the measured heart cycle of the determined minimum value of the rate of change of blood pressure;
deriving a tau parameter as a function of a set of samples of blood pressure values within a time window measured from the determined time in the measured heart cycle of the determined minimum value of the rate of change of blood pressure; and
storing the derived tau parameter. - View Dependent Claims (51, 52)
-
-
53. In an implantable medical device, a system for monitoring the state of heart failure of the heart of a patient as a function of the elastance of the heart comprising:
-
means for defining a heart cycle;
heart chamber volume measuring means for measuring the volume of a heart chamber over at least a portion of a heart cycle and providing a chamber volume value;
blood pressure measuring means for measuring blood pressure within a heart chamber over at least a portion of a heart cycle and providing a blood pressure value; and
elastance parameter deriving means for deriving an elastance parameter representing the slope of plotted sets of end systolic blood pressure versus end systolic chamber volume over a plurality of heart cycles further comprising;
(a) means for operating said blood pressure measuring means and said heart chamber volume measuring means to make N blood pressure (P) measurements and N volume (V) measurements of the heart chamber at a predetermined sample rate over a series of heart cycles following a natural, intrinsic, or paced depolarization of the heart chamber;
(b) means for selecting the end systolic blood pressure (PES) measurements and end systolic volume (VES) measurements at the end systolic point in each heart cycle;
(c) means for establishing a threshold correlation coefficient R2;
(d) means for accumulating n sets of end systolic [PES, VES] data points;
(e) means for performing a linear regression of the “
n”
sets of [PES, VES] data points to derive the slope of the sampled data set, a sample correlation coefficient R and a sample squared correlation coefficient R2;
(f) means for comparing the sample squared correlation coefficient R2 to the threshold squared correlation coefficient R2; and
(g) means for storing the derived slope as the end systolic elastance if the sample squared correlation coefficient R2 exceeds the threshold squared correlation coefficient R2. - View Dependent Claims (54, 55, 56, 57, 59, 60, 61, 62)
-
-
58. In an implantable medical device, a method of monitoring the state of heart failure of the heart of a patient as a function of the elastance of the heart comprising the steps of:
-
defining a heart cycle;
measuring the volume of a heart chamber over at least a portion of a heart cycle and providing a chamber volume value;
measuring blood pressure within a heart chamber over at least a portion of a heart cycle and providing a blood pressure value; and
deriving an elastance parameter representing the slope of plotted sets of end systolic blood pressure versus end systolic chamber volume over a plurality of heart cycles further comprising the steps of;
(a) operating said blood pressure measuring means and said heart chamber volume measuring means to make N blood pressure (P) measurements and N volume (V) measurements of the heart chamber at a predetermined sample rate over a series of heart cycles following a natural, intrinsic, or paced depolarization of the heart chamber;
(b) selecting the end systolic blood pressure (PES) measurements and end systolic volume (VES) measurements at the end systolic point in each heart cycle;
(c) establishing a threshold correlation coefficient R2;
(d) accumulating n sets of end systolic [PES, VES] data points;
(e) performing a linear regression of the “
n”
sets of [PES, VES] data points to derive the slope of the sampled data set, a sample correlation coefficient R and a sample squared correlation coefficient R2;
(f) comparing the sample squared correlation coefficient R2 to the threshold squared correlation coefficient R2; and
(g) storing the derived slope as the end systolic elastance if the sample squared correlation coefficient R2 exceeds the threshold squared correlation coefficient R2.
-
Specification