Method and apparatus for monitoring conduction times in a bi-chamber pacing system

• US 20030014084A1
• Filed: 07/16/2001
• Published: 01/16/2003
• Est. Priority Date: 07/16/2001
• Status: Active Grant

• Current Assignee: Medtronic Incorporated (Medtronic Plc)
• Original Assignee: Medtronic Incorporated (Medtronic Plc)
• Inventors: VanHout, Warren L.
• Granted Patent: US 6,668,194 B2
• Time in Patent Office: Days
• US Class Current: 607/9
• CPC Class Codes: A61N 1/3627 for treating a mechanical deficiency of the heart, e.g. congestive heart failure or cardiomyopathy
• CPC Class Codes: A61N 1/3684 for stimulating the heart at multiple sites of the ventricle or the atrium
• CPC Class Codes: A61N 1/36843 Bi-ventricular stimulation

Abstract

Multi-site cardiac pacing systems that pace and sense in at least a first site in the heart and sense conducted electrical signals at a second site in the heart and measure and accumulate electrical conduction times between the first and second sites to derive trend data indicative of the state of heart failure. Preferably the sites are right heart chamber and left heart chamber sites, e.g., right and left atrial sites or right and left ventricular sites. In a ventricular embodiment, a V-V conduction time is measured from a ventricular sense (VS) event or a ventricular pace (VP) pulse delivered to a selected one of first and second ventricular sites to the VS event at the other one of the first and second ventricular sites. The measured V-V conduction time can be one or more of a VS-VS conduction time, a VP-VS conduction time and a VS/VP-VS conduction time. In each case, a single data point measured V-V conduction time may be obtained and stored or the high and low measured V-V conduction times and an average V-V conduction time can be obtained from a series of measured V-V conduction times. The measured V-V conduction time or times as well as related data including a date and time stamp of the measurement event, the prevailing heart rate, and the activity level of the patient or other indicator of physiologic need for cardiac output are stored in IMD memory during each measurement session for subsequent analysis. Trend data evidencing any change in the intrinsic conduction time between the first and second ventricular sites gathered over a period of days, weeks and months provides a valuable indication as to whether the heart failure state is improving, worsening or staying about the same.

Claims

1. For use in a cardiac pacing system, the method comprising the methods of:

(a) detecting a first ventricular event in a selected one of the first and second ventricular sites;

(b) detecting a second ventricular depolarization in the other of the first and second ventricular sites;

(c) measuring an elapsed conduction time from the first ventricular event to the second ventricular depolarization; and

(d) utilizing the elapsed conduction time as an indicator of the state of heart failure.

2. The method of claim 1, wherein the first ventricular event of method (a) is a ventricular depolarization.

3. The method of claim 1, wherein method (d) includes storing the elapsed conduction time in a storage device.

4. The method of claim 3, and further including the method of repeating methods (a) through (d).

5. The method of claim 4, and further including the method of utilizing multiple measured elapsed conduction times to develop trend data representative of the state of heart failure.

6. The method of claim 1, and further including the methods of:

timing an escape interval prior to method (a); and

wherein the first ventricular event of method (a) is a first ventricular pace pulse delivered to the selected one of the first and second ventricular sites upon the expiration of the escape interval.

7. The method of claim 6, wherein the cardiac pacing system is capable of delivering a second ventricular pace pulse to the other of the first and second ventricular sites at a predetermined time relative to the first ventricular pace pulse and wherein method (b) includes the method of periodically suspending the delivery of the second ventricular pace pulse to detect the second ventricular depolarization.

8. A cardiac pacing system capable of delivering electrical stimulus to first and second ventricular sites, comprising:

a timing circuit to begin measuring a time interval from a first ventricular event occurring at a selected one of the first and second ventricular sites;

a sensing circuit coupled to the timing circuit to detect a second ventricular depolarization in the other of the first and second ventricular sites, wherein the timing circuit is capable of measuring an elapsed conduction time from the first ventricular event to the second ventricular depolarization and wherein the elapsed conduction time may be utilized as an indicator of the state of heart failure.

9. The system of claim 8, and further including a processing circuit coupled to the timing circuit to utilize the elapsed conduction time as an indicator of the state of heart failure.

10. The system of claim 8, wherein the first ventricular event is a first ventricular depolarization, and further including a sensing circuit coupled to the timing circuit to sense the first ventricular event.

11. The system of claim 8, wherein the first ventricular event is a first pacing pulse, and further including an output circuit coupled to the timing circuit to provide the first pacing pulse.

12. The system of claim 11, wherein the output circuit is capable of delivering a second pacing pulse to the other one of the first and second ventricular sites, and further including means for suspending the delivery of the second pacing pulse to allow the sensing circuit to detect the second ventricular depolarization.

13. The system of claim 8, and further including a storage device coupled to the timing circuit to store one or more elapsed conduction times.

14. The system of claim 13, and further including a processing circuit coupled to the timing circuit to develop trend data from the stored elapsed conduction times, the trend data being indicative of the state of heart failure.

