System and Method for Providing Improved Cardiac Pump Function Through Synchronization with the Natural Mechanical Contractions of the Heart

Abstract

A control system for a cardiac support device and the method of supporting the functionality and synchronized contraction of a heart. An optimal strain profile is calculated for a healthy heart. The cardiac support device is attached to the heart and a true ventricular strain profile is measured. The cardiac support device applies external forces to the heart, therein altering said ventricular strain profile of said heart to be closer to the optimal strain profile. The cardiac support device is dynamically controlled to synchronize with the beating rhythm of the heart. The external forces have an applied strain profile. The applied strain profile has a peak strain, a time to peak strain, and a cycle time. These variables can be adjusted either individually or in combinations to fine tune the cardiac support device and cause the altered strain profile of the heart to be closer to the optimal strain profile.

Claims

1. A method of supporting functionality of a patient's heart with a cardiac support device, wherein said patient's heart has ventricles that experience ventricular compressions as part of a beating rhythm, said method comprising the steps of: placing said cardiac support device in position to affect said patient's heart, wherein said cardiac support device selectively applies mechanical forces externally to said patient's heart that act to compress said ventricles; monitoring said patient's heart to determine when said patient's heart begins said ventricular compressions and determining said beating rhythm at which said ventricular compressions occur; controlling said cardiac support device to repeatedly apply said mechanical forces externally to said patient's heart during said ventricular compressions and in synchronization with said beating rhythm.

2. The method according to claim 1, wherein monitoring said patient's heart to determine when said patient's heart begins ventricular compressions includes monitoring a biometric variable of said patient's heart, wherein said biometric variable is selected from a group consisting of flow rate, arterial pressure, electrocardiogram, and ventricular strain.

3. The method according to claim 1, further including obtaining a ventricular strain profile for said patient's heart and controlling said mechanical forces externally applied by said cardiac support device to alter said ventricular strain profile to be closer to an optimal strain profile.

4. A method of supporting functionality of a patient's heart with a cardiac support device, wherein said patient's heart experiences ventricular compressions as part of a beating rhythm, said method comprising the steps of: determining an optical strain profile for a healthy heart; obtaining a ventricular strain profile for said patient's heart; placing said cardiac support device in position to affect said patient's heart, wherein said cardiac support device externally applies mechanical forces to said patient's heart, therein altering said ventricular strain profile of said patient's heart to be closer to said optimal strain profile.

5. The method according to claim 4, wherein said cardiac support device externally applies mechanical forces to said patient's heart in synchronization with said beating rhythm.

6. The method according to claim 5, wherein determining determining an optical strain profile for a healthy heart includes calculating said optimal strain profile for a healthy heart of similar physiological characteristics to said patient's heart.

7. The method according to claim 4, wherein said mechanical forces externally applied by said cardiac support device cause said patient's heart to have a modified strain profile that contains a peak strain, a time to peak strain, and a cycle time.

8. The method according to claim 7, wherein said modified strain profile is continuously compared to said optimal strain profile and said mechanical forces externally applied by said cardiac support device are continually modified to cause said modified strain profile to be closer to said optimal strain profile.

9. The method according to claim 8, wherein said mechanical forces externally applied by said cardiac support device are selectively changed to alter an element of said modified strain profile, wherein said element is selected from a group consisting of said peak strain, said time to peak strain, and said a cycle time.

10. The method according to claim 4, wherein placing said cardiac support device in position produces an area of contact between said cardiac support device and said patient's heart, wherein said cardiac support device deforms said patient's heart when activated, therein altering said beating rhythm.

11. The method according to claim 4, wherein placing said cardiac support device in position produces an area of contact between said cardiac support device and said patient's heart, wherein said cardiac support device deforms said patient's heart when activated, therein producing an altered area of contact, and therein producing an altered heart size.

12. The method according to claim 11, wherein said altered heart size is used in determining a size for said patient's heart and calculating an optimal strain profile for a healthy heart of said size.

13. The method according to claim 11, wherein said altered area of contact is used in determining said mechanical forces externally to said patient's heart by said cardiac contact device.

14. A method of supporting functionality of a heart with a cardiac support device, wherein said heart has a beating rhythm, said method comprising the steps of: placing said cardiac support device in position to affect the heart, wherein said cardiac support device is capable of externally applying mechanical forces to the heart; obtaining a ventricular strain profile for said heart; controlling said cardiac support device so that said mechanical forces applied to said heart alter said ventricular strain profile of said heart to produce a modified strain profile, wherein said modified strain profile is continuously compared to an optimal strain profile and is modified over time to be closer to said optimal strain profile.

