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.

Abstract: A method and apparatus sense a cardiac electrical signal and determine a signal quality parameter of the cardiac electrical signal. A number of shock pulses to be delivered to a patient's heart is determined in response to the signal quality parameter. Each of the shock pulses are scheduled to be delivered at a unique offset from a T-wave shock interval in one embodiment of the invention.

Abstract: Methods for determination of timing for electrical shocks to the heart to determine shock strength necessary to defibrillate a fibrillating heart. The timing corresponds the window of most vulnerability in the heart, which occurs during the T-wave of a heartbeat. Using a derivatized T-wave representation, the timing of most vulnerability is determined by a center of the area method, peak amplitude method, width method, or other similar methods. Devices are similarly disclosed embodying the methods of the present disclosure.

Abstract: A method for determining a cardiac shock strength, for example the programmed first-therapeutic shock strength of an implantable cardioverter defibrillator (ICD), including the steps of sensing a change in a T-wave of an electrogram with respect to time such as the maximum of the first derivative of a T-wave of an electrogram; delivering a test shock by (i) delivering a test shock at a test-shock strength and at a test-shock time relating to the maximum of the first derivative of the T-wave with respect to time; and (ii) sensing for cardiac fibrillation. If fibrillation is not sensed, test-shock delivery is repeated at the same test-shock strength and at specific, different test-shock times relating to the maximum of the first derivative of the T-wave. If fibrillation is still not sensed, the shock strength is decreased and test shocks are repeated at the same specific test shock times relative to the maximum of the first derivative of the T-wave.

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.

Abstract: A method and apparatus for validating a cardiac pacing pulse train preceding a T-shock. Validation of the pacing pulse train includes verifying capture of at least the last pacing pulse of the pulse train and verifying that intrinsic ventricular events are not sensed during a pacing train interval that includes at least the interval between the last pacing pulse and a scheduled T-shock delivery. Capture verification may include sensing an event during an ER sensing window, morphological analysis of a sensed event, and analysis of the temporal relationship between sensed events occurring on different EGM sources. The scheduled T-shock is delivered in response to a valid pacing pulse train. A response to an invalid pacing pulse train may include any of an invalid pacing train notification, withholding a scheduled T-shock, extension of the pacing train, repeating the pacing train, or adjusting the pacing pulse train parameters.