15. The system of claim 8, and further including a communication circuit coupled to the timing circuit to transfer one or more elapsed conduction times to an external device.

17. The method of claim 16, further comprising the step of suspending steps (d) and (e) while steps (a) through (c) and (f) through (h) are performed for one or more heart cycle.

18. The method of claim 17, wherein:

said first ventricular site is a right ventricular site in or adjacent to the right ventricle and said second ventricular site is a left ventricular site in or adjacent to the left ventricle; and

the first VS event signals are right VS event signals, and the second VS event signals are left VS event signals,

whereby spontaneous cardiac depolarizations of the right and left ventricles are sensed and VP pulses are delivered to the right and left heart ventricles during steps (a) through (e) for improving the hemodynamic efficiency of a sick heart suffering from conduction times in conducting spontaneous or evoked depolarizations through the right and left ventricles that compromise cardiac output.

19. The method of claim 17, wherein:

said first ventricular site is a left ventricular site in or adjacent to the left ventricle and said second ventricular site is a right ventricular site in or adjacent to the right ventricle; and

the first VS event signals are left VS event signals, and the second VS event signals are right VS event signals,

whereby spontaneous cardiac depolarizations of the right and left ventricles are sensed and VP pulses are delivered to the right and left heart ventricles during steps (a) through (e) for improving the hemodynamic efficiency of a sick heart suffering from conduction times in conducting spontaneous or evoked depolarizations through the right and left ventricles that compromise cardiac output.

20. The method of claim 17, further comprising:

repeating steps (a)-(c) and (f)-(h) to derive a plurality of measured ones of the elapsed VS-VS conduction time or the elapsed VP-VS conduction time; and

determining one or more of the longest, shortest, and average elapsed VS-VS conduction time or VP-VS conduction time; and

wherein;

step (h) further comprises storing the determined one or more of the longest, shortest, and average elapsed VS-VS conduction time or VP-VS conduction time.

21. The method of claim 17, wherein step (h) further comprises storing one or more related data including a date and time stamp of the measurement event, the prevailing heart rate, and an activity level of the patient or other indicator of physiologic need for cardiac output.

22. The method of claim 15, wherein:

step (c) further comprises selectively delivering a first VP pulse to the selected one of the first and second ventricular sites upon provision of the first VS event during time-out of the pacing escape interval as a VS/VP pulse;

step (d) further comprises timing the V-V pace delay from the first VP pulse delivered upon time-out of the pacing escape interval or selectively either from the VS/VP pulse delivered synchronously with the first VS event or from the first VS event occurring prior to the time-out of the pacing escape interval;

step (g) further comprises measuring one of the elapsed VP-VS conduction time from the first VP pulse delivered at the end of the pacing escape interval or the elapsed VS/VP-VS conduction time from the first VP pulse delivered upon a first VS event occurring during the time-out of the pacing escape interval or the VS-VS conduction time; and

step (h) further comprises storing in memory the measured one of the VP-VS conduction time, the VS/VP-VP conduction time or the VS-VS conduction time,

whereby trend data representative of the state of heart failure as evidenced by changes in the stored one of the elapsed VS-VS conduction time, the VP-VS conduction time, and the VS/VP-VS conduction time between the first and second ventricular sites is accumulated for analysis of the trend.

23. The method of claim 16, wherein:

said first ventricular site is a right ventricular site in or adjacent to the right ventricle and said second ventricular site is a left ventricular site in or adjacent to the left ventricle; and

the first VS event signals are right VS event signals, and the second VS event signals are left VS event signals,

whereby spontaneous cardiac depolarizations of the right and left ventricles are sensed and VP pulses are delivered to the right and left heart ventricles during steps (a) through (e) for improving the hemodynamic efficiency of a sick heart suffering from conduction times in conducting spontaneous or evoked depolarizations through the right and left ventricles that compromise cardiac output.

24. The method of claim 16, wherein:

said first ventricular site is a left ventricular site in or adjacent to the left ventricle and said second ventricular site is a right ventricular site in or adjacent to the right ventricle; and

the first VS event signals are left VS event signals, and the second VS event signals are right VS event signals,

whereby spontaneous cardiac depolarizations of the right and left ventricles are sensed and VP pulses are delivered to the right and left heart ventricles during steps (a) through (e) for improving the hemodynamic efficiency of a sick heart suffering from conduction times in conducting spontaneous or evoked depolarizations through the right and left ventricles that compromise cardiac output.

25. The method of claim 16, further comprising:

repeating steps (a)-(c) and (f)-(h) to derive a plurality of measured ones of the elapsed VS-VS conduction time or the elapsed VP-VS conduction time; and

determining one or more of the longest, shortest, and average elapsed VS-VS conduction time or VP-VS conduction time; and

wherein;

step (h) further comprises storing the determined one or more of the longest, shortest, and average elapsed VS-VS conduction time or VP-VS conduction time.

26. The method of claim 16, wherein step (h) further comprises storing one or more related data including a date and time stamp of the measurement event, the prevailing heart rate, and an activity level of the patient or other indicator of physiologic need for cardiac output.