15. The method according to claim 14, wherein said modified strain profile that contains a peak strain, a time to peak strain, and a cycle time.

16. The method according to claim 15, wherein said modified strain profile is further modified by altering said peak strain in said applied strain profile.

17. The method according to claim 15, wherein said modified strain profile is further modified by altering said time to peak strain in said applied strain profile.

18. The method according to claim 15, wherein said modified strain profile is further modified by altering said cycle time in said applied strain profile.

19. The method according to claim 14, wherein placing said cardiac support device in position produces an area of contact between said cardiac support device and said heart, wherein said cardiac support device deforms said heart when activated, therein producing an altered area of contact, and producing an altered heart size and an altered beating rhythm, and wherein said altered heart size is used in determining said optimal strain profile.

20. The method according to claim 18, wherein said altered area of contact and said altered beating rhythm are used in determining said external forces to said heart by said cardiac contact device.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0012] For a better understanding of the present invention, reference is made to the following description of exemplary embodiments thereof, considered in conjunction with the accompanying drawings, in which:

[0013] FIG. 1 is an exemplary schematic overview of the present invention system shown in conjunction with a heart;

[0014] FIG. 2 shows the exemplary embodiment of FIG. 1 engaging the heart;

[0015] FIG. 3 is a graph showing an exemplary ventricular strain profile produced by the cardiac support device of the present invention system;

[0016] FIG. 4 shows an alternate embodiment for the cardiac support device, that has a different area of contact than that of the exemplary embodiment of FIG. 1 and FIG. 2;

[0017] FIG. 5 shows the cardiac support device in engagement with a heart to illustrate surface area of contact and areas of displacement;

[0018] FIG. 6 is a graph that plots surface area of contact with pressures needed to be generated by the cardiac support device;

[0019] FIG. 7 is a flow diagram that illustrates an exemplary operating methodology; and

[0020] FIG. 8 is a graph depicting the cycles featuring loss of ventricular capture.

DETAILED DESCRIPTION OF THE DRAWINGS

[0021] Although the present invention system and methodology can be embodied in many ways, only two exemplary embodiments are illustrated. The exemplary embodiments are being shown for the purposes of explanation and description. The exemplary embodiments are selected in order to set forth some of the best modes contemplated for the invention. The illustrated embodiments, however, are merely exemplary and should not be considered as limitations when interpreting the scope of the appended claims.

[0022] Referring to FIG. 1, an exemplary embodiment illustrating the present invention system 10 is shown. In the illustrated embodiment, a heart 11 is shown for better understanding of context. Every individual has a different physiology. The heart 11 has measurable dimensions that are unique for a particular person. One of the measurable dimensions is AV diameter D.sub.(ED). The AV diameter D.sub.(ED) corresponds to the diameter of the myocardium at the atrioventricular (AV) groove as measured at the end of the diastolic cycle. Likewise, the heart 11 has a measurable length L.sub.(ED) that corresponds to the length of the ventricles at the end of the diastolic cycle. These dimensions of the heart 11 can be readily obtained from various medical scanning equipment, such as x-rays, ultrasounds, MRIs, and the like. Furthermore, it is understood that the heart 11 has a heartbeat, wherein the heart 11 contracts with a regular beat rhythm. Although the beat rhythm can be irregular, it has a general average rate of contraction over increments of time. The beat rhythm of the heart 11 can also be quantified using heart monitoring equipment 16, such as a blood pressure monitor or an ECG unit.

[0023] The measured AV diameter D.sub.(ED) and measured length L.sub.(ED) of the heart 11 can be used to accurately calculate other characteristics of the heart 11. For instance, the measured AV diameter D.sub.(ED) correlates directly to the volume V.sub.(ED) within the ventricles 12 at the end of the diastolic cycle. The relationship between the measured AV diameter D.sub.(ED) and the measured volume V.sub.(ED) is explained in detail in U.S. patent application Ser. No. 17/208,776, the disclosure of which is herein incorporated by reference.

