Cardiac assist device and method, including detection of heart events

Claim 4

An apparatus as claimed in claim 1 wherein said averaging means includes means for setting said time interval to correspond to a predetermined plurality of successive heart events as determined by said threshold detector means.

Claim 5

An apparatus as claimed in claim 1 wherein said predetermined plurality is in a range of 10 through 30 successive heart events.

Claim 6

A cardiac assist device comprising: signal pick-up means for acquiring a plurality of successive electrical signals each containing a signal component dependent on a heart event and background signal components, said electrical signal exhibiting a signal height; threshold detector means, supplied with said electrical signals from said signal pick-up means, for generating a detector signal indicating a presence of a heart event for each electrical signal having a signal height exceeding a threshold; means supplied with said detector signals for identifying a deflector margin of each detector signal, said detector margin corresponding to a difference between said signal height and said threshold; averaging means, supplied with said respective detector margins for each detector signal, for forming an average value of said detector margins over a time interval corresponding to a few breaths of said subject; enableable control means supplied with said average value for adjusting said threshold in relation to said acquired electrical signals by raising said threshold in relation to said acquired electrical signals by raising said threshold given an increasing value and lowering said threshold given a decreasing average value, and thereby setting a new threshold; means connected to said control means for generating a switching hysteresis by enabling said control means to set a new threshold only if said average value upwardly transgresses an upper limit value or downwardly transgresses a lower limit value; and a stimulation pulse generator means, supplied with said detector signals, for generating a stimulation pulse if a detector signal is not present within a base time interval following a preceding stimulation pulse or a preceding detector signal, and wherein said control means includes means for lowering said threshold of said threshold detector means by a predetermined amount after a first generation of a stimulation pulse following a detector signal.

Claim 7

A cardiac assist device comprising: signal pick-up means for acquiring a plurality of successive electrical signals each containing a signal component dependent on a heart event and background signal components, said electrical signal exhibiting a signal height; threshold detector means, supplied with said electrical signals from said signal pick-up means, for generating a detector signal indicating a presence of a heart event for each electrical signal having a signal height exceeding a threshold; means supplied with said detector signals for identifying a deflector margin of each detector signal, said detector margin corresponding to a difference between said signal height and said threshold; averaging means, supplied with said respective detector margins for each detector signal, for forming an average value of said detector margins over a time interval corresponding to a few breaths of said subject; enableable control means supplied with said average value for adjusting said threshold in relation to said acquired electrical signals by raising said threshold in relation to said acquired electrical signals by raising said threshold given an increasing value and lowering said threshold given a decreasing average value, and thereby setting a new threshold; means connected to said control means for generating a switching hysteresis by enabling said control means to set a new threshold only if said average value upwardly transgresses an upper limit value or downwardly transgresses a lower limit value; and a stimulation pulse generator means, supplied with said detector signals, for generating a stimulation pulse if a detector signal is not present within a base time interval following a preceding stimulation pulse or a preceding detector signal, and wherein said control means includes means for lowering said threshold of said threshold detector means by a predetermined amount after a first generation of a stimulation pulse following a detector signal.

Claim 8

An apparatus as claimed in claim 1 wherein said control means includes means for identifying a beat-to-beat variance of the signal heights of successive electrical signals used for forming said average value, and for raising said threshold by a predetermined amount if said variance exceeds a predetermined variance value.

Claim 9

An apparatus as claimed in claim 6 further comprising means for triggering said means for identifying said beat-to-beat variance only when the threshold of said threshold detector means is set below a minimum threshold value.

Claim 12

A method as claimed in claim 8 wherein the step of identifying a detector margin is further defined by identifying a detector margin using said new threshold each time a new threshold is set.

Claim 13

A method as claimed in claim 8 comprising the additional step of setting said time interval, over which said average is formed, to correspond to a predetermined plurality of successive heart events as determined by the steps of generating a detector signal.

Claim 14

A method as claimed in claim 10 wherein said predetermined plurality is in a range of 10 through 30 successive heart events.

Claim 15

A cardiac assist method comprising the steps of: acquiring a plurality of successive electrical signals from a heart, each containing a signal component dependent on a heart event and background signal components, said electrical signal exhibiting a signal height; generating a detector signal indicating a presence of a heart event for each electrical signal having a signal height exceeding a threshold; identifying a detector margin of each detector signal, said detector margin corresponding to a difference between said signal height and said threshold; forming an average value of said detector margins over a time interval corresponding to a few breaths of said subject; adjusting said threshold in relation to said acquired electrical signals by raising said threshold given an increasing average value and lowering said threshold given a decreasing average value, and thereby setting a new threshold; generating a switching hystersis by setting a new threshold only if said average value upwardly transgresses an upper limit value or downwardly transgresses a lower limit value; administering a stimulation pulse to said heart if a detector signal is not generated within a base time interval following a preceding stimulation pulse or a preceding detector signal; and lowering said threshold by a predetermined amount after a first administering of a stimulation pulse following a detector signal.

Claim 16

A cardiac assist method comprising the steps of: acquiring a plurality of successive electrical signals from a heart, each containing a signal component dependent on a heart event and background signal components, said electrical signal exhibiting a signal height; generating a detector signal indicating a presence of a heart event for each electrical signal having a signal height exceeding a threshold; identifying a detector margin of each detector signal, said detector margin corresponding to a difference between said signal height and said threshold; forming an average value of said detector margins over a time interval corresponding to a few breaths of said subject; adjusting said threshold in relation to said acquired electrical signals by raising said threshold given an increasing average value and lowering said threshold given a decreasing average value, and thereby setting a new threshold; generating a switching hystersis by setting a new threshold only if said average value upwardly transgresses an upper limit value or downwardly transgresses a lower limit value; administering a stimulation pulse to said heart if a detector signal is not generated within a base time interval following a preceding stimulation pulse or a preceding detector signal; and lowering said threshold by a predetermined amount after a first administering of a stimulation pulse following a detector signal.

Claim 17

A method as claimed in claim 8 comprising the additional steps of: identifying a beat-to-beat variance of the signal heights of successive electrical signals used for forming said average value; and raising said threshold by a predetermined amount if said variance exceeds a predetermined variance value.

Claim 18

A method as claimed in claim 13 wherein the step of identifying a beat-to-beat variance is further defined by identifying said beat-to-beat variance only when said threshold is set below a minimum threshold value.