27. The method of claim 16, wherein:

step (c) further comprises selectively delivering a first VP pulse to the selected one of the first and second ventricular sites upon provision of the first VS event during time-out of the pacing escape interval as a VS/VP pulse;

step (d) further comprises timing the V-V pace delay from the first VP pulse delivered upon time-out of the pacing escape interval or selectively either from the VS/VP pulse delivered synchronously with the first VS event or from the first VS event occurring prior to the time-out of the pacing escape interval;

step (g) further comprises measuring one of the elapsed VP-VS conduction time from the first VP pulse delivered at the end of the pacing escape interval or the elapsed VS/VP-VS conduction time from the first VP pulse delivered upon a first VS event occurring during the time-out of the pacing escape interval or the VS-VS conduction time; and

step (h) further comprises storing in memory the measured one of the VP-VS conduction time, the VS/VP-VP conduction time or the VS-VS conduction time,

whereby trend data representative of the state of heart failure as evidenced by changes in the stored one of the elapsed VS-VS conduction time, the VP-VS conduction time, and the VS/VP-VS conduction time between the first and second ventricular sites is accumulated for analysis of the trend.

29. The system of claim 28, wherein the apparatus for periodically deriving trend data representative of the state of heart failure as evidenced by ventricular conduction time between the first and second ventricular sites further comprises

suspending means for suspending the pace delay timing means for one or more heart cycles.

30. The system of claim 29, wherein:

said first ventricular site is a right ventricular site in or adjacent to the right ventricle and said second ventricular site is a left ventricular site in or adjacent to the left ventricle; and

the first VS event signals are right VS event signals, and the second VS event signals are left VS event signals,

whereby spontaneous cardiac depolarizations of the right and left ventricles are sensed and VP pulses are delivered to the right and left heart ventricles during steps (a) through (e) for improving the hemodynamic efficiency of a sick heart suffering from conduction times in conducting spontaneous or evoked depolarizations through the right and left ventricles that compromise cardiac output.

31. The system of claim 29, wherein:

said first ventricular site is a left ventricular site in or adjacent to the left ventricle and said second ventricular site is a right ventricular site in or adjacent to the right ventricle; and

the first VS event signals are left VS event signals, and the second VS event signals are right VS event signals,

whereby spontaneous cardiac depolarizations of the right and left ventricles are sensed and VP pulses are delivered to the right and left heart ventricles during steps (a) through (e) for improving the hemodynamic efficiency of a sick heart suffering from conduction times in conducting spontaneous or evoked depolarizations through the right and left ventricles that compromise cardiac output.

32. The system of claim 29, wherein:

the suspending means is operable over a plurality of heart cycles; and

the conduction time measuring means measures a plurality of measured ones of the elapsed VS-VS conduction time or the elapsed VP-VS conduction time and further comprising;

means for determining one or more of the longest, shortest, and average elapsed VS-VS conduction time or VP-VS conduction time; and

wherein;

the storing means stores the determined one or more of the longest, shortest, and average elapsed VS-VS conduction time or VP-VS conduction time.

33. The system of claim 29, wherein the storing means further comprises means for storing one or more related data including a date and time stamp of the measurement event, the prevailing heart rate, and an activity level of the patient or other indicator of physiologic need for cardiac output.

34. The system of claim 29, wherein

the first ventricular pace means is selectively operable for delivering a first VP pulse to the selected one of the first and second ventricular sites upon provision of the first VS event during time-out of the pacing escape interval as a VS/VP pulse;

the pace delay timing means includes means for timing the V-V pace delay from the first VP pulse delivered upon time-out of the pacing escape interval or selectively either from the VS/VP pulse delivered synchronously with the first VS event or from the first VS event occurring prior to the time-out of the pacing escape interval;

the conduction time measuring means includes means for measuring one of the elapsed VP-VS conduction time from the first VP pulse delivered at the end of the pacing escape interval or the elapsed VS/VP-VS conduction time from the first VP pulse delivered upon a first VS event occurring during the time-out of the pacing escape interval or the VS-VS conduction time; and

the storing means includes means for storing in memory the measured one of the VP-VS conduction time, the VS/VP-VP conduction time or the VS-VS conduction time,

whereby trend data representative of the state of heart failure as evidenced by changes in the stored one of the elapsed VS-VS conduction time, the VP-VS conduction time, and the VS/VP-VS conduction time between the first and second ventricular sites is accumulated for analysis of the trend.

35. The system of claim 28, wherein:

said first ventricular site is a right ventricular site in or adjacent to the right ventricle and said second ventricular site is a left ventricular site in or adjacent to the left ventricle; and

the first VS event signals are right VS event signals, and the second VS event signals are left VS event signals,

whereby spontaneous cardiac depolarizations of the right and left ventricles are sensed and VP pulses are delivered to the right and left heart ventricles during steps (a) through (e) for improving the hemodynamic efficiency of a sick heart suffering from conduction times in conducting spontaneous or evoked depolarizations through the right and left ventricles that compromise cardiac output.