[0024] A cardiac support device 20 is provided. There are multiple cardiac support devices 20 in the prior art and in the commercial marketplace, many of which can be adapted for use with the present invention system 10. The cardiac support device 20 illustrated is indicative of those known and available. Some cardiac support devices are positioned adjacent to the heart and externally apply mechanical forces to heart in the area of contact. In the illustrated embodiment, the cardiac support device 20 contains a cup or band 22 that surrounds the ventricles 12 of the heart 11 in part or in whole. Depending upon the make and model of the cardiac support device 20 selected, the band 22 expands and/or contracts, therein mechanically assisting the pumping action of the heart 10. The cardiac support device 20 contains various internal tubes and compartments that expand or contract depending upon the pressure supplied to those tubes and compartments. The pressure can be pneumatically or hydraulically supplied from an external pressure source 24, such as a hydraulic pump or air compressor. The pressure supplied to the various tubes and compartment is controlled by a valve manifold 26. The operation of the valve manifold 26 is controlled by application software 25 running in a central processing unit 28. The application software 25 produces drive profiles 30 that control the valve manifold 26. The drive profiles 30 cause the valve manifold 26 to regulate the pressures in the cardiac support device 20, wherein the cardiac support device 20 applies forces to the heart 11 that reflect the drive profiles 30. The present invention system 10 creates feedback between the heart 11 and the central processing unit 28, so that the drive profiles 30 controlling the operations of the cardiac support device 20 can better synchronize with the natural contractions of the heart 11.

[0025] The pumping characteristics of the heart 11 can be expressed using strain rate profiles. The strain rate profiles can be used to extrapolate the drive profiles 30 that are utilized by the central processing unit 28 to operate the cardiac support device 20. As can be seen in FIG. 2, the cardiac support device 20 is placed around the ventricles 12 of the heart 11. The ventricular strain profile of the heart is directly measured. This can be accomplished passively, using data from X-ray scan, MRI scans or other strain scans that image the heart. Alternatively, the ventricular strain profile can be actively obtained by placing strain gauges 32 on the heart 11. The active process of measure strain using strain gauges 32 is illustrated. Strain gauges 32, or the alternative strain scan, are used to directly measure any strain ε(t) experienced at the cardiac support device 20. If strain gauges 32 are used, the strain gauges 32 can be retroactively added to the device with adhesive. However, it is preferred that a cardiac support device 32 manufactured with integral strain gauges 32 be used.

[0026] When the effects of the cardiac support device 20 are ignored, the strain ε(t) is created by the inherent function of the heart 11. This assumes the heart 11 is not completely arrested and is capable of providing some pumping function. Should the heart 11 be fully arrested, the strain ε(t) would solely represent the function imparted by the cardiac support device 20. The goal of the overall system 10 is to regulate the cardiac support device 20 so that the forces applied by the cardiac support device 20, combined with the remaining inherent functionality of the heart, create the optimal strain/strain rate profiles for the heart 11.

[0027] In FIG. 1, a band line 34 is shown that represents the ventricular epicardium on the heart 11. To understand strain ε(t) in the heart 11, it should be imagined that the band line 34 is opened and flattened into a straight line. The band line 34 has a length L1. When the heart 11 contracts, that band line 34 has a shorter length L2. In the heart 11, strain ε(t) is the change in length ΔL over the initial length L1. Since the heart 11 can be considered as containing many stacked layers, both above and below the ventricular epicardium, strain ε(t) varies along the length and is therefore a function of length.

[0028] The cardiac support device 20 is controlled by drive profiles 30 in a manner that alters the ventricular strain profiles of the heart 11 in a complementary manner. Referring to FIG. 3, an optimal ventricular strain profile 36 for a healthy heart is shown, wherein the heart is average for the physiology of the patient. Such an optimal ventricular strain profile 36 can be generated for any heart of a given AV diameter D.sub.(ED). As can be seen, the strain ε(t) has a compression phase 38 and a retraction phase 40 over time (t). As can also be seen, there is a peak strain ε.sub.(peak), a time to peak strain t(peak), and an overall cycle period t(cycle).

[0029] An estimation for the strain ε(t)in the compression phase 38 can be estimated using the following equation:

[00001]$\begin{array}{cc}\epsilon \left(t\right)=\frac{{\epsilon }_{\mathrm{peak}}}{2}\left(\sin \left(\frac{\pi }{t_{\mathrm{peak}}}\times t-\frac{3}{2}\pi \right)-1\right)& \mathrm{Equation}1\end{array}$

[0030] An estimation for the strain ε(t)in the retraction phase 40 can be estimated using the following equation:

[00002]$\begin{array}{cc}\epsilon \left(t\right)=\frac{{\epsilon }_{\mathrm{peak}}}{2}(\sin \left(\frac{\pi }{t_{\mathrm{cycle}}-t_{\mathrm{peak}}}\times \left(t-t_{\mathrm{peak}}\right)-\frac{\pi }{2}\right)-1& \mathrm{Equation}2\end{array}$

[0031] The value for ε.sub.(peak) can be estimated from the measured AV diameter D.sub.(ED) of the heart 11 using the following equation:

ε.sub.(peak)≈−0.1254 (D.sub.(ED))−7.7135   Equation 3

[0032] The value for t.sub.(cycle) is determined by the following equation.

t.sub.(cycle)=(Activation Rate/60).sup.−1   Equation 4

[0033] The activation rate can be determined from the measured diameter D.sub.(ED) using the following equation.

Activation Rate≈−1.2089 D.sub.(ED)+221.46   Equation 5

[0034] From the above description and equations, it will be understood that an optimal ventricular strain profile 36 for healthy hearts of different physiologies can be estimated. What remains is the problem of how to actively control the cardiac control device 20 so that it applies the needed strains to a damaged or diseased heart so that the heart can better function near its optimal strain profile.

[0035] In FIG. 2, the cardiac control device 20 has a band that encircles the heart. Referring to FIG. 4, an alternate embodiment is shown, wherein the cardiac support device 31 does not encircle the heart 11 but contacts areas of the heart 11. Depending upon the size of the heart 11 and the make and model of the cardiac support device, there will be different areas of contact onto which forces are applied to the heart 11.

[0036] Referring to FIG. 5 in conjunction with FIG. 2, it will be understood that the exemplary cardiac support device 20 is applied to the heart 11 so that the cardiac support device 20 covers all, or part, of the ventricles 12. Accordingly, the surface area on the heart 11 that the cardiac support device 20 engages is very important in determining how much strain the cardiac support device 20 must supply. The force that the cardiac support device 20 applies to the heart 11 is divided by the surface area of contact. As such, a cardiac support device 20 that covers only part of the ventricles 12 must apply more force than one that covers most all of the ventricles 12, since force is inversely proportional to surface area.

[0037] Furthermore, if the cardiac support device 20 covers only part of the heart 11, as is shown, the cardiac support device 20 creates both direct displacement and indirect displacement of the heart tissue. Direct displacement is created by the forces applied directly to the heart 11 by the cardiac support device 20.

[0038] These direct forces compress the heart 11. This direct compression, in turn, causes displacement in adjacent heart tissue that is not in contact with the cardiac support device 20. This indirect displacement also alters the shape and volume of the heart 11. These changes can cause a change in beat rhythm. To further complicate matters, the direct displacement and the indirect displacement created by the cardiac support device 20 combine to elongate the heart 11. That is, the displacements provided by the cardiac support device 20 make the measured length L.sub.(ED) longer. As the heart elongates, a smaller percentage of the heart 11 remain in direct contact with the cardiac support device 20. This reduces contact surface area. This, in turn, requires that the contact surface area supply greater forces to maintain the same compression forces on the heart 11. The changes in the pressures that the cardiac support device 20 must provide as a function of surface area are shown in the graph of FIG. 6.

[0039] Referring to FIG. 5 in conjunction with FIG. 6, it will be understood that as the heart 11 elongates, changes in the volume of the heart 11 can be estimated by imagining the heart as a series of stacked disks 42 that number 1 to (n). Some of those stacked disks 42 are in the area of direct displacement. Other of the stacked disks 42 are in the areas of indirect displacement. The volume of each disk 42 in the area of direct displacement can be estimated using the following equation.

[00003]$\begin{array}{cc}{V}_{\mathrm{Disk}}={\pi \left(r_0\left(1+\frac{\mathrm{Strain}}{100}\right)\right)}^{2}h& \mathrm{Equation}6\end{array}$

[0040] The variable “V.sub.disk” is the volume of the disk. The variable “R.sub.o” is the original radius of the disk. The variable “H” is the height selected for the disk, which is the length increment between disks. The variable “n” is the number of disks.

[0041] The volume of the disks in the areas of indirect displacement can be estimated using the following equation.

V.sub.Disk=π(r.sub.0).sup.2h   Equation 7

[0042] The total volume of displacement can therefore be estimated using the following equation.

[00004]$\begin{array}{cc}{V}_{\mathrm{total}}=\underset{i=1}{\overset{n}{.Math.}}{V}_{{\mathrm{Disk}}_n}& \mathrm{Equation}8\end{array}$

[0043] Accordingly, the changes in volume of the heart 11 created by the application of compression forces by the cardiac support device 20 can be estimated. Changes in volume correspond to changes in heart length, which correspond to changes in surface area and pressure requirements via the graph of FIG. 6.

