Shock timing technology
First Claim
1. A method for accurately determining timing points for T-wave shocks, comprising the steps of:
- (a) deriving a first signal from a cardiac electrical signal, wherein the first derived signal relates to a change with respect to time of the cardiac electrical signal (b) deriving at least a second signal from a cardiac electrical signal, wherein the at least second derived signal relates to a change with respect to time of its respective cardiac electrical signal, and (c) selecting one or more timing points within a T wave of at least one of the derived signals.
1 Assignment
0 Petitions
Accused Products
Abstract
A method for accurately determining timing points for T-wave shocks is particularly useful in a system for determining a cardiac shock strength in an implantable cardioverter defibrillator (ICD. The method involves acquiring at least one first signal, acquiring at least a second signal, comparing the signals, and selecting a timing point with the T-wave of the signal. The first and second signals may be two different aspects of a single electrogram, first and second electrograms, or a combination thereof. Comparison preferably involves signal alignment and qualitative analysis.
80 Citations
54 Claims
-
1. A method for accurately determining timing points for T-wave shocks, comprising the steps of:
- (a) deriving a first signal from a cardiac electrical signal, wherein the first derived signal relates to a change with respect to time of the cardiac electrical signal (b) deriving at least a second signal from a cardiac electrical signal, wherein the at least second derived signal relates to a change with respect to time of its respective cardiac electrical signal, and (c) selecting one or more timing points within a T wave of at least one of the derived signals.
- View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47)
-
48. A method for determining an optimal programmed first-shock strength of a first therapeutic shock of an implanted cardioverter defibrillator relative to the upper limit of vulnerability, the implanted cardioverter defibrillator having at least one sensing electrode and at least one shocking electrode, comprising the steps of:
-
(a) setting an initial test-shock strength, four offset times, and a shock strength decrement;
(b) delivering a set of up to four test shocks with the implantable cardioverter defibrillator to the patient, each test shock member of the set of test shocks comprising the sub steps of;
(i) sensing a cardiac electrical signal from the patient;
(ii) detecting at least one predetermined base timing point prior to the T wave of the cardiac electrical signal;
(iii) differentiating the cardiac electrical signal with respect to time;
(iv) detecting at least one minimum of the absolute value (zero point) of the second derivative of the T wave with respect to time that occurs when the first derivative of T wave with respect to time is not zero. (v) measuring at least one base time interval from the at least one base timing point to the at least one minimum of the absolute value (zero point) of the second derivative of the T wave with respect to time that occurs when the first derivative of T wave with respect to time is not zero, (vi) delivering a test shock to the patient at the test-shock strength and at a test-shock time corresponding to the base time interval plus one of the offset times;
(vii) sensing for an induction of cardiac fibrillation for a predetermined sensing time period; and
(viii) if fibrillation is not sensed in step b(vii), then repeating sub steps b(i-vii), at the same test-shock strength, up to the fourth test shock, each test shock member of the set of test shocks having a different test-shock time corresponding to a base time interval plus an offset time; and
(c) if fibrillation is not sensed in step (b) by the fourth test shock, then repeating step (b) at a lower test-shock strength corresponding to the shock strength decrement, to deliver at least one additional set of up to four test shocks; and
(d) if fibrillation is sensed in step (b), then;
(i) defibrillating the patient; and
(ii) setting the programmed first-shock strength of the implantable cardioverter defibrillator at a predetermined higher level than the weakest test-shock strength at which fibrillation was not induced, which test-shock strength represents the upper limit of vulnerability.
-
-
49. A method for determining a cardiac shock strength, comprising the steps of:
-
(a) sensing at least two changes with respect to time in a T wave of an electrical cardiac signal, the at least two changes being selected from the group of changes consisting of two different changes with respect to time of a single cardiac electrical signal, at least two different cardiac electrical signals, or a combination thereof;
(b) delivering a test shock by;
(i) delivering a test shock at a test-shock strength and at a test-shock time relating to at least one of the sensed changes with respect to time in the T wave; and
(ii) sensing for cardiac fibrillation; and
(c) if fibrillation is not sensed, repeating step (b) at the test-shock strength and at a different test-shock time relating to the change in the T wave; and
(d) if fibrillation is sensed, setting the cardiac shock strength as a function of the test-shock strength.
-
-
50. An apparatus for determining a cardiac shock strength, comprising:
-
(a) a sensor for sensing the electrical activity of the heart, including at least two changes in the T wave with respect to time of a cardiac signal and including fibrillation; and
(b) a controller, connected to the sensor, which provides a test shock of a test-shock strength and at a test-shock time relating to the change in the T wave with respect to time, and to determine the cardiac shock strength as a function of the test-shock strength.
-
-
51. An apparatus for determining and delivering a therapeutic cardiac shock, comprising:
-
(a) a plurality of electrodes, at least one electrode being adapted for sensing cardiac signals and at least one electrode being adapted for delivering shocks to the heart;
(b) a shock subsystem connected to the at least one electrode for delivering shocks and which is capable of generating test shocks and therapeutic cardiac shocks; and
(c) a ULV subsystem connected to the shock subsystem and for providing test-shock information to the shock subsystem, the test-shock information including test-shock strength and test-shock time relating to at least two changes in one or more cardiac signals with respect to time, and for determining the shock strength of the therapeutic cardiac shocks as a function of the test-shock strength.
-
-
52. A method for determining a cardiac shock strength, comprising the steps of:
-
(a) sensing the T wave of an electrical cardiac signal recorded from a subcutaneous electrode;
(b) delivering a test shock by;
(i) delivering a test shock at a test-shock strength and at a test-shock time relating to a timing interval selected utilizing one, some, or all points in time in the T wave of the derived signal and (ii) sensing for cardiac fibrillation;
(c) if fibrillation is not sensed, repeating step (b) at the test-shock strength and at a different test-shock time relating to the change in the T wave; and
(d) if fibrillation is sensed, setting the cardiac shock strength as a function of the test-shock strength.
-
-
53. A method for determining a cardiac shock strength for a medical device connected to a patient and capable of delivering a shock, comprising the steps of:
-
(a) delivering a set of test shocks with the device to the patient, each member of the set comprising the sub steps of;
(i) sensing a cardiac electrical signal from the patient;
(ii) differentiating the T wave of the cardiac electrical signal;
(iii) digitally processing the differentiated signal (iv) integrating the processed, differentiated signal (iii) delivering a test shock to the patient at a test-shock strength and at a test-shock time relating to the maximum the T wave of the integrated signal;
(iv) sensing for induction of cardiac fibrillation; and
(v) if fibrillation is not sensed in step a(iv), then repeating sub-steps a(i-iv) at the test-shock strength up to a predetermined maximum set number, each member of the set having a different test-shock time relating to the maximum derivative of the T wave; and
(b) if fibrillation is not sensed in step (a) after the maximum set number, then repeating step (a) at a lower test-shock strength; and
(c) if fibrillation is sensed in step (a), then defibrillating the patient and setting the cardiac shock strength as a predetermined function of the test-shock strength that induced fibrillation. - View Dependent Claims (54)
-
Specification