36. The system of claim 28, wherein:

said first ventricular site is a left ventricular site in or adjacent to the left ventricle and said second ventricular site is a right ventricular site in or adjacent to the right ventricle; and

the first VS event signals are left VS event signals, and the second VS event signals are right VS event signals,

whereby spontaneous cardiac depolarizations of the right and left ventricles are sensed and VP pulses are delivered to the right and left heart ventricles during steps (a) through (e) for improving the hemodynamic efficiency of a sick heart suffering from conduction times in conducting spontaneous or evoked depolarizations through the right and left ventricles that compromise cardiac output.

37. The system of claim 28, wherein the conduction time measuring means measures a plurality of measured ones of the elapsed VS-VS conduction time or the elapsed VP-VS conduction time and further comprising:

means for determining one or more of the longest, shortest, and average elapsed VS-VS conduction time or VP-VS conduction time; and

wherein;

the storing means stores the determined one or more of the longest, shortest, and average elapsed VS-VS conduction time or VP-VS conduction time.

38. The system of claim 28, wherein the storing means further comprises means for storing one or more related data including a date and time stamp of the measurement event, the prevailing heart rate, and an activity level of the patient or other indicator of physiologic need for cardiac output.

39. The system of claim 28, wherein

the first ventricular pace means is selectively operable for delivering a first VP pulse to the selected one of the first and second ventricular sites upon provision of the first VS event during time-out of the pacing escape interval as a VS/VP pulse;

the pace delay timing means times the V-V pace delay from the first VP pulse delivered upon time-out of the pacing escape interval or selectively either from the VS/VP pulse delivered synchronously with the first VS event or from the first VS event occurring prior to the time-out of the pacing escape interval;

the conduction time measuring means measures one of the elapsed VP-VS conduction time from the first VP pulse delivered at the end of the pacing escape interval or the elapsed VS/VP-VS conduction time from the first VP pulse delivered upon a first VS event occurring during the time-out of the pacing escape interval or the VS-VS conduction time; and

the storing means stores in memory the measured one of the VP-VS conduction time, the VS/VP-VP conduction time or the VS-VS conduction time,

whereby trend data representative of the state of heart failure as evidenced by changes in the stored one of the elapsed VS-VS conduction time, the VP-VS conduction time, and the VS/VP-VS conduction time between the first and second ventricular sites is accumulated for analysis of the trend.

16. In a multi-site, cardiac pacing system having memory for storing data and wherein ventricular pacing pulses are delivered to first and second ventricular sites synchronously within a V-V pace delay at a predetermined pacing rate in accordance with the steps of:

(a) timing a ventricular pacing escape interval of a heart cycle;

(b) detecting a ventricular depolarization in a selected one of the first and second ventricular sites within the pacing escape interval and, in response, terminating the pacing escape interval and providing a first ventricular sense (VS) event;

(c) delivering a first ventricular pace (VP) pulse to the selected one of the first and second ventricular sites upon the time-out of the pacing escape interval without provision of a first VS event;

(d) timing the V-V pace delay from a first VS event occurring prior to the time-out of the pacing escape interval or from a first VP pulse delivered upon time-out of the pacing escape interval; and

(e) delivering a second VP pulse to the other of the first and second ventricular sites upon the time-out of the V-V pace delay;

a method of periodically deriving trend data representative of the state of heart failure as evidenced by ventricular conduction time between the first and second ventricular sites comprising the steps of;

(f) detecting a ventricular depolarization in the other of the first and second ventricular sites during the one or more heart cycle and providing a second VS event in response;

(g) measuring one of an elapsed VS-VS conduction time from a first VS event to the second VS event or an elapsed VP-VS conduction time from the first VP pulse to the second VS event; and

(h) storing in memory the measured one of the elapsed VS-VS conduction time or the elapsed VP-VS conduction time,

whereby trend data representative of the state of heart failure as evidenced by changes in the stored one of the elapsed VS-VS conduction time or the elapsed VP-VS conduction time between the first and second ventricular sites is accumulated for analysis of the trend.

28. In a multi-site, cardiac pacing system having memory for storing data and wherein ventricular pacing pulses are delivered to first and second ventricular sites synchronously within a V-V pace delay at a predetermined pacing rate by:

pacing escape interval timing means for timing a ventricular pacing escape interval of a heart cycle;

first ventricular sense event means for detecting a ventricular depolarization in a selected one of the first and second ventricular sites within the pacing escape interval and, in response, terminating the pacing escape interval and providing a first ventricular sense (VS) event;

first ventricular pace means for delivering a first ventricular pace (VP) pulse to the selected one of the first and second ventricular sites upon the time-out of the pacing escape interval without provision of a first VS event;

pace delay timing means for timing the V-V pace delay from a first VS event occurring prior to the time-out of the pacing escape interval or from a first VP pulse delivered upon time-out of the pacing escape interval; and

second ventricular pace means for delivering a second VP pulse to the other of the first and second ventricular sites upon the time-out of the V-V pace delay;