[0044] Returning to FIG. 1 and FIG. 2, it will be understood that the central processing unit 28 has various inputs. If stain gauges 32 are used to measure ventricular strain, then the central processing unit 28 is connected to the strain gauges 32 imbedded into the cardiac support device 20. In this manner, the central processing unit 28 can directly monitor strains and strain profiles in real time. If ventricular strain is measured using strain scan data from a heart imaging machine, then that strain scan data is fed to the central processing unit 28. Furthermore, the central processing unit 28 can receives signals from one or more other pieces of heart monitoring equipment 16. Such heart monitoring equipment 16 can monitor heartrate by blood flow rate, arterial pressure, electrocardiogram, peak strain, or the like. In this manner, the central processing unit 28 can dynamically monitor heart rate.

[0045] A user interface 44 is provided, wherein medical personnel can enter the type of cardiac support device 20 being used and the heart physiology of the patient. Given heart physiology and the make and model of the cardiac support device 20, the contact area between the heart 11 and the cardiac support device 20 of the heart 11 can be readily determined. The contact area corresponds to the area of direct displacement that will be affected by the cardiac support device 20. Given heart physiology and contact area, the area of indirect displacement can also be determined.

[0046] The central processing unit 28 runs application software 25 that synchronizes the operation of the cardia support device 20 with the heart in two ways. In a first process, a rhythm synchronization is achieved where the contraction of the cardiac support device 20 correspond to the rhythm of the heart. In a second process, the forces applied by the cardiac support device are dynamically adjusted to achieve proper mechanical cardiac synchrony. That is, the applied forces improve ventricular function by encouraging the ventricular muscles to contract in a more synchronous manner and alter the cardiac contractions from a dyssynchronous pattern to a more favorably pattern.

[0047] Referring to FIG. 7 in conjunction with FIG. 1 and FIG. 2, it will be understood that initial settings, such as the make/model of the cardiac support device 20 and the physiology of the heart 11 are entered. See Block 50. Likewise, the central processing unit 28 reads the dynamic variables. The dynamic variables include the strain readings from the strain gauges 32, or strain scans, and the heart waveform from the heart monitoring equipment 16. See Block 52 and Block 54.

[0048] The first process is rhythm synchronization where the contraction rate utilized by the cardiac support device 20 is matched to the contraction rate of the heart 11. As indicated by Block 56, rhythm synchronization is premised on the understanding that over time, the heart's inherent contraction rate may vary and therefore, re-interrogation is performed periodically to ensure the heart 11 and the cardiac support device 20 are at optimal synchronization. That is, the heart rate is continuously or periodically sampled using the readings from the heart monitoring equipment 16. The detected heart rate is then used to pace the cardiac support device 20. In this manner, the cardiac support device 20 can improve the heart's pump function while reducing the chance of the heart 11 working independently, which may put undue pressure on the heart 11 that is not fully functional.

[0049] The inherent beat rate of the heart 11 varies, but can be averaged over a period of time. The heart monitoring equipment 16 monitor heartrate by blood flow rate, arterial pressure, electrocardiograms, peak strain, or the like. In this manner, the central processing unit 28 can dynamically monitor heart rate. The central processing unit 28 generates drive profiles that begins the contraction of the cardiac support device 20 at the same moment that the heart 11 begins ventricular contraction.

[0050] Once the rhythm synchronization is optimized, the second process of achieving mechanical cardiac synchrony is started. The strain readings from the heart 11 are considered and are used to generate the drive profiles 30 that control the cardiac support device 20. One or more physiological parameters for the heart 11, such as size, is input into the central processing unit 28. Accordingly, an optimal strain profile 58 for a heathy heart having such parameters can be mathematically calculated. The central processing unit 28 attempts to achieve mechanical cardiac synchrony. Mechanical cardiac synchrony corresponds to the complex ventricular contractions that occur in the heart 11. The manner in which the ventricles contract can be quantified using strain analysis. Strain analysis can look at all different areas of the heart 11 and determine if contractions follows a relatively ideal contraction “profile”. Mechanical cardia synchrony for the heart 11 is achieved when the ventricular strain profile measured for the heart 11 matches the optimal strain profile 58. To do this, the central processing unit 28 generates drive profiles 30 for the cardiac support device 20 so that the forces applied by the cardiac support device 20 combine with the inherent functionality of the heart 11 to create a modified strain profile that approaches that of the optimal strain profile 58.