apparatus for periodically deriving trend data representative of the state of heart failure as evidenced by ventricular conduction time between the first and second ventricular sites comprising;

suspending means for suspending the pace delay timing means for one or more heart cycle;

second ventricular sense event means for detecting a ventricular depolarization in the other of the first and second ventricular sites during the one or more heart cycle following a first VS event or a first VP pulse and providing a second VS event in response;

conduction time measuring means for measuring one of an elapsed VS-VS conduction time from a first VS event to the second VS event or an elapsed VP-VS conduction time from the first VP pulse to the second VS event; and

storing means for storing in memory the measured one of the elapsed VS-VS conduction time or the elapsed VP-VS conduction time,

whereby trend data representative of the state of heart failure as evidenced by changes in the stored one of the elapsed VS-VS conduction time or the elapsed VP-VS conduction time between the first and second ventricular sites is accumulated for analysis of the trend.

40. In a multi-site, AV sequential, cardiac pacing system having memory for storing data and wherein ventricular pacing pulses are delivered to the right and left ventricles synchronously within a V-V pace delay following time-out of an AV delay from a preceding delivered atrial pace pulse or an atrial sense event in accordance with the steps of:

(a) timing an AV delay from a preceding delivered atrial pace pulse or an atrial sense event;

(b) detecting a ventricular depolarization in a selected one of the right and left ventricle within the AV delay and, in response, terminating the AV delay and providing a first ventricular sense (VS) event;

(c) delivering a first ventricular pace (VP) pulse to the selected one of the right and left ventricle upon either the time-out of the AV delay without provision of a first VS event or upon provision of the first VS event during time-out of the AV delay;

(d) timing the V-V pace delay from a first VS event occurring prior to the time-out of the AV delay or from a first VP pulse delivered either upon provision of the first VS event or upon time-out of the AV delay; and

(e) delivering a second VP pulse to the other of the right and left ventricle upon the time-out of the V-V pace delay;

a method of periodically deriving trend data representative of the state of heart failure as evidenced by ventricular conduction time between the right and left ventricle comprising the steps of;

(f) suspending steps (d) and (e) while steps (a) through (c) are performed for one or more heart cycle;

(g) detecting a ventricular depolarization in the other of the right and left ventricle during the one or more heart cycle and providing a second VS event in response;

(h) measuring one of the elapsed VS-VS conduction time from a first VS event or the elapsed VP-VS conduction time from the first VP pulse delivered at the end of the AV delay or the elapsed VS/VP-VS conduction time from the first VP pulse delivered upon a first VS event occurring during the time-out of the AV delay; and

(i) storing in memory the measured one of the elapsed VS-VS conduction time or the elapsed VP-VS conduction time or the elapsed VS/VP-VS conduction time

whereby trend data representative of the state of heart failure as evidenced by changes in the stored one of the elapsed VS-VS conduction time, the VP-VS conduction time, and the VS/VP-VS conduction time between the right and left ventricles is accumulated for analysis of the trend.

41. The method of claim 40, further comprising:

repeating steps (a)-(c) and (f)-(h) to derive a plurality of measured ones of the elapsed VS-VS conduction time or the VS/VP-VS conduction time or the elapsed VP-VS conduction time; and

determining one or more of the longest, shortest, and average elapsed VS-VS conduction time or VS/VP-VS conduction time or VP-VS conduction time; and

wherein;

step (i) further comprises storing the determined one or more of the longest, shortest, and average elapsed VS-VS conduction time or VS/VP-VS conduction time or VP-VS conduction time.

42. In a multi-site, AV sequential, cardiac pacing system having memory for storing data and wherein ventricular pacing pulses are delivered to the right and left ventricles synchronously within a V-V pace delay following time-out of an AV delay from a preceding delivered atrial pace pulse or an atrial sense event by:

(a) means for timing an AV delay from a preceding delivered atrial pace pulse or an atrial sense event;

(b) means for detecting a ventricular depolarization in a selected one of the right and left ventricle within the AV delay and, in response, terminating the AV delay and providing a first ventricular sense (VS) event;

(c) means for delivering a first ventricular pace (VP) pulse to the selected one of the right and left ventricle upon either the time-out of the AV delay without provision of a first VS event or upon provision of the first VS event during time-out of the AV delay;

(d) means for timing the V-V pace delay from a first VS event occurring prior to the time-out of the AV delay or from a first VP pulse delivered either upon provision of the first VS event or upon time-out of the AV delay; and

(e) means for delivering a second VP pulse to the other of the right and left ventricle upon the time-out of the V-V pace delay;

apparatus for periodically deriving trend data representative of the state of heart failure as evidenced by ventricular conduction time between the right and left ventricle comprising;

(f) means for suspending means (d) and (e) while means (a) through (c) operate for one or more heart cycle;

(g) means for detecting a ventricular depolarization in the other of the right and left ventricle during the one or more heart cycle and providing a second VS event in response; and

(g) means for measuring and storing in memory one of the elapsed VS-VS conduction time from a first VS event or the elapsed VP-VS conduction time from the first VP pulse delivered at the end of the AV delay or the elapsed VS/VP-VS conduction time from the first VP pulse delivered upon a first VS event occurring during the time-out of the AV delay,

whereby trend data representative of the state of heart failure as evidenced by changes in the stored one of the elapsed VS-VS conduction time, the VP-VS conduction time, and the VS/VP-VS conduction time between the right and left ventricles is accumulated for analysis of the trend.

43. The system of claim 42, wherein the conduction time measuring means measures a plurality of measured ones of the elapsed VS-VS conduction time or the elapsed VP-VS conduction time or the VS/VP-VS conduction time and further comprising:

means for determining one or more of the longest, shortest, and average the elapsed VS-VS conduction time or the VS/VP-VS conduction time or the elapsed VP-VS conduction time; and

wherein;

the storing means stores the determined one or more of the longest, shortest, and average elapsed VS-VS conduction time or VP-VS conduction time or VS/VP-VS conduction time.

44. In a multi-site, cardiac pacing system having memory for storing data and wherein ventricular pacing pulses are delivered to first and second ventricular sites synchronously within a V-V pace delay at a predetermined pacing rate for improving the hemodynamic efficiency of a sick heart, a method of obtaining conduction time data comprising the steps of:

sensing spontaneous atrial depolarizations and providing atrial sense event signals;

timing out an AV delay from the atrial sense event signals;

sensing spontaneous cardiac depolarizations at a first ventricular site and providing first ventricular sense (VS) event signals;

sensing spontaneous cardiac depolarizations at a second ventricular site and providing second ventricular sense (VS) event signals;

upon time-out of the AV delay, delivering a first ventricular pace (VP) pulse to a predetermined one of the first and second ventricular sites;

measuring a VP-VS conduction time from a VP pulse delivered to the predetermined one of the first and second ventricular sites until the sensing of a cardiac depolarization at the other one of the first and second ventricular sites as a VS event signal; and

storing in memory the VP-VS conduction time whereby trend data representative of the state of heart failure as evidenced by changes in the stored VP-VS conduction time between the first and second ventricular sites is accumulated for analysis of the trend.

45. The method of claim 44, wherein the first ventricular site is a right ventricular site and the second ventricular site is a left ventricular site and wherein:

the step of delivering a ventricular pace pulse to a predetermined one of the first and second ventricular sites upon provision of a first or second ventricular sense event signal during the timing out of the AV delay further comprises delivering a first VP pulse either as a right VP pulse to the right ventricular site to evoke a right ventricular depolarization or as a left VP pulse to the left ventricular site to evoke a left ventricular depolarization.

46. The method of claim 44, further comprising the steps of:

upon provision of a first or second ventricular sense event signal during the timing out of the AV delay, delivering a first VP pulse to the predetermined one of the first and second ventricular sites without delay as a VS/VP pulse;

measuring a VS/VP-VS conduction time from the VS/VP pulse until the sensing of a cardiac depolarization at the other one of the first and second ventricular sites as a VS event signal; and

storing in memory the VS/VP-VS conduction time whereby trend data representative of the state of heart failure as evidenced by changes in the stored VP-VS conduction time between the first and second ventricular sites is accumulated for analysis of the trend.

47. The method of claim 44, further comprising the steps of:

measuring a VS-VS conduction time from the VS event signal at the first or second ventricular site during the time-out of the AV delay until the second VS event signal at the other one of the first and second ventricular sites; and

storing in memory the VS-VS conduction time whereby trend data representative of the state of heart failure as evidenced by changes in the stored V-V conduction time between the first and second ventricular sites is accumulated for analysis of the trend.

48. The method of claim 44, further comprising the steps of:

delivering a first VP pulse to a selected one of the first and second ventricle upon either the time-out of the AV delay without provision of a first VS event or upon provision of the first VS event during time-out of the AV delay;

timing a V-V pace delay from a first VS event occurring prior to the time-out of the AV delay or from a first VP pulse delivered either upon provision of the first VS event or upon time-out of the AV delay; and

delivering a second VP pulse to the other of the right and left ventricle upon the timeout of the V-V pace delay.

50. The system of claim 49, wherein the pulse generator further comprises:

ventricular trigger pacing means coupled to said ventricular pace/sense lead means and operable in response to provision of a first or second VS event signal during the time-out of the AV delay for delivering a VP pulse to a predetermined one of said first and second pace/sense electrodes at said first and second ventricular sites without delay; and

V-A escape interval restarting means operable in response to provision of a first or second VS event signal during the time-out of the V-A escape interval for terminating and restarting the V-A escape interval,

whereby triggered ventricular pacing is provided to at least one of the first and second ventricular sites only when a first or second VS event signal is provided during time-out of the AV delay.

51. The system of claim 50, wherein the first ventricular site is a right ventricular site and the second ventricular site is a left ventricular site.