[0051] The goals of mechanical cardiac synchrony are three-fold. The first goal is to improve the heart's native contractile function, although it may have been severely or partially compromised. The second goal is to improve the likelihood that the compression cycle of the cardiac support device 20 is synchronized with that of the compression cycle for the heart 11. Lastly, the third goal is to improve the likelihood that that mechanical stimulus of the cardiac support device 20 leads to the mechanical contraction of the heart 11. When the heart 11 has no intrinsic pulses, the cardiac support device 20 can, therefore, stimulate the synchronization, and then adjust the level of external support based on how much the heart's native functions are restored.

[0052] When heart function is measurable, e.g., greater than approximately 20% of normal function, it is possible to accurately synchronize the cardiac support device 20 with the heart's native or intrinsic cyclic pump function. As is indicated by Block 60, after mechanical pacing is complete, the central processing unit 28 compares the strain profile measured directly from the strain gauges 32 to the optimal strain profile 58. If the measured strain profile is not the same as the optimal strain profile 58, then corrective measures are taken. The drive profiles 30 generated by the central processing unit 28 control the physical operation of the cardiac support device 20.

[0053] Accordingly, different drive profiles 30 cause the cardiac support device 20 to produce different pressure waveforms. The pressure waveforms are estimations produced using the formulations for strain previously described. The differences in strain profiles between the measured strain profiles and the optimal strain profile 58 are known. A drive profile 30 is generated that creates a strain profile that, when added to the measured strain profile, should approach the value of the optimal strain profile. The strain profile generated by the cardiac support device 20 in response to a drive profile 30 is compared to the heartbeat waveform detected by the heart monitoring equipment 16. See Block 62. Upon comparison of the waveforms, a coordination index (CI) between the two waveforms can be calculated using the following equation.

[00005]$\begin{array}{cc}\mathrm{CI}=\sqrt{\frac{1}{N-1}\underset{i=1}{\overset{N}{.Math.}}{\left(d_i-\stackrel{\_}{d}\right)}^2}& \mathrm{Equation}9\end{array}$

[0054] The variable “d.sub.i” is the time delay between peak heart signal (physiologic waveform) and device pressure waveform over one device pressure cycle. The variable “d” is the average delay over N number of cycles. The variable “N” is the number of consecutive cycles in recording (e.g., N can be any number greater than 3, but N>10 or any other arbitrary number with increasing N leading is preferred to increase accuracy. The coordination index (CI) is basically the standard deviation of delay between peaks.

[0055] During the waveform synchronization procedure, it will be understood that the physiologic waveform and the pressure waveforms of the cardiac support device 20 are compared and the difference in timing of peaks are analyzed. If it is determined that each physiologic peak is matched with a device pressure peak in one cycle, then the match, or lack thereof, is assessed over multiple cycles. If higher variability between peak mismatches are seen over repeated cycles, then an updated device profile 30 is created. See Block 64. The device profile 30 can be updates using any combination of three options. The peak time (t.sub.peak) of the cardiac support device 20 can be adjusted.

[0056] Second, the mechanical pacing can be adjusted so that the frequencies of contraction better align. Third, the peak strain ε(peak) produced by the cardiac support device 20 can be adjusted. If one or more of these corrective actions idealizes mechanical synchrony, then the device-specific pressure waveform is achieved. If mechanical cardiac synchrony is not idealized, then the adjustments are repeated. See loop line 66.

[0057] Referring to FIG. 8, a graph 70 is shown that illustrates the identification of the cycles featuring loss of ventricular capture. Loss of ventricular capture occurs when number of peaks from the heartbeat waveform is greater than 1. This is H.sub.1, H.sub.2 and the time between the two adjacent peaks is more than a certain percentage of the length of the device pressure cycle, e.g., >10% of the cycle length with less cycle length indicating more synchrony. It should be understood that the loss of ventricular capture, as represented in FIG. 8, can be detected, and can be corrected in the same manner in the same manner as that set forth in the methodology of FIG. 7. That is, the degree of loss can be detected, and an optimal device profile can be generated to minimize the loss in ventricular capture.

[0058] It will be understood that the embodiments of the present invention that are illustrated and described are merely exemplary and that a person skilled in the art can make many variations to those embodiments. All such embodiments are intended to be included within the scope of the present invention as defined by the claims.