52. The system of claim 49, wherein the pulse generator further comprises:

means operable upon provision of a first or second ventricular sense event signal during the timing out of the AV delay, delivering a first VP pulse to the predetermined one of the first and second ventricular sites without delay as a VS/VP pulse;

means for measuring a VS/VP-VS conduction time from the VS/VP pulse until the sensing of a cardiac depolarization at the other one of the first and second ventricular sites as a VS event signal; and

means for storing the VS/VP-VS conduction time in memory whereby trend data representative of the state of heart failure as evidenced by changes in the stored VP-VS conduction time between the first and second ventricular sites is accumulated for analysis of the trend.

53. The system of claim 49, wherein the pulse generator further comprises:

means for measuring a VS-VS conduction time from the VS event signal at the first or second ventricular site until the second VS event signal at the other one of the first and second ventricular sites; and

means for storing the VS-VS conduction time in memory whereby trend data representative of the state of heart failure as evidenced by changes in the stored V-V conduction time between the first and second ventricular sites is accumulated for analysis of the trend.

54. The system of claim 49, wherein the pulse generator further comprises:

means for delivering a first VP pulse to the selected one of the right and left ventricle upon either the time-out of the AV delay without provision of a first VS event or upon provision of the first VS event during time-out of the AV delay;

means for timing a V-V pace delay from a first VS event occurring prior to the timeout of the AV delay or from a first VP pulse delivered either upon provision of the first VS event or upon time-out of the AV delay; and

means for delivering a second VP pulse to the other of the right and left ventricle upon the time-out of the V-V pace delay.

49. A multi-site cardiac pacing system for selectively sensing spontaneous ventricular cardiac depolarizations at spaced apart ventricular sites and delivering pace pulses to the spaced apart ventricular sites for improving the hemodynamic efficiency of a sick heart and having memory for storing data, wherein said pacing system further comprises:

an atrial pace/sense lead adapted to be advanced into relation with an atrial chamber to situate an atrial pace/sense electrode in or adjacent to the atrial chamber;

ventricular pace/sense lead means for situating a first ventricular pace/sense electrode at a first ventricular site and a second ventricular pace/sense electrode at a second ventricular site spaced from said first ventricular site; and

a pace pulse generator coupled to said atrial pace/sense lead and said ventricular pace/sense lead means comprising;

an atrial sense amplifier coupled to said atrial pace/sense electrode for sensing spontaneous atrial depolarizations and providing atrial sense (AS) event signals;

an AV delay timer for timing out an AV delay from the AS event signals;

a first ventricular sense amplifier coupled to said first ventricular pace/sense electrode for sensing spontaneous cardiac depolarizations at the first ventricular site and providing first ventricular sense (VS) event signals;

a second ventricular sense amplifier coupled to said second ventricular electrode for sensing spontaneous cardiac depolarizations at the second ventricular site and providing second ventricular sense (VS) event signals;

an escape interval timer for timing out a V-A escape interval establishing a pacing rate from one of the first and second VS event signals occurring during the time-out of the AV delay or the V-A escape interval;

means for measuring a VP-VS conduction time from a VP pulse delivered to the predetermined one of the first and second ventricular sites until a VS event resulting from sensing of a cardiac depolarization at the other one of the first and second ventricular sites; and

means for storing the VP-VS conduction time in memory whereby trend data representative of the state of heart failure as evidenced by changes in the stored VP-VS conduction time between the first and second ventricular sites is accumulated for analysis of the trend.

55. In a multi-site, cardiac pacing system having memory for storing data and having the capability of sensing cardiac depolarizations in a right heart chamber (RHC) to develop an RHC sense (RHS) event signal and a left heart chamber (LHC) to develop an LHC sense (LHS) event signal and to selectively pace in the RHC and LHC whereby RHC pace (RHP) pulses are selectively delivered to the RHC and LHC pace (LHP) pulses are delivered to the LHC synchronously within an RHP-LHP delay at a predetermined pacing rate for improving the hemodynamic efficiency of a sick heart, a method of measuring the conduction time between the RHC and the LHC comprising the steps of:

timing out a pacing escape interval;

upon time-out of the pacing escape interval, delivering one of an RHP pulse to the RHC or an LHP pulse to the LHC;

after delivery of an RHP pulse, sensing an LHS event signal in the LHC;

after delivery of an LHP pulse, sensing an RHS event signal in the RHC;

measuring an RHP-LHS conduction time from an RHP pulse delivered to the RHC to the sensing of an LHS event in the LHC;

measuring an LHP-RHS conduction time from an LHP pulse delivered to the LHC to the sensing of an RHS event in the RHC;

storing in memory one of the RHP-LHS conduction time or the LHP-RHS conduction time, whereby trend data representative of the state of heart failure as evidenced by changes in the stored RHP-LHS conduction time or the LHP-RHS conduction time is accumulated for analysis of the trend.

56. The method of claim 55, wherein the RHC is the right atrium and the LHC is the left atrium.

57. The method of claim 55, wherein the RHC is the right ventricle and the LHC is the left ventricle.

59. The method of claim 58, wherein the RHC is the right atrium and the LHC is the left atrium.

60. The method of claim 58, wherein the RHC is the right ventricle and the LHC is the left ventricle.

61. The method of claim 58, further comprising the step of retrieving the trend data comprising the RHP-LHS conduction time and the LHP-RHS conduction time and comparing the stored RHP-LHS conduction times with the LHP-RHS conduction times.

58. In a multi-site, cardiac pacing system having memory for storing data and having the capability of sensing cardiac depolarizations in a right heart chamber (RHC) to develop an RHC sense (RHS) event signal and a left heart chamber (LHC) to develop an LHC sense (LHS) event signal and to selectively pace in the RHC and LHC whereby RHC pace (RHP) pulses are selectively delivered to the RHC and LHC pace (LHP) pulses are delivered to the LHC synchronously within an RHP-LHP delay at a predetermined pacing rate for improving the hemodynamic efficiency of a sick heart, a method of measuring the conduction time between the RHC and the LHC comprising the steps of:

timing out a pacing escape interval;

upon time-out of the pacing escape interval, delivering an RHP pulse to the RHC;

after delivery of the RHP pulse, sensing an LHS event signal in the LHC;

measuring an RHP-LHS conduction time from an RHP pulse delivered to the RHC to the sensing of an LHS event in the LHC;

storing the RHP-LHS conduction time in memory;

restarting the pacing escape interval;

upon time-out of the pacing escape interval, delivering an LHP pulse to the LHC;

after delivery of the LHP pulse, sensing an RHS event signal in the RHC;

measuring an LHP-RHS conduction time from an LHP pulse delivered to the LHC to the sensing of an RHS event in the RHC; and

storing the LHP-RHS conduction time in memory,

whereby trend data representative of the state of heart failure as evidenced by changes in the stored RHP-LHS conduction time and the LHP-RHS conduction time is accumulated for analysis of the trend.

62. In a multi-site, cardiac pacing system having memory for storing data and having the capability of sensing cardiac depolarizations in a right heart chamber (RHC) to develop an RHC sense (RHS) event signal and a left heart chamber (LHC) to develop an LHC sense (LHS) event signal and to selectively pace in the RHC and LHC whereby RHC pace (RHP) pulses are selectively delivered to the RHC and LHC pace (LHP) pulses are delivered to the LHC synchronously within an RHP-LHP delay at a predetermined pacing rate for improving the hemodynamic efficiency of a sick heart, apparatus for measuring the conduction time between the RHC and the LHC comprising:

means for timing out a pacing escape interval;

upon time-out of the pacing escape interval, delivering one of an RHP pulse to the RHC or an LHP pulse to the LHC;

means for sensing an LHS event signal in the LHC after delivery of an RHP pulse;

means for sensing an RHS event signal in the RHC after delivery of an LHP pulse;

means for measuring an RHP-LHS conduction time from an RHP pulse delivered to the RHC to the sensing of an LHS event in the LHC;

means for measuring an LHP-RHS conduction time from an LHP pulse delivered to the LHC to the sensing of an RHS event in the RHC;

means for storing in memory one of the RHP-LHS conduction time or the LHP-RHS conduction time, whereby trend data representative of the state of heart failure as evidenced by changes in the stored RHP-LHS conduction time or the LHP-RHS conduction time is accumulated for analysis of the trend.

63. The system of claim 62, wherein the RHC is the right atrium and the LHC is the left atrium.

64. The system of claim 62, wherein the RHC is the right ventricle and the LHC is the left ventricle.

65. In a multi-site, cardiac pacing system having memory for storing data and having the capability of sensing cardiac depolarizations in a right heart chamber (RHC) to develop an RHC sense (RHS) event signal and a left heart chamber (LHC) to develop an LHC sense (LHS) event signal and to selectively pace in the RHC and LHC whereby RHC pace (RHP) pulses are selectively delivered to the RHC and LHC pace (LHP) pulses are delivered to the LHC synchronously within an RHP-LHP delay at a predetermined pacing rate for improving the hemodynamic efficiency of a sick heart, apparatus for measuring the conduction time between the RHC and the LHC comprising:

means for timing out a pacing escape interval;

means for delivering an RHP pulse to the RHC upon time-out of the pacing escape interval;

means for sensing an LHS event signal in the LHC after delivery of the RHP pulse;

means for measuring an RHP-LHS conduction time from an RHP pulse delivered to the RHC to the sensing of an LHS event in the LHC;

means for storing the RHP-LHS conduction time in memory;

means for restarting the pacing escape interval;

means for delivering an LHP pulse to the LHC upon time-out of the pacing escape interval;

means for sensing an RHS event signal in the RHC after delivery of the LHP pulse;

means for measuring an LHP-RHS conduction time from an LHP pulse delivered to the LHC to the sensing of an RHS event in the RHC; and

means for storing the LHP-RHS conduction time in memory, whereby trend data representative of the state of heart failure as evidenced by changes in the stored RHP-LHS conduction time and the LHP-RHS conduction time is accumulated for analysis of the trend.

66. The system of claim 65, wherein the RHC is the right atrium and the LHC is the left atrium.

67. The system of claim 65, wherein the RHC is the right ventricle and the LHC is the left ventricle.